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Brand new throwout bearing and clutch smashedsad smiley

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ice Avatar
ice Gold Member Larry Ice
Lawrenceville, GA, USA   USA
Ok guys, seems the jury is still out on graphite vs bearings. When on of the guys (Gerard?) mentions about the arc being different and not good for the bearing it seems like the graphite TOB goes thru the same arc when the clutch is pushed in. Ok, if both types of bearings move thru an arc across the pressure plate bearing surface it would seem to me having a bearing that spins would at least cut down on the heat generated as the bearing moves across the pressure plate flange? Just some thoughts!



Iceman

Atlanta GA

60 AH MK1
62 AH MKII
67 Midget
71 Midget

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dickmoritz Avatar
dickmoritz Gold Member Dick Moritz
Philly 'burbs, PA, USA   USA
Graphite bearing works just fine a little off-center because it is still pressing against the flat disc on the pressure plate. It runs cool because it is self-lubricating. With the roller bearing, the disc on the pressure plate is omitted, such that the bearing bears against the pressure plate diaphragm fingers, and off-center will result in uneven release of the pressure plate's friction surface...

Dick

In reply to # 3553552 by ice Ok guys, seems the jury is still out on graphite vs bearings. When on of the guys (Gerard?) mentions about the arc being different and not good for the bearing it seems like the graphite TOB goes thru the same arc when the clutch is pushed in. Ok, if both types of bearings move thru an arc across the pressure plate bearing surface it would seem to me having a bearing that spins would at least cut down on the heat generated as the bearing moves across the pressure plate flange? Just some thoughts!



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

AN5L8016 Avatar
AN5L8016 Mark Haynes
Nederland, Colorado, USA   USA
Where did this come from, Dick?
In reply to a post by dickmoritz With the roller bearing, the disc on the pressure plate is omitted, such that the bearing bears against the pressure plate diaphragm fingers,
If you remove the plate for the back of the pressure plate, you change the contact point of the TO bearing such that, as you said, the bearing now contact off-center. The bearing-style TO should be made to the same distance from centerline dimensions as the original, so use of the plate on the PP is mandatory, and therefore retains the contact pressure as a distributed load on the PP fingers rather than a momentary load on the point of the fingers which would cause undue wear and premature failure of the PP fingers, No?



'58 Bugeye
'05 Mini Cooper S

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dickmoritz Avatar
dickmoritz Gold Member Dick Moritz
Philly 'burbs, PA, USA   USA
Thanks for the note, Mark. I may well be mistaken on this point, as I always use the clutch kits with the carbon bearing. I know with the 'murcan cars I've worked with over the years they've all used mechanical linkage and a ball/roller bearing riding directly on the diaphragm fingers, with no disc for the bearing to abut. I'll welcome you or someone else confirming that the pressure plate used with the roller bearing is the same configuration as that used for the carbon bearing.

Errabundi saepe... cool smiley

Dick

In reply to # 3553650 by AN5L8016 Where did this come from, Dick?
In reply to a post by dickmoritz With the roller bearing, the disc on the pressure plate is omitted, such that the bearing bears against the pressure plate diaphragm fingers,
If you remove the plate for the back of the pressure plate, you change the contact point of the TO bearing such that, as you said, the bearing now contact off-center. The bearing-style TO should be made to the same distance from centerline dimensions as the original, so use of the plate on the PP is mandatory, and therefore retains the contact pressure as a distributed load on the PP fingers rather than a momentary load on the point of the fingers which would cause undue wear and premature failure of the PP fingers, No?



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

refisk Avatar
refisk Rick Fisk
Frankenmuth, Michigan, USA   USA
Mark,

Cars with roller type throwout bearings usually do not have the disc on the pressure plate. The roller bearing rides concentrically on the "fingers" of the spring mechanism in the pressure plate. Because the throwout bearing is concentric with the transmission input shaft there is no grinding between the fingers and the throwout bearing. Our Spridgets use the disc on the pressure plate because the throwout bearing is not concentric with the disc and slippage has to occur throughout the life of the clutch.

Here is a Chevy pressure plate with no disc.....


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PeterC Avatar
PeterC Platinum Member Peter Caldwell
Madison Wisconsin, USA   USA
Couple of terms.... the "plate" on the pressure plate for the bearing is a thrust plate.
The sleeve that some cars use as a guide for the bearing to ride on over the input shaft is a quill.

Peter


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ice Avatar
ice Gold Member Larry Ice
Lawrenceville, GA, USA   USA
thnx for setting us straight Pete.



Iceman

Atlanta GA

60 AH MK1
62 AH MKII
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S1 Elan Kurt. Appley
Akron, Ia., USA   USA
Hap has been using them for years on race cars with, I presume, heavier duty pressure plates. That may be a good substitution in that case but I would still like to hear from someone that has put 40K miles on one. With the arrangement of the TO bearing in a Spridget I can see no way that the ball bearing wouldn't be turning all the time. Even if you tried to retract the Throw out the bearing would tip against the pad on the pressure plate fingers.

Kurt.

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AN5L8016 Avatar
AN5L8016 Mark Haynes
Nederland, Colorado, USA   USA
I was asking to be sure that Dick was not advocating removal of the (to be correct) Thrust Plate from the pressure plate if one is using a roller TO bearing, and that if such was the case that he had some reason for advocating so. As you can see from my thought process, I wholeheartedly believe that even with the use of a roller bearing, one needs to have the thrust plate in place.



'58 Bugeye
'05 Mini Cooper S

dickmoritz Avatar
dickmoritz Gold Member Dick Moritz
Philly 'burbs, PA, USA   USA
Thank you, Mark. I don't know enough about these roller bearing setups to advocate one way or another. I just know that the old-school American cars I've worked on do not use such a thrust plate, and I'm just uncomfortable with the lack of a proper pull-back mechanism, coupled with my good experiences with the carbon bearings, so I just stick with what works for me...

Appreciate the insights... smileys with beer

Dick

In reply to # 3554453 by AN5L8016 I was asking to be sure that Dick was not advocating removal of the (to be correct) Thrust Plate from the pressure plate if one is using a roller TO bearing, and that if such was the case that he had some reason for advocating so. As you can see from my thought process, I wholeheartedly believe that even with the use of a roller bearing, one needs to have the thrust plate in place.



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(Often wrong, but always certain)

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CtMGDude John R
New Fairfield, Ct, USA   USA
I think Hap answered the question and with great clarity and proven authority on the subject. Barring manufacturing errors, I will go the Roller bearing route the next time, or design and make one of those linear hydraulic roller bearing set ups, (maybe sealed needle?) set ups (it's nice to have a small machine shop! smiling smiley I have a heavy duty clutch in my car, and I worried that the graphite, or whatever it is bearing would wear sooner, which is why I don't use the clutch when put putting around down (up shift only of course). So far so good, and these engines do come out rather quickly and easily. winking smiley

Speedracer Avatar
Speedracer Platinum Member Hap Waldrop
Greenville, SC, USA   USA
1967 MG MGB Racecar "The Biscuit"
Peter May makes a guided T/O bearing set up, but I think it may only be for the 7.25" race clutch though, Mike Miller for years, I am sure still does, modified front trans cover by fabbing and welding an aluminum tube on them to help align them the bearing, of course the HTOB is nice, but can be a total PITA if not set up right and if you have a hydraulic failure, guess what you will be doing, yep pulling the engine, did that before with Taylor race box and it's POS SAAB 900 HTOB. All that happen here to Jan is the carbon material came unbonded, if it had worn out, you'd see remainder of it still there. All these designs have worked fine over time, but occasionally there are bad parts. I don't know that have a very strong opinion about of them, I have used them all overtime, and "knock on wood", all of them have done as they were designed.

There is another way as well, a floating bearing, this is exactly what many a A series racers has done over the years when using a typical slave cylinder set up and 7.25" race clutch, Winners Circle used what many have said was a Porsche 914 roller bearing, it had a fabbed center in it to let it center and loosely fit over the input shaft, then normal carbon bearing stays in place but it simply used as device to push the roller bearing into the clutch, this things were freaking bulletproof.



Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com


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Sprite1956 Roger Parry-Jones
Melbourne, Victoria, Australia   AUS
Guys,

I've used both types. I was frustrated to find the carbon bearing failed after two race days and I believe that until about 1990 the carbon throw out bearing was fine but "alternative sources" provided cheaper versions which seems to be all that is available now.

My early attempt to manufacture a roller bearing insert produced a slight difference in total bearing height but that seemed to be accommodated by the hydraulics. Unfortunately it was "nose heavy" and rattled on the first motion shaft until I took it out after about six months because I was changing the gearbox anyway. There used to be a replica ball bearing replacement for the 1275 which was lighter and worked well for me over several motor/gearbox combinations but that is no longer available. The advantage of no loss of rev's on gear changes was it's most useful attribute though. One problem was that the packed in bearing grease would over heat and fall out. They'd work fine for months and then start to rattle for a long time before I pulled them out for replacement but none ever actually failed. I've used Colin Dodd's and also Peter May's setup (second hand!) and found both to work as expected, flawlessly. Unfortunately I've got no advice as to longevity. The longest combination of road and track use was only about 13,500 kilometres (about 8,000 miles) but they were HARD MILES!

There's good advice about ensuring your new carbon throwout bearing is separately packed for shipping to you but I do think there's a problem with quality control and the type of carbon being used today. On consideration, I'd try a roller bearing again suited to the thrust plate on 6.5 inch or 7.25 inch clutch covers. With my record, they'd never stay in long enough to fail!

Good luck!
Roger

CtMGDude John R
New Fairfield, Ct, USA   USA
I believe that the general decline in good manufacturing has made the carbon bearings a Hit or Miss solution. It shouldn't be that way but it is. I like Hap's idea of the floating beating. I makes sense. I'd like to go to Tec Bearings, and talk with them about possible a thinner bearing, then machining an insert for the clutch so that the bearings rides on that surface, and concentrically there is not a problem. It seems that the solution could also be made to the insert bu having that float, and using a bearing rubbing against that. That may be easier as the shaft going into the tanks is thick, and long, and could be easily machined to accept a floating end cap that would be held in lace the the assembly of the unit.

I do like the Hydraulic Throwout unit posted earlier. that would be easy to make, just some lathe work. Obviously, careful dimensions, but in reality, most things made round on a good lathe are not hard to do. The unit below may be expensive, but I have stock that size, and with some measuring of the actual car, I believe I could knock one out. The stock is just hanging around doing nothing, and o-rings are cheap enough. It would be easy to incorporate a spring to pull it back too.

I'd sure like to her or read more about the Porche's floating throwout bearing, time to Good it, and see if I can find the info. If someone had it and could post a link, that would be nice. winking smiley




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