CVT and Gearing very interesting...

Busted Knuckles

I am doing a conversion on my cart Like ryan did and need some one to run over my calculations...


predator 212cc turns 3600 rpm stock.
The Tav2 has a 90:1 "10%" over drive and
a 2:7.1 lowend gear ratio on take off.

So on take off the "Tav2 just engaging" the Tav2 has a ratio of 2:7.1 plus the 12:44.1 in the rearend. So the take off the the 212cc should be geared pretty low. Does any one know how to combine those 2 ratios to find my true take off ratio? Then as the sheaves shift it achieves a overdrive of 10% 90:1. That works out great when you factor in the 0.92:1 8% overdrive you get from the 12t to 11t sprocket ratio.

So I can assume the lowend torque even with my big tires should be ok with that gearing. Its geared lower on take off that a stock cart would be.

Heres the top speed nitty gritty

3600 engine rpms results in 3960 rpms at the tav2 12 tooth sprocket due to the 10% overdrive.
Now the 3960 rpms and overdriven again going from a 12 tooth to a 11tooth by approx 8% 0.92:1 that equates to 4276.8 rpms at the rearend. So with my 22 tall tires my top speed should be if everything is optimum is 22.5 mph according to the buggies gone wilf converter.

but when I crunch the numbers here is what I get.
(4276.8 rpms X 22 "tire diameter") / (12.44 X 16 = MPH

94089.6 / 2089.92 = 45.02 mph I messed up on the math some where or I am gonna fly.

Can some one look at this and see how close I am.

BGW

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Busted Knuckles

On take off the cart is seeing a beginning ratio of approx. 15.14:1 I hope

garredondojr

Sounds like an interesting project. One problem you may run into is the converter not going to full ratio. It may come down to a weight, power, tire size battle. Hopefully I'm wrong. What I do know is my ez-go with a old worn 9hp robin with 24" mud lites won't get to full converter ratio nor will it get to max rpm. It will in neutral but not with a load.

roady89

Exactly, you have to take into account losses from wind drag, rolling resistance etc etc. You wont get 45mph from a 6.5hp engine, you'll be lucky to get 25-30.

sho305

With stock gearing and 22s it took my G9 a while to get to 28mph on dirt, and eventually would do 30gps on pavement. After about 25mph it huffed and puffed to go any faster. Yeah it was turning 5K rpm or something lol, and certainly they don't have high rpm cams in those stock 9.4hp engines.

I would consider pricing 390cc clones, but you can't use a TAV2 on them.