clutch thoughts
Turbo Mini Forums

had a think about clutches the other day ,and remembered that the clutch on my v8 has a system of rollers that fly out due to cetrifugal force ,and create more pressure on the plate , i think it goes up from 2200 to 2800 lb .
then i thought hey ,dont centerforce do something like that for diaphragm clutches ,where theres a ring of weights fixed onto the fingers of the diaphragm halfway from the release bearing surface down to the pressure plate body ,that also fly out and create more force ,wouldnt this be just the thing for a nice launch at the track with a soft cluch giving a bit ,then it grips at higher rpm ? i dont know if centerforce are still about but if they there ll be pics on their site ,should be quite easy to make some weights and try it !!
regards robert.



heres what i mean .

Edited by robert on 18th Jul, 2006.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

For what its worth, I think this is worth considering further.

This is a simple, proven method of improving the clamping pressure on a diaphragm clutch.

The Centerforce system just seems to use weights that fit between the diaphragm fingers and are held in place with a ring.

Thats a lot simpler than the old slipper clutch system that the top fuelers used to use in the 70s. They had pivot points and special arms for the weights. But then they used to tune the clutch by adding/removing washers from the arms.

Do you know if it possible to get hold of the weights separately?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

i just had the idea ,axel , and have done no research at all!! :$ but i would try to get a look at one and then make the weights , or call up centerforce and say oi ,can i have one of these clutches in the right size for my mini and see what they say .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

I've got a spare used 0.095 thick diaphragm verto cover that we could use as a trial.

But, I dont have an engine that will give out enough torque to test it!

I'll do some calcs to see how much extra clamping force we can generate from a selection of weights.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

cool , those are going to be some complicated calcs,with the force of the weight flying out ,acting in a rotating pivoting motion on the finger the flex of the finger ,the tangential force of the weight the distance of the weight from the pivot etc ,blimey !!prob better just to make it and spin it and see what the forces are with some sort of pressure plate force guage .probably hydraulic accting on a guage

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Nah,

Calculating centrifugal force is easy. mv2/r.

Simple vector diagram to calculate the effect of the centrifugal force on the fingers, then multiply it by the ratio of the length of the diaphragm fingers to the pivot point and the length from the pivot point to the point of contact on the backplate.

Need to take some measurements first though.

We also need to have an idea of the starting point. What is the clamping force of the standard verto 0.095" clutch?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Big probs I see with this system is that it's not putting a huge amount more load on the setup where you actually want it - ie 3200-3500 ish RPM.

It also needs the verto setup.

That said - it looks bloomin easy to make, and could well be an 'icing on the cake' to get you that little bit more clamping force.

The 'pukka' centrifugal drag clutches use the weights where they make more difference however - actually at the outside of the 'diaphram' I recall?

Right while the creative juices are flowing and before I get packing for hols, I thought I'd do these calcs.

Anyway, I've calculated that if you put 15 weights, each of 15grams at a radius of 40mm on a diaphram angled 10 degrees to the cover/flywheel then at 3000rpm you get an extra 15kg clamping force.

At 6000rpm you get 60kg because of the square law relationship of force and rpm.

Will this make much difference?

Vmax Stuart posted some data for verto clutches last year. He stated that the release force for the turbo clutch was about 80kg I recall. I guess that the clamping force is therefore around 100kg. (this might be bollocks)

So the answer maybe not a lot, perhaps 110 lbft before it slips instead of 95.

Something to consider, would you be able to disengage the clutch at 7000 rpm on an up-shift with all that force acting against you?????

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Edited by robert on 21st Jul, 2006.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Robert I've factored the force exerted on the fingers by the Sine of 10 degrees to allow for the angle of the diaphragm.

I've assumed that the weights would be placed 25mm from the pivot point of the fingers which happens to be about the same distance from the pivot point to the backplate, hence there is no leverage advantage to the force.

I've then factored the force at the other end by the Cosine of 10 degrees where the diagphragm spring bears on the backplate.

It's all taken into acoount, the only question is, is 10 degrees enough and does it change much during operation?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

axel its great that you mathematically conversant with these calcs ...but (theres allways a but)where have you taken into account
a) twisting force on the finger changing ratio and depleting the force to the pivot
b)the leverage effect of the block on the finger in a twisting motion ,which would have more effect at the face of the block furthest from the finger and least effect at the face adjacent to the finger ,where the forces are in shear.
c) the hieght of the block from the finger ,thus creating a leverage ratio the further it gets from the finger ,and changing the effective leverage mass from half lever half shear (approx) to wholy leverage .
robert

Edited by robert on 21st Jul, 2006.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Robert,

I accept that the calcs need more refinement, however, I believe that they show that it may be possible to increase the clamping pressure by 20-50%. This is similar to what your V8 clutch achieved with weights.

You can add more weight and maybe the 10 degrees is only conservative, but at the end of the day, this is not a solution that is going to allow you to use a verto clutch on 200hp!

It might be OK on a mild 998 Turbo though.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

au contrair axel mon ami !!!
i cant see why it cant create a torque capacity in line with its percentage pressure increase so if one sticks on enough weight ,and mounts it far enough from the fingers so it really twists the hell out of them ,well...the world is your oyster 400 lb /ft anyone!!!

i think the biggest prob would be making sure they run true.....can you imagine the vibration if they ran off centre !!!

Edited by robert on 21st Jul, 2006.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

You can't increase the weight much because of limited space.

The verto throughout bearing is about 70mm dia. and the pivot point is at about 130mm dia.

The closer you get to the pivot point, the less effect you can achieve.

I think 15gram weights on a 40mm radius is easily achieveable, but more, I don't know.

Having said that, I think we should give it a go.

Start simple and build on it, who knows how far it can be developed.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Good point Peter,

My proposed 15 off 15 gram weights add up to 225gram - half a pound - at a 40mm radius - so not a lot - just extra crank inertia effectively.

Might just about replace the weight machined off for the 36-1 tooth pulley. LOL.

However, something to consider if we go much heavier possibly.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

if we use this formula from peters link .
(od+id)/4=average radius of the disc..
and torque capacity=no of friction surfaces*radius in feet*coeff of friction*pressure.
then imeasure my old turbo plate at 181mm od132.38 id...
so .257ft is our ''r''
so hypotheticaly just as a test

2*.257*.25*1000=128.5lb/ft

sooo if we increase pp to 1500 lbs

lets see if that gives us a 50 percent increase in line with the pp increase

2*.257*.25*1500=192.75lb/ft
hmm seems so lets try 2000

2*.257*.25*2000=257lb/ft

ok so thats clear ,
then lets try a 1500lb effect pp with the 190mm plate

assuming a width similar to the 180 plate gives 190+140
so .270 ft

so 2*.270*.25*1500= 202.5 lb/ft



hmmmmm how much torque is a 200 bhp min putting out ,any graphs anyone ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Probably about 200 lbft.

The problem with the above is your are assuming that the std verto clamping pressure is 1000 lb. I think it is a lot less than that.

Work your calcs backwards.

We know that the std verto slips at 95ftlb so what clamping force is it exerting?

EDIT: about 750 lbs.

Edited by Paul S on 21st Jul, 2006.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

ah no axel that was all meant to be a bit hypothetical ,although i thought the turbo plate and cover had a bit more i think someone mentioned about 120 lb /ft .may be my imagination tho!!

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

heres another neat idea ,running 2 pressure plates with a plain plate in between
this would give more capacity with no more pressure ,ok lets run it through the formula..

4*.270*.25*750 (min lb)=202.5lb/ft

or
4*.270*.25*1000(max lb)= 270lb/ft!!!
WOOF!!

Edited by robert on 21st Jul, 2006.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

2 plates = twice as much work on the synchros. That's why I'll not be using them personally.

i dont know peter ,i just came across these pics on the net ,i do know that one can get a light flywheel and that id doubt the weight of another plate and plain plate would equal the weight of the reduction in a lightened wheel ,so even with 2 extra plates it may still be poss to get it lighter than a stock set up . its an intersting idea though?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

The analogy you have is on the right lines, but you're off the mark.
The inertia that we're 'concerned' about increasing by doubling up the clutch plates is called 'reffered inertia'.

Think about when you change gear - your left foot is pressing the pedal hard into the floor - and the clutch is 'open'.
When you disengage one gear, and pull into neutral the clutch disc(s) are rotating at the speed the last gear was being driven at (from the road wheels once you opened the clutch).

In short - the mass of anything attached to the crankshaft / flywheel is irrelevant in regards to the work the synchro has to do.

Once you start moving onto the next gear, the synchroniser has to slow down - or speed up next (still not engaged) gear. Remember, the synchro hub(s) are atached to the mainshaft, which is permanently connected to the wheels).
Attached to this (about to be synchronised) gear is - via numerous gears and shafts - the clutch friction disc(s). These therefore have to be sped up/slowed down - and all through the ratio of the (soon to be)synchronised gears.
Generally, upshifts are the easier to work around. Downshifts are the real killer for any synchro (I'm struggling with this right now at work!!!!)



Anyways, a drag-strip race is never going to be nice on synchro's no matter what - and I know from my personal knowledge of synchro design, and the noise my (perfect condition) synchros make when dragging my mini, that the stock units are already overworked.

That said - The closer ratio's of the SCCR transmission - together with the single organic plate are all helping make things better over a stock metro transmission with the heavyweight sprung friction plate.
But let's be honest. Mini synchros are fragile and antiquated. A modern synchro like in your mums corsa has around three times the friction area of a mini synchro. Or maybe if we're talking about a dual-cone (pretty common on very modern 1st/2nd synchro transmissions) six + times the friction area!
That is a BIG difference!




Incidentally - The Verto 'Turbo' cover has a peak clamping load of 960 lbs (note the use of the word PEAK), and a release load at the sleeve of 320 lbs.
My own measured data.

I aim to have a clamping load of around 2000lbs, and release load of around 300lbs peak on my setup...

Edited by TurboDave16V on 21st Jul, 2006.

Dave, Thanks for the info on the std verto clutch.

If it already has clamping loads as high as that then there is no point in pursuing the centrifugal assisted route.

Even if you could get enough weight in, you need to turn the force through 90 degrees along the diapragm fingers. With the diapragm at 10 degrees, you lose 85% of the force.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."