centrifugal clutch

[Scania]

in RC-Car & kart, they use centrifugal clutch to connect engine & drive belt/chain, when engine speed up, the clutch plate will fly out to transfer power.

so, when I release thottle, will the engine slow down suddenly--the clutch release quickly, or slow down with the clutch?

[Giblet]

I think, scania, if I understand your question, that a centrifugal clutch is entirely dependent on engine speed.

At a certain speed of the engine, the clutch is engaged.

As far as I know, this type of clutch is only used for single speed setups.

[flynfrog]

the clutches can be adjusted to how fast and how slow the engage and disengage through a combination of springs and weights.

they are also used on multi gear transmission in tandem with a plate clutch in some ATVs and dirt bikes

also they have multi gear rc cars that only use a centrifugal clutch

[Belatti]

true flynfrog, a friend used to have a Suzuki 160cc ATV with 5 gears and centrifugal clutch when we were kids (arround 14 y.o. wow that was 14 years ago) and we used to do wheelies

how?

driving slowly in 1st or 2nd gear you ketp the pedal gear lever pushed, accelerate the thing and release.... rrrrnnnnnnn taaac! wooohoooo!!!!

[Scania]

so, when I release the thottle, the engine speed will decrease suddenly?
because the clutch is only follow the engine, when thottle release, there are no load transfer to engine, so the car will also have no engine braking, am I right?

[flynfrog]

so, when I release the thottle, the engine speed will decrease suddenly?
because the clutch is only follow the engine, when thottle release, there are no load transfer to engine, so the car will also have no engine braking, am I right?

you will have some engine braking the clutch will stay engaged until i drops below its programed rpm.

the shoes mostly care that they are being spun now what is spinning them.

I think the atv clutches had a way of holding the shoes to the drum. I remember they would hold them selves on a hill and you could pop start them. Maybe autogyro could tell us why. I have yet to take one apart.

[flynfrog]

true flynfrog, a friend used to have a Suzuki 160cc ATV with 5 gears and centrifugal clutch when we were kids (arround 14 y.o. wow that was 14 years ago) and we used to do wheelies

how?

driving slowly in 1st or 2nd gear you ketp the pedal gear lever pushed, accelerate the thing and release.... rrrrnnnnnnn taaac! wooohoooo!!!!

who didnt do that.

[autogyro]

so, when I release the thottle, the engine speed will decrease suddenly?
because the clutch is only follow the engine, when thottle release, there are no load transfer to engine, so the car will also have no engine braking, am I right?

you will have some engine braking the clutch will stay engaged until i drops below its programed rpm.

the shoes mostly care that they are being spun now what is spinning them.

I think the atv clutches had a way of holding the shoes to the drum. I remember they would hold them selves on a hill and you could pop start them. Maybe autogyro could tell us why. I have yet to take one apart.

There are many different systems based on centrifugal clutches. Usualy there are weights that fly out as engine revs increase against adjustable springs. The weights bring friction material in contact with the stationary outer drum using shoes or disk plates.
Once the vehicle (output) is moving the rpm of the clutch remains high enough to keep the clutch engaged even when slowing down, until a pre set minimum speed that matches engine rpm to the throw out force is reached. It is difficult to operate a stepped gearbox with a centrifugal clutch unless the clutch can be manualy disengaged. Most applications include a CVT drive using two cones and a belt or chain. Such CVT transmissions use power (up to 2000ib force in snowmobiles) and are unreliable in high power applications. Most centrifugal clutches are used for low power applications and anciliary drives.

[flynfrog]

the ones in ATVs have two clutches one centrifugal and one plate clutch. Do you don't how we were able to pop start them as kids. Its been years since I have seen inside of one.

[autogyro]

the ones in ATVs have two clutches one centrifugal and one plate clutch. Do you don't how we were able to pop start them as kids. Its been years since I have seen inside of one.

I dont know flynfrog, as far as I know the Suzuki 160 has one cetrifugal clutch with friction shoes and radial springs.

[countersteer]

Digging really REALLY deep into my cobwebbed head (30 years?)... I remember a motocross/enduro type bike built by a European manufacturer (CZ?) that was developed for the military. As such, it had a 4 speed transmission with centrifugal clutches. It worked by having one way clutches and a dedicated centrifugal clutch per gear. The arrangement worked such that as speed increased, each successive gear was engaged as its centrifugal clutch engaged and overran the lower gears.

I know that's sketchy but I haven't thought about this for decades...

[flynfrog]

ahh yes they had a sprag clutch on them for engine braking and push staring

[flynfrog]

here you can see both clutches

[tommylommykins]

What would happen if you connected a centrifugal clutch to a freewheel in the order:
engine -> centrifugal clutch -> freewheel -> gears and wheels?

This would eliminate the need for a second manual clutch, since breaking the connection between the engine and the gears could be done at the freewheel instead of the centrifugal clutch.

Changing into higher gears would need you to let the revs drop a long way before changing (engaging the freewheel at the same time as engaging gears could be messy?) But changing down would just require a bit less gas before the freewheel did its job?

Have I got this right? Has anyone actually done this?

EDIT: Just looked pu what a sprag is.. In the diagram, and according to what Flynfrog said, this works completely opposite to what I described.. It's an unfreewheel...

[autogyro]

A sprag (clutch) is a 'one way' clutch that only allows drive in one rotational direction and freewheels in the other.
In Borg Warner automatic gearboxes you can easily instal the 'sprag' the wrong way round and lock the entire unit.
If the sprag is between the engine and the gearbox there would be no over run braking but changing manual gears would be easy if the throttle is lifted.
The unit pictured by flynfrog certainly looks like it has two clutches, one cetrifugal and one multi plated.
What unit is it?