[Kartbuilding] Help

Stephen Burke stephen at sburke.eu
Tue Oct 5 13:47:07 IST 2010


You are correct, if you put the large pulley on the engine, and the small 
pulley on the rear axle, the kart would go faster.

However, when you gear up for speed, you loose power and torque.
It would be like trying to drive a car in 5th gear. It would stall the 

Its actually a tough balance to get the sizes of pulleys correct. I 
typically find that having a rear pulley 4 to 5 times the diameter of the 
pulley on the engine gives a good speed and good take-off-power.

Also, if you do the maths, with RPM of the engine and size of the rear 
wheel, you would find that there would be large "theoritical" speeds 

A bicycle is a good example. The person has LOTS of power but low speed. 
Small engines have LOTS of speed, but relatively low power.

You could always try it yourself and see. Get a kart built and try 
different size pulleys and see what speeds and power you get.

Best of luck,

On Fri, 1 Oct 2010, Nat Snyder wrote:

> Hi, i am using you website for a guide to build a lawn mower go kart (using
> your V-belt Idea). I agree with almost everything you are saying except why
> you should weld a big pulley on the rear axle and a small pulley on the
> shaft of the engine. Why would it not be the other way around? It appears to
> me that if you have the smaller pulley on the rear axle you can reach a
> higher speed then having the larger pulley welded on the rear axle. Can you
> explain to me why you say to do it your way?
> Thanks
> Fellow Go kart builder

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