Don Terrill’s Speed-Talk

Has anyone tried a slipper clutch in a race car before? Bikes have be using them for years.

The diesel puller trucks and tractors have been using them for a long time. We're converting our diesel puller over to a slipper clutch this year - I don't know much about them specifically though.

My understanding of it was that they only slipped on braking. Basically a lack of engine braking. IIRC they have a sprag on the flywheel itself. I might be completely wrong though, I just can't imagine you'd want a clutch to slip on accel.

I use one in my pulling truck. Usually you use one so that you can bring the motor out in it's power band and not just blow the tires away. The "slipper clutches" in bikes are different, more like what 350sx had said. Also, because of the material used you dont' burn them up when they get slipped.

bubba2400 wrote:I use one in my pulling truck. Usually you use one so that you can bring the motor out in it's power band and not just blow the tires away. The "slipper clutches" in bikes are different, more like what 350sx had said. Also, because of the material used you dont' burn them up when they get slipped.

Worded different---On a bike it's more like a "one way" clutch... So you don't toss the rear end due to engine braking.

Not spinning out a car is important, but on a motorcycle, you don't spin out, you eat pavement and become the pedestrian in the middle of the freeway.

bubba2400 wrote:I use one in my pulling truck. Usually you use one so that you can bring the motor out in it's power band and not just blow the tires away. The "slipper clutches" in bikes are different, more like what 350sx had said. Also, because of the material used you dont' burn them up when they get slipped.

Dragbikes call this a lockup clutch, and it works just like bubba2400 stated for the pulling trucks. Same theory just different names.

Road race bikes use the a slipper clutch that acts as stated just above this post.

The so called "slipper clutch" on bikes which is designed to minimize rear wheel slippage with the throttle closed has been debated for years by motorcycle drag racers. For the most part the consensus is that it makes it more difficult to get a smooth launch though one turbo builder I know likes them because it helps prevent clutch slip with big HP.

I yanked the slipper clutch from mine.

Then there are also slider clutches and lockup clutches. The distinction is whether the weights are driven by the engine or the rear wheel. I'm sure that everyone here is familiar with an engine driven slider clutch.

The lockup clutch has the weights attached to the clutch hub and as the rear wheel speed increases so do the force imposed by the weights.

I've got one of these on my bike that I've been trying to set up so that I can throw the clutch away but so far I have not been able to get it to work. If I had a longer wheelbase or a normally aspirated bike this would probably not be the case but with a turbo and a short wheelbase so far no luck. This usually means an exciting ride, but so far not a particularly quick one.

As an aside I'm experimenting with a logic controlled clutch system.

Anyhow, here's a pic of the lockup clutch I'm using. The springs and weights are adjustable to change the rate of engagement.

Some clutch friction material allows for some slippage, then grabs when it heats up.

In the VW world, these are branded as "Black Magic" discs... Some sort of sintered iron.. when you do glaze them, you hit them with the bead blaster and reinstall.
Main usage is to take some of the shock load off the trans so you don't break it in half.