Please help me get this clutch working properly!!
07-03-2009, 02:14 AM
#136
And when I say moving.it is the position of the int. plate wrt the other discs. The int plate somehow moves forward and stays more foward not allowing it to release from the front disc..
07-03-2009, 02:24 AM
#137
Rennlist Member
There is no force acting on the intermediate plate forward. when clutch is released and you are checking the H gap, the pressure plate is as far forward as it will ever be. If adjusted properly, the Hs will have a 1mm gap. push in the clutch, and the only forces acting on the INT plate are the flat springs pushing the INT plate toward the pressure plate. its a light force.
There is a chance that the INT plate when rotating at max revs and engaging and disengaging with the flywheel, that its inertia can act on the flat springs and the disc seems to be able to vibrate and move backward to move the adjusters on its own in extreme cases. the INT plate cannot move more forward, even under vibration, as it is against a firm stop.... the flywheel. So, this is why it is puzzling that the adjusters are moving forward. Something has to act on the adjusters (H's) to move them forward, but rear ward the int plate can move in a number of situations to move the adjusters rearward.
mk
There is a chance that the INT plate when rotating at max revs and engaging and disengaging with the flywheel, that its inertia can act on the flat springs and the disc seems to be able to vibrate and move backward to move the adjusters on its own in extreme cases. the INT plate cannot move more forward, even under vibration, as it is against a firm stop.... the flywheel. So, this is why it is puzzling that the adjusters are moving forward. Something has to act on the adjusters (H's) to move them forward, but rear ward the int plate can move in a number of situations to move the adjusters rearward.
mk
07-03-2009, 02:27 AM
#138
Rennlist Member
again, the disc can only push on the disc and pressure plate. It can move forward, unless you have pieces mising off your front disc as Scot did when he had issues with clutch shudder.
nothing can act on the adjusters except the back part of the INT plate
nothing can act on the adjusters except the back part of the INT plate
07-03-2009, 02:59 AM
#139
I've been chatting with Colin on IM.. It's been a while since I've played with this particular double disc..I'll get it on the bench ...I think I'm describing it right..but probably using wrong parts descriptions or whatever.... Watch for me back in this thread in August 
.
.
07-03-2009, 05:00 AM
#140
Nordschleife Master
Ok,
This post is to help Tom mainly, but anyone else who has trouble understanding how this DD system works.
First a little animation I made showing the engaged an disengaged stages of the clutch.
In the animation you will see the bottom black piece is the flywheel, the middle black piece with the orange tab (this is attached to the IP) on it is the intermediate friction plate (IFP), and the top black is th PP friction plate.
The blue plates are the clutch discs, the red H is the H adjuster or "forks", the 2 grey bars on the side are the housing of the intermediate plate, the thin grey bar is the 2 piece spring one end is rivetted to the intermediate friction plate, the other end is rivetted to a tab on the outter IP housing, lets just call this the IP spring for now.
The purpose of the IP spring is to hold the IFP away from the flywheel when the clutch is disengaged to allow the primary (forward) disc to spin freely.
This H adj. or forks are designed to LIMIT the rearward travel of the IFP. These could have been made in a T shape to work. The reason however that they were made in the H shape was so that the 2 ears which are on the flywheel side of things are able to draw the H adjuster closer to the flywheel as the primary disc wore. This is was to aid in the engagement point of the clutch.
Now in order for this to work the factory must have maintained the proper tolerance of 1-1.2mm of clearance between the H adjuster and stopping ears of the IFP. If they did maintain the tolerances of these parts then the all the way back method would ALWAYS work UNLESS the H pieces became worn in that they could move around very freely, or that they wore and the gap increased past the 1.2mm of clearance as dave points out multiple times in his posts. This being said with the close attention to detail and tolerances that have gone into the rest of the parts, like the tolerances within the engine. I find it hard to believe, but not impossible that Porsche would not have known this and paid proper attention to these tolerances when assembling the IP new.
Now understanding this upto this point you can see that when the clutch was engaged the H adjusters would always be just barely touching the stops on the IFP. Coupling this with the normal vibration within any rotating assembly WILL CAUSE wear to the adjusters (on the opposite side that MK is really looking at haha). The reason that the wear appear minimal is that they would have worn reasonably fast increasing the total gap by around .25mm thereby preventing the "all the way back" technique to not work. As well quickly dropping the clutch pedal and allowing the PP to slam everything together quicly will only cause the H adj to move if they are in the all the way back position, and the amount of forward movement they would see is very minimal due to the friction and weight of them. The reason that the gap has not continued to increase to a point of weaing the H adj out entirely is that once the system wears past say .25mm the clutch drags and the car is undrivable. The H adj are then adjusted to the 1mm gap and at that time the IFP is not close enough to them to cause any further wear while the clutch is in the engaged position.
Now the reason that the clutch drags when the H adjusters are not adjusted properly is that if there is too much of a gap (over 1.2mm) then the IFP moves too far back causing the secondary friction disc to have resistance. And if they are too far forward then it limits its travel too much not allowing the primary disc to be fully released.
The reason it needs 1mm of movement is because of the springplate between the 2 friction pads per disc. These spring plates are here to aid with the smoothness of the engagement of the clutch. One of the reason that multi-puck clutchs are so difficult and chattery to drive is because they lack these spring plates.
If you do not wish to follow the 1mm of space camp of if it simply isnt working for you then actuate the clutch with a ratchet strap and adjust all the H adj with the clutch disengaged. While you are doing this watch the clearance between the IFP and primary disc. You can also have the car in nuetral and spin the shaft with the discs on it to see when you start to see drag when moving the adjusters forward. when you start to feel some drag back them off a very tiny amount. make sure yo do all 3. Then release the ratchet strap and ensure that all 3 adjusters have the same distance to them! Otherwise it will move the 2 that are more forward back.
Now if your clutch is NOT holding adjustment there can be a couple of reasons for this. If adjustment is lost after a couple of actuations of the clutch then the rivets which hold the H adjusters have streched, or the H adjusters have worn where the washer contacts them. Currently there is no real fix for this. Though when I get home I will be working on one that should be able to be EU repairable. However if your clutch is slipping only when you are REALLY pushing it, ei at the track shifting near redline. The reason for this is simply the design of the current IFP with the fix I am thinking about building this will be cured. And I am not talking about drilling out the rivet and replacing it with a bolt as users have seen this slip as well.
The reason for the H adj not holding position is due to the increased force that they see. When I was taking to Tom he didnt see how they saw any extra force from this type of use.
The extra force comes from inertia, and the speed at which disengagement happened. I may not explain this that clearly so if someone has trouble understanding this portion, I apologize in advance.
The IFP has a fair amount of mass to it and when you are spinning the assembly at 2000RPM and gently disengage the system the IFP stops gently touch down on the H adj stops, and the H adj do not move. But when you are spinning at 6000RPM and you disengage very rapidly, especially with the engine loaded (either compression or power) these forces will initiate an actual kickback of the IFP, which multiplies the rotating inirtia along with the normal spring force. This then SLAMS the IFP into the H adjusters. The amount of force difference between a gentle 2000RPM no load disengagement, and the later which I just explained is more than you would imagine! I wish I had numbers to lay down for this, but I simply do not. Trying to calculate all the variables would be impossible! Well at least for me.
But it is no wonder that they move unders those circumstances. This is why they can move with the bolt fashion as well.
What I have in mind for a fix will be able to stop this from happening under those circumstances as well, but until I get measurements from a wide range of discs I will not know if it is feasible to make something that that will be universally workable for all of the IP out there. It really depends on the manufacturing tolerances that we see.
I hope that this makes it easier for everyone who is interested in how this system works to understand how it all actually works.
This post is to help Tom mainly, but anyone else who has trouble understanding how this DD system works.
First a little animation I made showing the engaged an disengaged stages of the clutch.
In the animation you will see the bottom black piece is the flywheel, the middle black piece with the orange tab (this is attached to the IP) on it is the intermediate friction plate (IFP), and the top black is th PP friction plate.
The blue plates are the clutch discs, the red H is the H adjuster or "forks", the 2 grey bars on the side are the housing of the intermediate plate, the thin grey bar is the 2 piece spring one end is rivetted to the intermediate friction plate, the other end is rivetted to a tab on the outter IP housing, lets just call this the IP spring for now.
The purpose of the IP spring is to hold the IFP away from the flywheel when the clutch is disengaged to allow the primary (forward) disc to spin freely.
This H adj. or forks are designed to LIMIT the rearward travel of the IFP. These could have been made in a T shape to work. The reason however that they were made in the H shape was so that the 2 ears which are on the flywheel side of things are able to draw the H adjuster closer to the flywheel as the primary disc wore. This is was to aid in the engagement point of the clutch.
Now in order for this to work the factory must have maintained the proper tolerance of 1-1.2mm of clearance between the H adjuster and stopping ears of the IFP. If they did maintain the tolerances of these parts then the all the way back method would ALWAYS work UNLESS the H pieces became worn in that they could move around very freely, or that they wore and the gap increased past the 1.2mm of clearance as dave points out multiple times in his posts. This being said with the close attention to detail and tolerances that have gone into the rest of the parts, like the tolerances within the engine. I find it hard to believe, but not impossible that Porsche would not have known this and paid proper attention to these tolerances when assembling the IP new.
Now understanding this upto this point you can see that when the clutch was engaged the H adjusters would always be just barely touching the stops on the IFP. Coupling this with the normal vibration within any rotating assembly WILL CAUSE wear to the adjusters (on the opposite side that MK is really looking at haha). The reason that the wear appear minimal is that they would have worn reasonably fast increasing the total gap by around .25mm thereby preventing the "all the way back" technique to not work. As well quickly dropping the clutch pedal and allowing the PP to slam everything together quicly will only cause the H adj to move if they are in the all the way back position, and the amount of forward movement they would see is very minimal due to the friction and weight of them. The reason that the gap has not continued to increase to a point of weaing the H adj out entirely is that once the system wears past say .25mm the clutch drags and the car is undrivable. The H adj are then adjusted to the 1mm gap and at that time the IFP is not close enough to them to cause any further wear while the clutch is in the engaged position.
Now the reason that the clutch drags when the H adjusters are not adjusted properly is that if there is too much of a gap (over 1.2mm) then the IFP moves too far back causing the secondary friction disc to have resistance. And if they are too far forward then it limits its travel too much not allowing the primary disc to be fully released.
The reason it needs 1mm of movement is because of the springplate between the 2 friction pads per disc. These spring plates are here to aid with the smoothness of the engagement of the clutch. One of the reason that multi-puck clutchs are so difficult and chattery to drive is because they lack these spring plates.
If you do not wish to follow the 1mm of space camp of if it simply isnt working for you then actuate the clutch with a ratchet strap and adjust all the H adj with the clutch disengaged. While you are doing this watch the clearance between the IFP and primary disc. You can also have the car in nuetral and spin the shaft with the discs on it to see when you start to see drag when moving the adjusters forward. when you start to feel some drag back them off a very tiny amount. make sure yo do all 3. Then release the ratchet strap and ensure that all 3 adjusters have the same distance to them! Otherwise it will move the 2 that are more forward back.
Now if your clutch is NOT holding adjustment there can be a couple of reasons for this. If adjustment is lost after a couple of actuations of the clutch then the rivets which hold the H adjusters have streched, or the H adjusters have worn where the washer contacts them. Currently there is no real fix for this. Though when I get home I will be working on one that should be able to be EU repairable. However if your clutch is slipping only when you are REALLY pushing it, ei at the track shifting near redline. The reason for this is simply the design of the current IFP with the fix I am thinking about building this will be cured. And I am not talking about drilling out the rivet and replacing it with a bolt as users have seen this slip as well.
The reason for the H adj not holding position is due to the increased force that they see. When I was taking to Tom he didnt see how they saw any extra force from this type of use.
The extra force comes from inertia, and the speed at which disengagement happened. I may not explain this that clearly so if someone has trouble understanding this portion, I apologize in advance.
The IFP has a fair amount of mass to it and when you are spinning the assembly at 2000RPM and gently disengage the system the IFP stops gently touch down on the H adj stops, and the H adj do not move. But when you are spinning at 6000RPM and you disengage very rapidly, especially with the engine loaded (either compression or power) these forces will initiate an actual kickback of the IFP, which multiplies the rotating inirtia along with the normal spring force. This then SLAMS the IFP into the H adjusters. The amount of force difference between a gentle 2000RPM no load disengagement, and the later which I just explained is more than you would imagine! I wish I had numbers to lay down for this, but I simply do not. Trying to calculate all the variables would be impossible! Well at least for me.
But it is no wonder that they move unders those circumstances. This is why they can move with the bolt fashion as well.
What I have in mind for a fix will be able to stop this from happening under those circumstances as well, but until I get measurements from a wide range of discs I will not know if it is feasible to make something that that will be universally workable for all of the IP out there. It really depends on the manufacturing tolerances that we see.
I hope that this makes it easier for everyone who is interested in how this system works to understand how it all actually works.
07-03-2009, 04:12 PM
#141
Rennlist Member
Well Colin,
That earns my vote as the penultimate post to this thread
.... with a lingering but distinguished hint in the finish of " .... and put that in your pipe & smoke it" .....
That earns my vote as the penultimate post to this thread
.... with a lingering but distinguished hint in the finish of " .... and put that in your pipe & smoke it" .....
07-03-2009, 09:02 PM
#142
Rennlist Member
Colin. Nice diagram.
One small thing to add. The INT plate when the clutch is engaged, doesnt contact the front side of the"H" adjusters. So, there really is no wear patterns due to that. I like your theory on the vibration moving the H adjusters . I think its the only way the H adjusters move after adjustment.
The pressure plate cannot put wear on the INT hitting the H adjusters, no matter how fast you release the pedal. It moves an incredibly small distance and does it at a relatively slow speed.
One small thing to add. The INT plate when the clutch is engaged, doesnt contact the front side of the"H" adjusters. So, there really is no wear patterns due to that. I like your theory on the vibration moving the H adjusters . I think its the only way the H adjusters move after adjustment.
The pressure plate cannot put wear on the INT hitting the H adjusters, no matter how fast you release the pedal. It moves an incredibly small distance and does it at a relatively slow speed.
07-04-2009, 03:12 AM
#144
Rennlist Member
Not after the H adjuster was in contact with the INT so that the disc could be pressed on to the flywheel at that point, it would never touch ever again.
By the way, I just did some measurements again. the real old, 30 year old IN plate , still has a gap of 1.5mm, and the H adjusters dont seem to have any wear at all. that angle that Dave was talking about, is still there on the H tabs.
I took some pictures to show the angles of the H arms before the contact points.
Ill put up the pics if anyone is interesting to see.
anyone with an intermediate plate, expecially an older model can see the gap is 1.4mm or so, and never really could be 1.1mm unless the design changed.
By the way, I just did some measurements again. the real old, 30 year old IN plate , still has a gap of 1.5mm, and the H adjusters dont seem to have any wear at all. that angle that Dave was talking about, is still there on the H tabs.
I took some pictures to show the angles of the H arms before the contact points.
Ill put up the pics if anyone is interesting to see.
anyone with an intermediate plate, expecially an older model can see the gap is 1.4mm or so, and never really could be 1.1mm unless the design changed.
07-04-2009, 03:18 PM
#146
Rennlist Member
You are right. I though you were talking about with the clutch released. Yes, when the clutch is engaged, the INT plate rests on the H tabs with a very very light force. (finger pressure)
Im posting some pics that may clear up ALL misconceptions about the irrelavant wear concepts.
mk
Im posting some pics that may clear up ALL misconceptions about the irrelavant wear concepts.
mk
07-04-2009, 03:30 PM
#147
Rennlist Member
PICs of very old H adjusters (close ups at different angles with measurements)
Ok folks. Enough is enough! Here are some pics I took to show what the heck we are all talking about here with respect to the "H" adjusters (forks) and what certain gaps look like when they are adjusted. Also, it clearly will show that the H adjusters are NOT wear elements and have no bearing on adjustments.
We do not have conclusive evidence that there are not different casting/stamping versions of the H adjusters for all the model years, but this is the version and gaps ive seen on the earliest INT plate through the 84 (which is the newest).
Ive even got a very close up picture (and have a higher resolution pic if anyone wants a real close up for further proof), that shows that there is no wear on the rear side of the H adjusters. you can see the contact pad very clearly. It shows absolutely no sign of wear. Also, Ive provided the different camera angle that shows the optical allusion that the H adjuster arms are worn. they are not, but it would appear so due to the fact that they are angled at the arm ( an inward bend). Also, a lower picture angle as we have seen when on the car, also enhances this optical effect. Here is the proof, as always!
I have a strip of solder that i was able to use at full thickness which was close to 1.4mm. When I pounded it out, I was able to get a thickness of 1mm to show the difference in gap. Its a pretty significant difference. to think that the pads wear .25mm, is just not correct and extremely unlikely as shown by the clean pictures to follow. Enjoy!
mk
We do not have conclusive evidence that there are not different casting/stamping versions of the H adjusters for all the model years, but this is the version and gaps ive seen on the earliest INT plate through the 84 (which is the newest).
Ive even got a very close up picture (and have a higher resolution pic if anyone wants a real close up for further proof), that shows that there is no wear on the rear side of the H adjusters. you can see the contact pad very clearly. It shows absolutely no sign of wear. Also, Ive provided the different camera angle that shows the optical allusion that the H adjuster arms are worn. they are not, but it would appear so due to the fact that they are angled at the arm ( an inward bend). Also, a lower picture angle as we have seen when on the car, also enhances this optical effect. Here is the proof, as always!
I have a strip of solder that i was able to use at full thickness which was close to 1.4mm. When I pounded it out, I was able to get a thickness of 1mm to show the difference in gap. Its a pretty significant difference. to think that the pads wear .25mm, is just not correct and extremely unlikely as shown by the clean pictures to follow. Enjoy!
mk
Last edited by mark kibort; 07-04-2009 at 09:23 PM.
07-04-2009, 03:43 PM
#148
Rennlist Member
By the way, you can see from the last picture, that the contact patch for the H arm is very small and hasnt shown signs of wear. also, the max gap is measured at 1.4mm. Same as all of the INT plates I have measured. You can clearly see that the angle of the picture is very telling as to the wear of the components. Now, if there is a new INT plate that has a max gap of 1.1mm, that is clearly a design or part dimension change.
07-05-2009, 03:12 PM
#149
Rennlist Member
Bump! Dave, I took those pictures just for you! 
. Do you still think the H parts wear?
There is a 1mm square contact patch that you can see on the last picture. It is still pristine and is over 20 years old! The front side is a perfectly flush surface where no wear happens. Im not convinced that there is any metalurgy difference in the IN plate or the Hs, but even if there was, there are very few forcs ever acting on them. when the clutch is engaged , the rear and front of H adjusters have no contact on them. (1mm rear gap and about .4mm front gap) when the cutch is engaged, the only contact in the rear is the H's limiting contact on the INT plate. it is brief, and its engagment is relatively slow with a force of only the flat spring pressure. (finger pressure).
This has got me thinking. If there are a set of INT plates out there that have only a 1.1mm gap, I think I have an idea to how to repair those plates that are having moving H adjusters due to extreme racing , or normal operation. If a small weld is done to the front side (the flat contact side) and this closes up the gap that the H adjusters can move to the rear, that might be the answer to the problem! or, you could bend the sides of the H's down and create the same effect on the front side. hmm, ill have to do some experiementing.
Of course, there would be no margin for error, because as the front disc wears, you would reduce the H adjsters ability to move forward. But , in my case,i have negligible wear on the front disc. the part number writing is still visible on the disc surface, even after 7 full seasons of racing!
. Do you still think the H parts wear?There is a 1mm square contact patch that you can see on the last picture. It is still pristine and is over 20 years old! The front side is a perfectly flush surface where no wear happens. Im not convinced that there is any metalurgy difference in the IN plate or the Hs, but even if there was, there are very few forcs ever acting on them. when the clutch is engaged , the rear and front of H adjusters have no contact on them. (1mm rear gap and about .4mm front gap) when the cutch is engaged, the only contact in the rear is the H's limiting contact on the INT plate. it is brief, and its engagment is relatively slow with a force of only the flat spring pressure. (finger pressure).
This has got me thinking. If there are a set of INT plates out there that have only a 1.1mm gap, I think I have an idea to how to repair those plates that are having moving H adjusters due to extreme racing , or normal operation. If a small weld is done to the front side (the flat contact side) and this closes up the gap that the H adjusters can move to the rear, that might be the answer to the problem! or, you could bend the sides of the H's down and create the same effect on the front side. hmm, ill have to do some experiementing.
Of course, there would be no margin for error, because as the front disc wears, you would reduce the H adjsters ability to move forward. But , in my case,i have negligible wear on the front disc. the part number writing is still visible on the disc surface, even after 7 full seasons of racing!
07-05-2009, 04:27 PM
#150
Rennlist Member
Mark, that is another interesting single data point.
However, you have completely ignored my questions about the earlier picture that you yourself posted(unless I missed something). Where did this picture come from? What is the max gap on this fork? How do you reconcile these obvious signs of wear with your theory that they never ever wear at all? If you want to completely ignore a piece of data that does not agree with your theory, fine -- let's call it like it is. But if you want to contend that the forks never ever wear then we need an explanation for this picture(below) or you should probably qualify with "the forks that I choose to pay attention to do not show signs of wear"...
However, you have completely ignored my questions about the earlier picture that you yourself posted(unless I missed something). Where did this picture come from? What is the max gap on this fork? How do you reconcile these obvious signs of wear with your theory that they never ever wear at all? If you want to completely ignore a piece of data that does not agree with your theory, fine -- let's call it like it is. But if you want to contend that the forks never ever wear then we need an explanation for this picture(below) or you should probably qualify with "the forks that I choose to pay attention to do not show signs of wear"...