Re: Clutches Again & Pressure Plates

Posted by DJ.Voyce on April 06, 1998 at 08:25:52

In Reply to: Clutches Again
posted by MRR on April 03, 1998 at 09:39:48

G'Day MRR,
The answer to your question is YES. Now let me try & dispel all the rumours & untruths of the wonders or "Dark Science" of pressure plate operation & settings & put all those mysterious HobbGoblins to rest. There is indeed a machine available for checking the "clamp load", which is the amount of force that the face plate of the pressure plate has available to press the clutch disc against the flywheel face. These machines or setting tables also provide a facility for measuring & adjusting the lever height & can also check for correct operation or release characteristics of the unit. However as quite correctly stated in the postings, one of these machines would set you back a bit more than a bunch of roses for your sweetheart (girlfriend or wife. Who buys flowers for a car?) & might approximate more to a second mortgage on your house, so the average home handyman is unlikely to have one tucked away in the corner of his garage, but every pressure plate rebuilder should have one. The problem now is what should these specifications be for the A pressure plate as specified by Henry?. This question I'm unable to answer & we'll have to look to the Whiz Kids of this board for help, however what I can explain is the rule of thumb methods that we've been using for years to re-condition & set up some strange units which may have been imported from unknown little countries in order to aid their struggling economies, so here goes.
Firstly let me try & explain for the non-technical in laymans terms the function of the pressure plate, clutch disc assembly, & that is to provide a disconnectable mechanical (as opposed to fluid) drive between the engine & transmission. The drive is achieved by the spring pressure behind the face plate of the pressure plate, (which is bolted to the flywheel) sandwiching the clutch disc (which is splined to the transmission input shaft) tightly onto the flywheel, so causing the whole unit to turn as one. Release is achieved by pushing the levers (via the throwout bearing) towards the flywheel which acts against the spring pressure holding everything in the sandwiched position, & lifts the face plate away from the clutch disc, so allowing it to spin freely between the face plate & flywheel so disconnecting the engine from the transmission.
So much for the theory, now for the practical.I've always figured that some idiot must have put the thing together in the first place as its got pieces that fit a wrench, so it must be quite feasible for some other idiot to take it apart again. This is quite true, but the trick is to achieve this small task without endangering anyones life, (especially my own) the possibility of which is greatly improved by having a number of reasonably strong springs held captive under compression. This can be achieved fairly simply by using a spare/old or your own flywheel, preferably off the engine as it makes life a lot simpler, to clamp & strip the pressure plate assembly & can be carried out as follows.
1)Firstly you'll need about 2 feet of 5/16" N.C. threaded bar cut into 6 pieces (studs) 4 inches long & 6 nuts to suit.
2)Screw one piece of threaded rod into every alternate hole in the flywheel & tighten into the bottom of the flywheel holes by locking two nuts together at the top of the threads & screwing down until tight. N.B. this procedure is very important to prevent the stud/rod unscrewing itself when removing from the flywheel, which could also be a contributory factor to instant ill health.
3)With the clutch disc in position slide the pressure plate over the studs & tighten down onto the flywheel with the 6 nuts.
4)All the adjuster nuts can now be removed from the slotted bolts at no personal risk. A tip to prevent damaging or splaying the slotted bolt is to knock back the indented locks in the nut collars & grind a screwdriver to a parallel end as opposed to a chisel like point so it can fit right down into the bottom of the slot.
5)The 6 nuts can now be removed by backing off each one 2 to 3 turns at a time, working evenly around the circumference in a star type pattern then remove the cover assembly from the studs & voila it's now in pieces. (The only difference now between you & the idiot that first put it together is he knows how it goes back together).
6)Clean all parts & carry out the following inspections.
7)Take a ruler & check the face plate for flatness & if it's concave or convex, you can have it machined at your local machine shop.
8)Check the levers for wear on the ends where the throwout bearing contacts them & cracks around the pivot points, once again your machine stop could build up any wear with a stainless steel or hard facing type welding rod & re-grinding to shape.
9)Check for broken or collapsed springs.
10)Have the threads cleaned up on the slotted adjuster bolts to facilitate easy assembly.
11)Assembly is the reverse of the above procedure apart from setting up which is a fairly simple operation & goes as follows.
1)Measure the thickness of the clutch disc & find 3 equalspacers of equivalent thickness such as old nuts, a stack of washers etc. & place them approximately the same distance apart on the flywheel face.
2)Place the adjuster bolts through the face plate & place in the flywheel on top of these spacers. (It may be easier to use the cluch disc initially to stop the adjuster bolts dropping through, then remove the pressure plate & clutch disc & re-assemble with the spacers before carrying out the lever setting)
3)Fit the 6 anti-rattle springs over the adjuster bolts
4)Place the cover over the studs & slide the levers into position one by one with the rounded contact face for the throwout bearing facing upward & ensuring that they locate correctly in the cover & they're all above an adjuster bolt.
5)Run the 6 nuts down the studs & tighten evenly ensuring the adjuster bolts locate in the levers correctly & the pegs on the bottom of the cover enter the slots on the face plate.
6)Lift each lever one by one & fit the pivot washer with the legs facing downward, ensuring they locate in the indents in the lever correctly, the flat washer, & the adjuster nut.
7)Adjust each lever to a height of about 1 7/8" above the flywheel face where the clutch disc runs. It's easier to measure off the flywheel bolt face, so measure the distance from the clutch face down to the bolt face & add it to the 1 7/8" measurement to get a setting, then lock all the adjuster nuts by knocking the collar of the nut into the slot on the adjuster bolt.
8)The operation of the unit can now be checked by using a large bolt or piece of threaded bar with nut, & two discs the approximate size of the outside diameter of the throwout bearing with a hole in the centre to fit the bolt or bar. The test is carried out simply by placing a disc behind the flywheel on the crankshaft face with the bolt/ threaded bar through it & the second disc resting on the pressure platefingers. Then by using the nut the fingers are drawn downabout 3/8" to 1/2" with the second disc, the face plate shouldthen lift enough to allow it to clear the spacers or clutch disc & everythings OK. Remove the pressure plate & studs from the flywheel & you're in business.
There we have it. I hope this proves that there's no exorcism needed for the evil pressure plate demons. Feel free to E.Mail me if you think I've missed something or you need more help.
Regardz
DJ.
OutOfAfrica A's
: One more time, does anybody know if there is a way to test a pressure plate to see if it is serviceable?Other than bolting it on and engaging the peddle, can you take these guys to somebody (who?) to put on some test machine (what) to see if it meets spec?

Follow Ups:
Re: Clutches Again & Pressure Plates Glen Weilbaker April 06, 1998 at 11:40:48(1)
Re: Clutches Again & Pressure Plates DJ.Voyce April 07, 1998 at 01:25:10(0)
Now that's an answer! MRR April 06, 1998 at 10:59:21(2)
Re: Now that's an answer! Joe April 06, 1998 at 13:11:38(0)
Re: Now that's an answer! geo April 06, 1998 at 11:41:59(0)

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