Ultramafic brake bands

Posted by 56Clippers On 2017/10/15 13:30:43

I purchased relined brake bands as part of my Ultramatic rebuild. When I installed the reverse band, I noticed that it was easier then the removal of the old one. I then did the following comparison of the original and replacement bands. The picture shows all of the bands with the left sides aligned to show the variance on opening gaps. The relined bands are the top two.

The gaps, in inches, measure, from top to bottom band: 0.575, 0.865, 1.310, 1.329.
The force, in pounds, to reduce the gap to 0: 6, 9, 15, 15
When closed around the ring gear, the gap is 0.33
The force to close around the ring gear is 2, 5, 10, 10
The unbound (not held by the operating lever and the adjusting screw) clearance between the band and the ring gear is: 0.040, 0.085, 0.155, 0.155
I haven't measured the bound clearance when adjusted per the service manual because it requires everything to be assembled.

I would think that you would want as much spring to the band as possible as that is the only thing that retracts the band. If the band does not retract you would have drag and wear. With the pressure test range for the low brake of 75-100 pounds and the mechanical advantage of the lever arm it easily overcomes the spring force of the band.

I have found no mention of the correct brake band spring rate, spring force, clearance or unbound gap to know what is appropriate.

Does anyone have any information on this?

Thanks.

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