Author Topic: Brake Drum Skimming  (Read 5059 times)

Online RichardL

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Re: Brake Drum Skimming
« Reply #15 on: 12.09. 2010 13:41 »
Groily,

I agree with Markus, that is very clever tool, also works well as a clamp for your wallet. I have a few questions:

1. Apparently, you did not run into any extreme issues with alloy hardness. The cutter looks like it could even be common tool steel, but I am guessing it is probably carbide. I that correct?

2. I couldn't quite follow the "milled flat" issue. I assume that is to keep the round tool holder from turning, but if it's locked up, how does the tool bar push out with the feed screw?

3. Would you like to copy this post over to the "Home Made Tools" topic so it appears under your name, rather than mine, if I were to do it (crediting you, of course)?

4. Is it for loan or for rent?

5. How's that patent working out for you?

Richard L.

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Online groily

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Re: Brake Drum Skimming
« Reply #16 on: 12.09. 2010 17:26 »
You're far too kind Richard, as ever (and you too MG) - it's just that old 'Necessity Mother and Invention' thing plus I've plenty of time on my hands. The cutter is just a fly-cutter bit in HSS bought with a few others for a few pounds - but it's done a bit of work and I only sharpened it once I think.
The 'milled flat' description was a bit of short-hand really - there's a brass pad between the end of the screw with the  (small) tommy bar and the flat side of the toolholder. It's there for the reason you give - to keep things square. What I did was part-tighten the pad against the holder to keep a bit of friction on when using it - not really a proper approach, as an adjustable D-shaped gib strip of some sort the whole length would have been better.  And then some micrometer dials would have been nice, and and and! But hey, it did what I wanted on the day and it was only for private consumption.
By all means stick it in the tools section, hadn't thought of that - thanks.
I wasn't thinking of making any others, and I don't have a drawing - euphemism for 'actually, I can't draw' (I just did a rough sketch and then poked about for bits of scrap and took it from there). If anyone was really keen I could probably convince a mate who's truly competent to draw something up and maybe incorporate some of the improvements it needs. Be nice to think there was novelty in the thing, but think probably not (from the patents angle).

The problem with all these things is that the time taken to make them (by somebody properly-skilled using good materials rather than by optimistic lunatics out of farmyard scrap) makes them a worse financial proposition than the 75 pounds odd mentioned above for a perfect job + the right to complain afterwards! I have a whole box of things that took me a day or so to make and which work well for me, because I'm too mean to buy them, even if they exist. Clutch centre removers, bearing pullers, fork stanchion pullers and pushers, mag pinion and camshaft pinion extractors etc. I know many of us have the same or similar.
I was looking seriously the other day, guided by two better-informed others of our number, at those 'chuck pullers' for removing small bearing inner races that go tight up against stuff. . . they exist, but boy, at over 100 Euros and then needing some extra bits for the sorts of applications I had in kind (mag bearings in that case), I reckon it was better to have made my own ugly things to do the same job. And then there are things that just aren't really feasible at home for the want of tough enough materials - flywheel pullers for magnetic flywheels come straight to mind as I bust a newly-made mild steel item only yesterday trying to get the 'volant' off a (- very sorry -) classic Vespa scooter. Same story trying to make a tappet-guide puller for my Enfield twin - just not a sensible option. Sometimes you have to pay, or do without.
But I am tempted to make a nice valve guide remover having seen the brilliant torture chamber instrument posted on here recently! Personally, I enjoy playing in the shed, failures included, just as much as getting out there and breaking the toys on the road (just so they have to be mended). Funny thing is, BSAs don't seem to go wrong very often . . . I THINK that makes me happy.
Bill

Offline A10Boy

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Re: Brake Drum Skimming
« Reply #17 on: 13.09. 2010 10:19 »
In the UK, Supreme Motorcycles in Leicestershire will skim and fit oversized linings, you can even leave the tyre on.

Regards

Andy

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Online BSA_54A10

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Re: Brake Drum Skimming
« Reply #18 on: 13.09. 2010 11:14 »
Quote
Trevor,

Please don't take offense, but unless Nikasil is something completely different in English language use than in German, this can't be right.
"Nikasil" is a trademark owned by Mahle and was first used in the late 60s (afaik). It is a silicone-carbide coating (nickel matrix, hence the name) deposited in thin layers, mainly used as coating for alloy cylinders (with direct contact to the piston, thus cast iron liners can be omitted). So Nikasil (again, in German!) is a coating material, but definitely no casting alloy.
Maybe you meant Dural or Silumin?

The Ariel hubs I have simply have a steel ring cast in.

Cheers, Markus

Markus,

you are far too sensative.
I am never more happy than when I am proved to be wrong.
It is really the only way to be sure that you have the right information and a prime way of learning.
Never met a scientist nor engineer who was offended top be proven ( to their satisfaction ) wrong.

The Nickasil I am reffering to (& I might have the name wrong ) is a cast iron alloyed with Silicon & Nickel.
Some of the carbon ends up as a Silicon Nickel-carbide ( or is that a Nickel Silicon-carbide).
In any case it is as hard as hell but no more brittle than standard cast iron, the perfect stuff for a brake drum.


FWIW to those who do not understand what a brake dose.
As energy can neither be created nor destroyed a brakes job is to convert one form of energy ( kinetic ) into another form of energy ( heat) and in the case of my brakes a fair bit of sound energy as well.
As a by product of this the softer bit , the brake material, gets ground away while ( hopefully) the harder bit , the drum/ disc , remains intact.
This is why brakes fade, the drums get hot and can not generate enough heat from the friction with the pad.
Bike Beesa
Trevor

Offline MG

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Re: Brake Drum Skimming
« Reply #19 on: 13.09. 2010 13:54 »
Quote
Never met a scientist nor engineer who was offended top be proven ( to their satisfaction ) wrong.
I did, glad you are not one of those!  *smile*

The mentioning of "Nikasil" (or "Nickasil") led me in the wrong direction, thinking of aluminium as base material (i. e.  brake hubs), but there are literally hundreds of trade names for nickel-silicone-carbide materials of all kinds and I don't know what that special cast iron you mentioned would have been called.
But since 1966 Nikasil definitely is Mahle's brand name for the aluminium coating (it comes from the German words Nickel, Aluminium, Silizium). It was first used for the Wankel rotary engines (I did a bit of reading, as it raised my interest).

However, as this was far later the brake hub material might have had a very similar or even identical trade name, who knows.

Sorry for sabotageing your good advice on that material's (whatever it is called) hardness and potential problems in machining with superfluous discussion about brand names.  ;)

Cheers, Markus
1955 A7 Shooting Star
1956 A10 Golden Flash
1961 Matchless G12 CSR

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Offline Duncan R

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Re: Brake Drum Skimming
« Reply #20 on: 13.09. 2010 23:02 »
I contacted Hagon regarding a drum skim and they said they can do it without having to dismantle the wheel and possibly the same day for £50. They are only a 40 min drive from me.
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Online BSA_54A10

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Re: Brake Drum Skimming
« Reply #21 on: 14.09. 2010 07:44 »
Markus,
From memory ( and I have no intention of checking it ) the name comes from BSA.
Either in some advertising , a press release or a factory news letter.
I really should index these things so I can find them when I need to.
The hard drums became standard fitment to just about every thing post WWII.
The only exception I know of was the Ariel full width hubs which were bought in and not made at the BSA .
My daily ride BSA was a B40 and as such the drums did end up a bit oval so I sent them to be machined.
Got them back with an appology with an interior surface much like an 78 rpm record.
By the time we had ground them flat again they were .060 under size and just about US but being a poor uni student I managed to get them to work but it wasn't easy
Bike Beesa
Trevor

Offline A10Boy

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Re: Brake Drum Skimming
« Reply #22 on: 16.09. 2010 13:31 »
Brake fade has a lot to do with the coefficient of friction, as the temperature goes up, friction reduces.
Regards

Andy

1960 A10 - Black Golden Flash
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Offline beezalex

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Re: Brake Drum Skimming
« Reply #23 on: 16.09. 2010 16:50 »
FWIW, I gotta agree with Markus here on the Nikasil thing.

But that all seems to be woefully besides the point since it seems that every brake drum that BSA made used cast iron with the possible exception of the Ariel and 190mm hubs...dunno about those.
Alex

Too many BSA's


Offline Duncan R

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Re: Brake Drum Skimming
« Reply #24 on: 18.09. 2010 14:53 »
Hi All,

Rob at Hagons called me yesterday and said the drum had skimmed up nicely and all the grooves and heavy glazing had been removed. He said he done two cuts totalling 10 thou. Wheel is being delived by courier on Monday for &9.50. I could have collected it today but by the time I pay the tunnel tolls and petrol and sit in traffic jams it was cheaper to have it sent. Hopefully now I will have a working brake.
Anglo - Indian A7SS (Actually is a 650)
Kawasaki ZZR 1100
BMW R80GS
BMW R1100GS