VMAX 600 Questions

[Mikeysuds 2]

Hello. The internet is a great place for info, but sometimes you have to go to people that know what the hell their talking about! I hate to ask stupid questions, but since I'm so accomplished at it, I thought I'd showcase my prowess, so here goes. I'm well along in my build, a Raven Kitfox clone. I found a cheap Yamaha VMAX 600 engine. I'm rebuilding it from the ground up. Red line is 8500 RPMs, so I'm designing a 3.5:1 redrive for it using a Poly-V belt. I'm trying to workout whether or not a damper is necessary. I have an engineering background, but the math for calculating harmonics is unbelievably complex. Any recomendations? BTW any thoughts on a prop and since the prop flange and driven shaft are one peice, is there a "universal" prop hub I can machine? Thanks for the help.

[1avidflyer 2006]

Never heard of anyone using that Yamaha engine.  I would say you are in uncharted territory.  And aviation is not very forgiving about mistakes that play out in the air.  Sometimes the tried and proven solutions are the best.  

[Mikeysuds 2]

 "Tried and true" started somewhere didn't it? 

[wypaul 456]

The real question for me would be how much time I would be willing to spend to develop the concept and to prove it. One or two thousand hours added to the build time is probably a conservative estimate. 
I looked at swapping a Yamaha Apex for my 912, which has been done many times, but ultimately decided I would rather be flying those many hundred of hours necessary to make the swap and work out the bugs after the install. Just installing EFI on my 912 required an unexpected change in the fuel tank plumbing at he header tank, major changes ion the electrical system, a modification of the cowling and many hours of flight testing.  Was it worth the effort, I like to think so but I can tell you that I have not encouraged anyone to do the modifications. 
All of that said I truly admire pioneers that do take the initiative to step into the wilderness and follow their dreams.

[nlappos 415]

The Skytrax gearbox has several available ratios, including 3.45:1. It is relatively proven and available, might get rid of a bunch of engineering problems in one easy solution.

I am an aerospace engineer, and I think coming up with a reliable belt reduction at those rpms is a real challenge.

https://www.skytraxusa.com/yamaha4cylinder

https://www.skytraxusa.com/yamaha3cylinder