clutch thoughts
Turbo Mini Forums

Sorry it took so long for me to come round with the info - but I only just found it!

On 21/07/2006 21:43:29 TurboDave said:

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...

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

I don't know what to fully make of your response Robert, as I've told you the facts? I am a transmission engineer in case you hadn't realised (apologies if that sounds off, but there is no other way of saying it).

The fact is - when you move out of one gear, and into the next gear, the clutch is OPEN. Sure, you get the minutest of drag, slightly more from a badly-adjusted clutch - but that is a TINY proportion to the inertia of the friction discs alone.



Your quote "therefore having a lighter flywheel can make a very dramatic change in the speed of synchronization" is at best - optimistic... Sure - a lighter flywheel will, in those milliseconds that the engine is decelerating just as your foot first touches the clutch pedal (as the other foot eases off the accelerator) and until the clutch is disengagaed, make a slight difference and indeed help the synchros as it's seeing a 50-100rpm reduction in differential speed. That is nothing like enough to make a difference however - IMO.





Jumping back on the twin-plate setup you showed a picture of - the pre-verto diapham doesn't have sufficient range of clamping to tolerate the wear of four friction elements. The verto (turbo) one is a little better however, but still not quite there.

Edited by TurboDave16V on 23rd Jul, 2006.

that ok dave ,that doesnt seem off to me but very pertinant to the subject ,as i said ,my perspective may be total drivel or have a percentage of truth in it ,and im only going by seat of the pants experience ,not laboratory results ,however, i do think reducing the rotating mass ,however and wherever its done ,does ,in my exp ,seem to make a hell of a diff to gear change speed ,and was trying to find an explanation for that :) if it did reduce the differential by your higher estimate of 100 rpm ,and the next gear was a 500 rpm drop yhis would be a change of 20% which seems quite a lot to me?anyrd up ,
debate is the mother of research and its great to have a transmission engineers input on this topic,
regards robert.

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

just went and assumed my yogic thinking position ( one finger in ear left foot off floor and a small radish in left nostril)
and thought about you saying dave about the sufficient range of clamping ..
if the diaphragm acts like a cone ,and the furthur you push it in increases pressure up to the point where the cone goes past max mech adv ,and then gets steadily weaker ,couldnt one design the install heights to create an increase in clamping force as it wore ? by setting it say 100 lb less pressure past the max point ,then as it wore it would increase by the 100 lb gradually till it reached max adv ,then reduce again to the 100 less ,and that would give a greater window of wear and usage ,if the initial weight of 100 less was enough to get the job done ,is there any microscopic vestage of truth in this theory ??

Edited by robert on 23rd Jul, 2006.

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

Yeah - that is the only way you'd manage to achieve it.
Biggest problem is the spring characteristics of the diaphram cones; the load drops 'slightly' then increases hugely as it goes over centre - hence once you've set up your clutch to do work right for a torque capacity aspect, you're then going to run into damaging axial loads on the crank thrusts.
Something else I'd omitted to say - multi-plates need greater axial travel to cleanly disengage. Not much more on a sintered plate (around 20-40 thou) but you can double this figure if usingf the AP organic plates that are sprung apart.... It all adds up to a bad design.

That is why a clean sheet of paper needs to be adopted IMO. Enough f&*%ing about with 20/40 year old designs - do the job right!

yes id forgotten bout that greater clearance prob , and the marcel cushioning part , i had a paddle plate in the tvr ,and then went to a long type organic , it needed at least 40 thuo more movement if i remember correctly ,that a good point thanks for reminding me.

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

Can anyone here actually test clamping pressure of a Verto clutch ???

I have a very old rusty one here that I kept, which would be interesting to test. I'd say its close to what my old 1000cc mini verto is like, and it grips well.
I'd gladly send it to anyone who could test it....just out of curiosity.

Are there any multiplates available for the Mini ??
I'd think it would be difficult to design, based on how the verto bolts to the crank/flywheel.

Then I seen this multiplate carbon clutch the other day on another forum.
It would be bloody expensive, but the way the friction plates mate with the cover were interesting.





It would be a lot easier to make a flywheel with an open back and the cover bolted from the opposte side, like the verto assembly with this style of friction plate.

Any thoughts ?

Another option, although it can be horrible to drive, a lot of big power clutches that use a single pate, run a friction plate with an iron surface. They seem to have huge torque ratings compared to cerametallic and organic. They arent nice to drive, but they are driveable.

Edited by stevieturbo on 28th Jul, 2006.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I dont see why a multiplate clutch would be hard on crank thrusts...

Generally speaking, a multiplate will grip better than a single plate, for any given clamping pressure. So it could actually be made lighter.

The verto in my car, is extremely heavy for what it is, and I never had any thrust issues. But....last time I had the engine out, which is some years ago now, the fingers are quite badly worn, where the release bearing cup presses onto them. I must have done some 40-50,000 miles on that cover. Ive had a new friction surface fitted a couple of times, as it was the only clutch I ever had that gripped.

Just had a look at the Lynx AE....

It doesnt mention that its a single or multiplate ?? And its only rated to 160bhp.

Is that a conservative rating ?

Edited by stevieturbo on 29th Jul, 2006.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I can test the clamping - and torque capacity - but live a little far away!

The verto designs don't eat thrusts becuse the release loads are a hell of a lot less than a pre-verto as the fingers are operating like levers, effectivly reducing the load being reacted at the thrusts by (don't quote me here - this is a random number) around 1/4 - but requiring more axial travel to dis-engage of course!

Those pics above are interesting Steve. I'm guessing the inertia of the solid carbon plates is pretty low, which is why we need to avoid multi-plates if possible.

End of the day, we're only trying to put (approx) 250lb ft through a 7.25" plate, and the double-grey is proof that this is well inside the scope of the AP organic friction plate. It follws therefore that it 'just' needs an equivalent clamping load to the grey, but with the diaphram 'finger' style spring as adopted by the Verto.

Problem with the Lynx setup is that it's limited itself to a small diaphram in an attempt to keep the flywheel inertia low. The designer didn't fully - or didn't consider it important - appreciate the size of the bore you need to get over the verto centre as used in their design.

Even so - I know roughly what spring is used in that setup; and I'm actually suprised that they're experiencing thrust issues with the pretty light spring that must be fitted in that setup if it's only good for 160lbft (I reckon about 120 lb ft as a guess).

I've gone about it a different way - sourcing an OE diaphram that in the land of V8 engines is designed to have high clamping loads on a single plate. I guarantee those after an inertia equivalent to a KAD allow flywheel and backplate will be very dissapointed - but for everyone else, it will do the job!

what about a 200mm clutch plate?
I have a peugeot 200mm clutch plate, the mini clutch plate center can be adapted on it.
would this mod will increase the load it can take? by how many?
fab

200 mm plate... Well it'd be a little better - but not enough to make a real difference to the high-torque problems we have.
You'd also struggle to fit it inside the standard setup - to the point that you're aleady modifying parts.

I'm also of the belief that 'service items' (like clutch plates, brake pads, etc should be 'off the shelf' items - ie standard fit ones - that anyone in the world can purchase easilly.

143 lb /ft by the formula fab with a 200 mm plate ,thats about 20 lb/ft more .

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

thanks Robert, but Dave struggling thing are true :( . I mesured some flywheels and back plates(verto 1000 1300 pre verto 1 piece 2 piece and ulight)
verto (1000 and 1300 are the same) set up will quasi impossibly take more than a 192 mm plate..,and 5mm more inner (130mm diam on center)
pre verto,will take at least 190mm with some turning on the back plate (an easy job),and 10mm in center (125mm inner)
ulight will take at least 185mm but 120mm inner
so the gain with plates on vertos is near 0.
but with pre verto :

grey diaph;190mm (unstead of 180), and 125mm unstead of 135. then paddles (generally said to take 30% more load).what about?

pre verto u light:
185mm outer 120mm inner grey diaph and paddles?

what is the grey diaph. pressure ? anybody know ?

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

dont quote me on it, but I THINK it is around 1100 lbs clamp load, if thats what you are after...

thats great info andre, do you know where it came from ? regards robert.

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

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=9982

that one covers a bit about the clamp loads on the pre verto ones...

had a read in Des Hammils book:
blue:854 pounds
orange:1178 pounds, torque :120foot pounds
grey:1280 pounds,torque :138 foot pounds

thats good info fab ,thank you ,so maybe the verto turbo plate and cover are about the same as the orange... i wonder what people use with 200 lb ft ,maybe the double grey..

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

the double grey is 1250 lb..,and that works out to 176 lb ft using the formula ,but ae give it a 138 lb ft rating , formula wrong ,or ae using a super cautious safety factor ,it seems big bhp cars are surviving with the double grey ,so perhaps the latter!

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

so , done a bit more resaerch, and think a twin plate may actually be a poss with a verto and two organic plates withuot the marcel cushionning in them ,it depends i think on how easy it is to make a plain plate for the space between the 2 driven plates ,and how far the centre of the driven plate sits on the primary gear ,so more resaerch to do ,...
another avenue im exploring is the idea of taking the pressure plate apart ,and sticking a second diaphragm spring in it ,and so running two !!!
intensive care here i come !!!
robert.

Edited by robert on 4th Sep, 2006.

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