Craig Laycocks double end piston motor.

[J.A.W.]

Bolting a presumably aluminium piston running close to 300C with steel bolts through the crown is a recipe for disaster...

Why assume "steel bolts"?

Thermal expansion compatible Ti studs/countersunk sleeve nut fasteners instead, perhaps?

[63l8qrrfy6]

Ti has a very similar coefficient of thermal expansion to steel so it doesn't make a difference in that regard.

Also having crevices in the piston is not a good idea for combustion.

[coaster]

Correct Mudflap, it should be bolted from behind into a blind hole, maybe a locking washer or wire tie as insurance.

[J.A.W.]

Ti has a very similar coefficient of thermal expansion to steel so it doesn't make a difference in that regard.

Also having crevices in the piston is not a good idea for combustion.

Yet the alloy composition of the piston can be suited to the fasteners, TE-wise
then add - sodium-filled cylindrical studs too - if you'd like more heat transfer.

& if you'd like less, then a concentric ceramic crown, could also be considered.

What significant "crevices" would there be, with a flush-capped sleeve nut?
(& 4T poppet valve piston clearance "crevices" seem to manage combustion ok, no?).

[63l8qrrfy6]

Unfortunately it doesn't look simple to bolt from the other side in this scheme.

My biggest gripe with the piston bolt is that it introduces a high mean stress in a component which is subject to thermal stresses, creep and large alternating loads.

Aluminium pistons creep below 300c (about 40% of the material melting point) but they are not normally subjected to high constant mean stresses so it is rarely an issue.

[Big Tea]

How practical would it be to bond(stick) the surfaces?

[coaster]

Well he may just have to rewrite the rules and circulate some oil through plate to cool it all down yes?

[63l8qrrfy6]

Even if you invent an adhesive strong enough, it will be so strong it will turn the whole thing into a permanent assembly at which point it probably defeats the purpose?

[coaster]

There is another evolution update, not far from a feasible design, i think he will roll the dice with cap screws through the piston crown, clearly not a puritanical aproach. Youtube is his forum, he answers helpful advice.

[63l8qrrfy6]

If the goal is to build an engine that just runs under its own power that will probably do.

In that case the engine won't really amount to anything more than a curiosity.

[nzjrs]

No idea about the person behind this, but the software world has been like this for a while, people throw proof of concepts up on GitHub - it's usually when they are looking for a new job. It could also just be for curiosity of course, or I could be wrong.

[Greg Locock]

I'm not sure that random solidworks cartoons would get you a job as an engine designer, but perhaps that is the way it works these days. Or not.

[coaster]

Cad is fun as a hobby, but sitting at desk pumping detail after detail requires different temperance.

[Rodak]

Cad is fun as a hobby, but sitting at desk pumping detail after detail requires different temperance.

Yeah, I used to do that, both in aerospace and marine engineering; my productive work time was about four hours, 6:00 am till 10:00 am and then I was sapped of creative juices and simply did grunt stuff to make the day end. There was a lot of tedious work, checking clearances and travels and stuff like that, as well as making sure it could be built; I got burned out and became a winemaker.

I don't really see how the crank, gears, and pistons can be assembled on this thing but have only looked at it briefly; I imagine the case will be split, which might get rid of the piston head bolts - they aren't a good idea.

[coaster]

Interesting.