Re-lined Brake Bands

[A31ndrew]

I have recently had the brake bands of my A31 re-lined by Friction Services, who did an excellent job. Thanks, incidentally, to members who responded to my earlier post regarding suppliers.
The newly lined brake bands, however, are causing a problem and I wonder if anyone else has encountered the same. The brake bands were refitted to their original brake plates and the springs refitted in their original positions. When offered up to the drums, however, both brakes are permanently 'on'. My suspicion is that the lining material was cut from either a flat strip, or from one with a much larger radius and that the linings in their relaxed position are over expanded.

Suspecting that the return springs might be weak, I attached the same weight to each of the six (three each front and rear) and measured the extended length. All six were virtually the same, so they are either all in good order or all equally worn! To enable me to wheel the machine around the garage I've fitted large external springs on the external lever arms but, clearly, this isn't a permanent solution! All suggestions gratefully received.

Andrew

[Doug]

Andrew,

Unfortunately it is probably a little too late for this, but... Current practice is to glue on the linings. When doing so it is imperative to glue up the linings with the bands in and clamped to the drum. With the linings glued on, the assemble becomes so stiff that there is not a lot of range of motion for the band. Cases of the band material fracturing have been reported, when glued up with the band relaxed much too small. I suppose the reverse could be true if glued on with the band too large, the original springs are insufficient to pull it back.

To a certain extent this remains true with riveted on linings, though they retain a little more flexibility. Ideally you would want to also clamp the lining to the band, with the band in the drum. Practically, this means with the band partially in the drum so that you fix the ends with a rivet, or independently clamp the friction material to the band so that you can complete the riveting separate from the drum.

Whether glued or riveted, it is important to get the band circular and without kinks before applying the lining. Otherwise you will end up with a high spot rubbing, and use up all of your brake actuating travel making the band conform to the circular brake drum.

The continuous woven lining comes in large coils, which generally have a much larger radius than the brake drums. 

-Doug

[eddie]

Andrew,
            The brake lining material from Friction services becomes quite soft and pliable when heated. I would suggest pulling the band in to a diameter slightly smaller than the drum, then when SWMBO is not looking, warm it in the oven. There may have to be a bit of trial and error to get the desired result. (Brake band diameter that is, not reaction from the wife!).

 Regards,
              Eddie.

[A31ndrew]

Thanks, both, for your responses. As Eddie's will be easier to apply than Doug's, I shall try this first! As I have recently refitted the kitchen and have a spare oven sitting in the garage, domestic harmony should not be put at risk ...  If it is, at least I'll be able to cook my own meals out there!
Andrew