Exploding Clutch disc
Manny,
The problem is in the construction of the disc, and its severe usage. First, the material is attached to the marchal spring (the wavy surface that the clutch material is attached to) with rivits. The rivits have limited contact (it's only a fastener, holding the material to the metal disc). They don't even have full thickness, as the rivits are recessed!!
Second, when the clutch is engaged/disengaged, the rivits work on the holes in the material, weakening them. Eventually, the failure is at the rivit holes, cracks appear, and the material disintegrates. Examine the fragments from the blown disc, and I'll bet you can see the curved surfaces from the rivits holes!!!
A simple, long lasting solution (better than simply replacing the disc with a new one, and waiting for the next failure), is to take a used disc to a clutch rebuilder (find them in the yellow pages, too). Ask the reabuilder to Bond the disc to the marchal spring. Doing this will give the clutch material much, much greater surface adhesion to the metal spring, resisting any movement from the engagement forces, or very high RPM.
An added bonus is that you can request stronger springs be installed at the center of the disc...won't loosen up as easily as stock, AND....
The Bonding method requires the epoxy be baked to fasten the material to the machal. The consequence of this is to collapse the spring. This is good for racing, as it makes the shifting interval shorter...faster engagement of the clutch. (Marchal springs are installed to soften the engagement to make take-off from a dead stop smooth. You don't need this for racing.)
I've done this many, many times with the cars we have built. The clutches will last the lifetime of the material...which should be forever if you co-ordinate your shifting. You can even remove the rivits after bonding, for even longer life.
Hope this helps.
Good racing,
Bill