[Kartbuilding] centrifugal clutches

[Stephen Burke]

Hi Tim,

Centrifical clutches are very common. They are in mopeds/scooters and also 
on chainsaws. Yes - you are correct, they basically just engage when the 
engine speeds up. Imagine a centrifical clutch as follows:
If you were holding a bucket of water in your hand. If you started turing 
around fast, you would feel the bucket of water move outwards and rise up. 
The weights in a centrifical clutch act in the exact same way. As the 
engine speeds up, the weights are pulled outwards and they grip the outer 
bell housing and turns the sprocket. More information on centrifical 
clutches can be found on the kartbuilding blog at:
http://blog.kartbuilding.net/2007/06/26/using-a-centrifugal-clutch-and-chain-drive/

The 10hp Briggs and Stratton engine, although it sounds powerful, with a 
vertical shaft, it is going to be very difficult to get working. I would 
recommend you try and fine another engine, one with a horizontal output 
shaft.
If you did want to try and use the vertical shaft drive engine you have, 
you wont be able to use a chain and sprockets to drive the kart. What you 
could do is to mount the centrifical clutch onto the vertical shaft of the 
engine. Then instead of using the sprocket, you would have to use a V belt 
and V pulley wheel. If you ever look under the bonnet of an old car, you 
will see the V belt driving the alternator to charge the battery. By using 
a V belt, it can twist and rotate by 90 degrees, from the small pulley you 
would attach to the centrifical clutch to the larger V belt pulley wheel 
on the rear axle. You might get an idea of the above on this page:
http://www.kartbuilding.net/woodenkart/chassis_explained.htm
You would have the added advantage however of the automatic centrifical 
clutch, meaning the kart could be stationary and the engine idling.

Anyways, the best of luck with it. If you manage to build something, feel 
free to send on some photos of the kart and I can put them on 
kartbuilding.net to help other fellow kart builders.

-steve


On Sun, 27 Jan 2008, Tim Valis wrote:

> Hello, my name is Tim and I'm currently researching and planning to build a
> go-cart.  I feel awkward, but I'm not quite sure I fully understand how a
> centrifugal clutch works.  Does it basically just automatically disengage
> the engine when it is at low RPMs and then as the engine revs up, engage the
> driveshaft to the transaxle, etc?
>
> Also, I'm currently hoping to use a 10HP Briggs and Stratton engine for this
> go-cart, but it has a vertical shaft.  Is there any good way to go about
> this, or should I find a different engine? This is an engine that I received
> for free and I salvaged and rebuilt it.  Now it runs great!  A little rich,
> but an hour or so tuning the carb. tomorrow morning will take care of that.
> Anyways, on a vertical shaft engine, where would I put the centrifugal
> clutch and how can I trasmit my power to the rear end?  Any input on this
> would be greatly appreciated.
>
> Thanks for reading!
>
> -Tim
>