New Product: Rebuilt Clutch Intermediate Plates
10-04-2012, 11:42 AM
#31
Developer
Thread Starter
That mod is brilliant ... and a big thanks to Errka for his original post two years ago detailing it
I'm off to Road America with Mark Anderson and crew at 7 AM for the weekend. NASA GTS Midwest Championship races.... but I can get after this mod next week. I will post pics of what I come up with.
10-04-2012, 05:10 PM
#32
Rennlist Member
'78-79 version I
No centering pins. Entire package is just bolted together. Only centering action is flywheel outer rim which sort of forces pieces into line.
'80-83 version II
Three similar centering pins added to make sure all parts are properly centered. Flywheel changed to flat one. Parts can be installed any way compared to each other. All are internally balanced.
'84-86 version III
One centering pin is changed to different size. This makes sure intermediate ring can only be installed one way compared to flywheel and crankshaft. This is due to TDC trigger build into intermediate ring.
If aim is to make similar part as original factory setup H need to move. How much drag is correct is easy to answer when one understands whats purpose of said H tabs. Way intermediate plate works is that three flat springs around intermediate ring push it away from clutch disk I whenever pressure plate is moved back. Reason for H is that their try to stop intermediate plate from moving more than play between H has room. By limiting intermediate plate movement back towards disk II they give disk II room to move between intermediate and pressure plates. Thus H need to remain still and must be tight enough not to move when three flat springs push intermediate plate against them. But they must move when pressure plate pushes entire clutch together.
Reason for old advice to push three H all the way back is that when H work as they should installing clutch will set them automatically to correct position. When disk I wear thinner pressure plate will push intermediate ring forward and H's need to move with it. When they do they will automatically limit intermediate plate movement when pressure plate is pushed back and give both disks about same room to move freely between flywheel, intermediate and pressure plate.
So how to set H tightness is fairly simple. Make them tight enough so that they can be set manually in any position along their movement range and flat springs can't force them to move at all. At same time make sure they are not too tight and will move when pressure plate forces intermediate plate forward.
We did mod in message #5 pics almost decade a go to relatives car. It hasn't moved much over the years but I can give guarantee clutch works 10 times better than unmodified parts ever did.
No centering pins. Entire package is just bolted together. Only centering action is flywheel outer rim which sort of forces pieces into line.
'80-83 version II
Three similar centering pins added to make sure all parts are properly centered. Flywheel changed to flat one. Parts can be installed any way compared to each other. All are internally balanced.
'84-86 version III
One centering pin is changed to different size. This makes sure intermediate ring can only be installed one way compared to flywheel and crankshaft. This is due to TDC trigger build into intermediate ring.
If aim is to make similar part as original factory setup H need to move. How much drag is correct is easy to answer when one understands whats purpose of said H tabs. Way intermediate plate works is that three flat springs around intermediate ring push it away from clutch disk I whenever pressure plate is moved back. Reason for H is that their try to stop intermediate plate from moving more than play between H has room. By limiting intermediate plate movement back towards disk II they give disk II room to move between intermediate and pressure plates. Thus H need to remain still and must be tight enough not to move when three flat springs push intermediate plate against them. But they must move when pressure plate pushes entire clutch together.
Reason for old advice to push three H all the way back is that when H work as they should installing clutch will set them automatically to correct position. When disk I wear thinner pressure plate will push intermediate ring forward and H's need to move with it. When they do they will automatically limit intermediate plate movement when pressure plate is pushed back and give both disks about same room to move freely between flywheel, intermediate and pressure plate.
So how to set H tightness is fairly simple. Make them tight enough so that they can be set manually in any position along their movement range and flat springs can't force them to move at all. At same time make sure they are not too tight and will move when pressure plate forces intermediate plate forward.
We did mod in message #5 pics almost decade a go to relatives car. It hasn't moved much over the years but I can give guarantee clutch works 10 times better than unmodified parts ever did.
all right up until pushing the H adjusters rearward. this works ONLY if you are lucky to have enough space rear ward with the Hs in the max position to give the inter plate to retreat and not hit the pressure plate. usually , it WILL hit. no assembly of the clutch will move this position (except in extreme circumstances. the reason is, that the full retreat of the pressure plate is not much more than 1-2mms. (and the intermediate plate can rest on the flywheel and as the discs wear, it will have near 1mm to continue to move toward the flywheel too. THIS is the way it works. its not supposed to move under assembly and those Hs can be locked in place. problem is , we are adding up all sorts of components, disc thicknes of pressure plate, discs and flywheel. SO, its adjustable. you do it the right way, you set it at about 1mm. Carl, you stiffen those things up or you might give some one a beautiful piece of crap int plate if they move under race conditions. usually, on the street you should be ok if they are reasonably stiff. but racing, the vibration at clutch depression at 6000rpm can rattle the H's rear ward to then hit the pressure plate and drag. the flat springs cant move the H adjusters, thats not the issue here, the high rpm vibration of the floating int plate can, THIS IS THE PROBLEM!!!
10-04-2012, 05:42 PM
#34
Addict
Rennlist Member
Rennlist Member
all right up until pushing the H adjusters rearward. this works ONLY if you are lucky to have enough space rear ward with the Hs in the max position to give the inter plate to retreat and not hit the pressure plate. usually , it WILL hit. no assembly of the clutch will move this position (except in extreme circumstances. the reason is, that the full retreat of the pressure plate is not much more than 1-2mms. (and the intermediate plate can rest on the flywheel and as the discs wear, it will have near 1mm to continue to move toward the flywheel too. THIS is the way it works. its not supposed to move under assembly and those Hs can be locked in place.
the flat springs cant move the H adjusters, thats not the issue here
10-04-2012, 05:49 PM
#35
Rennlist Member
Position of H is meant to change when parts wear out. Thats only reason it was made moveable. Pressure plate will push intermediate plate forward which pushes three H forward. This will always give intermediate plate same space to move regardless of how much disk I is worn. There has to be enough space for disk II when pressure plate is moved back by work cylinder. If not, there is something wrong in setup like worn H adjusters which allow too much pressure plate movement. By adjusting H all the way to the back before clutch is bolted together automatically adjusts H into correct position which is not all the way to the back especially when parts are worn. If H needs to be in any other position for clutch to work than where pressure plate push it or H does not keep this position in all situations there is something wrong in some parts.
They can when intermediate plate is worn out. Whole point in making H tightness adjustable is to make sure H does not move in any other situation except when pressure plate is pushing intermediate plate forward.
They can when intermediate plate is worn out. Whole point in making H tightness adjustable is to make sure H does not move in any other situation except when pressure plate is pushing intermediate plate forward.
what you say is true regarding the wear of the discs and frontal contact, BUT, think about it, when that happens the wear has to be as much as the frontward gap. (which is about 1mm too) after that, the rearward gap doesnt matter much, and yes, as it wears past this point, the prssure plate will move the Hs forward, but at that point, you will be right. you can now put the H's all the way back and the pressure plate wil push the Hs all the way forward to make contact. BUT, this means the rear gap doesnt matter any more, unless its worn so far that the Hs are all the forward and the int plate cant retreat. its all real simple, but you still have to think about it!!! again, adjusting as you SAY, in your post is DEAD DEAD wrong for any kind of new or good shape int plate adustments. so please dont recomend it. all the clutchs ive worked on and ive done a lot, have required the factory space of 1mm, NOT "move them all the way rearward" !!!!! do that on my car, scot's or anyone with a dual disc that i know, and it will not move the H's forward by much, if at all .
10-04-2012, 05:59 PM
#36
Addict
Rennlist Member
Rennlist Member
When I speak about adjusting all the way back I mean adjustment is done when clutch fork is pulled back in same position as when work cylinder pushes it. This means when fork is released pressure plate will push three H forward to position where intermediate plate can move back distance H allows it to move. If this distance is too far and intermediate plate will keep disk II pressurised against pressure plate when clutch pedal is pressed there is something fundamentally wrong with the setup. Either mixed parts or some parts not working as they should.
If H needs to be set into some specific position and locked there it means that space given for disks I and II will change as they wear. Idea factory had when they used thight but pressure plate force moveable H was that both disks would always have about same space between them to move freely when pedal is pressed. Only way to achieve this when parts wear out is to have moving H piece.
If H needs to be set into some specific position and locked there it means that space given for disks I and II will change as they wear. Idea factory had when they used thight but pressure plate force moveable H was that both disks would always have about same space between them to move freely when pedal is pressed. Only way to achieve this when parts wear out is to have moving H piece.
10-04-2012, 09:07 PM
#37
Rennlist Member
When I speak about adjusting all the way back I mean adjustment is done when clutch fork is pulled back in same position as when work cylinder pushes it. This means when fork is released pressure plate will push three H forward to position where intermediate plate can move back distance H allows it to move. If this distance is too far and intermediate plate will keep disk II pressurised against pressure plate when clutch pedal is pressed there is something fundamentally wrong with the setup. Either mixed parts or some parts not working as they should.
If H needs to be set into some specific position and locked there it means that space given for disks I and II will change as they wear. Idea factory had when they used thight but pressure plate force moveable H was that both disks would always have about same space between them to move freely when pedal is pressed. Only way to achieve this when parts wear out is to have moving H piece.
If H needs to be set into some specific position and locked there it means that space given for disks I and II will change as they wear. Idea factory had when they used thight but pressure plate force moveable H was that both disks would always have about same space between them to move freely when pedal is pressed. Only way to achieve this when parts wear out is to have moving H piece.
Look, pushing it all the way back will allow travel of the intermediate plate of MORE than 1mm, and for which it WILL contact the rear surface (pressure plate) and drag the drive shaft . THIS IS THE REASON that there is a 1mm gap, so that when the clutch is depressed, the INT plate can only travel rearward by 1mm. thats it. 1mm!!!!!!!!! any more, and it will contact the pressure plate surface! this is how it works. NOW, if you have a system that pulls the surface rearward by more, or if the discs are worn badly, you can push the H adjusters unitl you get to the rear ward limit and you might get lucky and have it be far enough away from the pressure plate surface so that it doesnt drag. THIS IS A SLIM chance. if you have done this, you got lucky.
now to your second thought. the design is to use the H adjusters Only for rearward limits. once that is set correctly on a system in decent shape, there will be an equal distance frontward for the pressure plate to make contact and put pressure on the flywheel. as the discs wear, that distance may greaten, until it hits the limit of the H adjuster and at that point, releasing the clutch will move the H adjusters actually forward to make sure there is sufficient contact on the flywheel. the rearward gap will be presevered by design.
PROOF. i nailed my H adusters so that they cant move. you have one shot at this , because if you are too narrow in the gap, the flyweel still makes contact under clutch pedal depression. if its too much, the INT makes contact with the pressure plate. but, if it is correct, the rear ward gap is correct and allows the int plate to retreat, but not contact the pressure plate. as the discs wear, and wear, there will be a point where the INT plate will not be able to move to hit the flywheel because the H 's are nailed down. this is a lot of disc wear. at that point, normally, the H would move and allow this self adjusting phenom to take place, not effecting the rear ward movement that inherently would be correctl as the discs wear. Make sense???
12-18-2021, 12:05 PM
#38
Rennlist Member
'78-79 version I
.........
So how to set H tightness is fairly simple. Make them tight enough so that they can be set manually in any position along their movement range and flat springs can't force them to move at all. At same time make sure they are not too tight and will move when pressure plate forces intermediate plate forward.
We did mod in message #5 pics almost decade a go to relatives car. It hasn't moved much over the years but I can give guarantee clutch works 10 times better than unmodified parts ever did.
.........
So how to set H tightness is fairly simple. Make them tight enough so that they can be set manually in any position along their movement range and flat springs can't force them to move at all. At same time make sure they are not too tight and will move when pressure plate forces intermediate plate forward.
We did mod in message #5 pics almost decade a go to relatives car. It hasn't moved much over the years but I can give guarantee clutch works 10 times better than unmodified parts ever did.
If it matters these are all 77-79 units.
Last edited by drooman; 12-18-2021 at 12:07 PM.
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islaTurbine (12-19-2021)
12-18-2021, 06:07 PM
#39
Former Sponsor
An "early" intermediate plate (not as much travel "built in" as a later plate), with a late front clutch disc (with Marcells), the "H" adjusters are almost always going to need to be all the way towards the rear, for the front disc to release, anyway.
The "issue" with the "H" adjusters moving too far to the rear generally is only on a "late" intermediate plate with worn "H" adjusters, allowing more than 1.5mm of travel, which allows the intermediate plate to release the front disc, but "trap" the rear disc.
The "issue" with the "H" adjusters moving too far to the rear generally is only on a "late" intermediate plate with worn "H" adjusters, allowing more than 1.5mm of travel, which allows the intermediate plate to release the front disc, but "trap" the rear disc.
12-19-2021, 10:54 AM
#40
Rennlist Member
An "early" intermediate plate (not as much travel "built in" as a later plate), with a late front clutch disc (with Marcells), the "H" adjusters are almost always going to need to be all the way towards the rear, for the front disc to release, anyway.
The "issue" with the "H" adjusters moving too far to the rear generally is only on a "late" intermediate plate with worn "H" adjusters, allowing more than 1.5mm of travel, which allows the intermediate plate to release the front disc, but "trap" the rear disc.
The "issue" with the "H" adjusters moving too far to the rear generally is only on a "late" intermediate plate with worn "H" adjusters, allowing more than 1.5mm of travel, which allows the intermediate plate to release the front disc, but "trap" the rear disc.
12-19-2021, 01:31 PM
#41
Former Sponsor
When I've ordered the original part number front disc 9281161123 I get a Marcell disc, for as long as I can remember. I have a few old NOS Sachs clutch kits with PP release bearing and two clutch discs, and those have a Marcell disc for the front as well. When you say "late" front Marcell disc does that mean the early original front discs were non Marcell? I've pulled aparts a few cars over the years that used two rear discs 92811601136 in there but I always assumed it was someone's idea of a cost saving measure.
I believe the Workshop Manual covers all the changes in these twin disc clutches, in several pages.
When Porsche went to the Marcell front disc, they added more travel in the "H" stops, to allow for the expansion of the Marcells (when released.)
There's an internet myth that the "H" stops never wear, but that's just nonsense. A little bit of wear in an early intermediate plate and a Marcell disc works fine. A little bit of wear in a later intermediate plate means that the stops can not be pushed all the way to the rear.
(With all new parts of the appropriate year, the "H" stops were simply pushed all the way to the rear, with clutch installed.)
12-20-2021, 08:57 AM
#42
Rennlist Member
Yes, definitely.
I believe the Workshop Manual covers all the changes in these twin disc clutches, in several pages.
When Porsche went to the Marcell front disc, they added more travel in the "H" stops, to allow for the expansion of the Marcells (when released.)
There's an internet myth that the "H" stops never wear, but that's just nonsense. A little bit of wear in an early intermediate plate and a Marcell disc works fine. A little bit of wear in a later intermediate plate means that the stops can not be pushed all the way to the rear.
(With all new parts of the appropriate year, the "H" stops were simply pushed all the way to the rear, with clutch installed.)
I believe the Workshop Manual covers all the changes in these twin disc clutches, in several pages.
When Porsche went to the Marcell front disc, they added more travel in the "H" stops, to allow for the expansion of the Marcells (when released.)
There's an internet myth that the "H" stops never wear, but that's just nonsense. A little bit of wear in an early intermediate plate and a Marcell disc works fine. A little bit of wear in a later intermediate plate means that the stops can not be pushed all the way to the rear.
(With all new parts of the appropriate year, the "H" stops were simply pushed all the way to the rear, with clutch installed.)
12-20-2021, 01:15 PM
#43
Former Sponsor
Thank you. I digested those pages of the WSM... One can get a sense of the frustration of Porsche trying to get this system to work optimally over the years. They have their note in there not to mix and match parts between the various design changes 77-83, kind of saying (without saying) to get a 80-83 type intermediate plate, shaft, and guide tube for use in 77-79 cars with the marcel disc. Interesting that real world observations of 43 years and many worn out clutch parts suggest it is perhaps a better combination to use the 77-79 parts with the marcel front clutch, at least with regard to inevitable intermediate plate wear.
In my "first" years of working on these vehicles, I actually planned on having to remove and change clutch parts a couple of times, before I was able to get one to function perfectly. (I call that first dozen or so years my "learning curve").
Once I figured out how all of the individual pieces interacted with each other and treated each clutch's pieces as unique, repairs got much easier, since the clutches I worked on, after this, generally functioned better....the "first" time I did them.
Last edited by GregBBRD; 12-20-2021 at 01:20 PM.
12-20-2021, 05:35 PM
#44
Drifting
Thank you. I digested those pages of the WSM... One can get a sense of the frustration of Porsche trying to get this system to work optimally over the years. They have their note in there not to mix and match parts between the various design changes 77-83, kind of saying (without saying) to get a 80-83 type intermediate plate, shaft, and guide tube for use in 77-79 cars with the marcel disc. Interesting that real world observations of 43 years and many worn out clutch parts suggest it is perhaps a better combination to use the 77-79 parts with the marcel front clutch, at least with regard to inevitable intermediate plate wear.
Last edited by islaTurbine; 12-20-2021 at 05:39 PM.
12-20-2021, 08:09 PM
#45
Former Sponsor
Pasha's entire clutch kit was worn, old, and hotspotted. The best I could do was to update her to the 80-83 intermediate plate and flywheel (which I found in remarkable condition on eBay), a new pressure plate, new marcel clutch discs, the original throwout arm (with a curved throwout bearing surface) and a new flat throwout bearing to coincide with the curved-surface arm. I always wondered why Porsche went to the pin-centered design instead of keeping the original 77-79 bolt-centered version? The pin-centered seemed like a bit more work to install.
There's no "slop" in the pins on the late model clutch.
But there has to be some "slop" in the flywheel on the early clutches, for the intermediate plate to fit in.
"Slop" increases the chance of things being out of balance.
Additionally (#1): (Although it may not have been considered by Porsche), most flywheels get "ground (instead of cut in a lathe) when they are resurfaced. And getting a square outer edge, on the stone used for grinding, is difficult to maintain. Therefore, right at the very edge of the flywheel where the 90 degree edge is present, a reground early flywheel almost always has a raised radius, instead of the "undercut" that Porsche originally put in the flywheels. This "raised radius" can keep the intermediate plate from sitting flat against the flywheel....leading to clutch chatter. (This is amazingly common....and we learned about this problem on the 911 series, before we saw this on the 928 series.)
Additionally (#2): (Also may not have been considered by Porsche), indexing a flywheel perfectly centered on a flywheel regrinding machine is difficult (not actually difficult, but takes time.) So, inevitably, the stone will hit one side of the 90 degree edge, before the other side. This increases the odds of the entire clutch being mounted even further out of balance.
Note that #1 and #2 do not occur on a "flat" flywheel, without the outer 90 degree edge.