Service Brake Actuating Arm

Bob/AZ

Bob/AZ

Senior Member
When I pin the new service brake actuating arm with the dust ring to the new camshaft it seems to be too stiff in movement. It takes a lot of pressure to move the arm. Without the dust ring it moves freely. Am I missing something here? Also, since it is a split ring and would allow dust in at the split why is it called a dust ring? Thanks for any help!
 
You might want to make sure the bushings are installed far enough that they aren't causing the excessive friction you are experiencing (both ends). Another potential problem is the dust ring might be a little to thick. Is it a repro dust ring? Just my thoughts.
 
I had that problem once on a powder coated backing plate. The powder coat was too thick where the dust ring seats. Even if you did not powder coat it, something is jamming in the distance between the ring and the back of the cam shaft.
 
Bob,

I just installed new rear brake camshafts & bushing-tubes/brake track assemblies on my '28.

One of the camshafts was a real tight fit in the bushing tube, and locked-up when camshaft was pushed all the way in ( the radiused "fillet" between the shaft and the cam head was binding in the end of the bushing.).

I "reamed" the outer 1/8" of the inner bushing, until the camshaft rotated easily ( could spin with thumb and forefinger) when bottomed against the brake-track, then assembled everything. I re-used my original brake arm.

There was no binding when everything was assembled ( including dust-ring ), so I went ahead and peened the pin.

All has been good for three weeks now...

Worth looking into.


SC Frank
 
It is a repro dust ring. The bushings on both ends are seated properly. I guess I will try reaming a little for the dust ring to have a little more room. I just hate to start removing metal until I get a few opinions from others. Sounds like the common sense thing to do though. I definitely cannot move the arm with thumb and forefinger although I thought that should be about right. Thanks for the input. Bob
 
The binding may be at the inner end - remember what I said about there being a small radius or curve as the cam-shaft meets that big cam-head - when you put the dust ring on and pin the lever, it might be pulling that curved "fillet" into the end of the inner bushing and that may be what's actually binding.

If the camshaft is stiff or binding in its operation, the brake will not release properly.

By the time I was done fitting mine, I could "spin" or "twirl" the assembled cam-shaft & lever.
 
Before you go cutting things up check the dust rings. There are two sizes. I can't remember if it is the rear brake lever or the front act arm but Bratton's cat pg 12 says to be careful PN 3080. One ring is smaller ID ring with large wire dia and the other is large ID ring with small wire dia. I had them assembled wrong and things didn't work right.
 
O.k. Here's what i did. I carefully opened the dust ring up so that it is still symmetrical but it rides a little higher on the taper of the actuating arm. Spins freely, and no end play. I think i will go with that.

One more question if you guys are still looking at this. Do you
upset the end of the pin by heating it and driving the end like a rivet or do you just peen it with a center punch. There is about a half inch sticking out.
 
Bob/AZ said:
O.k. Here's what i did. I carefully opened the dust ring up so that it is still symmetrical but it rides a little higher on the taper of the actuating arm. Spins freely, and no end play. I think i will go with that.
Click to expand...

I helped a friend with his brakes this winter and that's what we did; spread the ring open as the arm was pushed on the shaft. My other thought is the slightly open end of the ring should face down so water is restricted from getting in.

As for the pin, we heated the pin red hot with an oxy-act torch and used a 3x rivet air hammer with a shallow cupped punch. An anvil was used to back up the pin head. Worked great and took a couple of seconds to do each one. Looks darn near factory.

Cheers
Rich
 
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