Clutch Kiss point

[mach11]

Hey all,

The other day, david coulthard was explaining about the procedure on how drivers engage the clutch paddle shifts in the steering.

He says, the drivers use one paddle in a half pressed mode and the other in a full enagage position. Now as the lights go off... the fully engaged pedal is released and as the car begins to gain speed the other paddle is released....

1. Why is this done??
2. Is this something called clutch kiss point??
3. I thought the clutch was engaged automatically???

[raymondu999]

I'll do my best to answer your qn's.

1. There is just 1 clutch, but operated with 2 paddles. The clutch follows whichever paddle is pressed the most. They hold one half-in and one full-in so that when they release the one that is full-in, it snaps to position, held in by the paddle that is held half-in. Otherwise, they'd have to release 1 paddle quickly AND be specific and precise to move it to the optimum bite point for the best launch.
2. I believe it's called the "bite point" rather than the "kiss point"
3. The clutch is engaged automatically if you're about to stall the engine. No clutch is engaged, engine running, and the tyres are stopped. That would stall the engine, and the clutch kicks in to stop this. That's anti-stall

[WhiteBlue]

raymondu999 has explained the main points quite clearly. You have to consider that F1 cars start with a semi closed, slipping clutch with a clutch torque well under the full level available from the clutch. The proper clutch torque launch value is pre determined by the driver with his race engineer. The two lever method insures that the driver launches with exactly the pre determined amount of torque and slip. After the immediate launch when the revs have stabilized the driver drops the second lever for full clutch torque and the the slip is eliminated.

[mx_tifoso]

raymondu999 has explained the main points quite clearly. You have to consider that F1 cars start with a semi closed, slipping clutch with a clutch torque well under the full level available from the clutch. The proper clutch torque launch value is pre determined by the driver with his race engineer. The two lever method insures that the driver launches with exactly the pre determined amount of torque and slip. After the immediate launch when the revs have stabilized the driver drops the second lever for full clutch torque and the the slip is eliminated.

A highly crude way to establish vehicle inertia.
...

[mach11]

raymondu999 has explained the main points quite clearly. You have to consider that F1 cars start with a semi closed, slipping clutch with a clutch torque well under the full level available from the clutch. The proper clutch torque launch value is pre determined by the driver with his race engineer. The two lever method insures that the driver launches with exactly the pre determined amount of torque and slip. After the immediate launch when the revs have stabilized the driver drops the second lever for full clutch torque and the the slip is eliminated.

I understood how the driver works the paddals.... but i could not quiet understand the part where the slip is involved...

Also, this clutch torque value... what is that???

[WhiteBlue]

I understood how the driver works the paddals.... but i could not quiet understand the part where the slip is involved... Also, this clutch torque value... what is that???

If you look at the steel disk springs that compress the dry clutch package you can imagine that the clutch can be set with different forces by those springs. The force depends of how much the whole package is compressed. The spring force is translated into torque by the clutch. What the two lever system does is simply adjusting a partial compression of the clutch springs for launch. With the second lever the full spring load (full clutch torque) is applied.

[mach11]

thanks white blue,

But i need to read more on this... off to the books!!!!!

[mx_tifoso]

I understood how the driver works the paddals.... but i could not quiet understand the part where the slip is involved... Also, this clutch torque value... what is that???

[img]http://i805.photobucket.com/albums/yy338/aklracing/F1clutch.jpg[img]

If you look at the steel disk springs that compress the dry clutch package you can imagine that the clutch can be set with different forces by those springs. The force depends of how much the whole package is compressed. The spring force is translated into torque by the clutch. What the two lever system does is simply adjusting a partial compression of the clutch springs for launch. With the second lever the full spring load (full clutch torque) is applied.

...
When the clutches became small in diameter and the flywheel disapeared it turned the transmission into something barely controlable by a driver.
That is why this dual paddle compromise had to be cobbled up.
It is less efficient than the old method, so lots of effort had to go into material development to help the slipping components survive.
Backward step

[Pup]

Don't some teams use two separate, concentric clutch plates which operate separately at the start, but in unison when changing gears? We've heard on more than one occasion the drivers talking about the 'second clutch'. Or is it that they are simply referring to the second clutch paddle?

[RacingManiac]

...
When the clutches became small in diameter and the flywheel disapeared it turned the transmission into something barely controlable by a driver.
That is why this dual paddle compromise had to be cobbled up.
It is less efficient than the old method, so lots of effort had to go into material development to help the slipping components survive.
Backward step

Isn't everything in engineering about playing with trade-off and optimizing where you can? Small diameter clutch and flywheel means also much lower crank axis and you drop your CoG way down, which has benefits in other area that are important to the performance on a track....

[richard_leeds]

I can't see any rule that prohibits the use of two clutches.

As for controls my understanding is that teams use a single clutch with two controls as described by Raymond. The rules prohibit a preset biting point on the paddles, see 9.2.2.

So, when the driver is on the grid the use one hand to fine tune a paddle at the biting point, and the other is used for full on / full off. So a start consists of:

1 - Red lights - Full off hand & Partial hand -> full off clutch
2 - Lights off - Full on hand lets go & Partial hand holds -> partial clutch
3 - Gain traction after initial wheel spin - Both hands let go -> full on clutch

9.2 Clutch control :
The following applies only to the main drivetrain clutch or clutches, any clutch used exclusively as part of a KERS is exempt.

9.2.1 If multiple clutch operating devices are used, they must all have the same mechanical travel characteristics and be mapped identically.

9.2.2 Designs which allow specific points along the travel range of the clutch operating device to be identified by the driver or assist him to hold a position are not permitted.

9.2.3 The minimum and maximum travel positions of the clutch operating device must correspond to the clutch fully engaged normal rest position and fully disengaged (incapable of transmitting any useable torque) positions respectively.

9.2.4 Designs or systems which in addition to typical inherent hydraulic and mechanical properties are designed to, or have the effect of, adjusting or otherwise influencing the amount, or rate, of engagement being demanded by the FIA ECU, are not permitted.

[flynfrog]

raymondu999 has explained the main points quite clearly. You have to consider that F1 cars start with a semi closed, slipping clutch with a clutch torque well under the full level available from the clutch. The proper clutch torque launch value is pre determined by the driver with his race engineer. The two lever method insures that the driver launches with exactly the pre determined amount of torque and slip. After the immediate launch when the revs have stabilized the driver drops the second lever for full clutch torque and the the slip is eliminated.

I understood how the driver works the paddals.... but i could not quiet understand the part where the slip is involved...

Also, this clutch torque value... what is that???

Have you driven a stick shift car before? You don't just drop the clutch you slowly release it slipping it as you go. Once you have enough speed you can let it the rest of the way out. The two lever system lets the driver drop the clutch to the optimal point between tire spin and keeping the engine in optimal RPM range. the second lever lets him let the clutch the rest of the way out. See if you can find a video of a driver practicing launches and listen to the car it might make it more clear.

[Pup]

Hmm. I just can't imagine that there is enough feel or range of motion in a steering wheel paddle for a driver to control confidently.

[marcush.]

Hmm. I just can't imagine that there is enough feel or range of motion in a steering wheel paddle for a driver to control confidently.

errm ...the paddles are not levers on hydraulic pumps,are they? so if at all the
"feedback" is generic anyways...or am I leaving out something in my view ..the lever would act on a potentiometer or switch to trigger the electrohydraulic valve
releasing the clutch...not much to feel in the paddle there?

[raymondu999]

I think he's talking more on how people "feel" it rather than the sensation transmitted through the paddle Kind of like how we can feel a brake with our right foot (Well I can anyways) and a clutch pedal with my left but not the other way around