Clutch Wander

Just thinking out loud here (sorry, bad habit ).........

Blown alky with a clutch, roots or screw, are you guys taking any steps to prevent the clutch & flywheel from wobbling and walking and wreaking havoc with the crank and rear main bearing?

Steps like: controlling the air gap vs the motor plate, or running pressed-in bumpers at the back of the flywheel, or spin balancing the clutch, or rub pads pressed into the motor plate?

Saw something similar in a fuel application, and wondered if it might be of any benefit in an alky application, or not?

 

I posted on this awhile back, my brother got his from Rit Pusteri, top fuel guy. I think it happens because the metal from the floaters moves around from the heat and the clutch goes out of balance, not sure if you can understand what i mean, you know how the floaters get blue and they have high spots on them, thats what I'm talking about.. I don't have my engine balancer anymore but if some one would take a clutch set up after a run and put it in a engine /clutch balancer I'll bet its out of balance.

 

For what it's worth, we suspect that some rear main, and clutch issues, are caused by drivers that push in the clutch right at the finish line.

 

That's a good prognoses, when the clutch is pushed in if the floaters or disks are out of balance they would wobble even worse, good call.

 

The TFFC that I worked on last week had an east/west clutch. Pressed into the back of the Ti flywheel were three carbide bumpers which spun near the motor plate with about .030-.035" air gap. It was explained to me that without these bumpers the clutch would wobble & nutate and flex the crank and take out the rear main bearing. Even with the bumpers & air gaps, the rear main of this particular motor had begun to wear down to the copper in places after an aborted tire smoke run.

On the plane home, I began to wonder if it might make sense to somehow control the excursion of the clutch relative to the motor plate plane (perpendicular to the crank center line), and whether it might make sense to spin balance a clutch from time to time.

I'm going to try a couple of these ideas in our screw blown Pro Mod. I figure it can't hurt?.......

 

Pushing down a heavily counterweighted clutch at 9500 rpm puts a tremendous load on the crank, and in particular the thrust bearing. Also very hard on the throwout bearing and levers. The clutch does not release cleanly from the engine just like sitting on the starting line with the clutch down and you were to put the throttle wide open, the car would take off due to deflection in the clutch and linkage. Better to let off the throttle at the finish, then pull out one shift button, which puts the trans. into neutral.

On the subject of thrust bearings, always file a small relief at the edge on one half of the bearing from the oil groove to the rear side to pressure feed the thrust.

 

This might help you guys.
In roots blower motor tractor pulling, I've never even heard of it, but most of us use slipper clutches without pedals. So we can't "step in the clutch too soon".
Two different dyno guys we've been to watched the thrust clearence of the shaft behind the flywheel very close. And related this to blackening of bearings.
My $.02.

 

I don't know if it's been done yet or if they make one but I had this Idea a while back and mentioned it to an old schooler but they shot it down. If You have the machinery to make some type of one or two piece needle bearing or roller bearing set up behind the clutch so that it could mount to the back of the clutch and will ride on the motor plate or vise-versa. Some use a teflon ring, steel ring, and carbide bumpers, But think about when the clutch hits those teflon-steel-carbide rings! Don't think for a second that it's not causing more drag on the motor, more heat on the clutch and crank, and more friction on the disks! If a bearing were there to take up the slack you'll have alot less of all of that. Plus It would keep the clutch square to the block-crank and reduce all that crank blackening, bearing beatings, and wobbleing around bull shit. If I used a clutch I would Give it try. If it were easy every one would do it, but everyone likes easy. If someone makes a proto type before I do Don't forget who came up with the idea for lawsuit purposes HE-HE-HE
Just a thought I had
Thank God for Torque converters

 

From what I understand, ( and that ain't much ) the top fuel and funny car guys are using .004 more than normal clearance on the rear main.

 

Tol, after you ask a question do you read other peoples post, or do you just keep thinking on your own and keep posting your own toughts????

 

Eli, yes I read, but I'm also not afraid to keep thinking and/or expanding upon an idea. I added detail to show what a recent modern top fuel team was actually doing ......

Mike, yes, the BAE that we were working on had an aux feed specifically to the rear main.

Lorenzo, my thought was a ring shim affixed to the motor plate that the clutch could touch against if it felt so inclined. Something much harder than AL and something that could be shimmed or thickness controlled. Our rear motor plate is .500" AL, so we do have some meat to affix something to.

 

we had this issue big time last few times out with a new motor combo, spent last few weeks spare time measuring, indicating, inspecting all the parts, near as I can see the floaters (we were using the THICKER Ace pieces) didnt fit real tight to the stands and shows a lot of evidence that (floater) is the source of the 'wobble' (galling and slotting of stands, mushrooming stand relief in hat and studs pushed out enought to have to pound hat off), so I think ALL of you are right, pedaling (loading and unloading), gets the floaters into a 'wobble' cycle, gets progressively worse when clutch mass accelerates to high speed (spin tires) and final whacking of bearing when pushing clutch in an end of run to end the agony

at least I have a matched set of TFX rear main caps to use as bookends for the experience, theyre cute but a little toasty

and I dont think I will run
a)small stand clutch
b)thick ace floaters
c)without the buttons on midplate or clutch
d)no more pushing in clutch at lights

 

Mike, whome@look.ca. Yeah, sorry, my PM's need cleaning up........

 

As to Mike's question on feeding oil to rear main, we have modified our setup for '08 by going to System 1 oil pump and feeding the rear main via -6 line from oil pump to the top of the block. BAE blocks have ports in the top of the block over the rear main.
We have had multiple times in '07 that the rear main and often the crank, were destroyed after just one run. We came to the conclusion late in '07 that our clutch was getting out of balance somehow and causing the problem. We've now gone to a new clutch (Boninfante, pedal) but have not made but one run with it and had other problems (torched head...)
We are planning on making Belle Rose in a couple of weeks. With a little luck the changes will cure the rear main problem.
Wayne

 

I have been thinking about this some more and The bearing in the end of the crank could be causing this or adding to it, think about it your using the same size bearing that was used when a two disk clutch was being used, I think that the clutch shaft should be bigger the pilot bearing should be bigger, especially in the fuel cars, they use five disk , it must weigh 100 lbs.
Point is that little piece of S#!t bearing might be going first and letting the disks jump all over the place, and causing an out of balance condition. another thing ,some thing i said a million times before floaters should be round with holes not scalloped, a round hole will stay centered better than a half circle, with less chance of going out of balance. I know that the clutch guys want you to wear out parts, but when you start to break stuff like your running a fuel car then you got to do something, how many of you can afford to change a crank every run???