Giant scale Hellcat

[jpsaxnc]

A 7075 crankshaft is only compatible with two materials, eglide E and 954 aluminum bronze. I will put a 954 bronze bushing in the PIE crankcase that trashed. Hopefully I can still build a lighter motor.

[jpsaxnc]

This is the best solution, because the most critical factor is the clearance between the crankshaft and the bushing, to prevent air leakage. I can do it in metal with the simple tooling that I have.

[jpsaxnc]

Well, the 954 bronze bushing didn't workout either. I trashed two, I just couldn't get them to ream straight. 954 is resistant to being machined, and my lathe is a joke. The morris taper in the tail stock spindle, was bored at an angle, so nothing lines up. I have shimmed and fiddled with the tailstock, to get a reasonable hole. Finally I settled on making a Peek bushing, it is installed in the PEI crankcase, all looks good, so I can continue with the new motor. The crankcase and bushing weight 5.1 grams.

[jpsaxnc]

The new motor is coming together slowly, I'm making a new cylinder from 7075 aluminum. I tried a cylinder from 6061 aluminum but it was to soft and showed signs of wear pretty fast. I still have to make a new crankshaft, I have a cylinder head I can use from another motor, so things are coming along.

[jpsaxnc]

The new motor is running, it still needs some fine tuning. I had to use a bronze bushing along with the 7075 aluminum crankshaft, so it's only six grams lighter than the pervious motor, but I was able to make a prop hub from Peek polymer and attach the blades of a 7" Peck polymer prop to the hub and that came out 2 grams lighter that the 8x6 sf. prop. So I was able to shave 8 grams total off the motor weight. The rubber power style prop is a much better match the the rpm output of the motor.