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Radial engine build

#61
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
 

PeterT

Ultra Member
Premium Member
#62
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

Ultra Member
Premium Member
#63
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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#67
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