Slipper Clutch - Cat SX

[JackWood]

Sorry if this is a stupid question, but how do you know if the slipper clutch is set right?

If I do a full-bore start, or punch the throttle from low speed, I can hear what sounds like the clutch slipping i.e. it sounds like a slipping clutch on a car. The motor reves rise, but not in line with the cars speed.

There is not TONS of slip, but it is noticable.

Is this right, or should you never be able to detect the slipper working?

Is there a fool-proof way of setting the slipper tension, or is it just preference and feel?

Thanks again for any help and advice.

Jack

[geerno]

Hey Jack, this is a good question. I have been wondering the same thing. It's been 20 years since I last raced so re-learning everything.

I am racing on a slippery track, and did have the slipper adjusted like Jack said above. But now I have it really tight and try to control the wheel spin with the throttle. I get heaps more punch out of corners when straight, but it is harder to control.

It would be great to have some advice on how to set the slipper up, what the principles of it's use are.

[sosidge]

First thing is that the slipper should slip before the diff does - so check that the rear diff does not slip easily but still works freely.

You can check this by holding the spur and one wheel, and turning the other wheel by hand, it should take a decent amount of force before you feel any slip, and the slipper should slip first (or at least at the same time as the diff).

Once you have this basic setting, feel free to slacken off the slipper for a softer feel on low grip surfaces, although really it is better to learn to use a softer throttle thumb, because if you slacken the slipper too much the car becomes unresponsive to throttle/brake inputs.

You should only notice the slipper working for the first couple of feet from a standing start.

Hope this helps.

[Mossy]

Check your diffs first, best thing is to make sure they arent slipping aswell as this may fool you into thinking its the slipper.

Personally i do it by feel. Dont really adjust it for different track, although i did back it off at the Euros this year but only slightly. In the end i went down to a 6.5 and tightened it back up to ensure i could still clear the jumps.

To set its more on feel. You should be able to here a small amount of slip when you hit fall throttle, but not alot. Do it on a grippy surface to get the best message. After that its down to personal preference!

Hope this helps

Si

[JackWood]

Thank you both very much for the replies.

I tested as per sosidge's description and the slipper slips and the diff doesn't. But it still takes quite some force to get it to slip, so maybe my diffs are too tight as well.....

So how do you tell if your diffs are too tight or just right? Obviously these plate diffs don't spin like a bevelled gear diff, but exactly how do you set up the smoothness-to-non-slip ratio on them? Or is that all feel too?

Both diffs are set so that with the motor in place, but everything switched off, if you spin any wheel it only counter-rotates the opposite wheel on the axel, and doesn't drive any of the belts.

As a final note, I am geared quite low, with a 19T pinion, so obviously that is going to crank more torque through the slipper than it would if I ran a racing sized 21-23T pinion. Am I correct in thinking that if I gear up then it should produce less slip?

[sosidge]

Originally Posted by JackWood

Thank you both very much for the replies.

I tested as per sosidge's description and the slipper slips and the diff doesn't. But it still takes quite some force to get it to slip, so maybe my diffs are too tight as well.....

So how do you tell if your diffs are too tight or just right? Obviously these plate diffs don't spin like a bevelled gear diff, but exactly how do you set up the smoothness-to-non-slip ratio on them? Or is that all feel too?

Both diffs are set so that with the motor in place, but everything switched off, if you spin any wheel it only counter-rotates the opposite wheel on the axel, and doesn't drive any of the belts.

As a final note, I am geared quite low, with a 19T pinion, so obviously that is going to crank more torque through the slipper than it would if I ran a racing sized 21-23T pinion. Am I correct in thinking that if I gear up then it should produce less slip?

In terms of not slipping, your diffs can never be too tight. But the rear diff can be set too tight in terms of rotation and it will mess up the handling, making the car very loose on power.

It sounds like you are not far off, essentially the rear diff should rotate quite freely by hand but should not spin. At the end of the day feel and experience is about as good a guide as you will get, I wish I could give some torque settings but there aren't the tools to do it! Front diff usually set a smidge tighter, certainly no looser (oversteer again).

You are right about the ratio affecting torque on the spur but I don't think it is an issue anyone worries about, gear for the track not for the slipper clutch!

Originally Posted by Mossy

Check your diffs first, best thing is to make sure they arent slipping aswell as this may fool you into thinking its the slipper.

Personally i do it by feel. Dont really adjust it for different track, although i did back it off at the Euros this year but only slightly. In the end i went down to a 6.5 and tightened it back up to ensure i could still clear the jumps.

To set its more on feel. You should be able to here a small amount of slip when you hit fall throttle, but not alot. Do it on a grippy surface to get the best message. After that its down to personal preference!

Hope this helps

Si

Well done Simon,

Excellent post son.