How does a clutch on a chainsaw work?

Question

Hi,

I'm looking to use a chainsaw engine to power a go kart i know that when you hold the button on the handle the clutch engages and the chain goes round but i would like to know what happens when you hold that button down

for example: does it pull a wire ect ect

i know this question is a bit iffy but any answers would be appreciated

thanks

Answer 1

It's a centripital clutch.  It looks a lot like the inside of a brake drum, with a couple of springs on the pads.  When the engine speed gets fast enough, the outward force of the pads and the weights on them overcomes the resistance of the springs, the pads shift outward, and engage with the drum that is attached to the sprocket that drives the chain.  When you let off the throttle, the speed goes back down, and the pads retract again, disengaging from the drum & allowing the engine to idle again.  Yes, it's what most small go-karts use.

However; you will be very dissappointed with the power that you will get out of it, unless it is off of a HUGE chainsaw.  It also won't last very long..  most comsumer chainsaws have very short lifespan engines on them, and you're going to be asking a lot more of it with what you're doing.  You'll also have a hard time finding a chain that will go around the sprocket on that clutch; chainsaw chains are different from bicycle drive chains.

You're far better off with an old 4-stroke horizontal shaft one cyllinder engine and a clutch made for it.

Answer 2

it's probably a centrifugal clutch.

if you look at old drum car brakes, you see a cylinder attached to the wheel, and 2 brake shoes that expand when you step on the brake to scrape on the inside of that drum, to stop the car.

a centrifugal clutch is similar, except that as the inside pair of shoes (attached to the motor) turns, the "shoes" expand to engage the drum, and turn the shaft that moves the chain.

one could also design it so that the drum was inside, and the shoes were outside, with a lever forcing them closed on the shaft that turns the chain drive wheel.

in either case, as long as the engine is revving, it wants to turn the chain.  on a chain saw, there is a brake that stops the chain 2 ways.  it applies a brake to the chain drive shaft, and also likely disengages the clutch.  you probably want to look at how that works, and use it on your go kart, if you can.