I need to extend the propellor shaft on a 25cc methanol i.c. engine approx 600mm. for large scale model aircraft application.
Vital stats:2 stroke single cylinder 25 cc methanol engine. bore 32.5mm, stroke 30mm max torque 240 Kgf. mm at 7900 rpm turning an 18" propellor with 6" pitch
I would like to use carbon fibre (nice and light) and have been informed that o.d of 30mm should get by any shaft whirl as length 600mm, 30 diam, wall t=1.5 => 8000rpm first bending=234Hz natural bowing frequencies, so I won't require a supportive bearing in the middle....just either end.
My main problem at this stage in the planning, is that I cant find any u.v/couplers/joints to use either end that will take this sort of rpm, or aren't hugely expensive. Does anyone out there know of any suitable couplers. Or perhaps I could make something simple..diaphragm coupler? They need to be light. Looking forward to hearing from someone. Cheers, Chris.