D Appleby Flywheel & Sintered Twin Plate Clutch exp.

[mikey k]

Bouldermobile said:

Also, please excuse my ignorance, but why would a flatter design wear quicker than the pointed design, given the extra surface area in contact, etc.? Would the clutch assembly wear (i.e the bit in contact with the bearing) wear more or less depending upon the bearing design?

Would the clutch fingers be different on a sintered assembly when compared to an organic assembly?

The issue is maintaining the maximum contact area as the "fingers" move.
As you say it depends on the profile of the finger, if its not flat a curved release bearing will better maintain the contact area as the bearing moves in and out.
So flat fingers = curved bearing and profiled fingers = flat bearing

This isn't an Aston set up but gives you the idea

[Bouldermobile]

Mikey, thanks for the explanation.

To my untrained eyes the fingers shown in the photo in post #26 look quite flat when compared to the fingers shown for organic clutch on the current DAE website, and certainly look flatter than the fingers on what is left of my old clutch, do you concur when comparing the photos? Of course, internet photos are notoriously unreliable!

Also, did AM change the clutch design over time or just refine the bearing angle, hence the different part numbers?

Edited by Bouldermobile on Friday 17th April 11:36

[BamfordMike]

JohnG1 said:

The life of a race car clutch is very different to that of a road car. You don't slip a clutch on a race car and you don't need to edge forward in traffic or reverse up a hill...

I wonder if anyone has any experience of the life of this non-standard bearing in normal road use?

There is no race bearing, the factory 4.3L flat nose road car bearing is used on the race cars / clutches, so it's more a case of wrong road car bearing fitted to type of road car clutch in use. I don't think anybody would have experience of the factory flat nose release bearing running on a factory V12V twinplate clutch, because this arrangement deviates from factory specification. But further, I see no reason / benefit / gain from deviating from how the factory specify fitment type - so why would anybody do this???
Yes, the use of clutch in race world is mostly 100% on or 100% off, whereas road use needs a lot more modulation / slip and gradual change in clamp force. It is this state where the mismatch of flat nose bearing (instead of bull nose) will present the most issues / cause the most problems and wear prematurely as a result.

Bouldermobile said:

did AM change the clutch design over time or just refine the bearing angle, hence the different part numbers?

Edited by Bouldermobile on Friday 17th April 11:36

no, this is not so much a refinement over the years from flat nose to bull nose, more a requirement to change, a 'go - no go' 'fit or mismatch'. The current 4.7L singleplate clutch still uses the flat nose bearing whereas the current twinplate V12VS uses bull nose bearing. Stands to reason that if the bull nose was a refinement it would carry across the range, it clearly cant because would result in error.

mikey k said:

So flat fingers = curved bearing and profiled fingers = flat bearing

JohnG1 said:

The thrust bearing needs to match the clutch and NOT the engine it looks like you have the wrong part fitted.

Exactly these two comments, here is why...



Sintered twinplate race clutch on left is profiled fingers = flat bearing.
Organic road car clutch on right is flat fingers = curved bearing

This could be easy to confuse because the standard clutch in the car was a single plate with profiled fingers, and the sintered twinplate clutch from race world was profiled fingers too, both needing flat nose bearing. But, V12V factory organic twinplate clutch requires bull nose bearing and this type of clutch has never been fitted on the V8 range, hence why the comment the bearing matches the clutch not the car is correct.

here is picture of flat nose bearing sitting correctly on the sintered clutch



here is picture of the error state flat nose bearing sitting on organic twinplate clutch, the paint pen mark shows boundary of contact point.



here is picture of the organic twinplate clutch showing witness marks where the correct bearing was sitting, and the white paint pen mark of where the flat nose bearing would contact



Potential problem of flat nose bearing on flat finger clutch:
The picture above is of an un clamped clutch, but, once fitted to car the fingers will clamp meaning they will move into a much flatter position. As the paint pen mark shows, the flat nose bearing on flat fingers will now be acting upon the finger much further 'up' it. The fulcrum point is therefore no longer at the end of the finger, the stresses on the finger will be greater and cause premature wear to clutch. As for the bearing, it will be introduced to a side loading which will prematurely wear the bearing. However, the system is working but my guess is with a 'cam effect' to pedal and with shorter longevity than the system would of returned with correct bearing type. I dont think the OP should be concerned the clutch system will fail in the short term, but.....

x31james said:

the slight angle difference where it meets the clutch fingers doesn't seem to cause issue its been done like this on sintered version for years on the race cars with no issues... hope this helps

No, its not a slight angle difference, its a complete changing of fulcrum point from tip of finger to along the finger.
Yes, the sintered clutches have indeed run with factory flat nose bearings, that's because the fingers, like the road cars single plate clutch, are profiled. But, there has never been a V12V road car clutch fitted to a race car, if it were the factory would have fitted the bull nose bearing for the reasons stated and shown in pictures, so no, this configuration has not / ever run for "years" on race cars

hope this helps!

[Bouldermobile]

Mike, thanks for the post and the clarity contained within in it.

I see my logic was the wrong way round!

Would the 'spacer' referred to be needed because of this change in profile and therefore distance between bearing mounting and fingers. (accepting the fact it presumably has no affect on the angle/fulcrum point, etc.)?

[x31james]

I have spoken to DAE about this and they said that they arnt concerned however if i felt concerned then they are more than happy to change the bearing FOC, Would you recommend this then Bamford Mike??? Also i dont think "hope this helps" is particularly helpful, i was just passing on what id been told, im not an expert i was just passing on my experience.

Edited by x31james on Friday 17th April 15:23

[mikey k]

x31james said:

I have spoken to DAE about this and they said that they arnt concerned however if i felt concerned then they are more than happy to change the bearing FOC, Would you recommend this then Bamford Mike??? Also i dont think "hope this helps" is particularly helpful, i was just passing on what id been told, im not an expert i was just passing on my experience.

I found it extremely helpful and struggle to understand how you don't when it answers your question far better than anyone else has

[Jockman]

'Hope this Helps' is a friendly way of rounding off a posting. Sometimes abbreviated to HTH.

Nowt sinister about it, James

[BamfordMike]

Bouldermobile said:

Mike, thanks for the post and the clarity contained within in it.

I see my logic was the wrong way round!

Would the 'spacer' referred to be needed because of this change in profile and therefore distance between bearing mounting and fingers. (accepting the fact it presumably has no affect on the angle/fulcrum point, etc.)?

The spacer doesn't really have anything to do with profile of release bearing. A spacer is needed to go behind slave cylinder, yes. The thickness depends on clutch assembly stack height which will change for whatever configuration is employed (a given flywheel, a given clutch).

[BamfordMike]

x31james said:

I have spoken to DAE about this and they said that they arnt concerned however if i felt concerned then they are more than happy to change the bearing FOC, Would you recommend this then Bamford Mike??? Also i dont think "hope this helps" is particularly helpful, i was just passing on what id been told, im not an expert i was just passing on my experience.

Edited by x31james on Friday 17th April 15:23

I can't really say to you directly what to do, but i would think about it in 3 ways and make a choice.

1)trust your garage. 2)make your own informed judgement call or 3)go with factory fitting guideline

Respectively;

1-
If your garage is not concerned then fine, we bow to a higher intellect, leave it as it is, perhaps have them clearly explain the rationale of why the part was fitted in favour of factory configuration (bearing in mind the configuration you have has never been used on any race car so no obvious durability / performance data is to hand), be the test pilot and put the system to the long term test and report back to us - say in 50k miles time.

2-
Based on engineering principles and knowledge, make your own judgement call about being happy or not with a fulcrum point of the one pictured above which is bearing acting on clutch fingers where indicated and not tips

3-
Factory parts schematic states bull nose bearing fit with flat fingered clutch - insist on that because the factory must know what they are doing.

HTH!

[x31james]

Jockman said:

'Hope this Helps' is a friendly way of rounding off a posting. Sometimes abbreviated to HTH.

Nowt sinister about it, James

Well in that case then I apologise what's AMDBSNICK 's excuse??

[Neil1300r]

x31james said:

Jockman said:

'Hope this Helps' is a friendly way of rounding off a posting. Sometimes abbreviated to HTH.

Nowt sinister about it, James

Well in that case then I apologise what's AMDBSNICK 's excuse??

+

+

[AMDBSNick]

Neil1300r said:

x31james said:

Jockman said:

'Hope this Helps' is a friendly way of rounding off a posting. Sometimes abbreviated to HTH.

Nowt sinister about it, James

Well in that case then I apologise what's AMDBSNICK 's excuse??

+

+

On the same regime as you Spesh, big drive out tomorrow

[downr]

Surely if the bearing is acting further down the finger then it won't alter the stress at the fulcrum point?

Rather it would increase the force required to achieve the same movement? (Apologies, long time since I did physics a-level, so may have completely missed the point)

[KarlFranz]

downr said:

Surely if the bearing is acting further down the finger then it won't alter the stress at the fulcrum point?

Rather it would increase the force required to achieve the same movement? (Apologies, long time since I did physics a-level, so may have completely missed the point)

Actually, if the contact point of the bearing is closer to the edge of the fingers (as with the bull nose bearing) two things will happen. First, the "throw" will be longer which would allow you to finesse the clutch a little more. Second, the amount of force necessary to decouple the clutch will be less. Conversely, using the flat nose bearing will create a slightly more "digital" clutch pedal but will also increase the amount of pedal force required.

Think of it as trying a push a door open. If you push with your hand (bearing) on the door edge opposite to the hinges (fulcrum) it takes very little effort to move the door but your hand has to travel a greater distance to open the door a certain amount. Now if you try to open the door by pushing with your hand very close to the hinges it will take a lot more force to move the door but a smaller amount of hand movement will open the door the same amount as before.


This may be the same thing you were trying to say, but when you said "down the finger" i picture that as meaning traveling towards the tip which would be opposite of how it works. If you meant moving toward the base of the finger then, yes, we are in agreement.

Edited by KarlFranz on Friday 17th April 21:22

[mikey k]

Good point Karl and well explained

[Bouldermobile]

Thanks Karl, that explains the pedal movement issue very well.

I note the OP stated that the new pedal action was much easier to use so presumably even with the 'wrong' bearing it is still a vast improvement on the original. Although that then makes Mike's the 'factory knows what it is doing' a slightly moot point given the criticism of AM in general and the V8V clutch in particular. Obviously longevity of the 'wrong' bearing has yet to be proven.

James, did you decide whether to insist upon having the bearings swapped over or not?

[BamfordMike]

Bouldermobile said:

I note the OP stated that the new pedal action was much easier to use so presumably even with the 'wrong' bearing it is still a vast improvement on the original. Although that then makes Mike's the 'factory knows what it is doing' a slightly moot point given the criticism of AM in general and the V8V clutch in particular. Obviously longevity of the bearing has yet to be proven.

the factory knew what they were doing opting for single plate on V8, it was a conscious costdown compared twinplate. The live with it symptom of that decision is lower performance and heavy pedal feel. A worn out singleplate clutch's pressure plate is REALLY heavy to press, so anything will feel lighter in comparison including a twinplate with a 'cam effect' because incorrect bearing.

[Bouldermobile]

Mike, perhaps I should have phrased it differently: I know the factory knew what they were doing in opting for the single plate (as you imply 'saving money') but IMHO it is a shame they did because I feel the heavy clutch detracts from the overall driveability of of the car as a whole, especially as you say when heavily worn. The heavy clutch was often referred to in reviews and various posts over the years have stated the heavy clutch action was a reason for not purchasing or quickly selling on the car. Furthermore, the heavy clutch is often cited as a contributing factor to premature clutch wear, whether justified or not.

I agree with your point that the OPs new clutch is bound to be an improvement even if not fully implemented in the correct manner.

[x31james]

Bouldermobile said:

Thanks Karl, that explains the pedal movement issue very well.

I note the OP stated that the new pedal action was much easier to use so presumably even with the 'wrong' bearing it is still a vast improvement on the original. Although that then makes Mike's the 'factory knows what it is doing' a slightly moot point given the criticism of AM in general and the V8V clutch in particular. Obviously longevity of the 'wrong' bearing has yet to be proven.

James, did you decide whether to insist upon having the bearings swapped over or not?

I rang them up and they said if I wanted it changed then they were happy to do it FOC, Im going to get it changed to the bull head bearing seeing though that bearing was designed with the v12 clutch, from my understanding of this thread that is.

[downr]

KarlFranz said:

downr said:

Surely if the bearing is acting further down the finger then it won't alter the stress at the fulcrum point?

Rather it would increase the force required to achieve the same movement? (Apologies, long time since I did physics a-level, so may have completely missed the point)

Actually, if the contact point of the bearing is closer to the edge of the fingers (as with the bull nose bearing) two things will happen. First, the "throw" will be longer which would allow you to finesse the clutch a little more. Second, the amount of force necessary to decouple the clutch will be less. Conversely, using the flat nose bearing will create a slightly more "digital" clutch pedal but will also increase the amount of pedal force required.

Think of it as trying a push a door open. If you push with your hand (bearing) on the door edge opposite to the hinges (fulcrum) it takes very little effort to move the door but your hand has to travel a greater distance to open the door a certain amount. Now if you try to open the door by pushing with your hand very close to the hinges it will take a lot more force to move the door but a smaller amount of hand movement will open the door the same amount as before.


This may be the same thing you were trying to say, but when you said "down the finger" i picture that as meaning traveling towards the tip which would be opposite of how it works. If you meant moving toward the base of the finger then, yes, we are in agreement.

Edited by KarlFranz on Friday 17th April 21:22

Yes, that was kind of what I meant as the picture with the "incorrect" bearing shows it contacting further down (by which I mean away from the tip). That would increase the force required by the driver (simple lever physics) but shouldn't increase the pressures on the fulcrum point)