Cub 70 clutch teaser spring, broke again

[chzuck]

Seems like only a few years ago I replaced the clutch teaser spring on my Cub 70 and it just broke again. Anything in particular that would cause the spring to break? Prior to that, say at least the first 10 or so years I had it, no problems.

[Merk]

Are you using a cub cadet or aftermarket throw out bearing?
Does the driveshaft have any wear where the throw out rides?

[chzuck]

Cub throwout bearing. I will check that when I replace the spring, but I did not remember it being worn. Thanks for the suggestions. Gives me things to check.

[BigMike]

Merk,

Someone is offering an aftermarket TO bearing?
I thought I remembered discussion from long ago that those were a proprietary bearing.

[Merk]

Merk,

Someone is offering an aftermarket TO bearing?
I thought I remembered discussion from long ago that those were a proprietary bearing.

There is 1 or 2 aftermarket bearing(s) for sale. They are longer and don't hold up very long. I just rebuilt a clutch for someone using the longer bearing put the clutch assembly in a bind. The clutch lever had to be replace too.
Cub Cadet still makes/sells a throw out bearing.
Mid West Super Cub sells one that looks and perform like the Cub Cadet one does.

[Klapatta]

I think that those springs are prone to hooking on the slot of the driven disc. I put a thin 5/8' machine shim between the two before install.

[chzuck]

Thanks for that idea. I will do that when I replace the spring.

[Klapatta]

The problem is it's about a huge spring smashing against a much smaller one, always has. Lousy design. The matter was resolved in the later series as it should be but that does nothing for a narrow frame machine.
I fabricated up a spacer collar that takes away that undue stress on the spring by preventing it from bottoming out.

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Here it is mocked up before finish machine as well (no external chamfer)

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And final assembly.

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I have had this in my 102 for twelve ears now, still goin.
It will change the stroke somewhat and you may or may not have to add a small chamfer on the clutch fork at the point where it nears the steering box.

[chzuck]

I like that idea. I have a mini-lathe and could probably make that on there. So, does the clutch still operate the same. Problem when the spring is broken is lurching and not having a smooth take off. That's how I knew it broke again.

[Klapatta]

The clutch works the same. Given the added .110 stack thickness there will be a fork adjustment needed.
That little collar will be under a lot of stress and a high strength alloy is needed to avoid distortion at the face so if your thinking about using aluminum or something like that don't do it. I have heard of people having good lick with bellville spring washers although I've not tried that myself. They come in different thickness to adjust pressure ratings and if doubled up face to face that factor goes up 2X as well.

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[chzuck]

Bellville spring washer instead of the piece you made? I assume the washer would go ahead of the teaser spring?

[Klapatta]

Um, no. A group of belville washers to replace the existing teaser spring. I hear that it works well.
Just consider this, no sharp edges to catch on to-

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[chzuck]

I think I may make that piece you made. Can that be made from regular cold rolled steel?

[chzuck]

Soon time to do the teaser spring on my Cub 70 and I think I am game to try the belleville washers. What is the height of the original teaser spring so I know how many pairs of washers I need?

[Klapatta]

Charlie, a new teaser spring in it's totally relaxed state will measure around .475 across.
In it's totally compressed state it will measure around .325.
You will note in my sketch I allowed around .030 shy of complete crush, this is reflected by the .360- .350 dimension.

Keep in mind that when stacking Belville washers back to back you multiply your compression values. When they are stacked opposed to each other the compression value remains the same.

[Klapatta]

I think you ought to go with the 2X value stack

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[chzuck]

So glad you posted the drawing of the orientation of the washers. I would have placed them together with the out edges touching each other. Would you advise placing a shim washer at one or both ends of the belleville washers? So much appreciate your advice.