Dished clutch plate!!!

[doogalman]

It's nagging away at me, What is the reason that the clutchpack contains a dished clutch-plate????

[adam]

not sure, just make sure you put it in with the dot facing you.

[doogalman]

I can't.
I have a set of carbon faced alluminium plates fitted, but i have no dished drive plate!!!!

[andyb]

Originally posted by adam
not sure, just make sure you put it in with the dot facing you.

Thats not necessarily true as you can have more than one dished plate, even up to four!

In which case some would be fitted the other way around!

[Stealth]

OK... the dished plate is actually one of the steels and you usually have two which "face away from each other". The idea is, to stop chatter and slipping when you take off. Over time the dishing reduces through use and heat and this has an impact on the wear rate of the plates. The reduction in the dishing renders the plates more flat and so the overall stack height reduces. Apparently, the stack height is critical (particularly in slipper cluteches which wear more quickly). The dished steels should be checked from time to time and replaced if they have lost the cooncave or dish effect. If the stack height gets below 0.4 -0.5 (as the distance measured from the central splines) then you get increased wear and the plates wear against the basket more significantly.

Just to say .... I'm no expert on this and am repeating what Rick Hackett told me when replacing my plates and basket before going abroad over a week ago. I am only sadly spending time writing this on a sunny Sunday because my bike was nicked in Holland on Thursday - just so you don't think I am complete anorak (only slightly!!!!!!!!).:sing:

[doogalman]

Stealth2, Condolances on your recent loss. Hope insurance co pull out the stops for you.
With regard the plates, could explain why i am experiancing a small chatter on take off , will have to pull out thr pack and check if any of the flat plates were once dished. Will probably buy some spares anyway.

[adam]

standard clutches only have one dished plate with the dot facing out. I did have two with the slipper clutch.

[andyb]

Originally posted by stealth2
OK... the dished plate is actually one of the steels and you usually have two which "face away from each other". The idea is, to stop chatter and slipping when you take off. Over time the dishing reduces through use and heat and this has an impact on the wear rate of the plates. The reduction in the dishing renders the plates more flat and so the overall stack height reduces. Apparently, the stack height is critical (particularly in slipper cluteches which wear more quickly). The dished steels should be checked from time to time and replaced if they have lost the cooncave or dish effect. If the stack height gets below 0.4 -0.5 (as the distance measured from the central splines) then you get increased wear and the plates wear against the basket more significantly.

Just to say .... I'm no expert on this and am repeating what Rick Hackett told me when replacing my plates and basket before going abroad over a week ago. I am only sadly spending time writing this on a sunny Sunday because my bike was nicked in Holland on Thursday - just so you don't think I am complete anorak (only slightly!!!!!!!!).:sing:

I would describe them as facing each other! Take a dish bowl, sitting on a work surface. Now put another upside down on to the top of it.

that is how they should face, not the other way around.

[Stealth]

I'd agree with that. Excuse my poor phrasing. Definitely with inner circumferences not touching!

[Stealth]

oooops got that the wrong way round - heh heh!

Definitely not an expert........

[doogalman]

thanx guys.

[Shazaam!]

The key to smooth engagement is controlling the frictional force developed between the smooth plates (that are driven by the engine clutch hub) and the plates that contain friction material (that drive the rear wheel through the clutch basket.)

The amount of force developed between these plates is controlled by the stiffness of the clutch springs, specifically by the amount of preload on these springs. When the clutch is fully engaged, the friction force developed between the plates needs to be greater than the engine’s applied torque to prevent slip. About 430 lbs is needed on a stock superbike.

When you pull-in the clutch lever, the hydraulic pressure applied to the slave cylinder overcomes the spring’s preload and progressively reduces the force pushing the plates together until they begin to slip. During this time the dished plate(s) in the stack act to provide a progressive reduction in the inter-plate force as the plates separate a few millimeters and you get full disengagement.

When you engage the clutch the opposite occurs. The reduced hydraulic pressure on the slave cylinder allows the push-rod to move the spring-loaded pressure plate toward the plate stack (a millimeter or so) until the plates begin to touch. Keep in mind that when you move the lever you are changing the POSITION of the pressure plate. You have only indirect control over the forces between plates.

The forces between plates is controlled during this transition (between disengaged and fully engaged) by a dished plate that is included in the stack to smooth this transition. This plate acts as a spring (pushes back with a force) when it gets flattened between adjacent plates by the movement of the pressure plate.

So, the force pushing the plates together first come from the smaller force produced by flattening the dished spring plate, and later, a much greater force produced by the preloaded clutch springs.

I think you'll find that the dished plates don't loose their shape (spring effect) so they're reusable.

[Stealth]

Who is right??? JHP or Shazaam? Do dishes stay dishes or do they become flatties???

Shazaam, perhaps you could explain why slipper clutches as they get increased use, judder on take off. Is this not because the spring effect between the plates (i.e. the concave nature of the dieshed plates is diminished). Happy to be guided on this one.

[Shazaam!]

The higher the height of the clutch pack, the greater the clutch spring preload. So, as the clutch pack friction material wears-out, the pack height gets shorter, until the force between plates is insufficient and the clutch slips, at first under high torque conditions such as at launch, and later even when the lever is not pulled at speed. Time for a new clutch.

This is also the cause of the annoying phenomena of clutch “judder” such that when you release the lever, and while the spring plate is being compressed, the clutch springs can’t develop a sufficient force to prevent slipping so the plates slip, grab for an instant (causing vibration-induced slip,) grab, slip and so on, until the slipping stops as the engine torque is reduced when the bike acceleration eventually drops-off.

Here’s the Physics behind it. The friction force developed between two surfaces depends on whether the surfaces are sliding past each other or not. For a given amount of force pushing any two surfaces together, less frictional force will develop between sliding surfaces, than between surfaces that don’t. Once surfaces are together it takes more force to get them to slide than to keep them sliding. One they begin to side, however, they’ll keep sliding unless you push them together harder.

It’s these alternating higher-lower friction forces that cause the vibration that you perceive as judder. Sometimes adding a second spring plate to the pack will help to damp-out certain vibrations, so Ducati specifies a different number of flat plates, dished plates, plate thickness and stacking sequence for different models. The common spec however is stack height. Ducati clutch packs are stacked to 38mm ± 2mm.*

[rockhopper]

Do all the bikes have a dished plate then? I've changed the clutch on my 1999 ST4 and also stripped and cleaned it a number of times. I have never noticed a dished plate. I take the plates out and mix them around to even out wear (pressure and driven) and they all look the same to me!

[Edited on 5-9-2005 by rockhopper]

[Shazaam!]

There is usually one or more 1.5mm thick dished steel plates in a stack.*The 999RS has four. The curvature is barely*discernable so it is is marked with a* single "dot" (punch mark) near one of it's inner circumference serrations.* The mark is placed on the the concave side of plate curvature and should face toward you when assembled. If there are more, the second marked side faces inboard, outboard etc.
*
You can also check for a dished plate by placing it on a flat piece of glass and then pressing down with your*finger on the outer circumference of the plate.*The opposite*side (180 degrees) will rise off the surface of the glass.

[doogalman]

So! what is the small notch on the outer edge of the plates all about??????

[ericthered40]

Originally posted by doogalman
So! what is the small notch on the outer edge of the plates all about??????


yes what are they for? :puzzled:

[rockhopper]

I just line them all up. Looks nice like that.

[doogalman]

If you were to line them all up you would have a slight mis-balance in the weight of the plates.

[rockhopper]

Maybe the opposite side of the plate is made of ever so slightly heaver metal to counterbalance the cut out.