[dhanushs]

Hi All,

I have a Jeep, in which I've plonked a Nissan SD25 engine and I've turbocharged it. Its souped up pretty well for extreme offroading, and I use the Jeep only for offroading.

Now, with regular use in the farm, or mild offroading nothings wrong, however, after a pretty hard stint of offroading, which includes a number of high rpm clutch dumps, I notice that the clutch friction plate hub shakes (rotational shake).

I've tried to illustrate it in this picture:



Even when the hub is shaking, the vehicle runs without any problems or sounds. Twice I've noticed this problem only when I removed the gearbox for some other work.

I have a heavy duty Mahindra Pick up clutch plate and the friction plate has a spring type hub.

I've never seen or heard about this problem. What could be the cause?

Thanks,

Dhanush

[Aroy]

May be the excess torque has strained the springs, which are there to take care of the initial jerk when engaging. This may be one of those very rare cases where the springs have fatigued before the friction face has worn out. Testimony to rough use and excellent friction material.

Just check if the springs are loose. If so they are either of inferior quality (hence have just shortened due to fatigue), or are inadequate to take the torque.

In my opinion you should try to change the springs of better material (or thicker wire) which may be difficult to source (or measure).

[dhanushs]

Originally Posted by Aroy

This may be one of those very rare cases where the springs have fatigued before the friction face has worn out. Testimony to rough use and excellent friction material.

Thanks for the reply Aroy. The last 3 clutch plates of mine, have shown the same problem.

In my opinion you should try to change the springs of better material (or thicker wire) which may be difficult to source (or measure).

What do you suggest about using a non spring type hub? Yes, GB will take a hit when I dump the clutch, but again, would appreciate your take.

[Aroy]

Originally Posted by dhanushs

Thanks for the reply Aroy. The last 3 clutch plates of mine, have shown the same problem.

What do you suggest about using a non spring type hub? Yes, GB will take a hit when I dump the clutch, but again, would appreciate your take.

See if you can get clutch plates with better springs. May be some truck's clutch may be same size.

Here is how the clutch plate functions

"Among the numerous criteria used to determine clutch size and clamp load configuration, maximum engine torque and the resulting friction energy are especially significant. The greater the clamp load, the smaller the friction radius can be. The diameter should be as small as possible, because it greatly affects clutch weight and cost. But the clutch disc also has to be large enough to handle thermal loads and facing wear.

The clutch disc, also called friction lining, consists of a splined hub and a round metal plate covered with friction material (lining). The splines in the center of the clutch disc mesh with the splines on the input shaft of the manual transmission. This makes the input shaft and disc turn together. However, the disc is free to slide back and forth on the shaft.
Clutch disc torsion springs, also termed damping springs, absorb some of the vibration and shock produced by clutch engagement. They are small coil springs located between the clutch disc splined hub and the friction disc assembly. When the clutch is engaged, the pressure plate jams the stationary disc against the spinning flywheel. The torsion springs compress and soften, as the disc first begins to turn with the flywheel.
Clutch disc facing springs, also called the cushioning springs, are flat metal springs located under the friction lining of the disc. These springs have a slight wave or curve, allowing the lining to flex inward slightly during initial engagement. This also allows for smooth engagement.
The clutch disc friction material, also called disc lining or facing, is made of heat-resistant asbestos, cotton fibers, and copper wires woven or molded together. Grooves are cut into the friction material to aid cooling and release of the clutch disc. Rivets are used to bond the friction material to both sides of the metal body of the disc.

Most clutch facing have a base of asbestos. The number of friction surfaces is equal to twice the number of driven discs.

Large driven plates have a tendency to spin (i.e. to continue rotating after the clutch pedal is depressed). To limit this trouble, the plate should be made as light as possible.)

A material suitable for use as a friction surface must meet the following conditions:
- It must have a high coefficient of friction
- It must not be affected by moisture and oil
- It must resist wear
- It must be capable of resisting high temperatures caused by slippages
- It must be capable of resisting high axial pressure
- should have the given rapture strength,

Note that,
* There are groves in both sides of the friction-disc facings. These grooves prevent the facings from sticking to the flywheel face and pressure plate when the clutch is released. The groves break any vacuum that might form and cause the facing to stick to the flywheel or pressure plate.

** The facing or lining on the driven plate are secured by brass rivets, the heads being recessed into the lining to prevent scoring of the flywheel and pressure plate faces. As the lining wear down, the inner ends of the release leaver move away from the flywheel and after a predetermined a mount of wear has taken place; the lever will touch the cover.

Cushioning plate (center plate):
The cushioning plate, on which the friction facing are mounted, consists so series of cushion springs which is crimped radially.
During engagement, axial compression of the driven plate spreads the engagement over a great range of pedal travel and therefore makes it easier to make a smooth engagement.
During the disengagement, when the pedal is depressed, the clamping force will be released and the plate springs return back to its original position crimped (wavy) state, and that will get the driven plate to jump away from the flywheel to give ‘clear’ disengagement. While in this position, the linings will be held apart, and air will be pumped between the linings to take away the heat.
This plate is also slotted so that the heat generated does not cause distortion that would be liable to occur if it were a plain plate. This plate is of course thin to keep rotational inertia to a minimum.

Driven plate torsion springs:
The plate and its hub are entirely separate components, the drive being transmitted from one to the other through coil springs interposed between them. These springs are carried within rectangular holes or slots in the hub and plate and arranged with their axes aligned appropriately for transmitting the drive. These dampening springs are heavy coil springs set in a circle around the hub. The hub is driven through these springs. They help to smooth out the torsional vibration (the power pulses from the engine) so that the power flow to the transmission is smooth.
In a simple design all the springs may be identical, but in more sophisticated designs they are arranged in pairs located diametrically opposite, each pair having a different rate and different end clearances or using dual springs, where a smaller spring inside the original one.
The role of dual spring is progressively providing increasing spring rate to cater to wider torsional damping. Also, to avoid “plate float” which could happened when using identical springs with same rate (stiffness), plate float will happen if the vibration and torque variation became equal to the natural (resonance) frequency of the spring. Plate float will have negative effect on the transmission gears (gear rattling).

Driven plate torsional dampers:
It consists of friction plate and washer, to reduce gear rattling. The friction between the friction plate and the washer will damp the torsional vibration (as the roll of shock absorber in the car suspension).

http://www.thecartech.com/subjects/a...uto_Clutch.htm

One workaround is to cool the clutch adequately. If possible you can use a blower to force cold air into the bell housing, that will cool the clutch when used aggressively.

[Mpower]

Originally Posted by dhanushs

1. I have a Jeep, in which I've plonked a Nissan SD25 engine and I've turbocharged it. Its souped up pretty well for extreme offroading, and I use the Jeep only for offroading.
   
2. I notice that the clutch friction plate hub shakes (rotational shake).
   
3. Twice I've noticed this problem only when I removed the gearbox for some other work.
   
4. I have a heavy duty Mahindra Pick up clutch plate and the friction plate has a spring type hu

1. Do you have a feel for how much torque your SD25 is making after the mod?
2. How do you know its the hub that shaking? Visual/feel/data?
3. You noticed what on the clutch? some kind of wear pattern, got pics to share?
4. What torque is the Mahindra clutch plate rated for?

[Jeroen]

This might be a silly question, but did you install it correctly. Back and front might not be that apparent, but if you get them mixed up the spring dampeners won’t work.

Good luck
Jeroen

[dhanushs]

Originally Posted by Mpower

1. Do you have a feel for how much torque your SD25 is making after the mod?

1. Not sure. My guess is close to 30kgm.
   

   How do you know its the hub that shaking? Visual/feel/data?

   You can see it. When put a main shaft through the center, you can turn it like I've illustrated in the picture.
   

   You noticed what on the clutch? some kind of wear pattern, got pics to share?

   I noticed the clutch hub shaking. Meaning coming loose from the friction material. In a picture the friction material and the whole clutch plate looks like new, but, when you put a main shaft into the center and turn, the disc shakes, which it shouldnt.
   

   What torque is the Mahindra clutch plate rated for?

Again, not sure. However, what I do know is, Mahindra clutches are so rugged that almost nobody complains about them, even in the modification scene, its the axles etc people complain about not taking the engine power. Not the clutch.

Originally Posted by Jeroen

This might be a silly question, but did you install it correctly. Back and front might not be that apparent, but if you get them mixed up the spring dampeners won’t work.

Hi Jeroen, the last 3 clutch plates have the same symptoms. So, I dont think its the clutch installation issue. The engine is a Nissan engine, and the Gearbox is a Kia KMT90 gearbox - you mean this installation isnt correct?

[Jeroen]

Originally Posted by dhanushs

Hi Jeroen, the last 3 clutch plates have the same symptoms. So, I dont think its the clutch installation issue. The engine is a Nissan engine, and the Gearbox is a Kia KMT90 gearbox - you mean this installation isnt correct?

I cant comment on how the various components work together. But your friction plate should be installed in the correct way depending on which way the engine shaft turns. You put it in back to front, the spring dampners dont work. So you need to ensure the clutch plate has the correct orientation towards the turning direction of the shaft. Often, the clutch plate might fit either way. Back to front and front to bacl, but there is only one correct way. There might be markings on the clutch plate that tell you how it should rotate.

Good luck,
Jeroen

[dhanushs]

Originally Posted by Jeroen

I cant comment on how the various components work together. But your friction plate should be installed in the correct way depending on which way the engine shaft turns. You put it in back to front, the spring dampners dont work. So you need to ensure the clutch plate has the correct orientation towards the turning direction of the shaft. Often, the clutch plate might fit either way. Back to front and front to bacl, but there is only one correct way. There might be markings on the clutch plate that tell you how it should rotate.

Yes, I've made sure the friction plate orientation is correct. Thank you.

[SS-Traveller]

Dhanush, are the rivets holding the friction plate to the cushion plate working themselves loose? That's one way you'd be likely to get that kind of loosening of the friction plate. How many degrees approximately does the plate turn when you check it?

Maybe you can take apart an old plate and check the rivets and their holes for play / wear?

[VeyronSuperSprt]

The most likely reason for this would be the torque rating of your engine being higher than what the clutch is designed to handle.

As you do not have the torque rating of the clutch, the easiest way to figure out whether the clutch has a higher or lower rating than the engine would be the lightness of the clutch.

As a rule of thumb the lighter the clutch, the lower its torque rating. So, if the clutch is light to use, (say, lighter than when mated to its original Mahindra engine) the torque rating of the clutch could be lower than that of the current engine, and if it is a stiff clutch (stiffer than when mated to its original Mahindra engine) the rating that would be higher than the torque of the engine.

This would be one way of assessing whether you've put in the clutch with the right torque rating.

[dhanushs]

Originally Posted by SS-Traveller

Dhanush, are the rivets holding the friction plate to the cushion plate working themselves loose?

Hi SST,
I havent examined the old plates in detail, as the earlier plates I used were of a low torque vehicle. This time I used a proper heavy duty, 2 ton + load puller Mahindra's disc. I'll check and get back to you.

How many degrees approximately does the plate turn when you check it?

I'd say, around 5-10 degrees.

Maybe you can take apart an old plate and check the rivets and their holes for play / wear?

Yes, will do.

Originally Posted by VeyronSuperSprt

This would be one way of assessing whether you've put in the clutch with the right torque rating.

I have used the Nissan pressure plate and the Mahindra clutch plate. The Nissan pressure plate is harder.. much harder than the Mahindra.

[SS-Traveller]

Originally Posted by dhanushs

I'd say, around 5-10 degrees.

Wow - that's a lot.

Check those old plates for (a) rivets working loose and / or metal tear in the holes the rivets pass through; (b) tearing of the cushion spring seats; and (c) if the spring length has become shorter than original springs on a new plate.

[Aroy]

Originally Posted by SS-Traveller

Wow - that's a lot.

Check those old plates for (a) rivets working loose and / or metal tear in the holes the rivets pass through; (b) tearing of the cushion spring seats; and (c) if the spring length has become shorter than original springs on a new plate.

If any of these are true, then the clutch plate is of lower torque than you need, and you need a beefier clutch plate.

[VeyronSuperSprt]

Originally Posted by dhanushs

I have used the Nissan pressure plate and the Mahindra clutch plate. The Nissan pressure plate is harder.. much harder than the Mahindra.

The lightness in the Mahindra clutch indicates that it has a lower torque rating than that of the Nissan. The Nissan should last longer than the Mahindra, even if it does eventually give you the same problem because of the stresses of off roading.

Since it is a recurring problem, it does point towards the clutch having a lower torque rating than required.

Generally, the more you need to load your car / vehicle - very high performance / heavy load lugging / extreme off roading whatever, the stiffer the clutch needs to be to endure the excess load without issues cropping up.