Roller Style TOB

[Bill Hudson]

Went to my favorite NAPA this afternoon and was quizzed about a TOB similar to this http://www.ebay.com/itm/NEW-CLUTCH-THROW-OUT-BEARING-AUTO-ROLLER-STYLE-INTERNATIONAL-FARMALL-CUB-LOBOY-/281566753564?pt=LH_DefaultDomain_0&hash=item418eafb31c. I know there have been numerous threads concerning modifying the graphite TOB carrier to accept a Chevy (I think) TOB, has anyone had experience with this, or similar, TOB? I know this may be opening up the proverbial "which oil is best" can of worms, however, maybe technology is catching up to our 60 year old Cubs. If the technology is catching up, in a positive way, we need to take a close look at it. One of the fellows at NAPA needs to put in a new TOB and is considering this, or similar, as an option to the standard TOB. Oh, as an aside, I'll be involved with the TOB installation, no matter what style he uses.

Bill

Edit: I just went back and looked at the Ebay listing, the TOB is being sold by Hamilton Bob's and 100% satisfaction is guaranteed. I'm a lot more comfortable with choosing to use one of these now. Hamilton Bob's are good people, in addition to being a site sponsor.

[Donegal Cub]

The outcome will be looked forward to with interest by forum readers.
Bernard,
Donegal Cub.

[cub.bub]

I changed my TOB about 6 months ago and thought long and hard, after reading old post on the subject I decided if it lasted 60 years why not. But your right Bill, there has been great improvements over the years and (oil) is one of them.
The new bearing makes sense to me....just my 2 cents.
My only regret when doing the clutch and TOB, is not changing the rear main seal!
But that is happening soon, between snow and grass season.

[Bill V in Md]

Bill,
Clark Thompson has experience with the automotive style TOB's. Below is a link to a discussion on this topic:
http://www.farmallcub.com/phpBB2/viewtopic.php?p=684019#p684019

[tst]

I swapped out two of them that failed, I did not install them, they were so bad I do not know why they were blown apart, I put the old style back in
Tim

[Matt Kirsch]

I know a lot of people had problems with previous attempts at an automotive style TOB.

My understanding was that it wasn't necessarily the bearing, but the design of the mechanism that causes the problem. The Cub TOB is guided by the fork, which swings it through an arc. This only puts it in line with the spinning pressure plate fingers at one point during contact. The rest of the time they are misaligned and the fingers are "scrubbing" on the surface of the bearing, rather than spinning with it.

Sooner or later depending on the quality of the thrust surface of the bearing, bad things happen.

Some people have good luck with them. Whether it's because they don't stand on the clutch much or they happened to get a good bearing, I don't know.

Ultimately, none of the modern technology has addressed the basic design of the Cub throwout bearing system, which I believe is where the flaw lies.

[Scrivet]

..............The rest of the time they are misaligned and the fingers are "scrubbing" on the surface of the bearing, rather than spinning with it. ......

Matt, good statement and description with one minor point. The clutch fingers still spin with the bearing even when scrubbing. They just don't stay in the same spot on the face of the bearing like they should (I like your use of the term scrubbing for that). Misaligned, they spin and scrub, not just spin, like they should.

Kinda sounds like we're talking about a washing machine, not a Cub!

[Bus Driver]

It was stated on this forum long go that the earliest Volkswagen Beetles also used a graphite clutch release bearing.
The discussion about the pressure plate fingers randomly hitting the TOB is quite interesting. If a picture was posted of such a failed bearing it would be very helpful. I know of cars with 5 speed transmission that have gone over 150,000 miles on the original TOB.
Of the transmissions for on-highway vehicles that I have personally serviced, there is a sleeve on the front of the transmission on which the inner bore of the TOB slides, keeping it in rather close alignment with the pressure plate at all times.

https://www.google.com/search?q=borg+wa ... B600%3B300

[Don McCombs]

I think the photo posted above in this thread shows very clearly what happens.

[Scrivet]

..........
The discussion about the pressure plate fingers randomly hitting the TOB is quite interesting. If a picture was posted of such a failed bearing it would be very helpful.................

I don't think describing the pressure plate fingers as "randomly hit the TOB", is a valid statement, they still spin in a perfect circle. The problem is that the axis of the circle the automotive style TOB spins in can be a different axis from what the fingers spin in. That is the scrubbing mentioned above. Take a look at the first picture in the following thread. Imagine the graphite was a roller bearing and think what the fingers would be doing on the face of the roller bearing.
http://farmallcub.com/phpBB2/viewtopic.php?f=1&t=82134&p=657299&hilit=+textbook#p657229

It seems to me that the transmission sleeve you mention is an integral part of the roller bearing design. In my opinion, why some have success with the automotive style TOB and many do not, depends on the random (without the needed sleeve) alignment of the two axis's that varies from Cub to Cub, and how much the clutch is used. Good alignment and sparse use, should last a while. A way off alignment and frequent or prolonged clutch depression and you'll become an expert Cub splitter.

[Jim Becker]

I guess I might as well jump in on this topic -- again.

As already pointed out, the throwout bearing moves through an arc as the clutch is engaged/disengaged. Clearly the axis of a ball/roller throwout bearing can't stay in perfect alignment with the axis of the crankshaft/pressure plate. There is some designed-in vertical misalignment. Some scuffing of the fingers on the bearing face is unavoidable. The question becomes one of whether there is enough scuffing to matter. That in turn depends on several factors, some of which can be observed by inspection, some less obvious.

1) How much misalignment is there between the two axes? Wear/damage to the carrier will add to it. If you look at the picture Scrivet pointed out, most of the misalignment was horizontal. If a ball bearing was installed on that carrier with no repairs to the carrier, there would be A LOT of scuffing and the clutch would no doubt be doomed to an early failure. In the past it has been pointed out (by Clark, maybe others) that the carrier needs to be in good shape for a ball bearing to hold up. This picture clearly shows the validity of his point. Much can be done to minimize the misalignment for the ball bearing to have a chance. With misalignment as shown in the picture, the graphite bearing still holds up pretty well.



2) Given some misalignment and the resulting scuffing, how much effect will it have on the points of contact? This is not easy to measure by inspection. Bearing surfaces hold up better if the materials of both parts are not identical (thus bronze bushings on steel shafts etc.). The face of the throwout bearing is probably hardened (same material as the rest of the bearing!). The clutch fingers, maybe not. Quality clutch fingers of years back had hardened contact points. Today, who knows. Given the much greater surface area of the bearing than the fingers. The whole thing would probably hold up better if the bearing was the softer material, but that isn't likely the case. If somebody came up with a ball bearing that had a graphite face, we would probably have the best of both. I doubt we will see that because of the cost to create such a thing. The VW graphite bearings have been mentioned previously. I have only seen a few examples of the VW clutch, so I don't know if they all are the same. But the ones I have seen had a ring attached to the fingers giving full contact to the face of the graphite. This would considerably reduce the pressure on the contact surface of the graphite. If somebody wanted to "fix" the Cub throwout bearing problem, that might be a better approach than changing the bearing.

3) A ball bearing needs to be a real thrust bearing. Some of the failed ball bearings we have seen were designed to carry a radial load rather than axial load. This was another recipe for early failure. Hopefully, any that are available now are thrust bearings. That is a buyer beware question, as the difference may not be obvious from inspection.

4) Maintaining near perfect alignment of the bearing axis requires something similar to a sleeve on the transmission input shaft. This is commonly done on other machines. The complication with the Cub is the only readily available support for the sleeve would be the transmission input shaft. Unfortunately, the relevant portion of the shaft is not a machined surface, far from it. Installing a sleeve on the shaft would require turning the shaft to true up the portion the sleeve rides on. If that was done and the bearing put on an appropriate sleeve, it would be a minor problem to make sure the carrier was able to follow the bearing through straight linear motion. The big problem is that few of us have the capability to machine the shaft as needed. It would no longer be a DIY for most people. Most anyone that can do the machining could probably just as easily make the sleeve for the existing ball bearing. So have at it.

The bottom line for me is that if the carrier is in excellent condition and the alignment is as good as it can be and you have a quality thrust bearing, it will probably hold up OK. I'd make sure the face of the bearing and the tips of the fingers are coated with some lubricant. (Hypoid oil comes to mind.) I doubt most of us can guarantee the above, probably leaving you better off with a graphite bearing. I'm sticking with graphite bearings. By the way, making sure there is some lubrication on the bearing surfaces at assembly time is a good idea for the graphite bearing as well. At assembly, I put a light coating of grease on the face of the graphite and the tips of the fingers.

[Bill Hudson]

Folks,

Thanks for the input, it has been very informative. I don't know which TOB my friend will choose, however, after this discussion I'm going to stick with the marinated graphite bearings I have on the shelf.

Bill

[Bus Driver]

Scrivet and Jim have zeroed in on the issue. I will not confess how long it has been since I had one split but the memories of some of the details are fuzzy.
Jim mentioned a ring on the pressure plate fingers as a possible help.
What about a shallow cone shape on the front of the ball thrust TOB? That should serve to guide the bearing into concentricity with the described rotating circle of the pressure plate fingers. Is there space available for all that?
Will this give someone else a workable idea?

[Jim Becker]

What about a shallow cone shape on the front of the ball thrust TOB? That should serve to guide the bearing into concentricity with the described rotating circle of the pressure plate fingers. Is there space available for all that?

That seems to have potential. The 2 areas I can think of that would need to be looked into:
1) uniformity of shape/length of the tips of the clutch fingers. They weren't designed as a contact point. If for example one is longer than the others, it may force the bearing into following a circular path orbiting the center line of the crankshaft. Even if harmless, it might cause an unacceptable vibration and/or noise.
2) tips of the fingers move in an arc. There is some potential for binding.

I wouldn't claim either of these things kill the idea. They should be checked as part of trying to make such a bearing.

I think there is probably space for such a shape. There is quite a bit of range in the existing adjustments.

[Scrivet]

I am happy using a graphite bearing. If I was going to design a new "system" using the automotive style bearing I would look at totally removing the current TOB and hanger. I would use the two holes that the hanger rod fits in to secure the top portion of a bracket that held a tube for the automotive style bearing to ride on and the driveshaft to go through. I'm thinking something along the lines of an upside down Y or more likely an H shaped bracket. Don't know how the bottom would attach to the bell housing. Drill a couple holes? Maybe utilize the clutch hand hole somehow? Best would be some fixed point so it would always be the same and would work on any tractor. Which is the basis for the whole idea. The fingers are always located at the same point in space in relation to the bell housing. The TOB needs to be centered on the flywheel/pressure plate combination. So a fixed tube in the correct location should always align the TOB with the fingers.

The current rod from the clutch pedal should provide enough slide movement of the new TOB. It may provide to much travel since you are moving the same distance as the end of the old arc and not half way down where the graphite TOB was mounted. You would need some way to keep the new TOB from rotating. A couple of U shaped brackets attached to the mounting bracket for the tube with the TOB ears riding in them should do it.