CVT Setup With 100-135cc Two Cycle (Sudam, reedjet etc)

Several years ago I knew a guy that tried to develop a cvt for the micro-midgets. He ran a 250cc 2 stroke class and used the rotax snowmobile engines. The issues he had were with the clutch cycling back down. In other words in a straight line acceleration like on the starts it was real killer. But when he would have to lift in a corner like to make an adjustments to his line. There was a lag after the throttle was re-applied, where the engine would have to get back up to rpm's then the CVT would have to re set itself to the correct gear ratio, and then after all that it would start to pull. I'm not talking like a second long delay or anything, but just enough that it messed up the control of the chassis and cost an extra car length whenever letting off the throttle. He worked him self silly modifying the ramps, and springs in the clutch, and after a full season of frustration he went back to more conventional set-ups. I agree with the above comments, a V belt consumes a lot of energy, and extra weight in the drive system costs a lot of acceleration.
 
Anyone wishing to study the racing application of snowmobile clutches would do well to look up the SCCA Formula 440/500 class and read up on how they do it....
 
It worked well. Kept me nearest to Ben at Limerock when his Sudam? was running well that night. Never got it set right. Ran out of time. Engine never topped out and held 6000 RPM's the whole time from corner to corner. I have my tach photo somewhere.

Needed to reduce the weights for higher RPM's range and reduce the "shifting" time to get full benefit.


http://www.oleancomputers.com/Kart/CVT/Comet clutch.docx
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PD Power said:
Want to win kart races? Sure you do! Read how.....in the sentence following:

KEEP IT SIMPLE STUPID!!

KISS!!
Click to expand...

...says the guy who build a valve clanker with convoluted crank and rod installation and unique oiling system.... to each their' own, I say. And just give "attaboy's!" for innovative thinking and application.
 
seat wasn't a problem at all. That was KISS. belt drive variable jackshaft to take out the shock 4:1 with a little overdrive variable "tranny" to keep your 4-stroke engine from reving itself apart. PD you missed the boat...I just didn't visit the bigger tracks only twice. At Paradise it would have been AWESOME!
 
Wankle Biter is sitting on the shelf, waiting for action.
An unexpected order for 4 heavily modified engines has kept me, and it
on the shelf for a while.

I also await a new chassis.
 
I've done the KISS approach, but there's nothing wrong with trying something different. Extra weight may not be such a disadvantage as I may have to add some anyway, there's inertia and rotational mass to think of too of course, but lets not go too deep down that track just yet.
You might loose HP on the peak, but if your torque curve at the wheels looks like this ----------- on long straights I think it's worth exploring.

Rob can you tell me more about the setup, parts you used. I'd need to revise the setup a little since the motor will be turning around 13,500 ish.
 
There is no doubt that a CVT is the better set up. A centrifugal clutch is basically an on/switch. If it engages too low it will dog the engine until it reaches its power band. The CVT clutch will keep the engine at its peak power all of the time because it shifts. The converter is the brains in the whole deal. Snowmobile clutches/converters are cheap and durable but a little too heavy for karts. I am not sure if all of the right parts are available for roundie-round racing using the Jr. dragster CVT.
 
I don't think the Jr dragster stuff can handle 2 cycle rpms and the snowmobile stuff is too heavy... But still is there anybody out there working on it?
 
I'm confused, snowmobile clutches are CVT's. I believe they are heavier to handle more power that is produced. The 94c was a favorite of the old Odyssey oval track racers years ago and worked great. Unfortunately, CV racing never got off the ground in the UK and went under. IDK if they ever got any of these produced.
 
Apparently "CV Racing" and their CVT project was headed by "Steve" at Aim-Motorports, according to what I read in a forum about it.... I'm presuming that's the UK AiM office, but not sure. There may still be a few units kicking around even if the company has folded. Though it's not as variable, MarkB has a nice facebook post on a dual-ratio setup he's created for his project kart.
 
Yeah Ted I read the same thing about CV racing. Would be cool to get one of their cvts and see if it's applicable.
 
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