Meehanite Cast Iron Available Locally?

[PeterT]

Just curious, when the piston is hard plated like that, what is the matching prescribed liner bore protocol? Is it un-plated alloy or plated with something different?
I'm having trouble visualizing the break in equivalent of the modern race engines - 'hard' tapered liner & 'soft' cylindrical piston that molds itself into the magic barrel shape. But all this is above my pay grade.

 

[carrdo]

Hi Peter,

In the case of the Howler 15, the liner is specified as unplated "Leadloy" steel. My take on Leadloy is it was a good choice for cylinder liners where oil was always present but it is a terrible choice for any other use as you can almost hear it rust. If you leave a clean piece of Leadloy out in your workshop, even when using dehumidification, after a week it will be visibly rusty.

 

[PeterT]

Yup, I am familiar. I use 12L14 quite a bit in shop because it turns so nice. Its used for liners & cylinders in model gasoline engines, but methanol loves to attract water. The premix oil can't keep corrosion at bay. Some of the synthetic oils are also problematic from that standpoint. I've long been in the habit of partial teardown & flooding parts with storage oil over the winter. I heard Cox used 12L14 in many parts which to this day still mystifies me.

 

[Bandit]

Hi Peter,
In the case of the Howler 15, the liner is specified as unplated "Leadloy" steel. My take on Leadloy is it was a good choice for cylinder liners where oil was always present but it is a terrible choice for any other use as you can almost hear it rust. If you leave a clean piece of Leadloy out in your workshop, even when using dehumidification, after a week it will be visibly rusty.

 

[Bandit]

Had a fast look at that meehanite site from the maker, a bit of learning there! Anyway, what I did seem to see was that many cast iron crankshaft are made from that type of cast iron. I think the big old Cat crank would likely be a forged steel unit, many heavy duty cranks are forged. Run of the mill north American cranks are cast iron.
Maybe check an engine rebuilder if any around, for an older -60s to 90s engine cranks, should be some wiped ones in the junk pile Generally can tell if cast by the parting line, cast- very narrow, sharp line, forged- a wide ground line. The counter throws will have some nice chunks of iron without oiling holes.
Happy hunting, also noticed cam shafts can be the same, but likely lots of heat treating on them.

 

[PeterT]

On a model engineering forum I frequent, this place was mentioned as a source for custom rings. They supply to a lot of the smaller commercial engines & performance engines. Not of interest to the subject matter of sourcing CI locally, but they have some interesting technical information of alloy materials & such FWIW.

Catalogue | METEOR PISTON S.r.l.

www.meteorpiston.com

 

[carrdo]

Hi All,

Maidstone Model Engineering and College Engineering Supply in the UK carry grade 250 Meehanite cast iron and they both can supply it in small quantities. The minimum size of round solid bar starts at 1" (25 mm and larger) and they can supply many other shapes as well. Grade 250 Meehanite is a fine engineering grade which can be hard chromed to suit such purposes as I wanted it for.

I broke down and ordered a 300 mm long 25 mm dia piece. The price was reasonable (about $15. Canadian) but the shipping here was 3x that cost.

 

[PeterT]

Has it arrived or its being shipped into this postal sh*tstorm?

I'm interested to follow your project. Now have you made any inroads as to where you will get it hard chromed & how much? Reason I mention is somewhere in my travels I read that certain shops require certain dimensional undersize depending on their process or equipment or bumpiness or longevity of the bond. A clumsy way of saying the chrome thickness varies. That would be seem to factor into your machining?

 

[carrdo]

Hi Peter,

Only just shipped out today. Probably postal.

I haven't dealt with the chroming problem yet. I will need to talk to some of my model engineering buddies and see what they know (if anything).

 

[carrdo]

Hi All,

Just got back from sunny Spain (it was not so sunny this year) as the Mrs. hates Canadian winters.

The 1" diameter 250 grade Meehanite bar stock piston material arrived two days after we left so...

Anyway, Craig Asher says to start with the piston and grind up and polish a piece approx. 6" long as a first step. Quote "This way a long enough piece can be cut off to make one piston, leaving several more blanks in reserve in case of accidents or goofs".

The only issue is the OD of the piston is shown as 0.5912" and he gives a tolerance on this of +- 0.0001".

Yea, right, I work to this tolerance every day in my home shop.

The only thing I can think of (other than to hold my breath and to try and take it to a small commercial high precision grinding shop who won't want to look at such a small nuisance job like this) is to make up a split ring lap and lap it to that size? Any other suggestions?

Also, has anyone had any experience with the Timesaver lapping compounds as this is what I am thinking of using?

 

[Mcgyver]

It's a slightly challenging but a doable grinding job. You could lap it, no need for Time Saver though, just use regular lapping compound and a material for the lap that is softer than the CI. imo it will cut better than time saver whose only advantage is that it (supposedly) doesn't embed. Lapping in the round is somewhat self correcting (very different than flat lapping), but you can generate a banana shape if you are trying to take tons off. So best to first turn between centres and just take the last little bit off with fine lapping. Also with lapping, best to use a different lap for each grit. I like to set an indicator mic to a gauge block for measure to this tolerance.

 

[PeterT]

The only thing I can think of (other than to hold my breath and to try and take it to a small commercial high precision grinding shop who won't want to look at such a small nuisance job like this) is to make up a split ring lap and lap it to that size? Any other suggestions? Also, has anyone had any experience with the Timesaver lapping compounds as this is what I am thinking of using?

When I made the cast iron liners for my radial engine I made a lapping tool from aluminum. Partially mimicking a commercial version (pics) & partially a Robin Renzetti video which you should watch. What kind of made TLAR sense to me was a higher slit count & the relief holes quite close to the lap OD. So more like a collet in terms of radial reduction vs a simpler clam shell with one slit across. I drew it in CAD & had some generic blanks cut on a waterjet. The lathe pic shows making the bore with just a bit of pre load on the clamp bolt, then its basically ready to go. For this I used Clover brand lap which is silicon carbide in a hydrocarbon carrier, basically feels like grease. I've used Timesaver but I didn't get along as well. I felt like I had to babysit the slurry with oil & it breaks down very fast.

I've also used AliExpress diamond which cuts faster. You are not supposed to use it on CI because it can embed permanently in the pores. I've always wondered about this especially having seen some pics under extreme magnification of embedded particles that look like a boulder dragged by a glacier. If its embedded, its embedded so slight hardness difference is not going to be any kinder to the mating surface or piston rings. Another subject.

I think my liner OD's were within self imposed 0.0002". The bores were within 0.0001". My advice is your pre-lap OD to be no more than 0.002" over finished target unless you have lots of free time. Its like sanding a spruce 2x4 with 1000# hoping to take it down 1/16" sometime this century. Even with your finest lathe feed its beneficial to then block it down with abrasive paper, emery or (my preference) wet/dry using a flat backing block. MDF makes a decent block because its relatively hard. Machined aluminum would be better but less safe. I don't like folding over the paper on a block, I prefer to 3M spray it down. So maybe a 600# & 1000# sequence so all the hilltops are gone. Then lap. Once you get familiar with the workflow, (careful & frequent measurement is key!) you could leave only 0.001" for lapping & will shorten lap time & tool wear.

You need to be anal about cleaning the surface in between every measurement to avoid errors & not get lapping compound on your expensive measuring gear. I found wiping it dry as much as possible & then paper towel with WD40 & then paper towel so nothing shows. Take multiple measurements up & down the long axis and in different clock positions. An indicating micrometer is a really useful device over a digital with 0.00000 display. I bought a used one on Ebay for a good price & even get a metric (they are more prevalent for some reason) because you are basing it on a gage standard anyway. It really is a feel thing to work over an area & avoid another area by stroking. Pay attention to temperature & its smart to just take a break every so often to let the material stabilize. Good luck!

 

[PeterT]

Bores were lapped with a commercial lapping tool (Acro brand)

 

[PeterT]

Example indicating mic

 

[carrdo]

Hi Peter and Mcgyver,

Great answers!

Thank you for all of the information provided and your experience with lapping. I now have a work program to undertake. I will have a look at Robin R's video as well.