1921F Service Brake

[MikeW]

I'm having some trouble assembling and adjusting the brake on my 21F restoration. I'm using a reproduction drum, and the original back plate. The back plate has had the worn bearings for the operating mechanism replaced with newly machined items, welded in place and cleaned up to look close the original spec. The operating mechanism, cams and linkages are all newly machined by a friend using quality steel and exactly as per the originals. (I have chemically blackened and oiled them as a rust preventative.)

The original components, including the brake band, were heavily rusted and past restoration - especially for a safety-first item like a brake.

The brake band I'm using is a repro item from Antiquebike in Sweden, bought off Ebay - and not cheap.

The problem should be apparent from the attached photos. When the new band was put on the backplate, it didn't centre properly. You can see from the first photo that when the brake is fully pulled off, one side of the steel band comes up against its stud on the backplate, and everything stops, while the band on the other side is at least a quarter of an inch from its stud. As a result, the brake lining material projects from one side the backplate, and will rub against the drum. (Photo 2)

After some head-scratching I took off the repro item, dug up another battered original from the spares box and put that on the backplate. Photo 3 shows it nicely centred on the backplate, equidistant from the two studs.

To try and get to the root of the problem I then clamped the new brake band to the original item while it (the original) was still fitted to the backplate, using the locating pin sticking out of each band as the datum. Photo 4 shows this and, if you look at the two bands near the operating arm you can see clearly that the new band - the one on top - is significantly shorter on that side than the original. Hence, when you pull the brake off with the new band fitted, this short side comes up against its supporting stud on the backplate first, and stops any further movement.

My questions. 1. Has anyone out there used reproduction brake bands and experienced (and dealt with) this sort of problem? 2. My best option if I choose to stick with the reproduction band, which looks pretty good otherwise, seems to me to be to remove the locating pin in the back of the band, move and weld it into a place which centres the band on the back plate. Any views? 3 Alternatively, a sound original band might be an option?

4. A more general question - irrespective of the pros and cons of repro items, are there any recommendations on a suitable brake lining material for these old machines.?

As always, any help will be much appreciated.

Brake Drum and bands 003 (800x533).jpgBrake Drum and bands 004 (800x533).jpgBrake Drum and bands 001 (800x533).jpgBrake Drum and bands 007 (800x533).jpg

[Steve Swan]

Johhny Sells stocks original metal impregnated band lining. The lining is blank, so will need to be countersunk and drilled to set the rivets. I haven't seen any original bands lately, but sooner or later one might surface on ebay or perhaps Mark Masa has a pair. Otherwise, it sounds like your other option is to modify your repro bands....

[TechNoir]

Mike,

I cant comment on the use of reproduction bands. However, when I reassembled my brake on my 20F I had a problem with the pin which detached from the original band after I had had new linings installed. I removed a small piece of lining and riveted a new pin on (they are riveted on not welded.). So I dont see why you couldnt use the same approach to relocate your pin. However if it were my bike I would want to make sure that the geometry of the mechanism works if the new band is shorter than the original which it looks like to be the case from your picture.

See my post #99 here:

http://www.antiquemotorcycle.org/bbo...Model-F/page10

John

[MikeW]

Thank you Steve and John for the quick and helpful replies.

Steve, the lining material on the reproduction brake band is indeed metal filled - looks like small pieces or flecks of brass wire or similar embedded in the fibre material. I suspect that this is the same product stocked by Johnny Sells (whom I have dealt with in the past and found extremely helpful and courteous) though the lining is bonded to the band with no rivets. So this further encourages me to stick with the repro band if I can get it to align and engage properly with the drum over its full surface area - particularly as I have only the basic service brake - just the internal brake and no external heel brake fittings.

John, before making this enquiry I did search on the forum for references to brake bands and lining and the search machine threw up your post - which gave me the confidence to consider modifying the repro band. I confess that I had forgotten that you had pointed out that the locating pin is rivetted on. That certainly is a better solution that trying to weld with the lining material in place, and cooking the bonding compound as well as the lining, and maybe affecting the temper of the spring steel in the band.

So at this stage, and unless anyone expresses another view in the next few days, I'll remove the locating pin from the repro band, and then fit the band to the backplate. I'll turn up a new pin with a shoulder, and then mark its location with the brake fully off and the band equidistant from the two studs on the backplate. Then I can drill the band and rivet the new pin in the new location. I can test the geometry of this fix with some blacking material or similar on the brake drum to ensure that there is maximum surface contact.

I won't be in the shed for a few days but will take some photos of how I get on and post them on this thread. Even if this fix doesn't work it may help the sum of knowledge about 100 year old machinery!

On brakes, at the weekend I took a 5 hour drive north and looked in at the New Zealand two-yearly national vintage motorcycle rally. I saw two J models there, a 1924 and a 1925 with sidecar. The owner of the 24 is a rider rather than a polisher, (though the bike is very nice indeed), and had sensitively modified the brake with a linkage so that the footbrake operated both the internal and external bands simultaneously. More braking power for wet weather and modern traffic.