# Radial engine build



## PeterT (Jul 19, 2015)

Some work-in-progress pics of my current project. It’s a 5-cylinder 4-stroke model radial engine, 24mm bore x 22mm stroke 50cc total displacement. Uses RC methanol based fuel & glow plug ignition. About 950-5500 rpm. I bought (2d-paper) plans from a builder in Germany. This is my first attempt at anything like this. But basically model engineering / engine building is my longstanding dream / justification for metalworking machines.

I set a goal to make one complete cylinder stack ‘prototype’ & the related jigs/fixtures. If that pans out without too many ulcers I'll proceed on remaining cylinder replication mode & then crankcase etc. A cylinder stack means cylinder barrel + liner + piston + head + valve cages + valves + springs+ rocker perch/arm/cover assembly, inlet/exhaust fittings…. Many engine builders prefer to start with the ‘big chunk’ (the crankcase) & work their way outwards. But I’ve also noticed 90% of issues are lurking in the fiddly bits, particularly valve seal. So I’m attacking it from the other end. Wish me luck.


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## Janger (Jul 19, 2015)

Serious work there Peter! Will it look like an aircraft engine when completed?   Was this what you brought to protospace the tour evening? I missed your intro...


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## PeterT (Jul 19, 2015)

Yes it will look pretty much like a reduced scale aircraft engine in overall layout, less some typical FS ancillaries like distributer, magnetos oil/fuel pumps etc. Glow plugs simplify the spark ignition complexities. The front crankcase chamber contains splash oil bath for planetary gears & timing cams & methanol fuel has a bit of oil in it. This mitigates oil pump system. Yes I brought some of the cylinder parts to the first meeting at Protospace.


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## Alexander (Jul 20, 2015)

It is a little hard to tell on my phone. Is that the OS liner in your cylinder? Are you going to buy the liners from OS or are you machining them from scratch? That thing is a piece of art. Nice work so far.


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## Jwest7788 (Jul 20, 2015)

Alexander said:


> That thing is a piece of art. Nice work so far.


+1

JW


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## PeterT (Jul 20, 2015)

Hi Alex. Good eye. That is indeed the OS-56 liner stuck in there for picture taking purposes. The OS liner can't be used though, they need to be longer & some other features on the skirt to allow rod clearance. I've made 2 prototype liners (not shown) & they turned out well. The ID's are lapped within 0.0005", a whole procedure unto itself. The plans were a bit evasive on how the liner was fit into the cylinder barrel ID. I first thought I would (heat) shrink them. That part is relatively straightforward, but I was more concerned about future liner removal if necessary. Otherwise the whole assembly has to be tossed if the liner gets worn or scratched. This requires tighter tolerance control because the aluminum cylinder must sufficiently expand more than the steel liner since they are both mated going in the oven together. Typical RC liners are slip fit into the crankcase & I thought that was a better route.

So the OS liner was purchased as a glorified measurement gauge to serve a few purposes: it just so happens to have the same nominal bore as the radial design. It will act as a plug gauge so my cylinder ID boring for correct slip fit. Mostly it gives me accurate bore ID dimensions/finish to replicate because my plan is to use commercial rings for the first iteration. Home made (cast iron) piston rings at this scale are very finicky to make. They are about 0.045" x 0.050" in cross section & involve a series of jigs & fixtures & heat treating. I want this first engine to run & rings are crucial to success. So I will make my own liners & pistons (replicating the commercial dimensions), but use commercial rings initially. If that pans out I will then make my own rings.

So the only purchased bits are rings, bearings, fasteners & probably the carb initially to get sizing about right. The rest is all bar stock, no castings.


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## BradH (Aug 2, 2015)

Peter: looks like a tonne of work - great job!

Wow.

Brad


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## PeterT (Aug 2, 2015)

Thanks. Lately its been 3 steps forward, 2 back. I was having some difficulty with the valves sitting flush in the combustion bowl. This was a function of how 3 individual parts are machined & then mated to one another (the head, the valve cage & valve itself). I wont go into boring detail, but I had to chase down contributing culprits one by one (and learned quite a few things along the way). For example <newbie alerts> 
- end mills don't actually cut a square bottom hole, they have an angle relief in order to cut. Doh! there's a few thou.
- a square shoulder part turned on a lathe is not 90-deg like the drawing. Of course it has a fillet from cutting tool nose, so the opposing face requires chamfer to accommodate. Doh! few more thou.
- another culprit was my first attempt at making the hemi-shaped combustion chamber. I first tried by grinding a form tool from 5/8" HSS & plunged it axially to a defined depth. It looked good initially & seemed to measure up, but it wasn't actually quite as 'hemi' as I thought once the cages & valves were in. I also wasn't thrilled with pushing a tool in like this because it has a lot of cutting edge.

So I came up with this gizmo to cut hemispherical dome shape combustion chamber. Its a similar principle to those ball making accessories for lathes, but just dedicated to this particular task & geometry constraints. I have to remove the tool post to install + also required a new T mount plate. But it worked out in the end. I just take light, progressive skim cuts to total depth. Its more controlled, accurate & better finish. Maybe I should make one of those ball cutting jigs one day.


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## BradH (Aug 2, 2015)

Wow...!  I was going to ask how you cut the bowl...  I am interested in your cutter.  I have been giving thought to a similar tool with the intent of creating a large groove in a pulley for a friend.  I haven't gotten the material yet - supposed to be hard plastic.  The groove is to be a 7/8" diameter half-round... to mesh / engage some bar or pipe.   I figured mounting a 3/4" bar with a HSS tool bit like you did would do the trick, but hadn't figured the mounting geometry.  May be coming to pick your brain about that...

Your design looks much more elegant and simple than anything I had thought up so far.

Brad.


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## PeterT (Aug 3, 2015)

Brad, I made my radius cutting jig more as an experiment & using materials I had available. The downside is, its kind of limited to the range. In hindsight & now that I've used it a bit, I think a dedicated radius turning accessory like these (links) would have accomplished this job plus a range of future turning applications; both In-ees (internal groove type profiles ) and Out-ees (ball type profiles). I kind of like the way they used an insert sitting on a perch. Once the height is established, you are done. And I think you just flip the perch orientation for inner/outer range. On the other hand, HSS is cheap & allows latitude to grind different relief profiles, nose radius etc. Maybe making a sister perch with slot for HSS/tool blanks? Mine is kind of simplistic, the HSS blank also serves as the handle. Not really optimal or as safe, a proper handle is better.
http://bedair.org/Ball/ball.html
http://www.micro-machine-shop.com/ball_turner.htm

My bottom detail pic maybe deserves some explanation & I think the ball turners do something similar. The cap screw/washer draws in the rotating cutter body against the plate in order to adjust snugness. It needs to swivel freely, but no play. I made a brass shim washer to take the slide motion. The screw is set with blue locktite to hold the setting, or it can be tweaked later as required.

Another consideration is the lathe height. I should study those ball turner designs more but I think the compound is completely removed & ball turner mounted to Y cross carriage. I guess I could do that too, but was trying to limit setup it to just removing the dovetail tool post. But that didn't leave me a lot of room to center height (~ 1.28" on my lathe).

I haven't done a lot of plastic turning, some nylon & UHMW. I seem to recall it likes a very sharp cutting tool & more back relief tool. It cut very smooth & nice finish. Just have to watch the swarf can bunch up & tangle.


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## BradH (Aug 3, 2015)

Hi Peter:

I have seen this type of ball turner before...  I have intentions to build a different type to make handles etc.  But I think your simple cutter holder will serve as a good basis...  my job is simple, cutting a soft material, and a 1-off...  so lots of good thing there...

My center height is higher, so may need some sort of collar to hold it more rigid.

Thanks for sharing.

B.

PS - this is the type of ball turner I am looking at making...

http://www.conradhoffman.com/ballturner.htm


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## PeterT (Sep 19, 2015)

Made a bit of progress with the rocker perch, valve cover & spring retainers. Then I hit a small obstacle. The design calls for a very particular metric spring spec (wire diameter, coil ID/OD & free length). I located some imperial springs out of US that looked like they would work by specs, but turns out they were just a tad too large, rubbing & hanging up the valves a bit. Accommodating this larger size was going to a PITA because it affected quite a few inter-related parts & features. Some net hunting & I found some springs from German supplier, nice quality, cheap but holy friggen nightmare ordering. They don't do Visa or Paypal or Money orders or Checks or Bank drafts or Beaver pelts... Only wired funds. Ugh. Anyway, finally landed. They are perfect & now can proceed again. My next option was to wind my own & I may actually experiment with that a bit on the side.


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## PeterT (Dec 20, 2015)

Available shop time has been scarce for me lately but I've been working on some liners, trying different materials & methods. The thing to know is ID's have to be within +0.0000 -0.0005" of a target dimension (0.9445") in finished state and with the right surface finish. So lathe boring is really a roughing stage to get them about 0.002" under dimension, then they are lapped. I first thought I could ream as the last lathe operation to correct any barrelling & get decent pre-lap finish. That aspect worked pretty well, but what I did not count on is that the closest reamer size still left me 0.007" under to go. Well, in the lapping world that's equivalent to trying to take off 1/8" of oak with 220 sandpaper. So the trick is to hit the pre-lap dimensions with boring tools alone, nice & parallel & minimal tooling marks. Lets just say this has been a 'learning experience'. My first one was 12L14 which machines quite nice. But I has a tendency to get rust blotches & methanol fuel will accelerate this. It also can go 'Bwoing' a bit just sitting there (stress relieving). Cast iron is another favorite my model engineers. It has to be close grained stuff which is not easy to source around here. I finally got a 1-foot chunk of appropriate diameter out of USA... along with the UPS spanking. Despite no prior experience, CI is actually very neat material to machine. Messy but it cuts & finishes quite well.

This shows my (longer) CI liner against a commercial RC liner for target analog. It has seen the first lapping pass of 400 grit, maybe removed 0.0005" off the top of the hills so to speak. You can still see some tool cutter trough shadows but you would be hard pressed to actually feel them. The silky matt finish & longitudinal reflection lines is supposedly correct. It came out nice & parallel but there is a whole rigmarole to accurate measurement. So another 0.0015" to go with progressively finer lap & then then final crisscross surface honing. The commercial liners are electro hard chromed & ground so way outside the scope of my shop abilities, but many successful engines have been built with these home methods. Lapping is mind numbingly slow & crawls to turtle pace once in native material. You lap, clean, measure, re-charge... and then repeat over & over. Unfortunately what makes CI a good liner material for its hardness properties also makes it even slower lapping. Ugh. I'm also going to try some 1144 stress proof  which some guys have claimed good results. The journey continues...


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## PeterT (Feb 13, 2016)

The 5-cyl radial has 4 identical link rods & one master rod. I'm figuring out link rods & related jigs now. These prototypes have errors, but show the general procedure.  They are fussy little buggers with several sequential machining operations. But I am learning lots. One jig is to do the dog bone profiling & center flute on both sides. Another jig is for doing the round-over operation on both ends using a 4" Sherline rotary table. I'll take some pics of the RT baseplate I made, it gets held in my mill vise. I'm actually really impressed with the Sherline, its very accurate & functional & suits these smallish parts.


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## John Conroy (Feb 14, 2016)

Thanks for posting this project Peter. Very impressive! 

John


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## Geoff (Feb 14, 2016)

Very cool Peter!  You are an artist!  Lots of interesting setups and jigs!  I was also going to ask about the liner.  How are you honing it to tolerance?  Are you using a commercially available hone or did you make something?  Are you using stones or a lapping compound?


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## PeterT (Feb 15, 2016)

Thanks for the nice words. The final bore diameter/geometry/finish is accomplished with a brass lap. Some guys make their own but I found the Acro works well - relatively inexepensive & replaceable barrels.
http://www.acrolaps.com/
The stones like the sprung brake cylinder jobbies don't do well in this environment. They remove material better but at the risk of losing dimensional control & particularly bell-mouthing effect. They 'look' like the big boy Sunnen hones, but lack a lot of the control mechanism & stone quality. My understanding is they are more for deglazing/resurfacing hardened bores & typically longer, so less risk of messing things up. As I mentioned upstairs a few posts, lapping is a very accurate & controlled process but excruciatingly slow & somewhat messy process. You really need the lathe operation bored within a couple thou & good finish. Any more undersize & you just wear out the lap & are there forever. Especially cast iron. In the real world its machining > grinding > lapping (usually also because hardening is in there too). So going from machining > lapping is kind of missing an in between step. Tool post grinders are probably the way to go but they are not for the faint-of-wallet.

What I discovered most model guys are doing is getting the bore to 'whatever'. IOW they don't care if its 0.999" or 1.001" as long as the finish & bore geometry (roundness & parallelism) is there. So they lap multi-cylinders in sequential batches ending with the same tool/setting. However, now you must size both ring & piston to suit this bore. In my case its the reverse: I want to use a commercial ring, so that means my bore + finish must arrive at a specific dimension like 1.000" with very low tolerance. Making rings is a bit of finicky operation & challenges even the gurus. A 1" nominal bore translates into a ring of ~0.050" in cross section. They are cast iron so quite fragile. The machining isn't too bad but they need to be heat set on a pin/jig to a specific dimension & temp. This heat set alteration yields the appropriate radial sidewall force for gas sealing when compressed in the bore. http://homepage2.nifty.com/modelicengine/h9110101.htm
Eventually I want to get there, but for this first engine I figured treat myself to commercial rings for all of $10 each & use that as base line for running. In hindsight its choose your poison.


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## Geoff (Feb 15, 2016)

Very cool stuff, thanks for the detail!


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## Rudy Pekau (Apr 8, 2016)

PeterT said:


> Thanks for the nice words. The final bore diameter/geometry/finish is accomplished with a brass lap. Some guys make their own but I found the Acro works well - relatively inexepensive & replaceable barrels.
> http://www.acrolaps.com/
> The stones like the sprung brake cylinder jobbies don't do well in this environment. They remove material better but at the risk of losing dimensional control & particularly bell-mouthing effect. They 'look' like the big boy Sunnen hones, but lack a lot of the control mechanism & stone quality. My understanding is they are more for deglazing/resurfacing hardened bores & typically longer, so less risk of messing things up. As I mentioned upstairs a few posts, lapping is a very accurate & controlled process but excruciatingly slow & somewhat messy process. You really need the lathe operation bored within a couple thou & good finish. Any more undersize & you just wear out the lap & are there forever. Especially cast iron. In the real world its machining > grinding > lapping (usually also because hardening is in there too). So going from machining > lapping is kind of missing an in between step. Tool post grinders are probably the way to go but they are not for the faint-of-wallet.
> 
> ...




Interesting project,being a former RC model builder and flyer.

There is more out there: I am involved in a Toroidal Rotary engine project, several prototypes have been built.You can see an expander engine running on compressed air on youtube : type Roundengine July 2011
It was meant to go into an automotive hybrid with waste heat recovery. Wonder if there is anybody out there in getting involved ?

Any comments ? email to pekaudr@shaw.ca


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## Jyman (Apr 8, 2016)

Hey PeterT

That's a nice looking engine your building, I would love to build a radial engine at some point.  where did you get the blueprints from? And what did the plans cost you?

Jon


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## PeterT (Apr 8, 2016)

Hi Jon. The plans were purchased here, Martin Ohrdorf. http://www.engineman.de/
Bit of background story. I originally bought the 9-cyl plans a few years back, but it was for design reference when I was naively contemplating my own 5-cyl radial design. Then one day I noticed he subsequently offered a 5-cyl version that shares certain 9-cyl components. So I ended up getting the 5-cyl plans figuring the smaller brother would be a big enough challenge for me. Unfortunately he makes you buy both sets (or at least he did at the time) which is a bit goofy since they are 2D drawings of 3D Cad assembly which could be offered as standalone IMO. But since I already had the 9 plans, I took the leap. He also offers a V12 & a double row 7 (14 cyl corncob) which look to be similar design methodology. There are some Youtubes of his engines running. Correspondence is spotty at best (maybe language issue).

I’ll mention some other options because this absorbed a lot of my decision making time.

Free (legitimate free) PDF plans are available for the Edwards engine 5-cyl radial which is quite similar. I have a copy if you are interested (version A08a), otherwise I think you just need to join Yahoo R&R user group to access. There are some pros & cons & slight aesthetic differences. Edwards has integrated mechanical lubrication pump so it runs pure methanol as fuel & circulates oil where required. This would be my preference over the typical premix oil/methanol RC fuel, but they seem to run ok & the commercial engines are premix too. The Edwards has some documented builds on some forums, not the case with Ohrdorf. I was prepared to start the Edwards but found difficulty sourcing the internal (IMP) tooth ring gear. That’s the one critical thing you need to nail down beforehand on these radials. External spur gears can be made by hobby machinists but internal ring tooth form, especially at this scale & ideally hardened, not so easy. Unfortunately it’s the heart of the engine design because of physical size & requisite gear ratio combination for cam lobe timing etc. The euro engines use same crankshaft > idler > ring gear > lobe cam principal but use module (metric) gears. I was able to locate the metric one so that sealed the deal. Since then I’ve stumbled on the required Edwards ring gear, but too late now.

Here is another supplier which look to be pretty good designs. They also offer some simpler & lower cylinder count engines - probably what I should have pursued first, but oh well. They are also methanol fuel / glow ignition, all metric. And also a 5-cyl radial btw.
http://www.cad-jung-shop.de/epages/62479729.sf/de_DE/?ObjectPath=/Shops/62479729/Categories/Baupl%C3%A4ne/Bauplane_Modellmotore

This link shows some build pics of the 7-cyl radial.
http://philsradial.blogspot.ca/


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## PeterT (Feb 17, 2018)

Well it was almost a year ago, roughing out this very same lump of steel that my lathe power feed decided to cough a fur ball. Long saga but its all better now. So finally time to get after the crankshaft for this radial engine again. It was a very fussy bit of machining - several bearing surfaces to pretty tight tolerances, retaining ring grooves, bearing bosses, eccentric crankpin machined from solid, nice fit to master rod bronze bushing, web cut outs.... Its made from solid 1144 stress proof steel. First time I've used this but I like the material. Its quite tough but finishes well & does most important does not banana with all the metal removed which is key. 

I almost botched one of the critical bearing surfaces. After lapping down to OD where bearings were a nice reasonably tight but position-able fit, I quit for the night. Next day the bearing slid on with alarming easiness. Not rocking buy way looser than it was the day before. I re-miked & sure enough was 0.0003" under what I wrote down the day before. WTF? Apparently I still had resident heat in the bar, enough that it was still under thermal expansion even while working the last couple thou & lapping for probably an hour after turning. I just assumed it had returned to close enough to room temp. Lesson learned, disaster avoided. Actually the front gearbox assembly requires retaining compound so worked out in the end. Well this was my first crankshaft, glad it turned & behind me. Now I can proceed to the next parts in line - planetary gear assembly, cams etc.


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## PeterT (Feb 17, 2018)

Crankpin stuff


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## PeterT (Feb 17, 2018)

Web removal & finishing. 
An additional counterweight segment gets bolted to the two M3 thread holes.


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## John Conroy (Feb 17, 2018)

Very nice work Peter!


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## Alexander (Feb 17, 2018)

Wow that turned out great.


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## Janger (Feb 17, 2018)

Wow Peter well done. Inspiring. Thanks for posting.


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## DPittman (Feb 17, 2018)

Ok for a good laugh.....here's an example of the greatly different skill levels on this forum....you've seen Peters' amazing skills on that crank.....now for something completely different....
Here's a picture of my first ever attempt at a little crank I made just today on my lathe and home made milling attachment.  Overall dimension is 1".

Humbling but inspiring to see such knowhow as yours Peter!

Don


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## Janger (Feb 17, 2018)

That looks good to me. What is it for Don?


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## DPittman (Feb 17, 2018)

Well, no particular engine yet, I'm just trying out some component making.  I want to make some very small steam/air wobbler engines. Here's a shot of some very tiny machining I also did in making a steam shut off valve for a not yet made boiler.
I have no clue how to make a boiler either so any advice is always welcome .


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## Everett (Feb 17, 2018)

That is absolutely awesome.  Thank you for sharing this with us!


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## PeterT (Feb 21, 2018)

Another finicky part (half done). This is the gear plate. The small boss OD slide fits into the crankcase within 0.0005" & has bearing recess. The bigger boss OD will slide fit the nose case to same tolerance. It still needs some fastener holes, counter bore & shaft hole for idler gear. The business end of the planetary gear cluster & lobe cams reference off this & crankshaft geometry. 

What caught me off guard was the drawing shows 1.5mm width groove for 1.5mm nominal O-ring section which I followed. These seal the nose case oil bath from entering the CC, but you also have to get the parts on & off. In hindsight I should have realized the same 1.5mm groove/O-ring nominal width cant work (and they didn't). No way I could push the CC on test fitting on the lathe. The gap needs to be wider to allow O-ring squish room to oval out. This is 70 durometer Viton cord. In retrospect I should have made a test coupon beforehand to pre-establish the fit vs winging it on the real part.

Turns out many variables affect gap width apparently: the durometer, groove ID, tolerance of O-ring section & nominal diameter, what kind of seal is required (degree of interference fit). Anyway I was already committed to the groove depth so basically crept up on the width until I got the right fit. This engine design is German, very few instructions. I figure either he used some super soft silicone O-rings or just left the drawing as guideline starting point.  And on we go!


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## PeterT (Feb 21, 2018)

DPittman said:


> Humbling but inspiring to see such knowhow as yours Peter!
> Don



Thanks for the nice words. Your parts look great. I probably should have started on something simpler myself. Oh well.


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## RobinHood (Feb 22, 2018)

Super cool PeterT! Beautiful work.

I remember reading up on that build on a German forum quite some time ago. Just can’t recall which one....


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## johnnielsen (Feb 25, 2018)

Your results are inspiring, accurate and beautiful to look at.
Kudos.


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## PeterT (Feb 25, 2018)

Brass counterweight addition for crankshaft. One of those 5 minute jobs that took 3 hours  It has a relief arc cut to accommodate the master rod, but its center occurs at a different center than the OD, so required 2nd setup in the 4 jaw. I integrated that registration point in the same fixture used to hold the crankshaft for crank pin turning. Sometime one spends the same time on fixtures as the part. Brass face mills really nice with the sharp uncoated inserts used on aluminum.


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## PeterT (Mar 3, 2018)

Sh*ts getting real now! ha-ha. After making a few more drive line parts, I spent the day getting my brain around the planetary gear assembly. The gears are modified from steel commercial Mod-1 (metric) gears, so will require special fixtures to hold them. But I think I'm going to make some (OD/ID/pitch diameter) mock-up gear blanks because there are so many inter-related fits above & beyond them just meshing.

The short story is the crankshaft has a 15-tooth gear attached. It drives an idler cluster 15-tooth / 10-tooth & the 10 drives the 40 tooth internal (ring) gear... which gives the 4:1 ratio & drives the intake/exhaust cams.


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## Alexander (Mar 3, 2018)

Cool that looks great nice progress so far.


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## PeterT (Apr 5, 2018)

Turning a commercially purchased 40-tooth Mod-1 internal gear. This is part of the planetary gear drive train that drives the 2 lobed cams at 4:1. Ring gears, or more specifically ring gear internal tooth profiles are very difficult to make accurately in home shop environment. In fact I was just real happy to get this to size without botching it, because they are not exactly easy to source. It had to be reduced in both diameter and in thickness to fit an aluminum bearing cup, which I made beforehand. 

The trick is to maintain accurate concentricity on the teeth & also not allow the gear to move under 2 different machining steps.  So I turned a very snug fitting shoulder spigot in the lathe insitu, then without removing it from chuck, applied my CA-glue treatment, positioned the gear & clamped with a plate. This steel is tough stuff so light cuts & patience. Luckily it held during the facing job too. If I did this again I would make provisions for a brass pin to rest against a gear acting kind of like an internal dog. But I also didn't want to have too many things glued in place because they can be a bugger removing even with butane torch heat.


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## johnnielsen (Apr 8, 2018)

You are doing some amazing stuff.


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## PeterT (Apr 12, 2018)

Finally! The cam plates are done. Made from A2 tool steel. Never worked with this stuff before. Its quite tough but light cuts & patience finished up OK. These need to be hardened so I've made contact with a local knife maker guy who has the appropriate equipment. Because the thinness & non-symmetrical shape & array of holes etc. I decided to try A (air) over O (oil) quenching tool steel. I figure with the work that went into them I just didn't want to add extra risk of 'potato chip' distortion if it were to hit a liquid quenched. So after heating in a stainless bag they get 'air' quenched but sandwiched between 2 aluminum plates. Then tempering to whatever temp to target hardness.

One lathe fixture was to hold the blank for center hole boring & reducing thickness to 3.5mm (metric plans) from IMP stock. Then part transferred to another mini rotary table fixture to mill the 2 (valve closed) radius arcs, then screw holes & lightening holes. One cam is intake, the other is exhaust, so the relative phasing once stacked comes about by orientation of M3 tap & clearance holes. So lots of RT angle positions to remember. Then I cut the ears off & utilized the holes to secure it to another lathe fixture for the OD (valve open) turning. Then some careful Dremel grinding to make a nice transition up the ramp of the lobe & polishing with rubberized abrasive.

I think I'm going to make these next so I can send them out together. Basically I want the followers to be a couple Rockwell points under the cam plates so the wear is on the easier to replace part. They are made from 4mm O1 round stock. They have a hemi-ball shape on the end that runs along these cam profiles. The other end is an internal (ball mill divot) here the rocker pushrods locates into.


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## PeterT (Apr 28, 2018)

Made a good start on the tappets. Material is O1 tool steel. Only about .0015" has to come off stock diameter but pretty much impossible to turn this small amount on something so skinny, long & somewhat tough material. But it needs to be 0.0005" clearance relative to 3mm reamed hole in tappet guide. This was a PITA.  I messed around with lapping fixtures, but in the end it was net faster to just work it down with various grits of paper & measuring often.

The end that runs against the cam profile plate has a dome profile, basically a point contact. The profile itself is not super critical because its essentially a point contact, but I wanted all 10 (+ 2 spares) to be the same. So I held in 5C collet chuck & used Radii turning tool to form the basic shape. Then I chucked the rod in my Dremel & to remove tooling marks, progressively finer WD paper & finally lapping compound embedded in felt. 

What remains now is turn to each to final length. Then cut a dome recess on the other side for the pushrod using 2mm ball end mill, polishing etc. Monotonous but relativity straightforward. With the cams & tappets complete, I can send the parts away for & prescribe hardening. Cross my fingers nothing warps too bad given the time invested. I'm really not sure what to expect there so wish me luck.

The actual tappet guides are made of bronze, I caught that detail after I made mockup from brass. But I think I'll hold off making those until the parts come back from hardening.


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## DPittman (Apr 28, 2018)

PeterT said:


> Made a good start on the tappets. Material is O1 tool steel. Only about .0015" has to come off stock diameter but pretty much impossible to turn this small amount on something so skinny, long & somewhat tough material. But it needs to be 0.0005" clearance relative to 3mm reamed hole in tappet guide. This was a PITA.  I messed around with lapping fixtures, but in the end it was net faster to just work it down with various grits of paper & measuring often.
> 
> The end that runs against the cam profile plate has a dome profile, basically a point contact. The profile itself is not super critical because its essentially a point contact, but I wanted all 10 (+ 2 spares) to be the same. So I held in 5C collet chuck & used Radii turning tool to form the basic shape. Then I chucked the rod in my Dremel & to remove tooling marks, progressively finer WD paper & finally lapping compound embedded in felt.
> 
> ...


Wow. Just simply wow.


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## johnnielsen (Apr 29, 2018)

I have used skiving with success on small items like that. Glad the abrasive route worked so well for you.


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## PeterT (Apr 29, 2018)

Im not familiar with skiving, do you have a link or sample pic


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## johnnielsen (Apr 30, 2018)

https://www.productionmachining.com/articles/the-forgotten-art-of-skiving

https://www.sommatool.com/manuscripts/is-13a.asp

http://www.practicalmachinist.com/v...l-skiving-tool-283635/?highlight=Skiving+tool

It takes some playing around but once you get the angles right it is amazing. The way I remember it was like taking a long cylinder cutting pass on  wood lathe where the tool has a flat straight 90 degree nose that is held at a 15 to 30 degree angle from the vertical. The back side has a relief angle on the back to ensure only the front edge touches the work piece. Picture a manual type wood chisel  with an 80 degree bevel instead of a 25 degree bevel.


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## johnnielsen (Apr 30, 2018)

Some more info.

http://www.gadgetbuilder.com/VerticalShearBit.html

The skiving I did was on straight turning, no fancy profiles. I wanted perfect size and perfect finish, relatively speaking. I would remove max .002 inch.


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## PeterT (Apr 30, 2018)

I'm definitely going to experiment with that. Thanks!


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## PeterT (May 19, 2018)

Progress on the front gear plate & planetary drive. The metric spur gears are commercial (steel) but each had to be modified to make the idler cluster.
The 5mm idler shaft is O1 which I hardened myself with torch. I discovered it is sufficiently hard because there is a fiddly 90-deg partial countersink for M2.5 flathead bolt & it was a teeny bit shallow. I had a bugger of a time deepening it with HSS so had to grind on it a bit. All good though, everything seems to run smooth.


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## John Conroy (May 20, 2018)

Amazing work Peter!


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## johnnielsen (May 20, 2018)

I second that!


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## PeterT (Jun 2, 2018)

Here is the rear intake manifold / engine mount plate progress. Fuel enters from the rear through the center hole via a (commercially purchased ) RC carburetor into the crankcase chamber. Because the methanol fuel has some oil added, this internal detour helps lubricate the connecting rod assembly. In a 'real' radial, this aspect of lubrication is handled by an oil pump, squirter tubes & recycle. From the crankcase, the inlet charge exits back out through one of the 5 radial ports up its respective induction tube into the head. You can see some nozzle-ettes that eventually get Loctited into place. I still have to turn some bosses which go into respective counterbores on the outside manifold section. They have internal o-ring grooves t seal the tube, so I will have to muck around with what kind of induction tubing I will use & pre-establish fits etc because these bosses also become permanently attached. Mostly this was lathe turning & rotary table work in lay-down & up-right positions. Thee is only one way it goes on the crankcase, so several alignments to keep in the noodle.


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## PeterT (Jun 2, 2018)

The 5 ports are first pilot drilled then bored with a ball end mill to depth. Then do this at 90-deg in the other plane & results a smooth-ish gas passage corner.


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## PeterT (Jun 2, 2018)

Here is the nose case in progress. I still have to drill the 5 front attachment bolts & 10 radial tappet counterbores. Most of it was conventional turning but a few dimensions had to be trial & error fitted, namely the front bearing ID & lip ID which fits against an O-ring seal on the gear plate. I originally thought i could use the Radii cutter for the front profiling but the case is too large for the Radii swing. So I worked out a table of XY intercepts, blued the stair steps & filed & sanded until no more blue showing.

The original plans had some complicated internal pocket relief milling features which I stared at for a long time, wondering why he did things this particular way. I didn't like how the bolt holes were landed through material half open which I was sure was going to cause me drill deflection grief. The pocket milling leaves a bit more meat for the tappet guides to reside in but maybe not enough to justify the setup work & my endmill looked a bit short for the job. So.............. I 'simplified' it a bit & therefore running the risk of making this part all again if I discover something I hadn't considered properly. TBC. This nose case houses the planetary gears & & cam plates, so it is half filled with oil so these parts get splashy happy in the lubrication.


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## PeterT (Jun 2, 2018)

Backside turning.


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## PeterT (Jun 10, 2018)

Nose case mounting holes & radial tappet holes operation completed. I made a fixture which fits the ID of the nose case & retained with a threaded stud & washer disc. That then gets dialed in & clamped in 4-jaw chuck which is turn is mounted to RT. The fixture lip needs to be quite snug fit but based on a dicey prior experience, I was more concerned about getting them apart because its aluminum on aluminum & lots of close fitting contact area. So  I used a light smear of ant-seize compound. That for sure helped. 

Its looking like my modification will work out. Relief, I really didn't want to make this part again. One more tapped hole to make on the front face for oil fill plug & that's it.


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## Janger (Jun 10, 2018)

We’re going to have to have a party at Peters to celebrate this odyssey. When can we see it run?


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## PeterT (Jun 10, 2018)

HaHa. My goal was to get this 'middle engine stuff' done by end of summer (crankshaft drive train, crankcase, manifold...). I think I'm mostly on track (and breathing a sigh of relief). Then comes '5 times everything' mode, meaning 5 assemblies of cylinders/liners/heads/pistons/valves... Maybe this time next year if its a productive winter? I'd like to get out to the flying field now because our summers are so dang short. So I'll pick away at some smaller tasks over the next few months.


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## DPittman (Jun 10, 2018)

Peter....you're a pilot?  Whatcha fly?

Don


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## PeterT (Jun 10, 2018)

Only radio control models. Been doing it since I was a kid. Started on typical sport models, then pattern (aerobatics) for quite a while, then pylon racing, then a brief stint with heli's (the dark side). Now I'm messing around with 4m span electric sailplanes. The motors are just to get to altitude, then its basically a thermal event. I've kind of done RC events in 10 year chunks for whatever reason, so I'll probably stick with this for a while. The reflexes aren't quite what they used to be LOL.


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## DPittman (Jun 10, 2018)

PeterT said:


> Only radio control models. Been doing it since I was a kid. Started on typical sport models, then pattern (aerobatics) for quite a while, then pylon racing, then a brief stint with heli's (the dark side). Now I'm messing around with 4m span electric sailplanes. The motors are just to get to altitude, then its basically a thermal event. I've kind of done RC events in 10 year chunks for whatever reason, so I'll probably stick with this for a while. The reflexes aren't quite what they used to be LOL.


Sounds fun. One of my childhood friends built RC planes and eventually a helicopter. It always intrigue me and I loved the engines.  I had cast off Cox 0.49 engines that I would make snow sleds and boats for.  Neat hobby RC stuff.  I am now nearing completion of a 2 seater ultralight airplane I built (kit form) . Just some bigger than your sailplanes!  It's taken forever to get this far (reasons not related to actual building) and now it's pretty high on the bucket list to actually get it flying.  I fear the bucket might go flying first!  
Don


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## PeterT (Jun 21, 2018)

My hardened tool steel goodies arrived back from the nice folks at Canadian Knifemaker out of Sundre. https://www.knifemaker.ca/
Big shout out to them. I couldn't be happier because they are not in the business of miniature radial engines but obviously know how to heat treat metal. I dropped them in the mail with some verbiage, followed up with a phone call. A short while later they arrived back by post at very reasonable price. This resource has opened up new avenues for me (and saved me looking for a $ oven hopefully many years).

The cam plates are A2 (air quench) tool steel chosen for minimal distortion in quench. I asked for 55 hardness. So they go into sealed foil bags with a oxygen consumable, raised to temperature & soak time. Then get quenched at room temp by clamping between aluminum plates. Then back in the oven for tempering at specific reduced temperature/time to achieve the desired hardness. They came out this silky black color which can be removed by hard scuffing but I'll probably leave it for no other reason than monitor any wear from the tappets. The big relief was no measurable distortion in the plate in the potatoe chip orientation. The bore shrunk about .0015" which was totally acceptable. It fin teh ring gear cup no problem. YAY.

The tappets are O1 (oil quench) tool steel. I could have gone A2 too excep they are 3mm nominal stock & O1 was all I could find. Anyway, same story except these are target 50 hardness to wear preferentially. They get oil quenched & I was actually more concerned they might bow & be problematic in the sliding fit of bronze guides. Here I spun them in the Dremel & 1200 paper to remove the black & buff them to final sliding fit. I have no way of verifying the hardness numbers were achieved but I have to trust the process. And its 100% better than I could have achieved with my Neanderthal fire stick & can of oil.


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## PeterT (Jun 21, 2018)

These are the bronze tappet guides. They are pretty straightforward, drilled & reamed & tapered. But its amazing when parts get small scale like this even a tiny burr from chamfering or reaming can be felt in the fit. So I used a brass lap with 1000G compound which made them all consistent. Then the compound has to be removed so consecutive cleaning baths of thinners & Q-tips. 

For machining I find a sharp un-coated insert tool works best (same one I prefer on aluminum). Drilling small diameters isnt a big deal but larger drills definitely need edge dubbing or the material can grab mess things up. Another big relief is my nose case modification from the plans seems to have worked out, at least AFAIK. The guides eventually get installed with permanent Loctite.


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## PeterT (Jun 21, 2018)

Its coming along but still a long ways to go.


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## Tom O (Jun 22, 2018)

nice


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## YYCHM (Mar 13, 2019)

WOW!  The precision and finish is just amazing.


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## Brian H (Mar 13, 2019)

That is some fine work! Well done. I am very intrigued. I am hoping to do some scale stem engine build at some point. However being a very new metal worker, I will need to hone my skills somewhat before I tackle an actual engine.
Thanks for sharing


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## PeterT (Sep 16, 2019)

Well, I feel fall weather coming so figured its time to migrate back to the shop & pick up on the radial build. I left the project this spring with some specific problems to solve on the head.

1) I needed to sort out how to make the induction & exhaust tubes, their end flares & coupling nuts into the head. I think that aspect got dealt with here.
https://canadianhobbymetalworkers.com/threads/brake-line-flare.1314/#post-13421

2) Making the intake/exhaust ports has been challenging. They enter the head at a funky compound angle, they must intercept the valve cage at a precise spot, the holes are counter-bored & threaded to accept the tubing nuts and the thread depth is stupidly shallow. I thought I could accomplish this with careful setup in the mill & using modified taps but that turned out to be problematic. Its very hard for a tap to engage properly when the tap is only cutting on half its body for 6 or more initial threads until the whole body is cutting. So I tweaked the head diameter to net me slightly more material to work with and I've come up with a new lathe based jig that has the angle & offset incorporated. I will attempt single point threading the head in the lathe. More to come on that front

3) I had to finalize the valve cage assembly into the hemi shaped combustion chamber. Judging by engine forums, valve seal is the singlemost trouble maker for scale engines. A minor leak stops you dead in your tracks despite the usual blueing & lapping methods. Its one of those things that just doesn't 'scale' from the full size engines. So best results are when the seat itself is cut teeny, like 0.010-0.015" across the 45-deg vs say 2-3X that if it was scaled. The theory is less seat is better, the valve settles in quicker, finds a happy home & kind of wears itself into a seal if everything goes right. So I had to depart from the plans & redesign the cage a bit. But I also achieved better conformance of the valve bridging flat across the hemi bowl. They can't protrude much before getting dangerously close to the piston. They also cant be recessed too much because it makes nooks & crannies for crud to build up & the head volume is very sensitive to compression ratio changes. Anyways, I think I have a method I can replicate. Here is the bronze valve cage & stainless steel valve. The cage is pilot drilled then bored to ID with little boring bar. Unfortunately the cages have to be installed first, then lots more machining to the heads before I can test seal using vacuum draw down. Fingers crossed, if not, frowny face day.


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## PeterT (Nov 9, 2019)

I think I finally have the cylinder head intake/exhaust ports figured out. They look innocent enough but took me a few tries experimenting how NOT to make them. The gas passage comes in at a funky angle & must intersect the bronze valve cage at a specific point. At this stage the cages are permanently bonded into the head with high temp Loctite & a few hours put into the head. The port is counter-bored & threaded 7/16-28 for the tubing retention nut. What makes the operation tricky is the tap is only cutting on one side for 3 or 4 threads before its body becomes fully engaged in the full hole ID & cuts normally. Then it only fully threads beyond that for a shallow depth before reaching the counter bore step, so not a lot of thread engagement.

I came up with this fixture which holds the head at the correct offset & orientation angle so the port axis is in alignment with the spindle. Unfortunately because of the geometry, 2 fixtures are needed, 1 for intake, 1 for exhaust. So the operation goes: spot face a flat, center drill, drill gas passage hole through into cage, drill roughing hole, mini bore to correct thread ID, plug tap thread, bottoming tap thread. With the tap gripped in the TS chuck & quill locked, by carefully pushing on the TS & rotating the chuck with the other hand, it made a pretty nice thread form. I have to pay close attention to the very start & backing the chuck slightly to break the chips.

I really thought I was going to be single point threading these buggers & rather dreading it because there was just no room to make a groove relief & threading into blind hole towards the HS with RH threading tool. Tiny LH tools are not easy to find or make to thread in reverse direction from HS to TS. My next step was going to be inverting a RH tool & threading HS to TS, something I intend to practice.  

Anyways, this was one of the last of major obstacles so slowly getting into a position to make 5 heads in replication mode.


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## DPittman (Nov 9, 2019)

Cuz it's all lights years ahead and above me, I have nothing intelligent to say, but can't help saying "wow, cool stuff Peter!"


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## John Conroy (Nov 9, 2019)

Really impressive work Peter!!


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## PeterT (Nov 24, 2019)

Well. I'm REEEEALLY hoping I have all the issues sorted out on the prototype head. Because it finally became time to make 5 (plus 1 spare = 6). The good news is, things go a bit quicker when you have a common operation going. All the tools are out, the procedure is fresh in your brain etc. But its also easy to get hypnotized & make errors with a mental lapse. Here are some hilite shots. My original plan was to make them from 7071 or 2024. But I've been using 6061 for the testers & had a keeper in the bag, so used 6061 for the set.  It sure feels good to have a functioning mill from where I was at a year ago, thanks again John & John for your help.

Pic shows a needle file handle holding an abrasive rubber wheel in its collet. It works good for certain de-burring & blending by hand on weird edges.

Next step is bronze valve cages & valves. More fussy work.


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## David_R8 (Nov 27, 2019)

One word for this work: Wow!
Very impressive stuff!


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## DPittman (Nov 27, 2019)

Damn cool.


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## PeterT (Nov 27, 2019)

Thanks guys. Working on the valves & cages now. A few more tweaks to the testers and then its 'make 10 + spares' mode. One day I'll take a picture of the false tries & misfits. Those are measured by the bag full LOL. The valves are being made from 303 stainless which isn't my favorite material especially for holding dimensions on several critical surfaces, but I'm slowly figuring it out.


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## PeterT (Dec 21, 2019)

The valves are done. Whew! The are machined from 7/16" diameter 303 stainless. I made some prior testers from 416 which machines a bit better but I started to have reservations about corrosion which is bad enough on these methanol burners. Turns out 303 isn't so bad once you have the tools & speeds & a few techniques figured out. I like this particular DCMT insert. The stems are 3mm (0.118") to give you scale. Stock is held in 5C chuck & supported on end with my newly acquired Shars slender nose live center.


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## PeterT (Dec 21, 2019)

I turn the stems about 2 thou oversize & then use these simple lapping tools. They are just blocks of steel or aluminum that were sandwiched, drilled through with 3mm drill. I made a few other contraptions but these 'clam shell' styles were easy to make & quick to apply to the part since the tail stock lump is still intact for support. The compound is inexpensive AliExpress diamond paste which cuts very well & washes off easily with thinner. So basically charge the groove with paste, apply it to the part & with finger pressure just go back & forth. Its very controlled. The steel ones were for rouging, the aluminum was for finishing. As they wear, I just dress the flats on some sandpaper & that closes the effective diameter again. I check it with a 3mm reference rod to make sure it wont cut undersize.


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## PeterT (Dec 21, 2019)

I forgot to take a picture of the trumpet shaping but its a 6mm diameter carbide tool (again AliExpress). Then the valve is parted off, the end blobby cut off with hack saw & the valve body faced to a fixed thickness. Then I use a collet stop and a machined fixture which is slightly larger diameter than the valve head so it can be flipped around & the stem cut to exact & consistent length.


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## PeterT (Dec 21, 2019)

The 45-deg valve face is cut with a parting tool corner in shallow passes. The stock is pre-blued with Sharpie so the valve seat profile is done when there is 0.010" blue remaining. I hold up vernier with jaws opened 0.010" & a magnifier. Trying to jig things at this scale isn't practical.

Then to dress the valve face, I've concluded its best to get it off the lathe. I hold it in my Dremel (Milwaukee cordless actually) with a collet & spin it at lowest RPM. Then its a matter of blueing it & carefully taking the surface down in progressive stages, rinse &repeat so the machining record player tracks are completely gone. I start at 1000 -1200 grit (blocks with wet-o-dry paper). Then I found these nail file boards work really well, it has 3000 on one side. Initially I was paranoid of freehanding the faces like this worrying about roundover but its actually quite cotrolled as long as you blue often & observe. After doing a bunch of vacuum pull tests trying many different ways, my conclusion was leakage was inevitably related to machining ridges remaining. The corresponding valve seat (on the valve cage) is about 0.010" wide so it just lands somewhere in the middle of the valve face.


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## PeterT (Dec 21, 2019)

Back they go into the stop jig, lightly dress the end with a grinding wheel & make the e-clip groove.


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## PeterT (Dec 24, 2019)

Bronze Valve Cages. I won't bore you with the behind the scenes testing & details of how I eventually landed on this final configuration other than to say model valves & seats don't really 'scale' to a FS engine. The valve 45-deg face is ~.050" across but the seat in the cage is only ~ 0.010". The seat could actually be more, but its actually pretty difficult to machine & finish properly at this scale. When I took apart some commercial RC 4-S engines I was able to see the same thing, teeny thin valve seats.

A good method I came across from a successful builder is to insert a known good 'reference' valve into a newly machined cage & pull a vacuum from the top side. If the needle 'holds' meaning it slowly declines over some period like 30 secs, it is deemed good. Turns out this is more difficult than it sounds for many underlying reasons I had to figure out. Its rather humbling when the valve faces look perfect & the needle goes Fffft to zero in a short span. The tester valve has a flat ground on a portion of the stem so the vacuum isn't tricked by the close annular fit of the stem portion.


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## PeterT (Dec 24, 2019)

The bronze I'm using is 932. On another post we were discussing the stripey outside of 'bearing bronze'. This has the same look, so just mentioning FWIW - you can maybe distinguish bronze from brass (no stripes) but probably not between bronzes. 

Basic turning to size.


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## PeterT (Dec 24, 2019)

Flip the cage in the collet chuck. Spot drill, rough drill cage hole drill, inner spot drill, drill stem hole, boring tool to final ID. 

Bronze can be a B*tch to hold trueness of small drills I found. It is grabby so very sensitive to tip geometry & drill stiffness. Regular HSS jobber drills were drifting a couple thou on me. Shorter drills improved. Short carbide (which is stiffer) better yet. Eventually I landed on these parabolic HSS drills & magical cutting cream & it just worked like a dream. Why all the fuss? If the valve stem hole is angled even a tiny bit, that influences the way the valve meets the seat & therefore poor seal. I was initialy also reaming the stem holes but I found just the drills were the right combo of fit & trueness.


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## PeterT (Dec 24, 2019)

Initially I was drilling the valve stem hole in the first operation but not getting consistent results. Now, all the operations that influence valve alignment are done in one setting. If the collet/chuck is concentric with the cage body & drilling went well, the exit hole should be concentric.


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## PeterT (Dec 24, 2019)

This leaves the seat cutting job. The edge of the cage is colored with dark Sharpie. I use a 45-deg reamer cutter with a modified pilot pin to match my 3mm stems. The cutters are used by gunsmiths, sorry I don't know what for exactly but they are sharp & accurate. Cutting the seat is kind of a light feel thing. It doesn't photo well without lighting banding but we are looking for a uniform consistent shiny band about 0.010" wide. If its even non-uniform something went amiss & will likely fail the vacuum test miserably.


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## PeterT (Dec 24, 2019)

Last job on the heads before bonding the valve cages is cutting the cooling fins with 0.045" slitting saw ~ 0.200" deep about 0.025" DOC per pass. About 200 rpm felt right on 3" OD cutter. This is a messy, mind numbing job. Its important to keep a steady feed rate, use lots of WD-40, clean the teeth & trench of swarf between passes because there is very little clearance & aluminum is a gummy material. I've read horror stories where guys folded up the cutter on the proverbial 'last pass' & at this stage a lot of work has gone into the part.


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## PeterT (Dec 24, 2019)

Deburring & cleanup. Last step is permanent bonding of cages into heads & making the inlet/outlet cross holes. 
Family shot before Xmas break.


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## John Conroy (Dec 24, 2019)

Beautiful work Peter. Must feel good to get those parts all done.


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## PeterT (Jan 3, 2020)

Carrying on with the permanent valve cage installation. I did some hole conditioning with fine lapping compound, it left the hole a nice mat finish. Then everything was cleaned spotless with thinner, acetone & many Q-tips. The cages are an easy slip fit into the holes being about 0.001-0.002" diameter undersize which is on the low allowable end recommended for Loctite 680 high temp retaining compound. I discovered a rather amazing thing happens (fortunately on a prior tester). Something about bronze & aluminum, possible copper content or the combinations, the working time is dramatically decreased. You don't have a lot of doddle time to position it or twirl it around for even coating before it kicks off. I tried some scrap parts with steel & brass to see if I was hallucinating & those alloys behave normally, ample working time. Anyways the cages all landed in correct position. Allowed a day to cure before machining.

Then onto the fixture for spot drill, gas passage hole, counterboring, tapping (7/16-28). I think I already mentioned the holes enter the head at a weird angle so the tap threads only catch on one side for a bit & unfortunately through the cooling fins which is a PITA. I found the best way was lock the tap in the TS chuck & just gently push the TS casting body straight into the hole as I turned the chuck with my other hand. Reverse the direction about every half turn to break the chip & continue on. Then repeat this with a bottoming tap with all the end threads ground off to get the last 3 or 4 threads as deep as I can. One new learning was that Tapmatic cream lube really does work better than either the aluminum or regular cutting fluids I use. You can feel it has less resistance. Its really important to vacate the tapping chips often so the compressor nozzle was always close by.


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## PeterT (Jan 3, 2020)

There are a lot of sharp angles & fragile corners & variable geometry created by the combination of the side entry port hole, the threads & the cooling fins. I found the best treatment was these green rubberized abrasive in a Dremel on low speed. They are dirt cheap on AliExpress. They do wear but you can reshape them with 60-80 grit blue sandpaper. The rubber shrapnel washes off easy with thinner or WD-40. I was paranoid of messing up my valve seat during all these operations while they were exposed to machining & conditioning. I usually had tape covering them but I also had to debur the edge of the bronze port hole. I had an afterthought maybe I could have applied a bead of glue gun glue as a temporary barrier but I didn't want to experiment at this stage of the game.


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## PeterT (Jan 3, 2020)

Valve spring retainers made from 303 stainless. Fiddly little buggers. 
In hindsight I probably made them bass-akwards, I could have done all the ops in one setting with the cup side facing out. Oh well.


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## PeterT (Jan 3, 2020)

A dozen nuts made from 0.5" 303 stainless hex. These retain the (end flared) intake & exhaust tubes in the head. The thread relief groove is made using Nicole radiused insert of 1.5mm (0.059") diameter. The groove width doesn't allow for much error in reaction time to disengage the lathe threading half nuts. I didn't consider until I got going the thread point has to terminate in the middle of the circular groove which is only half the groove width. Not that I have a lot of threading experience but I am sold on these Ebay/Ali threading inserts. I was concerned my lathe rpm might be too slow for the carbide in this particular application, but they cut nicely.


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## John Conroy (Jan 4, 2020)

You have gotten a lot done in the last couple of months! I'm going to have to make a trip down to Cowtown soon to check out all those beautiful parts in person.Amazing work Peter!


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## PeterT (Jan 4, 2020)

Thanks John. Its back to work on Monday from Xmas time off, so the pace might slow down a bit with only the evening shift LOL. 
Look forward to the visit.


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## Chicken lights (Jan 4, 2020)

Can I ask a dumb question?

Why wouldn’t you lap the valves to the seats? 

Very impressive work, sir!


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## PeterT (Jan 4, 2020)

Yeah that discussion comes up a lot on the model engine forums. The bottom line is that it just doesn't seem to work, even by experienced builders. But the reasons are maybe not well understood. People have lots of experience doing this with full size engines but many things like this just don't 'scale down' the same way. Unfortunately the combustion temperature is about the same, the seal requirement is the same, but the surface contact area of FS engine is exponentially larger. Much higher valve spring force on a FS engine but it would be interesting to know force/contact area comparison.

Home made model valves are rarely hardened because the skinny shape would surely distort during quench. You would have to turn them oversize from some kind of tool steel & grind them all over which would be challenging at this size. So we are kind of stuck with the base alloy hardness. FS valves are tougher/harder material and are precision ground on the stems & valve faces. A lot of guys make a big deal about setting the lathe compound at some angle (lets say is 45.4 deg vs target of 45.0) but leaving it this way for all seat operations on both valve & cage so its the same. Personally I find this impractical & my own testing has shown the machining itself is way more critical (the micro record player grooves). Theoretically you could have a flat valve seat and a slightly convex curved valve face and it will point contact seal. I actually think this is what might be going on so some degree when we polish the valve face. Its not how you would do things a real FS engine obviously but we do what we have to to get the job done.

I'm not really sure about valve lapping aspect in FS engines to be honest. Typically in lapping, the material which is softer than the other will be the embedder of lapping compound. It becomes a cutting 'form tool' to remove material from the other surface. In my case the valves are 303 stainless which is 83 RB hardness, the cage/seat is 544 bronze which is only 40 RB. So by this it seems like the lapping abrasive would become embedded in the narrow bronze seat & basically wear a thin ring on the valve face? This is kind of what I saw fiddling around with some testers. So it might better to have a dedicated lapping tool that gets the wear but which you can re-surface back to 45-deg. I made one out of brass for future tune-up. So far it is showing the wear ring even though the hardness is quite similar to bronze.

I really cant speak for FS engines, maybe some of you know the relative hardness between valve & seat. Supposedly when you have two more equal hardness surfaces, the abrasive does more of a rolling cutting action & both surfaces wear to one another. I think cast iron acts a bit differently in lapping. Even though it is very hard compared to other steel alloys, it has a matrix of open pores from the carbon inclusions & these form natural pockets for the abrasive to lodge in & thus it becomes the sandpaper 'lap'. But I don't think FS engines have integral cast iron valve seats anymore do they?

All I know is a 4S model engine I disassembled has this same bronze valve seat with a tiny band of area & we run the crap out of them. Someone more knowledgeable than me said the valve fit must be very close to begin with but then it basically micro-peens itself to a final fit. I'm not sure about this & I intend to test the hardness of the commercial valve. But I'm basically following the recipe of others who have gone down this path before me.


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## PeterT (Jan 28, 2020)

Cylinder making time. When I modified my heads to a slightly larger diameter, I assumed they would look OK mounted to the (now relatively smaller) diameter stock cylinders. But once I had the tester assembled, my eyes decided it didn't look right so I expanded the diameter of the cylinder to suit. This created a few cascading headaches changing the taper, the skirt relief, layout & depth of the cooling fins. So I spent some time on the computer adjusting things. I think the effort was worth it in the end.

They start out as drops of 6061-T6. I rough drilled them 7/8" in a batch just to get it over with. Then each is chucked & machined basically to completion to preserve the setup: bored to 0.005" undersized with single point CCMT carbide boring bar & reamed (1.0625"). Consistent ID & finish is kind of important because the liners will be lapped to a specific OD & heat shrunk into the cylinder.


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## PeterT (Jan 28, 2020)

Series of basic turning ops. 
Lots of swarf heading for my motor - but the new screen door is on... no room at the Inn! LOL


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## PeterT (Jan 28, 2020)

Fin grooving using 0.043" wide Nikcole insert. They cut like a dream, just keep a bit of aluminum cutting fluid on it. The depths are slightly different so I had to have my notebook handy. The top 3 grooves are a bit shallower to accommodate the threaded head bolts. The next 3 are limited by maximum DOC of the insert. I want to say its about 0.220". Then the remainder grooves are one constant diameter which then matches the skirt diameter. I chamfered the edges with one of those HSS triangular scraper & parted it off.


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## PeterT (Jan 28, 2020)

Machinable expansion arbor holds the cylinders so they can be machined to length.


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## PeterT (Jan 28, 2020)

I machined a collar so I could chuck the head because the skirt flange is a larger diameter. Drill & tap 5 x M3 holes. Now I have a way of holding the head inverted on a fixture to drill & mill the flange.


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## PeterT (Jan 28, 2020)

I just HAD to assemble some components. Starting to look more like an engine.


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## YYCHM (Jan 28, 2020)

That's Freeking Awesome!!!!

Can you please put a ruler in one of your images to give some sense of scale.

Thanks


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## John Conroy (Jan 29, 2020)

Amazing work Peter. Looks like most of the parts are finished. What's left to do?


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## DPittman (Jan 29, 2020)

PeterT said:


> I just HAD to assemble some components. Starting to look more like an engine.


Now if that just isn't a thing of machining beauty I don't know what is.


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## Tom Kitta (Jan 29, 2020)

You should start filming your work - it would be a hit on youtube. This stuff is more advanced and show more skill then 90% of stuff done on youtube.


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## PeterT (Jan 29, 2020)

Thanks for the compliments guys.
- just for scale it will fit in about 10-12" diameter circle with the head do-dads on
- remaining parts: cylinder liners, rocker perch's, rockers, valve covers, inlet/exhaust tubes, pistons, link rods, master rod, pushrod tubes, gear timing....
- my plan is to use commercial piston rings to get it baseline running. But I also intend to make rings & then swap them in to compare. It involves some fixtures & heat treating
- I already machined the rear induction manifold as per plans, but I can see some room for improvement so will cross that bridge come induction tube time. Might be a re-do.
- Another issue is to whether I adopt the partially oil filled nose case or not. That's what the plans call for but I just cant see how oil is not going to seep out of the lower tappet guides. Lubrication was kind of glossed over in the (very brief) description although he did the same on the 9-cyl big brother. Other engines have the gear plate open & fuel induction charge mist comes through the crankcase in & out which is how the rod assembly is lubricated anyways because the fuel is methanol+oil premix & quite common for RC engines. The Edwards radial you may have seen posted on the forum is quite similar in overall configuration but has a separate oil pump/re-circulation system. There are pros & cons to either (for model engines).


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## DPittman (Jan 29, 2020)

Sorry if you have stated it and I missed it....but is the engine going to power anything?  An RC plane maybe?


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## PeterT (Jan 29, 2020)

Well.. maybe, I dunno. I've been around RC forever so building & flying would be familiar territory although its been many years since I assembled a Crunchy as we call them. Some of my Composites Comrades are rediscovering scratch building, maybe a nostalgia throwback to their youth. I guess my goal & personal challenge is focused on the machining/mechanical side & (fingers crossed) seeing it run. So see what happens after that. I've also been around RC long enough to write a book titled 10,001 ways a plane can come to rest in a shallow grave LOL.

This guy built a nice 7-cylinder glow & promptly stuck it in a bipe. Gotta love the sound of 'round' engines!
http://philsradial.blogspot.com/


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## DPittman (Jan 30, 2020)

PeterT said:


> Well.. maybe, I dunno. I've been around RC forever so building & flying would be familiar territory although its been many years since I assembled a Crunchy as we call them. Some of my Composites Comrades are rediscovering scratch building, maybe a nostalgia throwback to their youth. I guess my goal & personal challenge is focused on the machining/mechanical side & (fingers crossed) seeing it run. So see what happens after that. I've also been around RC long enough to write a book titled 10,001 ways a plane can come to rest in a shallow grave LOL.
> 
> This guy built a nice 7-cylinder glow & promptly stuck it in a bipe. Gotta love the sound of 'round' engines!
> http://philsradial.blogspot.com/


Yes, I have a friend that used to build rc planes as a kid and I was always intrigued with them and their engines.  Crashing them seemed to be the end of them as opposed to wearing them out.  He never had anything more than single cylinder engines.  I'm love to see the size and complexity of the plane that your radial engine could fly.  Heck if you built one or two more of them I think I could use them on my ultralight!


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## John Conroy (Jan 30, 2020)

After spending all that time machining and building that engine there is no way in hell I would ever send it to an almost sure death on an RC plane!! Lol

Peter, what is the maximum safe engine speed of those radial engines? How do you prevent over speed?


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## DPittman (Jan 30, 2020)

John Conroy said:


> After spending all that time machining and building that engine there is no way in hell I would ever send it to an almost sure death on an RC plane!! Lol
> 
> Peter, what is the maximum safe engine speed of those radial engines? How do you prevent over speed?


I think I agree.  Maybe Peter should make an air boat or a ground rig for that engine.  A running engine is cool but making it do some work is cooler.


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## PeterT (Jan 30, 2020)

John I think the stated rpm range is 1500-5000 but its probably only rough nominal guidance. I know some of the commercial model radials say 7000 rpm but generally these have a power band that favors torque at lower rpms. In real life a prop pitch/diameter is selected for thrust at airspeed & sometimes practicalities like ground clearance. Compared to things like machines, prop load is always 'on' to a higher degree pushing air & load increases by some exponent (square?) of rpm. In my case bolted to a picnic table, it will be a glorified cooling fan. If the engine is static the prop load is also a bit higher than if moving in air as a function of the blade angle. Some guys cut down the diameter of a wider pitch prop just for walkaround safety on the test stand. 

So I guess I'm saying there is no real independent rev limiter as such. The worst thing that can happen is a prop disintegrates with throttle stuck wide open. The load is instantly removed, probably lots of valve bounce bad things happen. This unfortunately happens too often on methanol racing 2S engines like a parted blade or mid-air. They generally have a high temp heart attack with piston permanently seized after about 10 seconds. Glow engines are kind of funky because there is no distributed spark to advance or retard (control) like a FS engine. Fuel fires when the compression is right. The carb selected has as much to do with trying to achieve a reasonable idle which usually favor slightly smaller throat over larger. Same thing with cam timing. So I think between the breathing & the disproportionately increasing load, this largely self-limit upper rpms under normal running load conditions. 

Side note but radials are additionally quirky. If you phase the link rods equally around the master rod (for example 360 deg / 5 cylinders = 72 deg spacing) you actually get un-equal throw. That means with identical cylinder/head dimensions, un-equal compression ratio across the cylinders. Its just a function of the motion geometry. But that's a bad thing for a multi-cylinder glow engine to have say 10:1 on the #1 and 9.6 on #2 & 8.5 on #3 because glow ignition timing is largely influenced by CR. So on this engine, the master rod is 'compensated' meaning slightly adjusted unequal spacing to achieve ~equal CR. The Edwards radial has equal MR/LR angles but requires you to shave heads or add head shims, kind of volumetrically to achieve equal CR. Choose your poison. This effect was known on FS radials back in the day & different engines handled it differently. If you can pack the link rods very close to the MR crank pin, the effect is diminished (never eliminated). If you juggle geometry to have equal throw then TDC now occurs at non-equal crankshaft positions, which doesn't play as well with equal cam and ignition timing which is a function of crankshaft angle. I think the cam discrepancy is nearly negligible because of the high planetary gear ratio & cam lobe ramp. But I was told some radials had distributors (mags) with compensated non-equal firing phasing to match up with the mechanical discrepancy. Crazy stuff.


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## John Conroy (Jan 30, 2020)

Interesting stuff. Thanks.


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## DPittman (Jan 30, 2020)

PeterT said:


> John I think the stated rpm range is 1500-5000 but its probably only rough nominal guidance. I know some of the commercial model radials say 7000 rpm but generally these have a power band that favors torque at lower rpms. In real life a prop pitch/diameter is selected for thrust at airspeed & sometimes practicalities like ground clearance. Compared to things like machines, prop load is always 'on' to a higher degree pushing air & load increases by some exponent (square?) of rpm. In my case bolted to a picnic table, it will be a glorified cooling fan. If the engine is static the prop load is also a bit higher than if moving in air as a function of the blade angle. Some guys cut down the diameter of a wider pitch prop just for walkaround safety on the test stand.
> 
> So I guess I'm saying there is no real independent rev limiter as such. The worst thing that can happen is a prop disintegrates with throttle stuck wide open. The load is instantly removed, probably lots of valve bounce bad things happen. This unfortunately happens too often on methanol racing 2S engines like a parted blade or mid-air. They generally have a high temp heart attack with piston permanently seized after about 10 seconds. Glow engines are kind of funky because there is no distributed spark to advance or retard (control) like a FS engine. Fuel fires when the compression is right. The carb selected has as much to do with trying to achieve a reasonable idle which usually favor slightly smaller throat over larger. Same thing with cam timing. So I think between the breathing & the disproportionately increasing load, this largely self-limit upper rpms under normal running load conditions.
> 
> Side note but radials are additionally quirky. If you phase the link rods equally around the master rod (for example 360 deg / 5 cylinders = 72 deg spacing) you actually get un-equal throw. That means with identical cylinder/head dimensions, un-equal compression ratio across the cylinders. Its just a function of the motion geometry. But that's a bad thing for a multi-cylinder glow engine to have say 10:1 on the #1 and 9.6 on #2 & 8.5 on #3 because glow ignition timing is largely influenced by CR. So on this engine, the master rod is 'compensated' meaning slightly adjusted unequal spacing to achieve ~equal CR. The Edwards radial has equal MR/LR angles but requires you to shave heads or add head shims, kind of volumetrically to achieve equal CR. Choose your poison. This effect was known on FS radials back in the day & different engines handled it differently. If you can pack the link rods very close to the MR crank pin, the effect is diminished (never eliminated). If you juggle geometry to have equal throw then TDC now occurs at non-equal crankshaft positions, which doesn't play as well with equal cam and ignition timing which is a function of crankshaft angle. I think the cam discrepancy is nearly negligible because of the high planetary gear ratio & cam lobe ramp. But I was told some radials had distributors (mags) with compensated non-equal firing phasing to match up with the mechanical discrepancy. Crazy stuff.


I think I'd like to buy you a beer (or coffee or tea or whatever you prefer) sometime, I think it would be fascinating to learn "stuff" from you Peter.


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## John Conroy (Jan 30, 2020)

Looking at this radial engine connecting rod assembly I see what you mean Peter. The rod angularity is way different on the master rod compared to the others. The TDC events are not going to be evenly spaced


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## RobinHood (Jan 30, 2020)

Can’t wait to see the engine run. Going to be amazing.


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## PeterT (Jan 30, 2020)

Sounds good, Don.
Thanks for the encouragement guys. I'll feel more confident about engine building once it runs!


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## David_R8 (Jan 30, 2020)

I’m late tagging in to the game here. 
All I can say is WOW! 
That’s really amazing work!


Sent from my iPhone using Tapatalk


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## PeterT (Feb 17, 2020)

Work has commenced on the liners. They start out as drops of 1.25" diameter Class 40 grey cast iron, which comes delivered as more like 1.35" nominal. I think that overage is so that you get consistent machining properties under the skin. A while back I made some test liners out of 12L14 and 1144 stressproof but decided to stick with CI. I took a skim cut then pilot drilled 0.375, then 0.875, then bored to 0.940 which lands me with 0.005" to take off for the final 0.945" bore. I did the drilling & boring while I had more meat on the wall to try & keep a nice even bore. CI is quite inert compared to most alloys so you can hold dimensions quite well (just account for heat). It cuts quite well but is very messy so I cover the ways.


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## PeterT (Feb 17, 2020)

Turning the lip and OD that will mate the aluminum cylinder. The cylinder ID is 1.0625 (1-1/16" reamer). The CI OD is 1.0640-1.0645 so heat shrink interference fit.


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## PeterT (Feb 17, 2020)

I left the turning about 0.003" oversize. The first 0.001" or comes off with full width homebrew sanding sticks made from 2" wide MDF with wet-o-dry bonded with 3M spray adhesive. The next 0.001-0.0015"" comes off with a lapping tool. This is kind of an experimental thing I tried because CI is so friggen hard it takes a while to work the surface to both a consistent diameter and finish. I made a CAD drawing & send it to a waterjet outfit. They cut the profile & then I drilled a retention screw to apply set pressure. The lapping compound is cheapo oil based Ali diamond paste I had good results with on the valves. I left the last 0.0005" for 1000 or 1200 paper. Interesting how CI can get a finish, eh?


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## PeterT (Feb 17, 2020)

The skirt has a chamfer to give allowance for the rods and a small relief groove under the lip. Knock down any burrs, one last finish check, then part off. 
Then apply some protection tape, hold in collet chuck & dress the lip to size


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## PeterT (Feb 17, 2020)

I heated the cylinder to 450F in my little toaster oven & the liner dropped in no problem. It was at ambient temperature, I didn't have to chill it. But reversing the process didn't quite go according to plan. After another 5 minute baking session the 2 parts did not want to separate. Supposedly the thermal expansion between the 2 materials is completely reversible. Even though the surface finish is pretty decent, those tiny machining marks on either surface can add some gription. I also remembered that in between my prototype I only had 0.0005-0.001" diameter interference. I subsequently ran across an article that suggested this increased interference for proper heat dissipation. 

Anyways, the whole plan was to do the finish ID boring operation on all liners outside of the cylinders mostly because they can be held properly. These were my sacrificial testers so I decided they were going to come apart now. I hate using a torch but have had to do it occasionally on the RC engines when they get gummed up with caked fuel residue. So I put the assembly into a corner of fire bricks & danced the torch around until they parted ways. Interestingly after cooling the bores were identical so nothing distorted. That was good to know.

So one more liner to go and then its finishing time. I have a few things to do to prepare for that, so fingers crossed. The learning continues


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## PeterT (Mar 29, 2020)

I put in a fair amount of work lately but one would never know it just looking at the parts. I've had to learn some important things about interference fit & tolerances that resulted in taking the long road around. I mentioned the CI liner is heat shrunk in the aluminum cylinder. My plans/instructions were very vague about this & tester in previous post showed this. In lightweight air cooled engines like this, liners cant really be a loose-ish sliding fit because you wont get proper contact for thermal dissipation once its running & other mechanical issues. It also cant be too much interference or else removing the parts is difficult if not impossible. Plus its not good when both parts are under strain like that.

Another consideration is that any amount of interference literally puts the squeeze on the liner. So assuming you had a perfect liner bore beforehand, it now will be smaller once shrunk in place. I assumed this amount would be quite small because CI is stronger than aluminum & slightly more wall thickness. In reality it was quite significant, about 50-75% times the diametric interference in my case.  Another complication is the diameter squeeze reduction shrink may not be uniform if there is more cylinder mass at the top than the bottom as is the case. Anyways I naively lapped my liners within 0.0001" each (outside the cylinder), which in hindsight was a complete waste of time for reasons above. They needed to be re-lapped once married to the cylinder. More on this later but for now some more build pics.

After the liners were OD finished & rough turned inside all in same initial lathe setup, they all got returned to the 5C collet chuck for consistent finish boring. This was my first serious go with a tool post grinder. The plan was to bring them to within about 0.002" & leave the last for lapping operation to simultaneously true any egging + final bore + final finish. I wasn't super thrilled by the grinder finish but it looks worse than it is. Lapping removed the harmonic pattern very quickly so they are probably less than tenth deep. I have some ideas of how to improve the TPG with stiffer arbor. The grinding was quite accurate & process was controlled so that's important. In reality I need a 1/4 scale Sunnen hone LOL


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## PeterT (Mar 29, 2020)

The laps I used are Acro brand. They are reasonably priced for what you get & the difficulty to make your own. The arbor is a steel shaft with a threaded end on the shank. the barrel is brass with double tapered ID & radial slits along the body. Basically you incrementally screw in the tapered end screw, it then expands the lap in the middle. I've tried different lapping compounds, they have their pros & cons in terms of how they cut, how they break down, how/if they embed. The one common factor is they are messy. You have to completely clean the part spotless in order to mic bore, rinse & repeat.


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## PeterT (Mar 29, 2020)

So back to the saga. I was between a rock & hard spot. The cylinder bores were nicely finished with reamer. The liner ODs were nicely finished by lapping. But one of the two had to be altered in order to reduce correct ~ 0.002" of interference screw up. The finished liners were very hard to accurately grip on an ID type expanding mandrel & I wasn't about to re-make them. So I opted to lap the aluminum cylinders thing they will benefit by being trued better than the reamer finish & aluminum is softer so should go quickly.

So here we go again... another 45$ lap because its a different size. 800 compound grit leaves a satin finish but its very true. The slight shiny irregularity you see (looks like a scratch in the pic) is just the ball of the bore mic. Into the ultrasonic to remove lapping gunk.


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## PeterT (Mar 29, 2020)

And finally, with proper OD/ID interference of ~ 0.0005", the cylinders went into the mini toaster oven at 450F for 5 minutes & then room temp liner dropped in place. Allow cookies to cool to room temp & then lap the assembled CI liner bores. This time I used a different brand (Clover) lapping compound 600 grit thinking it would cut faster & then I'd switch to finer with the last 0.0002" or so. This stuff has more oil content which offers benefits IMO. You can feel the cutting pressure better as opposed to drier compound which can get 'cakey' if that makes sense. It cleans off the surface much better with common paint thinner. The aggregate is a bit sharper & doesn't break down quite so fast. I cant detect any remaining lap embedded in any surfaces so I think that is maybe an issue you hear more abound with diamond.

I think I now have 5 complete cylinder assemblies.


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## John Conroy (Mar 29, 2020)

You are a patient man Peter! Beautiful work as usual.


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## PeterT (Apr 8, 2020)

Piston making time. They are made from 7075 aluminum. I love machining this stuff, to bad its spendy. 

Picture shows an RC commercial forged aluminum piston from an OS-56 4-stroke alongside my tester blank. The OS is the same nominal bore as my 5-cylinder so I made a decision early on in this project to use the rings, at least initially, to give me the best chance of running success. Rings are finicky to make being about 0.043" square section. the tolerances are pretty demanding at this scale & rings require special fixtures & oven to heat set the opening. I am going to make rings now that I found a guy with an oven. Anyways I bought the commercial piston to mimic the critical dimensions: the OD, the reduced crown, the ring gap, trough OD, width etc.


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## PeterT (Apr 8, 2020)

The crown is slightly reduced which is the norm to ease ring stretch a bit when installing. The ring width was made with a Nikole grooving tool. Because I had to open the width by only 0.0010" I couldnt trust by carriage DRO so I set up a tenths indicator on the carriage after cutting the first depth, zeroed it, then moved the carriage over this time watching the needle deflection. Verify fit with feeler gauge stack that matched the commercial piston. The ring trough diameter was measured with blade mic.


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## PeterT (Apr 9, 2020)

The pistons are 0.0025" undersized to liner so just requires careful finishing & measuring using the same micrometer. Protect the ring area with tape & part off. I also use tape to protect the OD from the collet grip when facing the bottoms to length.


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## PeterT (Apr 9, 2020)

I decided to drill & ream the wristpin hole while the blank was solid. On my prior tester I drilled them subsequent to inner body material removed & didn't like feel of the drill & reamer breaking into the chamber & restarting hole on the other side. I couldn't actually measure out-of-square but just preferred this solid method, basically pecking 0.050", clear chips, add cutting fluid, rinse & repeat. I had a vise stop but just to make sure of center used an edge finder on either side, used DRO center & compared the digits. Wrist pins are 5mm reamed.


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## PeterT (Apr 9, 2020)

Back to the lathe. Drill a .375 pilot hole to remove material & counterbore the skirt ID


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## PeterT (Apr 9, 2020)

I made a fixture to hold the piston with dummy pin to align. Then into mill to make the rod pocket. Clean, de-bur, recheck dimensions. 
I installed a ring & did a push fit in the oiled liner, so far so good.


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## Chicken lights (Apr 9, 2020)

Very nice work!!


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## PeterT (May 10, 2020)

Rocker covers made from 6061 aluminum. I had 2 successful testers so needed 8 more for 10 total. Apparently optimistic that I would have no boo-boos along the way.
Trimmed stock, drill & c/bore M2 hold-down screws.

Forgot to mention I tried a technique I saw on Tom Lipton video. (Left hand picture). He stacked blocks & took a pass across all to save time doing them onsey-twosey. But this is an accident waiting to happen if there is even a thou difference in thicknesses; the vise will only tighten on the fattest one & others may come loose. Tom used an aluminum TIG rod on the moving jaw to squash & conform to this difference. I don't have those rods but I used ~ 1/16" diameter solder. Its much more malleable  & takes up the difference quite well, very positive holding. But. I'm still not convinced I like this technique if you need absolute squareness. Its possible the stack-up gaps can vary a bit among the pieces & by the time you get to the end of row, it may not be 100% square to the first one. It has its place though if you aren't thou chasing.


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## PeterT (May 10, 2020)

5mm radius bull nose profiling. This is best done while the block is solid as its kind of an interrupted cut feel & not a lot to grip in the vise in certain orientations. I've learned to make some witness lines beforehand. The vertical depth is a bit easier to set because the cutter has kind of extended wings (not all cutters have this). Then graduate in from the fixed jaw side until the radius just kisses both witness lines. Then always set the part to the fixed jaw. About 0.050" DOC/pass. Rinse & repeat


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## PeterT (May 10, 2020)

The recess has a deeper slot (10mm EM). I found things went better with a starter relief hole & plunge the EM mostly into that (as opposed to solid metal). Then I can take a deeper DOC. I don't really care about the side wall finish but it actually stayed pretty clean. The big issue in slot milling is clearing chips often or it can make a mess regrinding shrapnel. I vacuumed for the most part. Low pressure compressed air works too but chips go everywhere (potentially your face & eyes). I think I'm going to make a clear plastic shield with a small hole in it, poke my air nozzle tube through that so I can see what I'm shooting at. Maybe that will block the bits from coming back to me?


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## PeterT (May 10, 2020)

Now the pocket milling, 0.500" depth with 8mm diameter EM. I first plunged each corner hole with X&Y locked. Then on the 4th corner once at depth, I ran the perimeter, conventional milling direction. The inner width is the more critical dimension as it has to slide fit over the rocker perch axle ears. The external corner points get blended to the bull nose profile with a Dremel come finishing time.


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## Hruul (May 22, 2020)

Wow!! Amazing work Peter.


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## PeterT (May 22, 2020)

Thanks! Working on the rocker perches now.


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## PeterT (Aug 20, 2020)

Not much radial machining over the past months because summer goes by so fast in Calgary. But I was cleaning up some files & found my wrist pin pics, so here they are.

They were time consuming little buggers. O-1 drill rod in this ~5mm diameter is usually 0.001-0.002" oversize but its also usually oblong/elliptical in section  by 0.001". So the stock is brought to dimension by lapping. The mating hole in the piston is reamed so they are the same, the wristpin OD is basically a hand-fit procedure. They shouldn't be loose enough to spin & its not easy to interference press them during assembly. So basically a tightish fingernail push fit.... which isn't in the Machineries Handbook lol

The ends are counter drilled slightly to receive aluminum end pads. I heat treated the pins manual mode with torch & oil quench. Then tempered in my mini (ex kitchen) toaster oven. No drama there, went very well. Then spun them in my drill for final finish. The little hole in the end pad is to allow any excess Loctite bleed, otherwise the parts can get fluid locked out of position. Once they are bonded the pads get turned to finish length & chamfered.


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## PeterT (Oct 24, 2020)

I redesigned my original link rod (LR) prototype & fixtures so it would be a bit easier to make. I started with sticks of 7075-T6 face milled to correct thickness. The outboard holes are just temporary hold-downs to get the wrist pin & crank pin holes exactly same length, reamed 5mm & 6mm respectively.


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## PeterT (Oct 24, 2020)

Milling the width & first radius 'dog bone' profile. This is a good application for the mill table stops.


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## PeterT (Oct 24, 2020)

Ball EM to make the center  profile, again using the table stop.


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## PeterT (Oct 24, 2020)

The LR ends were trimmed to remove excess material. This is where the rotary table tooling plate came in. LR was attached to fixture which was attached to tooling plate using coincident thread holes. Then it was a matter of milling the round over profile from 2 angle positions.


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## PeterT (Oct 24, 2020)

Another fixture to drill the oil lubrication weep poles. The lower end contains a dummy pin so it can rotate until the side makes contact with a positioning pin. Then its clamped in the mill vise this way. I have a stop on the jaw so the fixture goes in the exact same way each time a new LR is loaded. Then spot & drill the holes into the journal opening. I thought I would have to flip the LR to the other side so contemplated another stop pin there, but actually I just needed to flip the LR itself because the oil holes are off center so it was just a rinse & repeat job.


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## PeterT (Oct 24, 2020)

5 cylinders = 4 link rods + 1 master rod. Why is it when you make spares expecting to mess up, you don't mess up. But if you make the exact number of parts, you mess one up & have to remake one from start to finish? I'm becoming superstitious. And I guess its nice to have spares.


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## francist (Oct 24, 2020)

Sweet.


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## PeterT (Nov 24, 2020)

The master rod is made from 7075 aluminum. After the bar was face milled to width all the holes are drilled & reamed in one setup. Then some profile milling to thin the #1 cylinder main rod & fillets with ball EM. Then I band sawed the rough profile but left the thickness tab on the end for subsequent operations. A lot of these operations were kind of seat of pants - you have a rough plan of how to go about it, but you also have to think a few more steps down the line when it comes to gripping & fixtures.


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## PeterT (Nov 24, 2020)

Dummy proof jig to mill the main rod taper


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## PeterT (Nov 24, 2020)

My initial plan was to file the knuckle rounds using OD buttons & the axle pins. So I milled some excess off. I like hand work but turns out this was a time consuming & I wasnt really happy with how it was coming out. Onto plan B....


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## PeterT (Nov 24, 2020)

I made a fixture, dialed it into the RT & milled the profile. I didn't want the part to snatch so I stayed about 0.010" outside the radius & crept down on 0.050" increments. I had the tangent marks scribed on the blue so on final pass did the full cleanup. A bit more setup work but better results.


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## PeterT (Nov 24, 2020)

The slot for the link rods was a fussy bit of machining. I almost botched it on a few occasions. There are some odd angles & offsets, just the way the linkage geometry is. But I couldn't rotate & mill on one operation because of this it had to be done in 2 arc halves if that makes sense. I center slotted mostly to depth, then did the inside faces. Somehow it all worked out. One thing I didn't consider is all EM's have a slight radius & because the EM itself was offset, the resulting fillet at bottom of slot is exaggerated. My link rods weren't fitting well until I realized what was going on. The blueing makes it look worse than it was but took some careful hand filing with a safe edge to get the inside corner sharp without mucking up the faces. This is the difference between drawing something in CAD & making something it in real life LOL.


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## PeterT (Nov 24, 2020)

Yet another fixture for top end round over. Drill the oil passages, remove any burrs & final lap the wrist pin hole


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## PeterT (Nov 24, 2020)

Some interim assembly.


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## PeterT (Nov 24, 2020)

O1 type drill rod is about 0.001" oversize but its also typically oblong, not round. I messed around with a lot of lapping jigs & finally came up with this. Turns out simpler is better. I mic'd a bunch of my wet/dry paper & found they were amazingly similar in thickness, even among different grits. So I figured out the annular thickness relative to the hole size, drilled that diameter on the split line, then milled off the requisite amount from each face. Then its a relatively simple matter of loading in paper & spinning the O1 stock in a drill. Its an amazingly controllable process to get the stock down within tenths & truly round. I think in real life, full scale, this would be centerless grinder work on already hardened pins.

The axles are hollow drilled then I did the torch hardening & oil quench. Tempering was done in the mini oven at 450F & they turn out this straw color. They just run in the aluminum rod ends as per design. I don't think there is enough material left to run bronze bushings strength wise.


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## francist (Nov 24, 2020)

That’s some really nice work there — very clean, very crisp. I know exactly what you mean with hand filing the rod fillets though. Been there done that, and it always sounds like such a pleasing thing to do until about halfway through the second one....

Nice work.

-frank


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## Sailor (Nov 24, 2020)

Very beautiful work Peter.


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## Hruul (Nov 25, 2020)

Amazing work!!  This is a newbie question, but what kind of oil do you use for the oil quench?


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## PeterT (Nov 25, 2020)

Thanks. I keep reading that any oil will work, some people use used motor oil. I had some leftover (new) medium weight hydraulic oil so just keep a jar for this purpose. So far its worked very well on O1 but I am no expert. I do pre-heat the oil by heating up a dummy part & dropping in. With this oil the parts initially have a light soot coating but 90% of it falls off right in the oil & the rest comes off with no effort just cleaning prior to tempering, so that's a plus. For some reason this oil seems to smoke less but that could also be the small parts I'm doing lately. I've also tried cooking oil but from reading it seems like its more about the initial quench temp than the lower viscosity (ie. avoid cold oil). The cooking oil makes your shop smell like french fries if that's a plus LOL but it also can get a gamey rancid smell over time. I cant recall exactly but seems like the part cleanup was a bit more stubborn.

I don't have a graduated hardness kit for scratch test to verifying RN hardness. I use a spare crappy file. If it skates across then I call it good. My toaster oven is only good for 425-450F so that's all I can get - which corresponds to the light straw which is most things I do. If I wanted softer (higher temp) I'd have to do something else for tempering. I'd love a HT oven for better control but hard to justify the cost for what little I do. When I did my cam plates (A tool steel) I sent them to a knifemaker dude who has the whole HT enchilada, oven, salt bath, clamping plates... Hope this helps, good luck.


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## Hruul (Nov 25, 2020)

Thanks that was very helpful.  I have not done any heat treating as of yet, but it is on my list of things to learn.


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## RobinHood (Nov 25, 2020)

And the perfection continues.... Awesome!

You must be getting close to have this thing make noise?


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## PeterT (Nov 25, 2020)

Thanks Rudy. Well, close-ER haha. Sometimes I think I see the goal posts, but alas, its just a mirage. Next up is the rockers.


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## YotaBota (Nov 25, 2020)

Just like building a real airplane, 90% done with 90% left to do,,,,,
Beautiful work.


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## PeterT (Dec 21, 2020)

Looks like I forgot to post pics of the rocker perch's. I think they were done May-ish. This will make more sense in conjunction with the rocker arms which I just finished, but need to organize pics. The perch's are made from 6061. I have the valve hole drilled & counterbored which aligns to the head. But I'm still mulling over the pushrod hole on the other end so un-drilled. I made alignment jigs for the funky 3D angle of pushrod entry. The original design calls for pushrod tubes which I like. I'm not sure they circulate lubrication oil vs maybe just contain the mess a bit. But I'm not fond of how he retains the tubes into the perch with a teeny M2 setscrew. I'd like some kind of dampening O-ring but there isn't much material meat to play with anywhere. Same thing for the bottom end where the tubes meet the bronze lifter bushings. This is why most radials I see are tube-less'. I could go that route too & make slightly larger section pushrod from thin wall steel tubes & ball ends. I need to have the assembly in front to resolve this stuff so kicking the can down the road for now.


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## PeterT (Dec 21, 2020)

More machining steps. The footprint of the perch matches the rocker covers.


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## Brent H (Dec 21, 2020)

Nice work!


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## PeterT (Dec 21, 2020)

Here we go with rocker arms. 

When I made a prototype directly from the plans (a long time ago) I figured I must have messed something up because the contact pad was not properly centered on the valve stem. I did modify the heads slightly, but didn't mess with any of this core geometry. 

What makes this engine a bit funky is he uses some parts from the bigger 9-cyl radial, some parts specific to 5-cyl only & some parts which are modified from the 9 cyl. I wish it was just one set of plans but it is what it is. I checked everything I could think of and also in conjunction with other parts of the assembly which must fit one another & came to the conclusion he had a rouge dimension. Unfortunately it was a critical dimension. It would have been a bad day to make all the rocker arms & have this issue crop up. Unfortunately I hear stories like this all too often on model engineering forums. Plans are generally made by hobbyists or transcribed from parts or workshop sketches. These plans were 99% accurate from what I can tell. European drafting standards are a bit differentthan ours & sometimes minimalist dimensioning. I've learned to validate as much as possible & make some testers before committing to batch mode. This is where CAD programs are really beneficial.


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## PeterT (Dec 21, 2020)

The rocker arms are made from 0.25" x 0.5" O1 tool steel. I got mine from KBC, happened to be Starrett brand. The curved contact pad area should be hardened but I'm not sure I can control the heat  & quench that the whole arm wont be the same hardness, but I'll cross that bridge when the time comes. Here I'm pre-drilling all the (5mm) end mill slot holes so I can plunge before traversing. Lots of fiddly fillet transitions that have to tangent connect one another, so I found this to be a good method. 

The jig is aluminum with very close fitting 6-21 capscrews to both align & clamp. Pins would be better but over this length it was quite accurate & simpler. Just lots of screwing & uncrewing with part swaps.


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## PeterT (Dec 21, 2020)

Slot milling the inner features & profile milling the outer dimensions.


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## PeterT (Dec 21, 2020)

Different jig in the RT to mill the valve contact pad


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## PeterT (Dec 21, 2020)

Same jig, different RT center position to mill the axle hub rounds.


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## PeterT (Dec 21, 2020)

Same jig, back to the mill vise. Ball mill what will become fillet & flat mill the thin section. I'm hanging onto those original stock screw hold-down flat areas for as long as I can. I love my Wera mini hex ratchet wrench.


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## PeterT (Dec 21, 2020)

Cut off one end in the bandsaw, mill the end to same length.
Tap the M3 hole for pushrod adjuster.


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## PeterT (Dec 21, 2020)

Lop off other end & mill to length.
O1 has this crazy attribute while milling, the chips become semi magnetic & form these furry looking icicles.
What can I make with the O1 scraps - mini toe jacks? LOL


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## PeterT (Dec 21, 2020)

Mockup assembly. Hopefully like the CAD model <gulp>


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## DPittman (Dec 21, 2020)

Your work, documentation and detail is nothing short of exquisite.


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## PeterT (Dec 24, 2020)

Rocker pushrod adjusters. I thought I might be able to make these from M3 capscrews. Unfortunately the dimensions of the socket head doesn't lend itself to necessary dimensions of the part. Also the fine print says the the ball end socket must be hardened so making them from scratch from 4mm OD O1.

Basic turning to 3mm shank size. No way I was going to change headstock gears & cut M3 threads LOL. I broke out my made in India threading die head. The quality is kind of rough but for small thread like this it worked fine. I had to experiment trial & error with the die clam shell set screw to get the right thread fit.

_Side note, when I made my own die head a while back with a tommy bar handle, I made a very snug fit to the nominal die OD. I think this may have been a mistake & might explain why my threads sometimes are slightly undersize even when I think I've adjusted the set screw properly. Possibly the die is opened up sufficiently but its getting collapsed again when I push it in the head. I think I'm going to make something better._

Once the threaded shank OD was turned to size I put lathe on low speed, some cutting oil & just fed die by hand. Once it gets close to the shoulder just let go & the head spins on the tailstock shaft. The M3 die is KBC euro brand. It cut very well.


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## PeterT (Dec 24, 2020)

Give the threads a very slight sandover with 600 grit wet/dry paper bonded to a flat stick. I make my own by the dozen using 3M spray adhesive. This cleans up the tops of the crests which can have raised burrs from threading. Then with the chuck still spinning I use this rotary polishing spider which does a great job of cleaning the threads. I've gotten into this habit because it doesn't take much time & helps condition the threads. I found when I was single point threading fine threads, half the issue was +/- false measurements.

Leftover threaded jig so the head length can be be made batch mode.


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## PeterT (Dec 24, 2020)

Into a jig made from scrap aluminum. The part is threaded into a hole, then a nut to keep it put, then slit 0.025" x 0.050" deep. Then the 2mm ball end mill for pushrod end. Shows how it sits on rocker arm & jeweler screwdriver to make adjustment. Basically done aside from hardening them.


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## PeterT (Jan 9, 2021)

Some overdue items arrived in the mailbox. Aliexpress radius mills, so was able to finish the roundover profile on the rocker arms. 8-32 Mitee Bite claps so made for a convenient way to lock the arm position against a stop pin, flip the part & radius the other side.

I decided to lock the rocker axle from spinning so milled a flat & tapped a teeny M2 hole in the perch. the axles are hardened now.

The rocker perch get these rings Loctite in counterbore so they self align to the valve hole.

Fiddly bits, fiddly bits, endless fiddly bits....


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## Johnwa (Jan 27, 2021)

@PeterT This video made me think of you!


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## David_R8 (Jan 27, 2021)

That was awesome @Johnwa!


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## PeterT (Jan 27, 2021)

Thanks Johnwa, yes I've seen that vid. What impressed me is he is building a FS engine on hobby size lathe & mill. Never underestimate the power of a hobbyist amateur on a mission! LOL
Seems like VW engine parts are somewhat suited for aeronautical powerplants, at least among the homebuilt crowd. I've see other cylinder layout configurations.


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## PeterT (Jul 31, 2021)

Well I've been deliberating over the lubrication issue long enough, it was time to bite the bullet. The original design calls for the nose case to be partially filled with oil so that the cams & planetary gears get splashed. That part seemed pretty straightforward initially. But as time progressed some nagging thoughts I had started to become more clear. The nose case chamber is isolated from the crankcase with O-rings on the front gear plate which were kind of a PITA to make but they seal. Issue-1 is I think oil is going to get by the submerged tappets on the bottom side as they are working away. Issue-2 there is a crankshaft bearing in the nose case which is specified as sealed but I think oil is going to make its way backwards into the crankcase through the seals eventually. In methanol glow engines we always remove the internal shields because the methanol acts as a solvent on the grease over time. The premix oil is completely satisfactory to lubricate parts. The brief German instructions make reference to 'sealant & silicon' which makes me suspicious.

After some research I concluded this engine (well and his 9-cylinder) is the only one I've seen with an oil bath chamber like this. There are engines with scavenging oil pumps (to late for me). And there are engines including several commercial radials with apertures or windows that allow the raw intake charge mist to flow around & coat all internal parts. I was a bit concerned of the distance though, mist reaching forward ina tortuous path to coat the cam plates. But every RC engine I have ever dismantled is liberally coated with oil everywhere, all the nooks & crannies. Sometimes too much, often you find puddles in low areas. Many engines have a blow-by nipple to drain buildup fuel/oil residue.

So... I decided to modify my existing parts
- nose case will have a screw in fitting to squirt a bit of heavier weight oil over the cams before a run just for insurance
- front plate will have openings to allow forward mist flow
- ring gear cup will have holes to match the cam plate holes (which I did before hardening in case this day would come)


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## PeterT (Jul 31, 2021)

Putting these new features on the parts required stepping back & making jig plates so alignment could be established again. It would have been easier when the parts were made, but oh well.
Drill jig for ring gear cup which the cam plates are bolted too.


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## PeterT (Jul 31, 2021)

Jig for modifying the front plate. Its a bit swiss cheesed with the new holes but its 2024 alloy & well supported so hopefully strong enough. I managed to get the 2 lower holes slightly intersecting the gear cluster so hoping it gets directly misted. Fingers crossed. I'll just have to be careful during break-in runs to open the nose case early & often to see how wet things are.


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## PeterT (Jul 31, 2021)

I found an RC post where a guy acquired a commercial radial made by O.S. & began refurbishing. Unfortunately it was in sad shape. The original owner just let it sit for a couple years, never inspected or applied after run / storage oil coating to parts. Between the methanol fuel & acids in the oil, corrosion can set in quick & get real ugly. But the pictures told me wherever there was rust there was fuel mist & it was alll over the cams, gears & bearings.  AFAIK nobody has ever seized an engine in these areas. Seems primitive but I guess it works.


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## PeterT (Aug 1, 2021)

The next thing on my 'less than happy' list is induction manifold assembly. The original design had the tubes going into counterbores with recessed O-rings to seal the tube. I wasn't keen on machining those but mostly the end result seemed sketchy on multiple fronts. How to get the candy cane intake tube in the hole landed in O-ring then shimmy the other end into the head with a threaded coupler over the trumpet end.... Ack! I could see those O-rings leaking & leaning out the mixture or worse. So I made extended manifold pipe-etts & figured I could mask the connections with a hose coupler. I was not thrilled by the geometry & miters but just put aesthetics aside for now.

Then (3 years after the fact) I started to think about the RC carb I bought & for which the manifold was machined to match. The plans mentioned an engine no longer produced. I thought it was a 0.40 CI engine, but turns out it was actually smaller. The issue is after a lot of searching & digging I'm pretty certain the 8mm venturi throat is too big for this engine, it should be more like 5.5-6.0mm. I'm not after max power necessarily but too big a throat & it doesn't draw fuel properly for idle & transition. Turns out RC engines are becoming more & more scarce these days as the hobby shrinks & people are going electric. I found some carbs online closer to correct size to test but the body diameters are different. So that was the final nail in the coffin. I decided to redesign the manifold & clean up all these issues simultaneously.


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## PeterT (Aug 1, 2021)

The CAD exercise highlighted why my tubes were never going to match no-how. It would have to be a funky 3D shape to come off the head on one axis & end up in the manifold at another axis. The plans led me down the garden path. Its hard enough to bend tubing in 1 plane to a target angle, never mind this 3D challenge. I know some guys fill them with bizmuth or whatever but they still need to be shaped consistently. 

So my plan is start with 'simple' tubes made from my fixed radius bender with straight segments on either side. Quite similar to what I have actually, but now the manifold ports will be properly realigned to suite. I also made provisions for a standardized carb adapter plate so I can just bolt on any carb with whatever body diameter & leave the manifold alone. I also altered the engine mount lugs which was another thing that bugged me. Slowly...moving....forward.....


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## kevin.decelles (Aug 1, 2021)

I always feel like a caveman after reading your posts. Thank you.

Fantastic stuff! Motivates me to keep learning. Keep it coming


Sent from my iPhone using Tapatalk


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## DPittman (Aug 1, 2021)

kevin.decelles said:


> I always feel like a caveman after reading your posts. Thank you.
> 
> Fantastic stuff! Motivates me to keep learning. Keep it coming
> 
> ...


Exactly!  Good to know I'm not the only one!


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## John Conroy (Aug 1, 2021)

Ditto


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## combustable herbage (Aug 1, 2021)

I have to get back to my 12 piece puzzle now.
Very nice work Pete


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## Proxule (Aug 1, 2021)

I am clearly late to the party but when I searched the forum I stumbled on the castings thread and steam engine stuff, This is a whole new world. Very impressive stuff peter, I must admit my reasoning behind my machinery is for this stuff ( steam engines / hit and miss / hot bulb etc etc ) as well. I will keenly keep an eye on this thread and read through it all and digest it ASAP.

Thanks for sharing and keeping this thread alive.


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## PeterT (Aug 22, 2021)

I don't think I showed making the intake pipes so here are some pics. As mentioned, I wasn't happy with the stock design manifold & how the pipes made those miters, but part of that was I was limited to my hand bender which had a defined radius. So bottom line was either make a custom bending tool in order to bend a specific radius (lots of work) or accept the bend radius of my tool & redesign the manifold & piping system around it (slightly less work).

Most of this stuff is specific to fitting the engine, so after some fudging experimentation it was basically repeat the ritual. The tubing is 5/16" OD aluminum Versatube from AS&S. Unfortunately they send the material coiled in a 6" box which is a PITA to straighten. I was too lazy & impatient to make the roller straightener tool but I will eventually. The pipe section is only about 4.5" long so I lightly pre-rolled it between to pieces of hard MDF pizza dough style until I had a straight segment to begin with.


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## PeterT (Aug 22, 2021)

Shows my trumpet flaring die. The plywood on the end is so I could cut the excess & face it exactly square. Then it has correct stickout for the flare. Slight chamfer helps


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## PeterT (Aug 22, 2021)

My home brew flaring tool. That face gets dressed slightly too.


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## PeterT (Aug 22, 2021)

The flaring block ID is lightly threaded in order to grip the tube otherwise it slips back during flaring. The marring looks worse than it is. Needle file cleanup & the flange OD gets dressed to fit the port hole


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## PeterT (Aug 22, 2021)

Some cutting & fit up to what will be permanent nozzles glued in the manifold. The tubing/nozzle joint will have a short length of 8mm black silicon tubing overlap & little wire ring clamps.


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## PeterT (Aug 22, 2021)

Before all this, after I made the new manifold & single tester pipe, I realized an error on my part. A series of mounting bolts is partially blanked by the nozzle/tube because of the new tubing entry angle orientation. Therefore no way to get a hex wrench in there to tighten the cap screw, even ball ended hex. Some last minute fudging the nozzle & thankfully I used a loose fit clearance holes for M3 bolts on the manifold. I can barely drop the cap screw in & tighten it. Note to future self - remember those little design details like IT HAS TO BE ASSEMBLEABLE!


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## RobinHood (Aug 22, 2021)

Nice progress.



PeterT said:


> The flaring block ID is lightly threaded in order to grip the tube otherwise it slips back during flaring.



Could one put a close fitting steel plug inside the pipe for clamping?

The inside of the tube would then be prevented from deforming and thus increase the effectiveness of the clamping block. No threads might be required and thus would leave the outside of the tube without marks. If the plug had a little treaded hole in it, one could screw in an extraction screw to help in pulling it out after the flare is complete.


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## PeterT (Aug 22, 2021)

That's an good idea, never occurred to me. I basically mimicked what I saw on commercial units although I drilled probably most of my threads off so it would have just enough bite to hold, but ideally keep mangling to minimum. Another fellow suggested Cerrobend might have a similar effect of filling the ID with something solid, but I was trying to avoid all that melting business and I wasn't quite sure ow I would spot a plug of it but still leaving room for the flaring cone. These tubing parts are fiddly buggers for sure.

On a side note, radials typically have a ring exhaust collector as opposed to my rear facing open mini stacks which makes for more noise & oily goggles LoL. I've thought about how to form the big donut & making the connections. Some brave souls have done it. But for now the focus is just keep plodding forward towards making it run.


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## RobinHood (Aug 23, 2021)

The ring exhaust on the full size engines must give some sort of performance advantage - be it to make it easier to route the exhaust stream overboard through one opening, controlling back pressure, or do some sort of exhaust tuning, etc. I am no engine expert and am only guessing. Now, on the full size engines the exhaust ring(s) is typically made from many individual sections either welded together or fitted inside each other and held by springs. It would be very difficult to make something like that in miniature. From the pictures you provided, it looks like some people have done it though…


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## Tom O (Aug 23, 2021)

What is the diameter of the ring? I would think that making two separate parts and silver soldered together would work.


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## PeterT (Aug 23, 2021)

Tom, the plans didn't presume a collector ring but my eyeball guess would be maybe 7" diameter by maybe .75" section. I've been looking at different kinds of tubing rollers more out of morbid curiosity. I have a feeling this might fall in the geared crank handle style with multiple passes but I really don't know. I think a tool to roll things would be pretty useful. Some of the model locomotive builders pretty much need this kind of equipment but so far I have danced around the issue. In terms of material, more guessing. Lots of our conventional RC engines exhausts use aluminum but from what I can tell the collector rings I've seen seem to be thin wall steel for some reason. Probably TIG welded joints but that's just a guess.


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## PeterT (Feb 5, 2022)

Sheesh, I am really falling behind on posting. Well, I made some progress on the pushrod tubes. I made the tappet bushings according to plans a long time ago. But once I had all the parts & engine assembled to this point, I could see some major issues. 

Number one, the pushrods enter the rocker boxes at different 3D angles. One angle component is related to how the rocker boxes sit on the head viewed from front relative to cylinder center line. The other angle component is because the intake & exhaust cam plates are fore & aft of each other, which is where the tappet/pushrod originate from. So intake & exhaust rocker box holes are different to each other. Something always seemed fishy with the plans in this regard. I could never make the parts fit in CAD, so so I drew it up from scratch. Things get more more interesting because the pushrod moves in a 3D motion. the bottom goes up & down an axis via the tappet, but the top moves in an arc via the rocker. So I found the min/max from cam throw & orientated the new hole center to the average point, then extruded a 3D hole into the rocker box plate. These aren't the actual drawings but hopefully show what I mean.


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## PeterT (Feb 5, 2022)

I made 2 separate fixtures to drill the 3D hole in the rocker box base. One fixture for intake, the other for exhaust. The angles are established by 3mm pins. One set establishes the perch datum which is shaved off the block. The other set positions the block to coincide with the fore-aft pushrod angle. 2 more pins to align the rocker. Indicate of 2 edges.... and finally drill the 7mm hole.


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## PeterT (Feb 5, 2022)

The 3D hole in the rocker box based fit perfect so that was established. Next issue was the pushrod tube. The plans called for bronze tappet bushings which a conical shape to kind of allow the tubing to rest on in a 3D-ish manner. I wasn't keen about metal on metal. To retain it in place he had a teeny M2 set screw drilled laterally in the rocker box base into a hole. None of this looked appealing. I posted a question here
https://canadianhobbymetalworkers.com/threads/pushrod-tubes.4388/

I made some silicone couplers molded off turned aluminum fixtures which turned out well considering how small they are, but I still wasn't wasn't thrilled by the chunky look & external clamps. So back to the drawing board. I made this prototype which has 2 O-rings. The upper O-ring seals against the pushrod tube ID & self centers the bushing. The lower O-ring is kind of a snub so the pushrod can sit on a bit of cushion, so no more metal to metal. It fits nice so now I have to replicate 10 in bronze.


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## PeterT (Feb 5, 2022)

The last issue was how to retain the pushrod tube in the rocker box. I machined a collar which will eventually be bonded to the tube, but offset from the rocker box bottom surface just enough to accomodate another 1mm section silicone O-ring. The trick was to make that same 3D miter angle again on a fiddly little part. Here I cheated & just took care of the larger planar angle (12-15 deg) & hoped the O-ring squish would mask the fore-aft angle (1-6 deg). 

Another fixture plate where I can insert 5 exhaust couplers same time, plane off the angle, then repeat for intake. I tested 2 to see if the jig would work. I bonded with epoxy, milled the miter, then heated with torch to release. It held up during machining but cleanup took a bit longer. I used to have some hardware store 5-min epoxy that just softened, turned a toffee color & peeled off like wax. I ran out & used some of my good stuff & it put up more of a fight. It comes off with 3M pad eventually. Maybe I'll try CA glue but I've had mixed results with that too.


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## CWelkie (Feb 6, 2022)

Good looking and serviceable solution. I'm glad you found a pleasing way to do this.


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## combustable herbage (Feb 6, 2022)

Nice work Peter that is quite the challenge!


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## Gearhead88 (Feb 6, 2022)

Awesome build !!!!!


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## Gearhead88 (Feb 6, 2022)

If the need arises to hone cylinders again , no matter the size , you can use my sunnen machine.
Tolerances of less than .0001" are possible , I have bore gauges to accomodate  a variety of sizes .
 I have an abundance of mandrels , from spending too much time and money on ebay .

A small sample .....................


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## PeterT (Feb 6, 2022)

Gearhead88 said:


> If the need arises to hone cylinders again , no matter the size , you can use my sunnen machine.
> Tolerances of less than .0001" are possible , I have bore gauges to accomodate  a variety of sizes .
> I have an abundance of mandrels , from spending too much time and money on ebay .
> 
> A small sample .....................



OooohhhYaaa. What a nice offer. We are definitely going to have to talk. Lapping these liners was not the most fun job in the world. Times two because I underestimated the amount of shrink once landed in the cylinders. What made it more challenging was creeping up & hitting a target tenth on all 5 cylinder bores (plus one spare). Because on this engine I'm using commercial rings. The better way is to make the liner bores 'all the same' & then make the rings on that measured basis. If the bores are a thou over or under doesn't matter as long as they are the same & within tolerance. I didn't feel confident enough to make my own rings at the time. Actually, more specifically, I didn't have wherewithal to heat treat them. So if this runs WHEN this engine runs, the next project will likely have more cylinders.


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## Gearhead88 (Feb 6, 2022)

PeterT said:


> OooohhhYaaa. What a nice offer. We are definitely going to have to talk. Lapping these liners was not the most fun job in the world. Times two because I underestimated the amount of shrink once landed in the cylinders. What made it more challenging was creeping up & hitting a target tenth on all 5 cylinder bores (plus one spare). Because on this engine I'm using commercial rings. The better way is to make the liner bores 'all the same' & then make the rings on that measured basis. If the bores are a thou over or under doesn't matter as long as they are the same & within tolerance. I didn't feel confident enough to make my own rings at the time. Actually, more specifically, I didn't have wherewithal to heat treat them. So if this runs WHEN this engine runs, the next project will likely have more cylinders.


A Sunnen hone will save a bunch of time . What I do is , my piston size is zero on my bore gauge , as I am honing I sneak up on that and once I’m on the plus side of zero that is my clearance , I can then put that measurement wherever I want it , very accurately . The trick is to keep the hole straight and round , not difficult when using the right abrasives and being mindful of cutting pressure and closely monitoring size / material removed as you go . You gotta use a bore gauge that measures to .0001”.


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## Gearhead88 (Feb 6, 2022)

I’m balancing a crankshaft today , I got bushings for the small end of the rods on Friday , oversized rod rollers & new cages too , so I could proceed , Once I had the bushings pressed in and sized . Everything gets weighed to a tenth of a gram , some calculations , then you build a bob weight to fasten to the crank pin hole on the flywheel .


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## PeterT (Feb 6, 2022)

Gearhead88 said:


> You gotta use a bore gauge that measures to .0001”.



Next engine - I'll bring the bore gage & the beer! LOL


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## Gearhead88 (Feb 6, 2022)

PeterT said:


> Next engine - I'll bring the bore gage & the beer! LOL


Cool ,     I've got Mitutoyo bore gauges from .2" to 6" in a variety of flavours


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## PeterT (Feb 22, 2022)

With my modified tappet guides, rocker box & pushrod tubes nailed down its now rinse & repeat time. 5 cylinders times 2 per + 1 spare (just because) = 11 total. Thought you might be interested in sequential operations all done in one chuck setting so everything is axial. The guides are C544 bronze. The body OD is 6mm, fits 5mm hole in crankcase, 3mm reamed hole for tappets. The cutters are Nikcole, kind of spendy but last forever & I've used them for many aspects on this project. The round profile matched my 1mm section O-ring. Hopefully pics are self explanatory, otherwise just ask.


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## RobinHood (Feb 22, 2022)

PeterT said:


> The cutters are Nikcole, kind of spendy but last forever & I've used them for many aspects on this project.



So they are different profile inserts for a holder? Are they an ISO standard or something proprietary?

That engine build is coming along very well. Looks awesome!


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## Darren (Feb 22, 2022)

incredible work!


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## PeterT (Feb 22, 2022)

RobinHood said:


> So they are different profile inserts for a holder? Are they an ISO standard or something proprietary?


Yes, many standard widths, square, vee, profile, 2-way cutting, left hand, right hand.... They must have changed the web link but here is some catalog info. I bought a combo shank / insert set many years ago from KBC for like 150 on sale, but they are nutty prices now. Unfortunately I haven't found a clone to these. I can tell you the shank is made from Kryptonite. I wanted to squeeze a bit more depth on my cylinder finning & wanted to take a bit off the shank end that was interfering. The end mill just skipped across & said, nope, not gunna do it.

I've examined the pocket recess & think it could be replicated without too much effort. That would open up new possibilities to shop make holders & take the sting out of the price.


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## PeterT (Apr 3, 2022)

The radial requires (5) gasket seals under each cylinder flange and (2) for the crankcase front & rear. I found some 0.003" thick teflon sheet from Aliexpress. By making a CAD template from MDF I was able to score through & cut the inner/outer shape no problem. But making clean holes for the M3 bolts required a tool because drilling just makes a tattered mess. I didn't want to make a matching plate to kind of die punch it so came up with this. Its ~3mm O1 tool steel but the end is relieved by a ~4mm ball end mill which gives it a sharp peripheral edge. I decided to harden it, I didn't bother tempering. So I just spin it through the template over one of those cutting mats & out comes a clean little confetti dot.


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## PeterT (Apr 3, 2022)

I used 3M spray adhesive to first tack the material to the template, it stays in place to do the cutting, then a spritz of alcohol dissolves the glue residue & off she comes.


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## PeterT (Apr 3, 2022)

0.060" thick Teflon washers for the inlet & exhaust ports, another Aliexpress purchase. (I sure hope its the real thing for the 5 hot ones). It turns very nice but tooling must be sharp.


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## PeterT (Apr 3, 2022)

I debated hardening the rockers because of the axle hole & M2.5 threads & skinny asymmetrical features (potential distortion or cracking). But the hardness of annealed O1 is only a point or so higher than 303 stainless (valve stems) so the thought of wearing the rocker pads I spent to much time on was enough to vote for harden. The tops of the valve stems will preferentially wear, but no problem there.

I didn't take any pics while heating but I was able to focus the torch on the pad segment & just let the heat flow backwards. Once the pad end was carrot red for 10mm or so, in the quench oil it went. So the other 70% will not be fully hardened but that's fine, desirable actually. I buffed off the black & tempered at 450F in my (shop) toaster oven. No noticeable distortion, everything fit nicely.


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## PeterT (Apr 20, 2022)

My prop arrived from China. Eventually I'll laminate some veneer & make a cool antique profile but this one will do just provide load & blow air on the test stand. Unfortunately I realized the plans assumed a bit thicker prop hub thickness. This one is just under 20mm. So that started a domino effect annoying re-makes. I had to make a thicker drive washer to compensate. That felt a bit overly meaty, so I also drilled some radial lightening holes. But the added thickness then required a matching brass tapered split bushing, so new one of those too. Then a jig & alignment pin to drill the prop screw holes. Well once everything was mounted it was fun to twirl the prop & watch the rockers & pushrods doing their thing.


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## Darren (Apr 20, 2022)

Very nice work Peter


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## Mcgyver (Apr 21, 2022)

yes, very nice!


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## David_R8 (Apr 21, 2022)

Wow...just wow. So much awesomeness!


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## CWelkie (Apr 21, 2022)

Excellent work.  The old adage about changing one thing leads to 10 other revisions comes to mind ...

In case you decide to purchase a propeller with a thicker and larger diameter hub, Falcon Propellers does some nice wooden props in a couple styles.  (I've no connection, just a satisfied customer.) I'm sure they would provide any dimensions you require knowledge of prior to ordering.


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## John Conroy (Apr 21, 2022)

Amazing work as always Peter. You must be nearly ready to make some noise with it.


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## PeterT (Apr 21, 2022)

Thanks for nice comments. Yes hoping this will be the summer of smoke & noise!

@CWelkie thanks for reminder about Falcon. You even mentioned same on the other forum & I've bookmarked it. Hope your projects are going well!


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## DPittman (Apr 21, 2022)

PeterT said:


> Thanks for nice comments. Yes hoping this will be the summer of smoke & noise!
> 
> @CWelkie thanks for reminder about Falcon. You even mentioned same on the other forum & I've bookmarked it. Hope your projects are going well!


I don't believe you've mentioned it in a previous post but if you have pardon me.... do you have an end use for this fantastic engine (rc plane)  or will you just enjoy it on its' own?


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## PeterT (Apr 21, 2022)

@DPittman Haha, this question comes up a lot. I haven't given a model much thought. I mean I'm capable of constructing something that would suite the engine but I guess the short answer is Scale modelling was never really my 'thing' although I certainly appreciate that facet of the hobby. With somewhat limited play time, I'm more looking forward to the 'next' engine. Maybe inline, maybe Vee, maybe spark ignition. I have some plans & thoughts, but first things first, this radial must run!

Speaking of the package deal, check out this guy. Because building a rotary wasn't enough, he is doing an excellent job on an airframe. That's dedication.








						Engflyer
					

Explore Engflyer’s 968 photos on Flickr!




					www.flickr.com


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## DPittman (Apr 21, 2022)

PeterT said:


> @DPittman Haha, this question comes up a lot. I haven't given a model much thought. I mean I'm capable of constructing something that would suite the engine but I guess the short answer is Scale modelling was never really my 'thing' although I certainly appreciate that facet of the hobby. With somewhat limited play time, I'm more looking forward to the 'next' engine. Maybe inline, maybe Vee, maybe spark ignition. I have some plans & thoughts, but first things first, this radial must run!
> 
> Speaking of the package deal, check out this guy. Because building a rotary wasn't enough, he is doing an excellent job on an airframe. That's dedication.
> 
> ...


Wow that is something huh.

Maybe you should just build another 2 or 3 of those same engines and hang them on a full size ultralight and we can go flying together.


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## YYCHM (Apr 21, 2022)

DPittman said:


> Maybe you should just build another 2 or 3 of those same engines and hang them on a full size ultralight and we can go flying together.



Is that ultralight of yours actually airworthy


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## DPittman (Apr 21, 2022)

YYCHM said:


> Is that ultralight of yours actually airworthy


Not yet..  95% done.   Maybe by the time Peter gets another 3 radial engines made and an airframe to put them on I'll get mine done.


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## DaveMc (May 3, 2022)

Hi Don

Now that I see who you are, I cannot thank you enough for your comments on my artwork. Very high praise indeed from someone with your skills


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