Forgot to answer this. I used a regular Zenoah clutch from the RC version engines. The bell is mounted to the wheel shaft and I machined an adapter going from the engine to the shoe housing. The way I mount it to an engine is that the adapter has the same female thread as the outer part of the Zenoah Collet. I mount the male collet piece to the crank and screw on the clutch adapter which had the clutch shoes mounted to it. I will try and get some picture up...there are some on here already somewhere.

Thanks Marc. Then other clutch I had mentioned is an O'Neil Brother Racing clutch. I will look for more info on the Zenoah clutch.

I'm sure either one will work, they are quite similar if not the same. When I was building mine, I looked around trying to find one-way bearings, which I though would be a better design, but didn't find anything that I was certain would put up with the load and RPM, at least not in the price range of the Zenoah clutch. Plus you need a way of letting the engine start and rev up before engaging the wheel so a clutch really is a must. The one-way bearing used in conjunction with the clutch would be the best I think.

One-way bearings would obviously have made it easier to do the run-down tests on the dyno anyway!

I did a search a while ago for small engine dyno's and found one that a guy built using a optic mouse scroll wheel pickup, He even had free software to download that gave a complete readout. Thinking about it now I will see if I can find it again, He used a wheel that you just had to input the weight of for inertial mass the wheel had a cut out in it and the mouse scroll pickup would read this gap once every revolution. I think you could just enter the weight of your flywheel and mount the pickup to the engine somehow. Would give you a readout of hp torque rpm etc at your flywheel. I will see if I can find it again and give it a go myself.

www.sci-spot.com/Mechanical/dyno.htm

I'm pretty sure this is the guy you are referring to.

Some neat projects on that site!

Interesting concept, but the commercial dyno systems use a data aquisition unit because computers can't handle the data input speed and/or volume.I think you would still need the "black box" which is a large part of the cost of a commercial system.
Plus with Performance Trends mini usb system only 500 its hard to beat.
Not to sound like a PT spokesman, but its hard to beat their software because the dyno software and other software will integrate.

I agree. The mini USB system from Performance Trends definitely will get you going for a VERY reasonable cost.

marc wrote:
Gentlemen.... when i built my dyno, I found it easier to make my own one way bearing rather than find and pay the $ for a oneway that could hold the torque and high rpm required for our aplication...

I used a ratchet design... by cutting a part of the axel out and cutting & shaping the end of a square key way into an oval shape to allow it to rotate from a fixed point... A small low tention coil spring allow's the key way to be positioned to sit in the cut out of the axel in one direction (locked)& move out of the axel cut when spun in the opposite direction or the weight/flywheels speed exceed's that of the engine..(WHEN engine is slowing down from a run (got the idea from pulling an old ratchet apart)

David, this is VERY interesting!!! Can you by any chance post some pictures and/or drawings of this? I think I understand what you are saying, but would really like to see it. I like the idea of the one-way bearing, as with the clutch alone the engine and wheel stay locked-in from about 3k rpm and up...

I take it you still have to use a clutch in the system though right? You need the engine to run free to start it up....