Clutch slippage - South bend 9A

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martik777

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In both longitudinal and cross-feed my clutch will disengage after a few secs when under moderate to heavy load, unless I tighten the start knob about as much as I can by hand. I re/re'd and cleaned the apron a few months ago and all parts looked unworn and it has remained clean. It doesn't engage until the star wheel is turned almost all the way in and I can make it slip by holding the cross feed or handcrank wheel unless it is very tight. Oil sump is full. Any ideas?

Here are some pics of the same clutch on a clone:

http://steammachine.com/hercus/page5.html

Also, if anyone has the dimensions of those two 1/2 circle discs I would appreciate it.
 
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OK, you got me curious now so I just took it apart. I think there are a few wear areas contributing to the problem.


1. The outside of the shoes are showing some wear but feel smooth in the direction of rotation. maybe not polished but some roughing up may help.

2. The butterfly leaves that expand the shoes are worn on the edges but not the middle. (reversing them may help)

3. The inside of the shoes have a groove worn where the middle of the butterfly leaves ride. (doubt this has much affect)

I think the easiest fix may be to fabricate some new butterfly leaves but I will try the emery cloth on the outside of the shoes first. Well, maybe not so easy with no mill and my only lathe in pieces!

clutch_shoe2.jpg clutch_shoe3.jpg clutch_shoe4.jpg
 
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Did you check the recess that the two pieces fit into for taper? Perhaps they are worn more on one side than the other, which would give you a much reduced friction area. Even if the recess it tapered it may be worth checking to see if the taper is consistent, that is not a barrel shape in the middle.

If necessary you could machine the recess and make new shoes to fit.
 
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