Electric to gas conversion ... Gearing Question..

[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 168 ) = 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. Here is a pdf of the tav2 info.

http://www.bmikarts.com/PDF/Comet_TA..._Converter.pdf

[Busted Knuckles]

Just want to make sure I am going to order the right parts. I am to the point where I buy every thing and mock it up.

[B-Well]

Originally Posted by 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

lots of misplaced decimals and colons lol

should be
0.90:1 overdrive (multiply by 1.11)
2.7:1 low gear (multiply by 0.37)

im guessing the rear end radio should be 12.44:1? (0.08 )

216000(engine revs per hour) *1.11(overdrive) *0.08(axle ratio) *69.11(tire circumfrence)/63360(inches in a mile)=20.92(mph)

[Busted Knuckles]

Originally Posted by B-Well

lots of misplaced decimals and colons lol

should be
0.90:1 overdrive (multiply by 1.11)
2.7:1 low gear (multiply by 0.37)

im guessing the rear end radio should be 12.44:1? (0.08 )

216000(engine revs per hour) *1.11(overdrive) *0.08(axle ratio) *69.11(tire circumfrence)/63360(inches in a mile)=20.92(mph)

That takes some weight off my shoulders. I didn't want to pull the trigger on the parts till I knew for sure that it would be geared the way I needed it. That should be geared low enough for take off and if it does 20 mph top speed that should be pleanty fast for what its needed for. Thank you B.

[Busted Knuckles]

Originally Posted by B-Well

lots of misplaced decimals and colons lol

should be
0.90:1 overdrive (multiply by 1.11)
2.7:1 low gear (multiply by 0.37)

im guessing the rear end radio should be 12.44:1? (0.08 )

216000(engine revs per hour) *1.11(overdrive) *0.08(axle ratio) *69.11(tire circumference)/63360(inches in a mile)=20.92(mph)

How do you get 1.11 out of 0.90:1? I cant figure out how to convert the ratio to a percentage.

Also I have another dooozy of a question. I need to see how this combo is going look...

Top Speed?
3600 stock rpm speed = 216000 (engine revs per hour)
0.90:1 = 1.11 overdrive 1 (inside TAV2 caused by pulley sheaves)
0.48:1 = ???? overdrive 2 (TAV2 output sprocket 23T sprocket to the 11T on the diff)
12.44:1 = 0.08 rear differential ratio

I am gonna show my work for you can see where I am messing up.

216000(engine revs per hour) *1.11(overdrive 1) *????(overdrive 2)*0.08(axle ratio) *69.11(tire circumference)/63360(inches in a mile)=????(mph)


When the clutch in the TAV2 engages at 2200 rpm with the low gearing I am trying to figure out the lowend starting gear ratio. I have the information but dont know how to put it all together. I ultimately want to know the final gear ratio using the (TAVs 2.7:1 + 0.48:1 sprockets + 12.44:1 in the diff) = ???? final starting ratio

Engagement Gearing?
2200 rpm engagement = 132000 (engine revs per hour)
2.7:1 = 0.37 underdrive 1 (inside TAV2 caused by pulley sheaves)
0.48:1 = ???? overdrive 2 (TAV2 output sprocket 23T sprocket to the 11T on the diff)
12.44:1 = 0.08 rear differential ratio


132000(engine revs per hour) *0.37(underdrive 1) *????(overdrive 2)*0.08(axle ratio) *69.11(tire circumference)/63360(inches in a mile)=????(mph)



If you can help again B I would greatly appreciate it.
If this set-ups numbers look right it there will be a 420cc predator connected to this.