Tim,
Clutches truly have there own personality. Every manufacture is using a different recipe in the friction material and design. A compromise in clamping force to hold horsepower and maintain smooth engagement for driveability. My experiance lately has been mixed, we used a dual friction kevlar based friction on one side of the disc made by spec and mcleod and the spec was horrible, chattered like crazy, all with a brand new engine, well balanced fresh cut flywheel and new mounts. The mcleod was ok, but had a slight chatter when hot, needed to be slipped slightly. We ended up using a stock LS7 clutch and it had fantastic engagment, it appeared to be some kind of organic mix on both sides. Also had good expeiarances with the centerforce dual frictions smooth with good clamping force. If your trying to harness over 600 hp and launch the car agressivelly then just go with a dual disk.
You didnt mention what your using. Heres some tech on how those little springs and center wave plate between the frictions help dampen and prevent chatter.
Clutch linings. The linings of the disc used to be made of asbestos. They're now made of fiberglass or other materials that do not contain asbestos due to the effects of asbestos to our health. However, asbestos provides superior cushioning and better wear than the newer materials at this time. The linings contain copper and/or bronze metal strands to aid heat dissipation and to help prolong disc life. The linings have grooves cut in their faces for air ventilation and to help prevent lining dust build up. Dust build up causes chatter and slipping due to the slip/grab action of the dust. The 6 to 9 springs around the disc hub may range from loose to tight. Not to worry, the looseness/tightness does not affect the operation of the disc. They're there to asborb shock and help eliminate engine pulsations (lumpy cams). By far the most critical element of the disc in eliminating chatter is the "marcel". This is the term given to the crimped plate, or wafer, between the 2 clutch linings. The purpose of the marcel is to prevent clutch chatter by giving the clutch disc some "give" during clutch engagement. The marcel also helps prevent the lining from sticking to the flywheel and/or pressure plate (due to the spring effect of the marcel) when the clutch is being disengaged. The marcel thickness (the distance the linings are held apart by the marcel when the disc is not under compression) will vary depending on the type of use the disc is designed and built for. Basically the thicker the marcel, the smoother the clutch will engage and the spongier it feels to your foot. The absence of marcel makes the clutch grab, but makes for a much more postive lockup (less slippage and ability to handle more horsepower). As the marcel thickness increases, it will require more clutch lever travel to engage/disengage the clutch. A pure drag/race car clutch marcel will be from 0.000" to 0.010" since engagement is quick and abrupt and chatter is not a problem. Truck clutches use marcels in this area also. A street/strip clutch will generally have marcels from 0.015" to 0.025". Pure street clutches will use marcels in excess of 0.025". A super soft clutch uses marcel in the neighborhood of 0.030" to 0.040". Mine is 0.025" and works well with no slippage and no chatter. When the marcel gets up to 0.030" and more, it may require as much as 60% of the clutch travel to engage. In 1949 or so, Ford advertised a "cushione clutch" in the Mercs and Lincolns. With the newer disc materials the marcel thickness has increased to 0.050" to 0.060" since there is little cushioning affect of the harder materials. When marcels are used, the linings are riveted. When they aren't used, the linings are bonded or riveted and bonded.
Hope this helps- Rich
|