Dual disc brakes on commando

madass140 said:

it would also require a change of hub and brake rotors.

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In any case, especially the hub.

acotrel said:

I would not weld the slider unless you know the post-welding heat treatment needed to bring it back up to strength as well as the correct welding rod to prevent dilution of elements in the weld. If the slider fails when you are braking, you might land on your head. If somebody such as Mick Hemmings or Nourish was prepared to manufacture the left hand slider and calliper, there might be money in it for him.

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Tig-welding probably wouldn't affect the original heat treatment. If it can be done to die-cast crankcases (Milyard) and used for crack repair Norton gearboxes and cases) a fork leg and/or caliper should be easy, and if you find someone with a mirror-image setup, I'd wager that's how it was done. Again, not rocket science.

Stock, for a first generation disc brake (from the early '70s) it's a good set up if you sleeve the master cylinder and fabricate a fork brace. The forks too will always be limited by the age of their design but they can be made acceptable.

If you are willing to go non-stock, go to Maddass for his sliders and different calipers; or, find a different set of forks altogether - such as those Marzzochis or a set off of some late'70s or early 80's Japanese bike.

The stock calipers assume a thick disk, so it's hard to lighten them, especially if you go with two of them. Further the calipers, while good looking are not lightweight either. The fact that they use a large diameter pad hinders them, again a function of the fact that they are a first generation design.

Danno said:

acotrel said:

I would not weld the slider unless you know the post-welding heat treatment needed to bring it back up to strength as well as the correct welding rod to prevent dilution of elements in the weld. If the slider fails when you are braking, you might land on your head. If somebody such as Mick Hemmings or Nourish was prepared to manufacture the left hand slider and calliper, there might be money in it for him.

Click to expand...

Tig-welding probably wouldn't affect the original heat treatment. If it can be done to die-cast crankcases (Milyard) and used for crack repair Norton gearboxes and cases) a fork leg and/or caliper should be easy, and if you find someone with a mirror-image setup, I'd wager that's how it was done. Again, not rocket science.

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My experience with welding (TIG) lugs on a Norton slider was that it distorted the bore enough that I had to have a machine shop hone it oversize to true it. I made new top bushings, and machined the bottom bush to take a Suzuki lower fork split Teflon/bronze bushing with the right fit, and it worked fine for years. With a lot of care in the welding, you might be able to avoid the problem. I was using a fairly large lug, and put a lot of heat into the slider. Welding in smaller beads with cooling between passes might have kept the warpage down.

Ken

with only a 4mm wall thickness I cant see how it would be possible to put that much weld without distortion, you only need .001" distortion and the bushings probably wont fit correctly so that the forks arent binding etc
Don

I once grafted a RD350 front caliper onto a 450 Desmo by welding two aluminum tabs onto one of the sliders.
Got away with it. Slight binding fixed with gentle application of a hydraulic press.

Even with TIG welding, it is normal to apply heat with a torch first. That softens the aluminium so it needs solution heat treatment to get it back up to strength. I am very careful when I play with brake parts and fork yokes. I was running one race meeting and watched one guy do a complete forward roll when his fork yokes broke off completely as he braked. Someone had used the forged steel ones as a pattern for aluminium replacements. Also a friend of mine was killed when the front discs on his RG500 Suzuki exploded off the bike at the end of Conrod Straight at Bathurst. His father had made grey cast iron replacements for the chrome plated aluminium ones, because the chrome used to spall.
I suggest twin discs in the front are essential on any Commando which is to be ridden fast. The single disc can never be enough, regardless of what pads you use. And the twin-leading shoe drum brake is simply stupid. The only time I'd ever use one would be if I really wanted to race in Historic Class Period 3 and I don't do that. It's a good way to get hurt.

Acotrel, I'm intrigued by your high speed steel discs, seeing as most of my lathe tools are HSS. Solution treating is the soaking of duralumin at 200 degrees c to allow it to be bent or formed. It can be maintained in this soft state by storing in a fridge. Thats my understanding.