[Jeroen]

Originally Posted by rathsubhajeet

The friction material is attached to the clutch plate in such a way that while disengagement of clutch, during cushion deflection phase, only the pressure plate side friction surface has axial movement and not the entire clutch plate. Only after that the clutch plate starts to move and the clutch disengages.


.

So you are saying the clutch starts to disengage before the clutch plate moves?

The basic operation of a clutch is due to the clutch plate axial movement. There is nothing else. If your clutch disengages (even minutely) without the clutch plate having moved (axially) as well, you must live in a different universe with very different physical laws.

Jeroen

[rathsubhajeet]

Originally Posted by Jeroen

So you are saying the clutch starts to disengage before the clutch plate moves?

The basic operation of a clutch is due to the clutch plate axial movement. There is nothing else. If your clutch disengages (even minutely) without the clutch plate having moved (axially) as well, you must live in a different universe with very different physical laws.

Jeroen

Kindly read about cushion deflection online.

[joybhowmik]

Originally Posted by Sutripta

Design caters to a shock load in one direction only.

Originally Posted by Jeroen

It all depends on how well those springs and their mountings can take a load in either direction.

Originally Posted by Sutripta

Sudevji,
The outer part of the clutch plate (carrying the lining) is not rigidly connected to the inner part (carrying the splined hub). If you take apart the clutch plate (you have to bust a lot of rivets) you will find it is not a symmetric design.

Originally Posted by Jeroen

I'm not sure what a-symetrc riveting would look like. But if you take the rivets out and take the clutch apart I would dare say you are likely to see an asymmetric design on how the springs absorb drive line vibration.

Originally Posted by Sutripta

A function of what the springs do, and how they these are setup.

Originally Posted by joybhowmik

So are Sutripta and Jeroen saying that this action will be compromised if clutch plate were reversed? Please explain - why.

Image courtesy: Google
Riveting looks fairly symmetric to me based on ^^^. Still cannot understand why the compression on the springs in the clutch plate will be compromised if it is mounted the other way around.

[SS-Traveller]

Originally Posted by Sutripta

A function of what the springs do, and how they these are setup.

Originally Posted by Jeroen

...you are likely to see an asymmetric design on how the springs absorb drive line vibration.

Originally Posted by joybhowmik

Attachment 1288699
Riveting looks fairly symmetric to me...

If Sutripta / Jeroen are asking you to look at the springs, why would you look at the rivets? That too, diagrams and not the real thing?

Go to your local FNG, ask him to give you an old worn friction plate, and then take it apart to study how the springs are fixed on.

I just did.

[joybhowmik]

Originally Posted by SS-Traveller

If Sutripta / Jeroen are asking you to look at the springs, why would you look at the rivets? That too, diagrams and not the real thing?

The springs are also symmetrically arranged based on ^^^ and other pictures including those on this thread.... the comment on symmetric riveting from prior observation about asymmetric riveting.

Just trying to understand the physics behind what happens with the springs when the clutch plate is reverse mounted.

Looking at a worn out plate, or even a new one , won't offer the explanation. So I beg your patience and request an explanation.

[SS-Traveller]

Originally Posted by joybhowmik

The springs are also symmetrically arranged based on ^^^ and other pictures...
Looking at a worn out plate, or even a new one , won't offer the explanation.

Originally Posted by SS-Traveller

...study how the springs are fixed on.

Don't look at the pictures any more. Look at the real thing, and it becomes quite obvious. Look at the design of the springs on both ends. Look at the seats at the ends of the springs.

And don't beg!

[joybhowmik]

Originally Posted by SS-Traveller

Don't look at the pictures any more. Look at the real thing, and it becomes quite obvious. Look at the design of the springs on both ends. Look at the seats at the ends of the springs.

Yes - time I looked at them again. My last memory of these was when I was fitting them in the bell housing in the gearbox line for Tata 1210 @ TELCO, Jamshedpur in 1994 - part of my GET training.
So, in the absence of the real thing - pictures are the next available choice. Not sure if you can bring the clutch plate with you when we meet for lunch on Sunday.

And don't beg!

Not at all - only a manner of speech.

[Jeroen]

Originally Posted by rathsubhajeet

Kindly read about cushion deflection online.

I dont need to read online, because Ive done some clutch and clutch damper design in the past, but here is a link that shows you the math and yes the clutch plate does move during the cushion deflection phase.

http://books.google.co.in/books?id=N...clutch&f=false

Jeroen

[rathsubhajeet]

Originally Posted by Jeroen

I dont need to read online, because Ive done some clutch and clutch damper design in the past, but here is a link that shows you the math and yes the clutch plate does move during the cushion deflection phase.

http://books.google.co.in/books?id=N...clutch&f=false

Jeroen

Brother, nice of you to share your expertise and the book is also quiet insightful. However, if you read carefully, it says that during disengagement, initially, expansion happens in cushion springs. Then the pp lift-off takes place. Only after that there is a separation in pressure plate and clutch plate. The axial movement of clutch plate can only happen after that.

What I was trying to explain earlier was that if you take out a clutch compress the cushion spring manually, you will realize that the pressure plate side friction surface and the rest of the clutch have relative motion. So at disengagement imagine that the pressure plate side is slowly moving away from the flywheel. During cushion deflection, which ever side is facing the pp, will start moving. If its the pp side only the friction surface moves, if the flywheel side the rest of the assembly moves.

PS: I could not view some of the pages on that book. If you have the soft copy, I'd appreciate if you could share.
E-mail ID: rathsubhajeet@gmail.com

[Sutripta]

Originally Posted by rathsubhajeet

The friction material is attached to the clutch plate in such a way that while disengagement of clutch, during cushion deflection phase, only the pressure plate side friction surface has axial movement and not the entire clutch plate. Only after that the clutch plate starts to move and the clutch disengages.

If the clutch were reverse fitted the entire clutch plate will have axial movement during cushion deflection.

I've tried to observe that in a vehicle by deliberately fitting the clutch in the reverse direction. It is perceivable only if you are really skilled in Clutch Characteristics Evaluation.

Also the extra movement in the clutch can cause an additional wear that may lead to durability issues. But I can not make an absolute statement without testing this on a vehicle.

Hi,
Don't take it the wrong way, but if you have actually measured the load-deflection curve for a clutch plate, you are either very passionate/ obsessed with/ specialising in clutches. And given the fact that your profile states that you are an R&D engineer at MM, I will take it that your questions are rhetorical!

It would be very interesting if you could post the pictures of the fully dismantled clutch plate in question.

BTW, have you come across a SDP clutch where the manufacturer said it could be installed in either direction?

Regards
Sutripta

[rathsubhajeet]

Originally Posted by Sutripta

Hi,
Don't take it the wrong way, but if you have actually measured the load-deflection curve for a clutch plate, you are either very passionate/ obsessed with/ specialising in clutches. And given the fact that your profile states that you are an R&D engineer at MM, I will take it that your questions are rhetorical!

It would be very interesting if you could post the pictures of the fully dismantled clutch plate in question.

BTW, have you come across a SDP clutch where the manufacturer said it could be installed in either direction?

Regards
Sutripta

Being bluntly honest, I don't know much about clutch. But I've spoken to a few suppliers and a few people in my firm, who know more than me. The trouble is I'm not quiet convinced by there explanations.

My questions are not rhetorical. Its just that I'm a slow learner and I don't back out of an argument until I completely understand the concept.

My expectations from this thread is to gain any additional point which I had previously missed and there implications on Clutch performance and Life.

Also, it is difficult for me to quote specific examples, as most of the products i work on are Proto-products, and I'm suppose to maintain information security. Which is also the reason I'm not posting pictures. I'll still try to find pics online and give a better explanation.

PS: No manufacturer will ever say that a clutch could be reverse fitted, even if that is possible.

[SS-Traveller]

Originally Posted by rathsubhajeet

PS: No manufacturer will ever say that a clutch could be reverse fitted, even if that is possible.

Why not? If tyres manufacturers can specify their tyres to be bi-directional or uni-directional, why can't that apply for clutch (if it is feasible)?

BTW, why does your question relate to DMFs only?

...with most Dual Mass Flywheels, it is possible to fit the clutch in the reverse direction.

[Jeroen]

Originally Posted by rathsubhajeet

Brother, nice of you to share your expertise and the book is also quiet insightful. However, if you read carefully, it says that during disengagement, initially, expansion happens in cushion springs. Then the pp lift-off takes place. Only after that there is a separation in pressure plate and clutch plate. The axial movement of clutch plate can only happen after that.
]

You need to read the article carefully to fully understand what is happening.

It says, "therefor, the total displacement of pressure plate in the the first phase (aka cushion deflection phase) just before disengagement is etc etc. (gives the formulae). So it states very specifically that the pressure plate moves (axially of course) during this first phase. It even states the formulae.

Now, how can the pressure plate move away from the flywheel, without the clutch actually starting to disengage fully?

What actually happens is that the friction material on the clutch plate expands, as the pressure plate moves aft. The expansian is effectively an aximal movement. If you have a clutch plate with friction material on both side, the clutch plate will move half the distance of the pressure plate. (it has friction material on both side, each contributes through its expansion to filling up 50% of the distance.

The actual deflection of the pressure plate in the first phase is pretty minute and therefor a 50% of that is even half of pretty minute.

However, from a design point of view, these initial engagement/disengagment phases are really important and need to be considered in great detail.

The little spings as we have been discussing as part of the assymetrical design come into their own big time during these phases as this is where inital vibration and some other unwanted related effects are very dynamic.


The "cushion deflection phase" is essentially where the friction material expands. And you will agree, that when something like friction material expands it actually takes more space, which in the case of a clutch plate means it actually moves in the same direction as the pressure plate.

Hope this makes you understand it better

Jeroen

[rathsubhajeet]

Originally Posted by SS-Traveller

Why not? If tyres manufacturers can specify their tyres to be bi-directional or uni-directional, why can't that apply for clutch (if it is feasible)?

BTW, why does your question relate to DMFs only?

That's the standard practice being followed in the industry. No supplier would ask his customer to do something which has even a minute chance of failure. Comparing tyres and clutches, Tyre change is much easier than clutch. Control on clutch figment is much higher. So it is wise to develop tyres that are bidirectional. Same thing need not be done on clutches.

Regarding dmf, I've only seen that reverse fitment of a clutch is possible in vehicles that have dmf. With SMF, some kind of fitment issues are always there.

Originally Posted by Jeroen

You need to read the article carefully to fully understand what is happening.

It says, "therefor, the total displacement of pressure plate in the the first phase (aka cushion deflection phase) just before disengagement is etc etc. (gives the formulae). So it states very specifically that the pressure plate moves (axially of course) during this first phase. It even states the formulae.

Now, how can the pressure plate move away from the flywheel, without the clutch actually starting to disengage fully?

What actually happens is that the friction material on the clutch plate expands, as the pressure plate moves aft. The expansian is effectively an aximal movement. If you have a clutch plate with friction material on both side, the clutch plate will move half the distance of the pressure plate. (it has friction material on both side, each contributes through its expansion to filling up 50% of the distance.

The actual deflection of the pressure plate in the first phase is pretty minute and therefor a 50% of that is even half of pretty minute.

However, from a design point of view, these initial engagement/disengagment phases are really important and need to be considered in great detail.

The little spings as we have been discussing as part of the assymetrical design come into their own big time during these phases as this is where inital vibration and some other unwanted related effects are very dynamic.


The "cushion deflection phase" is essentially where the friction material expands. And you will agree, that when something like friction material expands it actually takes more space, which in the case of a clutch plate means it actually moves in the same direction as the pressure plate.

Hope this makes you understand it better

Jeroen

Let us assume that the cushion spring expansion is 1 mm. The pp side friction material will have 1 mm axial movement. The flywheel side friction surface will have no movement. Now the cushion spring are designed in such a way that the rest of the assembly will have say 0.15 mm movement.

If the clutch is reverse fitted, the rest of the assembly will have 0.85 mm movement.

You are right that friction material expansion is a big part of cushion deflection. And even if you factor that, my argument holds good.

[Jeroen]

Originally Posted by rathsubhajeet

You are right that friction material expansion is a big part of cushion deflection. And even if you factor that, my argument holds good.

Not sure which argument holds if we agree that the friction material expanse it also moves the clutch plate during the initial phase?