My riff on the Upshur Twin

[Vietti]

Why not make the cylinder out of CI? I always, in the past, made AL cylinders with CI liners, but building the Hoglet I went with CI cylinders as suggested by the author. They turned out fine and I'm glad I did. Makes a mess but that's OK. Seems not to be an issue for cooling. Might simplify the stud issues.

 

[timo_gross]

Cylinders were initially fixed to the crankcase via screws through a flange at the bottom. The cylinder heads were attached to the cooling fins shrunk onto the cast iron cylinders. This arrangement didn't work, because the aluminum cooling fins would lose their shrink fit on the iron as the engine got hot, and the heads and fins would move outward from the crankcase! I ended up retrofitting long studs extending all the way through the heads, fins, fins, and crankcase tying everything together a la old Porsches. I hogged the crankcases out of solid blocks of 7075-T6 aluminum. That material is stronger and machines more nicely than 6061-T6, but also tends to pit if water-based mist coolant is not dried off quickly, as I found out the hard way.

Thanks for the insight. 6061-T6 is much easier to buy for me, so I never got hold of any 7075-T6. The 6061-T6 machines very O.K. (I admit I broke few endmills, with built up, operator mistakes )

 

[timo_gross]

Why not make the cylinder out of CI? I always, in the past, made AL cylinders with CI liners, but building the Hoglet I went with CI cylinders as suggested by the author. They turned out fine and I'm glad I did. Makes a mess but that's OK. Seems not to be an issue for cooling. Might simplify the stud issues.

I would guess. The weight will be higher and the heat transfer might be different. Maybe it matters if you want to run the engines at high power for longer time?
Usually all the aircraft model engines I saw ( as a spectator, never owned one) were made out of Aluminium.

 

[Jasonb]

The model Aircraft engines were most likely intended to fly so weight comes into it. Very few of "our" models will get off the display stand.

Leaving the top flange of the cylinder a few though proud of the fins will allow the head to clamps down onto the liner, that way the interference fit is only there to transfer heat away.

 

[rklopp]

Why not make the cylinder out of CI? I always, in the past, made AL cylinders with CI liners, but building the Hoglet I went with CI cylinders as suggested by the author. They turned out fine and I'm glad I did. Makes a mess but that's OK. Seems not to be an issue for cooling. Might simplify the stud issues.

I'm not looking for simplicity or the quick and easy solution. I think what I did was more elegant and was an interesting challenge regardless.