The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Frame => Topic started by: Rex on 24.11. 2017 21:36
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Can anyone recommend someone who can skim a brake drum on a built wheel, preferably in the South of England?
I know SRM do it, but I'd probably have to sell the bike to pay their bills...
Thanks.
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Maybe Hagon?
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Down here most brake and clutch shops can do it with the rim still wired in.
Cheers
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You can do it yourself with stick on emery cloth. With a bit of patience you will end up with a perfect job. Really doesn't take long.
Glen
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Down here most brake and clutch shops can do it with the rim still wired in.
Cheers
I would try a brake and clutch shop that specializes in big trucks. They have brake laths that can handle large diameters.
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My local bike shop has a lathe and the owners Dad does these on a Saturday for £25. Bikewise Progress Road Rayleigh Essex. You just need a man with a lathe.
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That would be a very large swing'd lathe.
Apparently it's also possible on a reasonably-sized milling machine.
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There is a feature on many larger lathes called a Gap Bed, its a part of the ways that is removable by the chuck.
It takes about 5 minutes to take out, and 3 hours to put back in properly if you hardly ever use it. Its a lot of tom foolery to get that gap back in perfectly.
Lee
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Done on a milling machine - https://www.youtube.com/watch?v=qvLvoNMhbG8
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There is a feature on many larger lathes called a Gap Bed, its a part of the ways that is removable by the chuck.
Lee
I was allowing for the gap bed.....it's still one Hell of a swing!
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I used to get mine done at a bike shop.
He had a large face plate set up with an arbour that he slipped in the back of the hollow spindle on his 6 " lathe.
So with the wheel mounted at the back, he used a pedistal grinder on a slide.
Perfect job and no skipping.
BSA used nickle silicon iron for their drums and that is bloody hard.
Most drum machines that use a lathe type tool will skip and put grooves in your drum.
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Here in the US its the land of prolific litigants and their lawyers. So, this can be challenging to find someone to do this. I have a local guy who runs a machine and fab shop who is also passionate about motorcycles but he is the exception to the rule. Most places as soon as you say "Motorcycle" they cant get off the phone or away from you fast enough.
Depends on the brake hub assy as some distort more than others and Ally hub with cast liner or cast iron hub entirely? or a bolt up arrangement can differ.. But it IS worth doing as it does make a huge improvement. Down in California is a shop called Vintage Brake and they reline and will skim and can transform a old bikes brakes, but for me, shipping a complete assy is very expensive,
See: http://www.vintagebrake.com/
But perhaps some good info can be learned from them.
I know a local guy, "Panhead Jeff" who in his day job is an engineer and while his interests are primarily American bikes he played around with upgrading early HD and Indian brakes and got really impressive results, as Radar said about his Indian Scout "I can skid both wheels now and it never did that before"
So, because of the aforementioned aversion to liability, Jeff could not find anyone who would reline old shoes with some of the modern materials so he bought a variety of high tech brake materials in bulk and relined them himself. He found some carbon fibre or other high zoot materials that worked really well.
I tried some of his bikes and was really impressed with the results, He skimmed the drums, optimized the actuation, and with the modern materials transformed the braking.
As he pointed out, A drum brake has more theoretical contact area than any disc brake so its a question of getting it working right and dealing with the heat issues. Most vintage bikes I serviced when my shop was active were using about 25% of their contact pad due to poor fitment, installation and poor bedding in. Probably the biggest misunderstood drum brake out there is the Conical brakes/hubs fitted to 1971-73 Triumphs and BSA. (They actually work quite well when properly adjusted) They dont deserve their moniker of "Comical brakes"
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The stick on emery does a perfect job in no time. Uses your wheel as a lathe. It only takes off what is needed, no more. You can feel when it's perfectly round, all pulsation disappears.
Use stick on 180 grit stuck to the shoes and grinding on drum first, then when the drum is done go the other way round to arc the shoes to the drum.
The whole job can be completed in the time it would take to load the wheel in the car and drive it somewhere local.
I have a big lathe here that can handle a wheel. I used to true drums in the lathe but don't do it that way anymore.
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The stick on emery does a perfect job in no time. Uses your wheel as a lathe. It only takes off what is needed, no more. You can feel when it's perfectly round, all pulsation disappears.
Use stick on 180 grit stuck to the shoes and grinding on drum first, then when the drum is done go the other way round to arc the shoes to the drum.
The whole job can be completed in the time it would take to load the wheel in the car and drive it somewhere local.
I have a big lathe here that can handle a wheel. I used to true drums in the lathe but don't do it that way anymore.
That does sound much easier and simple, well worth doing, especially the arcing in of the shoes as few people do that and it makes a big difference. Depends on the materials used as well, but "Bedding in" the friction material after install is another neglected area. I have read some pretty indepth recommendations in a variety of OEM Shop manuals and while many materials have changed over the years, it seems to be still a good idea.
I imagine just turning the wheel by hand is probably adequate for arcing in and truing the drum, but one note of caution if someone is considering driving the wheel by the motor or using another bike/car/electric motor while lifted off the ground. The tire at speed changes shape and when there is only a small gap between the tire and the ground (Center stand or lift) the tire CAN grow and make contact which can have an unfortunate result. Have seen a few bikes launched across a work shop or off a lift. There is an amusing story Bob McKenzie and a few others up in BC Canada circulate about "The Devil Bike" which was a BSA single,, it took off on its own by other means but it would be sad to hear of a BSA coming to woe for this reason.
When I came back from overseas and took a job in a trucking company maint shop I saw this in even more dramatic fashion. At the time they were calibrating a K-DEC unit which was on board computer monitoring system (Kind of a Nanny Cam monitor). They had a Freightliner conventional up on jack stands in the shop and running it hard thru the gears. For some reason I could not put my finger on it made me nervous so I left the shop to do yard inspections on other units. At 65-70 MPH there was a huge explosion and debris began falling from the sky. What happened is the Drive tires had re-cap tires on it and had grown in size enough to contact the shop floor. 2 things resulted,,, It launched off the stands and into the backend of a flat bed trailer in the shared shop bay luckily the mechanic in the other bay was clear of the wreckage. The explosion was the cap on one of the 4 drive tires which weighed around 70 pounds separated from the tire carcass and launched thru the roof of the shop which scattered debris in a wide arc. Clearly this is far more massxforce=distance than any BSA but the law of physics is not to be trifled with.
It was the shop foreman who was running it, and I imagine had it been me or the other mechanics we would have been fired on the spot. It was a sore topic never to be spoken of again during my employment there.
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Suggest you look for someone who refurbishes truck brake systems.
They usually have a stand-alone machine designed to machine truck and trailer (bogey) brake drums (the large cast iron ones you see on every truck).
A local shop does all my bike wheels. I supply the complete wheel (with tyre fitted, spokes tensioned, etc), but bearings removed from the hub. This allows his large centres to engage in the hub.
5 minutes work, and $20 later, a concentric and beautifully finished braking surface.
After the wheels have been spoked, the hubs will be up to 0.010"out of round.
Richard
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Right Sluggo, just turn the wheel by hand. It can also be done with the wheel in place in the bike, then everything is in the " home" position.
It's quite rewarding to feel the pulsation of an out of round hub slowly switch to perfectly even drag all the way around.
I use a c Clamp (G Cramp UK) to clamp the brake lever at a light drag, then gradually tighten the clamp as the high spots abrade away.
Glen
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I did mine using the stick on emery paper, I did it off the bike, stuck the paper onto the shoes and then turned the brake, it didn't take too long.
I then stuck the paper onto the brake drum and turned the brake to arch the shoes.
WARNING, It soon removes the brake shoe material so don't over do it.
Roy.
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round here (oxon/Bucks borders) there is a very clever enginer who has built his own jig for doing this and he does it with the wheel assembled and with the tyre on as he uses the tyre as the drive for spinning the wheel, a very simple jig and very good. he has done quite a few for the local classic bike scene. it works well and is very accurate. he preferes to do them this way as he says this is what the wheel is like when in use and thats the way it needs to be trued up .
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(If the pic comes through) a little tool I made for the job, which attaches to the spindle of an assembled wheel.
Just a flycutter bit on a bar but has done a decent job when needed.
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The stick on emery does a perfect job in no time. Uses your wheel as a lathe. It only takes off what is needed, no more. You can feel when it's perfectly round, all pulsation disappears.
Use stick on 180 grit stuck to the shoes and grinding on drum first, then when the drum is done go the other way round to arc the shoes to the drum.
The whole job can be completed in the time it would take to load the wheel in the car and drive it somewhere local.
I have a big lathe here that can handle a wheel. I used to true drums in the lathe but don't do it that way anymore.
Hi there,
I know that it’s some time since this was posted.
I have a 190mm front brake fitted to my RGS replica and it vibrates when braking is applied.
I like your idea, sounds so simple, so will give it a try - but how do you glue/apply the emery paper?/cloth? to the brake shoes and the drum securely? What type of glue, and just as importantly how go you get it off?
Thanks for your help
Regards Rojah
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I would expect double sided tape would do that job ok Rojah, easily removed from both surfaces afterwards, but Roy could probably be more specific perhaps....
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The stick on emery does a perfect job in no time. Uses your wheel as a lathe. It only takes off what is needed, no more. You can feel when it's perfectly round, all pulsation disappears.
Use stick on 180 grit stuck to the shoes and grinding on drum first, then when the drum is done go the other way round to arc the shoes to the drum.
The whole job can be completed in the time it would take to load the wheel in the car and drive it somewhere local.
I have a big lathe here that can handle a wheel. I used to true drums in the lathe but don't do it that way anymore.
Hi there,
I know that it’s some time since this was posted.
I have a 190mm front brake fitted to my RGS replica and it vibrates when braking is applied.
I like your idea, sounds so simple, so will give it a try - but how do you glue/apply the emery paper?/cloth? to the brake shoes and the drum securely? What type of glue, and just as importantly how go you get it off?
Thanks for your help
Regards Rojah
I used “car moulding tape” which is (sort of) double sided tape, should be cheap, you stick it to the drum then peel the backing layer off and it leaves a sticky residue behind on the drum to stick the sandpaper too. It comes off the drum with brakeclean fluid or similar.
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Some double sided carpet tape from any DIY shop will do the trick. I used 80 grade metal emery.
But if the pulsating is as severe as mine was, the emery treatment won’t work and the drum will need a skim. Any well equipped workshop should be able to do that. Won’t need to disassemble the wheel, just taking the tyre off will do. I paid €25 for one wheel
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Before skimmimg any drum, check the spokes. If some are tighter than others, they'll pull the drum out of round and 'normalising' that merely creares a 2nd problem. Indeed, a bike that's had a new rim fitted recently is a candidate for checking, as many of today's rims are nowhere near round at the weld and building a wheel often means having to tension spokes irregularly in order to get a nearly-round rim. I've had to return new rims before now - and panel beat others because they were so bad. Try to pull that into almost-round with the spokes and the drum will be the shape of the wheel rim before you started.
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Interesting that this thread has reactivated. My SP370 has a definite warp at the front. Front rim is original but has been replaced at some point so something presumable wasn't done quite right, but perhaps as an off roader it had previously taken a bit of a ding. Might try the emery cloth approach first, though the shop mentioned way up earlier is actually fairly local to me.
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Sticking the self-adhesive abrasive pads on the brake drum surface to radius the shoes works well, but sticking the pads to the shoes to cure brake drum ovality or warping sounds dubious.
It would some abrasive to remove 10 thou+ of work-hardened cast iron..
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I had my front drum skimmed and brake shoes relined and machined to fit by a guy in the West Byfleet (south of london) area. He can swing an 18 inch wheel with tyre fitted but 19 inch has to have tyre removed. transformed my stopping power, can almost bottom the forks now. (PM me for name and tel no. )
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I had my front drum skimmed and brake shoes relined and machined to fit by a guy in the West Byfleet
transformed my stopping power, can almost bottom the forks now.
Hello, you may post info in this board https://www.a7a10.net/forum/index.php?board=46.0
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... though the shop mentioned way up earlier is actually fairly local to me.
I rang that shop btw. They no longer offer that service - not a lot of call for that sort of thing these days.
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The stick on emery does a perfect job in no time. Uses your wheel as a lathe. It only takes off what is needed, no more. You can feel when it's perfectly round, all pulsation disappears.
Use stick on 180 grit stuck to the shoes and grinding on drum first, then when the drum is done go the other way round to arc the shoes to the drum.
The whole job can be completed in the time it would take to load the wheel in the car and drive it somewhere local.
I have a big lathe here that can handle a wheel. I used to true drums in the lathe but don't do it that way anymore.
Hi there,
I know that it’s some time since this was posted.
I have a 190mm front brake fitted to my RGS replica and it vibrates when braking is applied.
I like your idea, sounds so simple, so will give it a try - but how do you glue/apply the emery paper?/cloth? to the brake shoes and the drum securely? What type of glue, and just as importantly how go you get it off?
Thanks for your help
Regards Rojah
I use stick on emery paper.
Auto supply stores sell it in discs.
I have a roll of 100 discs in 80 grit that I am slowly using up.
I cut strips of the correct width from the centre portion of these 7" discs.
It doesn't leave any residue when peeled off, in fact it removes dust in the pores of the brake linings. When used the other way to arc the shoes, it comes off the drum cleanly.
Glen
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Sticking the self-adhesive abrasive pads on the brake drum surface to radius the shoes works well, but sticking the pads to the shoes to cure brake drum ovality or warping sounds dubious.
It would some abrasive to remove 10 thou+ of work-hardened cast iron..
That's would be an assumption.
I've done this on 3 machines now, the worst of which was my A10. It was almost unrideable, the pulsation was so severe. If I recall correctly, it measured 7 thou out of round.
Took an hour or two to correct the drum. There is lots of mechanical advantage to work with. Almost too much going the other way on the linings. That only takes minutes.
Glen
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did the emery trick on my back brake that was non existent because the lever is only short compared to a std lever. did the shoes and drum and now have a brake that can lock the back wheel ---- if I put my big heavy boots on.
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That's would be an assumption.
Glen
If I'd known that I could whack seven thou off a piece of cast iron so easily I wouldn't bother with so many lathe tools, but just keep a stock of this modern abrasive paper to hand.
My existing rolls of emery cloth in various grades don't alter the work piece dimensionally to any appreciable degree.
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The reason the Emery works for this is due to the mechanical advantage available with both the wheel for rotation and clamped brake arm /cam for pressure.
It's quite a different thing than just rubbing some emery over some metal, or even doing so in a lathe.
I wouldn't advise selling your machine tools and investing the proceeds in abrasive rolls.
I still use my lathes and mill for lots of things, just not this.
If it was much more than 7 thou I would likely use the mill as it's large enough to leave the tire on a 20" wheel and still reach the drum face. With the lathe I have to take the tire off and then remount, plus jig up.
It's quicker just to use the Emery if the out of round is a just few thou or so. More importantly, the end result is a perfect brake with the absolute minimum amount of material removed from the drum.
You can feel when all comes smooth.
Glen
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Gonna try it on the front of my SP370 anyway.
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I finally found a reasonably local person to skim the A7 front drum. He has an industrial-standard workshop in the grounds of his house, complete with lathes, milling machine etc and the remnants of his days building (and sponsoring) race bikes, namely a couple of semi-built Goldie engines, self-built frames etc.
He trued the drum in less than 30 minutes (we went to the local cafe for a cuppa while he did it) on the biggest lathe using a roller on the tyre to spin the wheel. Sadly through age he's now selling his equipment and taking it easy, and won't be doing many/any more wheels, so I got in just in time.
Shame that, not too many old-style machine shops who have an understanding of bikes still left now. *sad2*
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I agree Rex, I did the same a few years ago with the worn headstock on my frame, found a guy with a machine shop in his backyard about 2 hrs away in a country town. Dropped the frame with him in the morning then we had an explore and lunch in town, went back at the end of the day and picked up the frame and drove home.. *smile*...again he was "retired" with a restored Goldie, but was about to shut it all down to look after his wife *sad2*...