Eurocardan clutch springs

[orezok]

I have a British made root-tiller (Blecavator) that uses a Eurocardan slip clutch. This clutch is different as it uses Belleville springs in lieu of coil springs. The springs are non adjustable as they are diaphragm springs. Both springs are cracked and the clutch is slipping.

Replacement springs are about $100 and new clutch discs are $70. For just a little more money I can buy a new style clutch.

The issue is that I only use this tiller once or twice a year and that doesn't justify the cost of a new clutch.

Any thoughts on welding the cracks back together? A C-clamp pulls the crack together and reestablishes a more curved profile to the spring which would add more pressure. They are about 0.115" thick. If I welded it and it failed again it would be no loss other than my time.

The steel in the springs is most likely 50CrV4 which has .5 C, .4 SI, 1.0 MN, 1.0 CR AND .2V

So the questions are:

V out or just butt
Tig or Mig
309 or mild steel

 

[Arc weld]

I think you'd have to re-temper them after welding. I think TIG would be better but use a 312 SS if you can find it. That's what's recommended on stick for welding spring steel or unknown steels. Like a 309 on steroids. I know cultivator shanks can be successfully welded with the right procedures but that includes re-tempering them.

 

[CNC Dan]

If welded, it will need to be re-heat treated.

 

[orezok]

I'm thinking that if I keep the rest of the disc cool, that the HAZ will be minimal and not affect the "spring" of the rest of the disc. What do I have to lose by trying?

Here is the heat treat recommendations for 50CrV4. I have the knowledge on heat treating as my degree in metallurgy would suppose, but not the equipment to accomplish it. Of course, since that was 45 years ago and that I only worked 6 months in my preferred field before moving on to construction management I've probably forgot 99.9% of what I thought I once knew! :laughing:

 

[MinnesotaDaveChalmers]

Heck, although I agree the "spring" could likely be affected - if it were mine I'd weld it just to see how long it works

I vote tig also - I have some 309, but none of the 312, so I'd clamp it, "V" it if needed and give it a go

 

[Arc weld]

Wouldn't hurt to try welding it. It's already broke. Maybe you could just heat the weld similar to how bandsaw blades are done. Heated to temperature for a couple seconds but then slowly move the flame away to let it slowly cool? Another thing you might try is welding about an inch at a time, letting it cool and then do another inch and not letting it get too hot? You can get Block It paste that will keep the heat from transferring to the adjacent metal. Then like you say, you'd have a small HAZ.

 

[orezok]

No joy here. I Tig'd it and the welds looked good, but I'm certainly no master welder. I torch heated the weld zone to the A1 line and slow cooled them in cat litter. Both discs "popped" as soon as I put tension on them during assembly. Oh well. it was a good try.

New Belleville springs are only about $100 delivered. I was able to clean up the clutch plates and they will work again.

 

[MinnesotaDaveChalmers]

That's too bad - hoped it would work for a while anyway.

Oh well, good try

 

[Big Barn]

That's too bad - hoped it would work for a while anyway. Oh well, good try

Same here. Glad you tried though. As mentioned, you had nothing to lose.

Terry

 

[orezok]

I looked at the failure and it was a perfect tensile failure with no elongation. That is, the metal pulled apart in plane at the weld zone.

These springs are designed to hold over 600 Ft Lbs of torque and the mild steel weld could not handle the stress. To install them you have to flatten them from their concave shape with 4 bolts and then bend the locking tabs. After locking the tabs the bolts are backed off to allow the spring to go back to it concave shape. If you look at my first pic that will make more sense. I'm guessing that that puts double the force on them as opposed to their in use condition.

This is the second clutch of this type I've seen that has has broken diaphragm springs (European design). I decided to dump this clutch and get a conventional wound spring clutch.