Clutch Creep

[peanutaxis]

What on earth causes it? It doesn't seem at all sensible. Why would the clutch spring start to fail just because it's being engaged? But then, I'm missing something....

[riff_raff]

With a carbon/carbon clutch, slight friction in the clutch plates will generate heat, and that heat build-up will increase the friction coefficient in the clutch plates. The process becomes a self-perpetuating cycle. More friction, more heat, more friction, etc. The clutch diaphragm spring is metal, and when it gets hot enough from being in close proximity to the carbon clutch plates it will begin to lose its heat treatment. When it becomes hot enough, it will anneal and turn very soft, losing all of its preload force.

[peanutaxis]

With a carbon/carbon clutch, slight friction in the clutch plates will generate heat, and that heat build-up will increase the friction coefficient in the clutch plates. The process becomes a self-perpetuating cycle. More friction, more heat, more friction, etc. The clutch diaphragm spring is metal, and when it gets hot enough from being in close proximity to the carbon clutch plates it will begin to lose its heat treatment. When it becomes hot enough, it will anneal and turn very soft, losing all of its preload force.

But the drivers do not sit there with the clutches slipping while waiting for the lights. So there's no friction, and no heat buildup.

[riff_raff]

But the drivers do not sit there with the clutches slipping while waiting for the lights. So there's no friction, and no heat buildup.

While I do not have any specific knowledge of current F1 clutch design, I do know a bit in general about carbon clutch/brake design. It's a fact that carbon friction materials perform best at elevated temperatures. Their friction properties increase with temperature, and the increase in friction as the material heats up can be quite abrupt. Combined with the very small thermal mass of an F1 clutch pack, it would be very difficult to smoothly modulate a cold carbon clutch in a standing start. Using a small amount of slip to create heat in the carbon clutch pack would reduce the transient rise in friction coefficient, and make modulation of the clutch during a standing start much easier.

The clutch slippage would also produce a small amount of load on the engine which would help with throttle response in a standing start.