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When technologies and problems collide…

Over time, it has been interesting to observe how technologies developed outside the immediate high performance or motorsports communities become potential solutions to problems found within these automotive market segments.  Here’s a vivid example.

Around the time the so-called “slider clutch” evolved in drag racing (circa 1968), I had the good fortune to be working with a high performance industry pioneer, Paul Schiefer of Schiefer clutches.  On my way to joining Edelbrock, for whom Vic was not one of Paul’s favorite people, a problem had arisen with deliberately-slipping clutches.  In a number of cases, excessively heated clutch components were failing and exiting Top Fuel and Top Gas cars, resulting in catastrophic results and in some cases driver fatalities.  The situation had arisen as a result of one notable Top Fuel dragster that produced virtually a “smokeless” run, trimming its elapsed time below the car’s best to date and causing other racers to experiment on their own for comparable results.  There were no guidelines and no limits to which the parts could be modified, only gauged by performance gains and too-often bad consequences.

“We’re allowing our friends to kill themselves, Jim” was Paul’s observation.  “Our parts are failing because of what the racers are doing to them and we need to find a solution.”  Beyond his characteristic feelings of compassion for any troubling situation, Paul wanted to fix the problem.  It was completely his style.

The situation was exacerbated by the fact there was more than one way to modify a clutch to create slippage.  Static spring pressure in the pressure plate could be reduced (often excessively), centrifugally-assisted release lever weight could be decreased, or actual spring removals were all among the more common approaches.  Paul had already perfected a way to spray a copper-based material onto flywheel and pressure plate friction surfaces, but even these were giving way to the grossly-excessive temperatures to which they were being subjected. 
Top Fuel and Top Gas clutch packages were then a combination of flywheel and two friction discs (typically with sintered iron surfaces) separated by a so-called “floater” plate and all bolted to the pressure plate assembly.  While it would be later that the number of friction discs and floaters would be increased, the initial problem centered on the two-disc system.  Keep in mind that the flywheel and pressure plate friction surfaces were coated with the copper-based composite coating. 

As racers “experimented” with lower total clutch pressures, the attending slippage allowed heat generation that exceeded the limits of the materials involved.  On more than one occasion, during night-time races, I saw what was “white hot” clutch parts thrown high in the air and cars literally cut in half by the explosive force of exiting pieces.  These were all in front-engine cars where the driver’s legs and feet where in close proximity to the engine’s bell housing.  No further description of the environment for potential disaster should be necessary.
An immediate solution appeared to be the identification and application of friction surface material that would reduce that amount of heat delivered to friction surfaces. Paul reckoned that if we could prevent critical parts from absorbing the high temperatures developed during slippage, it might begin to calm the storm.  As it turned out, a considerable amount of aerospace-related research was afoot in the greater Los Angeles, CA area, so we began searching that landscape for help.

 

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