keatonx
Member
I guess you could do that, but I don't see why. The variator changes the ratio on it's own based on rpm and load. But it has to overcome resistance by your chain tensioner. So you can adjust the spring tension on the belt to what you feel keeps the engine at a safe rpm and gives it the most power.
Here's a pocketbike CVT I have- these have the smallest variators you'll be able to find.
View attachment 51734And yet even with the belt running as far on the inside as possible it would still be equivalent to a 1,7/8" pulley. That's too big for your average high rpm engine (especially since the diameter increases to around 3.25" at high rpm) so you would have to use a low rpm engine, ie. A small predator engine. Then your ratios would work out very well. Here's a beautidrawing of how it would all go-
View attachment 51735
Theres 2 ways you can do this- you can use a drive variate pulley and have that force the belt to ride at a larger diameter,
or you could have a simple spring loaded variator (the output one) as your drive and use a belt tensioner that's weaker than the spring in the variator. So when the engine is under heavy load, the belt naturally slides towards the centre of the sheaves and therefore gives it a better fitting gear ratio.
Both of these would require a bit of experimentation with different sized springs.
I'd much rather go with the 2nd option because the belt tension can be adjusted without changing the ratio, as long as both the tensioner spring and variator spring are both increased/decreased at the same time (on the other option you can only change the tensioner). The simple spring loaded output variators are also much cheaper, and practically nothing can go wrong that can't be fixed by changing out a spring or two.
As for clutching you could just let the belt slip via a cable on the tensioner.
You would probably need to use a notched v-belt (ax series would be best suited) or this could happen-
That's from my lawnmower bike; the regular belts don't always like to be flexed. But wit such a large drive pulley I don't think this would happen anyways.
