David.... you'd need to read the original thread to see what I claimed. I do NOT claim we 'vibrate' the pedal.... we don't need to.
Our ride is SO stiff that the merest bump in the road surface makes the kart go 'lighter' and 'heavier' in it's 'ground pressure' throughout the braking zone. This is enough to allow the wheel to lock and unlock THEMSLEVES repeatedly as the kart reacts to the rapidly changing grip levels.
You are now moving into esoterics.... please tell us at what STAGE you judge the tyre to have LOCKED , non-locked and to be rotating at around 80% of the 'rolling speed'. Once the tyre is no longer in FIXED contact with the track, we are moving into the realms of Kinetic Friction where the object (tyre) is moving OVER the 'surface' (track).
Personally, I would judge the tyre to be EFFECTIVELY 'skidding' as when the contact patch is moving at ANYTHING less/more than 'static' in relation to the track! Other than the fact that the tyre is exchanging one contact patch for another, momentarily, your '20% below rolling speed' and 'locked' as, logically, identical. They both involve Kinetic Friction and do NOT^ involve Dry Friction.
The Karting technique (Semi-lock) only differs from the 20% reduction (that you accept as 'perfect') in that we don't do it as one SMOOTH reduction in rotation speed but that we give the same EFFECT in a series of short (duration and distance) LOCKS!
The 'threshold' argument does not convince me that a car driver CAN tell if he has locked a wheel or not! By definition, one of the four will ARRIVE at 'lock' before the other three as the grip level available to each tyre is NEVER consistent throughout a braking manouvre. Overall, the four tyres may AVERAGE-out as 'never being locked' but you can bet your bottom dollar that if you manage to get all FOUR to 'slow'.... at least ONE of them will be locking.... and releasing (or not).
It's MUCH easier for us karters and it's HOW we do it. When we lock ONE wheel.... we lock ALL the braking wheels at EXACTLY the same moment and on EVERY occasion. We can thus control that lock-release point MUCH more subtly and at will WITHOUT needing to vibrate our pedals..... the track surface does that FOR us!
I'd be honoured to think that I have been managing to 'slow the rotation' of my tyres when I brake rather than the MUCH more crude lock-release-lock that I THINK we I am doing.
Again..... I challenge YOU to go to the braking zone at Kimbolton's main straight and WATCH the tyres alternate between being LOCKED and moving forward a FRACTION. The locked moments are clearly visible as you can see the WRITING on the tyres at those instants!
Ian
|
|
