how to arc floating brake shoe linings

[mikeb]

I'm back to my front brake again - a TLS off a 69 triumph. I'm getting new soft linings fitted so am revisiting how to arc them.

option 1 is sandpaper in the drum and space out the non-cam end with a 'shim'.

option 2 is arc them in a lathe. with the sls I've previously made turnbuckles etc as per Orabanda's great post: https://www.a7a10.net/forum/index.php?topic=7252.msg50596#msg50596
but how to hold floating shoes? probably some kind of backing plate needs to be made up. So how to make a suitable backing plate? my first thought is is a piece of wood (mdf?) with a centre hold for the axel (then for the mandrel in the lathe) and when the shoes are held in place against the drum put screws through the spring holes to secure. sounds terrible. i guess i could use some steel

has anyone got better ideas on making a backing plate? or some photos of how they did it? or better ideas?

thanks!

[BagONails]

Hi mikeb, I would suggest getting the brake shoes relined with oversize linings (so they will not fit the drum), then get someone with a big lathe to skim the drum contact surface to provide a 100% contact area that is square. (This will be somewhat dependent on how worn the drum is before you machine it but if you can't clean it up then maybe you shouldn't be using it...)

Then fit the O/S shoes to your brake plate, centralise them and lock them in the closed position. Mount the brake plate in the lathe such that the bearing/spindle bore is running true. Provided there is no asbestos in the shoe material, machine the shoes so, with the spindle in the hub bearing you can JUST get the shoes into the drum. This is an old trick to get the best out of what you already have.

[RichardL]

Bago, if you get a chance, check out the link Mike posted to Richard (Orabanda's) brake shoe turning technique.

Mike, thanks for pointing me back to Richard's post.  This is a very timely topic for me, as I am about to do my own Ariel brake shoes.  Back then, before I had the '57 A7, or a lathe, I was curious about it for my half-width '55 drums. I knew little about 4-jaw chucks (still know little, but a little more). I even asked Richard to send me his lathe. It never arrived. That's not even the start of when I wished I'd had one, but now I do (nothing as slick as Richard's).

Richard L.

 

[orabanda]

When assembling the shoes (after machining) install the pair of springs so that the hooks face down on one spring, but up on the other. The shoes will sit squarer than if the hooks on each spring face the same way.

With the '69 TLS, a jig (plate) is required to hold the shoes central in the lathe chuck.

A car brake disc from a car wrecker makes a cheap and substantial jig. Easy to hold in a chuck, and machines easily.

Machine the shoes to just under the drum diameter. Excessive clearance will result in too much free travel of the backing plate brake linkage , which will reduce the efficiency of the spindle cams.

Re the 7" ariel full width hubs; I have got a couple of bikes with these hubs, and the brakes have always disappointed.

I put a dial indicator on each shoe (opposite the cam), and found the cam profile is such that the trailing shoe is moving twice as far as the leading shoe i.e the trailing shoe touches the drum before the LS, which will reduce the brake's efficiency.

Time to make new cam profiles. The existing cam is easily removed / replaced; it keys onto the shaft. I think the profile should be altered such that there is a flatter "heel) on the side acting on the trailing shoe.

I will also try fitting a trailing shoe without linings; this should increase the abysmal braking by allowing the LS to fully contact the drum.
I hope to get around to this in  after Easter; stay tuned!

Richard

[RichardL]

(Moved from "Endless Loop" topic.)

Richard,

Probably forgot, or didn't need to, complete my reply at the time back in 2013. However, right now, I can thank you (again?) for the great post and explanation. Also, I have a question that occurs to me now that I actually own Ariel hubs, and having re-read your post. You say to push the adjusters out at the fixed end to allow for adjustment. If they are already all the way out when the shoes are turned, doesn't that favor adjusting to a looser fit and may not provide enough adjustment if they need to be tighter? I'm thinking, maybe, midway on the fixed-end adjusters. What do you think? (He asked nine years later.) 

Richard L.

[BagONails]

Bago, if you get a chance, check out the link Mike posted to Richard (Orabanda's) brake shoe turning technique.

Richard L.

Doh! Sorry guys, looks like Richard O is all over this subject I will pack up my soap box and move on 
Great thread by the way, thanks for the link Mike.

[mikeb]

thanks for the comments guys.

Orabanda - any chance you'd have a  photo of a car disc brake plate is suitable form? i'm struggling to imagine how you set it to hold the shoes at the right diameter

Richard L - what's 9 years? shows persistence!

[JulianS]

I use a low tech, time honoured solution - having no access nor skill in lathe use.

Last used about 4 years ago on the TLS fitted to m y A10.

Assemble the brake in the wheel, balancing the tie rod. Gently apply brake and revolve wheel. Remve brake, see the high spots and, with suitable protection, ease the high spots with a file. Repeat until satisfied. Then use bike and allow them to bed in.

When choosing a lining ascertain the characteristics from the supplier. Some linings are much slower to bed in than others. Some squeal. Some of the anonymous grey stuff just does not work well.

[mikeb]

Thanks Julian - i may well end up there. with the SLS, the small lathe I've got and turnbuckles easily allowed turning down and arcing slightly oversized linings, and was an enjoyable project. but the floating TLS shoes are a whole new challenge. good to have a low-tech fallback!

[mikeb]

i've finished arcing the new floating shoe linings largely as per Julian's suggestion and now have a new problem that I've never before encountered on my BSAs - I CAN LOCK UP AND SKID THE FRONT WHEEL !!!  

the new linings were slightly oversized for the drum and took quite a bit of sanding down, eventually assisted by hand-held light rolling touches against a mounted belt sander and checking back against the drum with feeler gauges and chalk. the belt sander felt drastic but the touches were light and the sanded face was a lot flatter (across the shoe face) than me filing or sanding by hand, and faster. So this is also saying I could not figure out a reliable way to mount and arc the floating shoe linings in the lathe.

For the kiwis reading - the linings were provided and fixed to the shoes by waikato bonding services - I asked for the softest compound they have for a cable brake and the invoice reassuringly said 'british bike'. recommended.

Thanks to those who commented above in this thread.

[RDfella]

I CAN LOCK UP AND SKID THE FRONT WHEEL

That can be dangerous. My moderns won't lock the front - but that's because I ease back on the brake once the rear wheel reaches a foot clear of the ground.
Only ever locked a front once - when hill-climbing my B31. It has an 8" single-sided brake with extended brake arm - and of course the bike is light. Coming into a hairpin a bit hot a few years back I gave it plenty brake only to be rewarded with a helluva tank-slapper (actually hurt my leg on the tank). Fortunately there was a slip road .....
After that I moved the cable closer to the pivot!