Up-date on the Caliper mounting, actually a small warning (advice really) to anyone thinking of pursuing the 'dream' of better (a lot better than most drum brakes I think) brakes....
Aligning the mounts... not at all easy, at least if you want the brakes to work properly, I guess you could mount the calipers so sloppy that they literally float into alignment, good idea but you'd need a Lot of brake lever travel to take up the 'play' before the brake actually starts it's braking job...
A caliper mount needs to be aligned straight and square to the disc, no twist or binding or things don't work, and our point is to have more than just a slightly better brake. By the way, one disc can be enough, again if it works properly, a larger disc is better (swept area, heat dissipation etc) Oh, and discs in the wet? never a problem, a brake pad will dry and warm a disc instantly! An advantage for us fitting a single disc would be that the stock speedo drive could be used on the other side to the disc and a flat disc can be sourced, and easier to mount than finding a suitably dished disc. Single discs work fine, with negligible fork flex in use, ie slowing and stopping.. although fork twist can seem alarming on ,say, a Harley "Wide Glide" (especially with extended forks) if you hold the brake lever and 'bounce' a stationary machine... on the road, like I said, not noticeable at all (in normal operation)
I don't really see a problem with discs on a Brampton, probably the suspension and damping will get a bit out of shape but the real problem would more likely be just the stresses on the 70 year old forks, and they really weren't designed with those stresses involved... try running into the car with ABS in front of you and see the effects of old girders succumbing to a bit of forced retardation....
Anyway, back to the immediate issue, alignment of the calipers... I found the caliper can only be tightly held by the axle, when the axle nut is tightened the mount is rigidly held in a 'sort of' square plane to the axle, except only 'sort of' as when the forks were made by the factory the machining of the axle hole faces were not necessarily perfectly square (to the axle) or even parallel, even the two fork blades are not perfectly parallel to one another, with drum brakes this is not so critical. For correctly functioning disc brakes alignment is very important.
So the 'stop-pin' needs some 'float' and the fender mounting bolt which was going through the mount was holding the mount slightly skew, this had to be modified with a shouldered spacer with some lateral play, the fender mounting bolt now has only that job to do, it never was in tension in any direction before, as I said, but now it's not interfering with the caliper mounting.
However, I still haven't completed the job, and many may be put off this task... I'm sure the "Dutch" brake or even the 8" unit is adequate, but I have been set on this route for a while.
My thought has also always been that the suspension/steering needs modification if the full potential of better braking performance is to be realized, yes quite likely this the real issue with Bramptons. Again I thank Norman, and AVO (and Thornton etc of course) for their constant striving to improve the Vincent.
I can imagine the PCV thinking he should improve the brakes but knowing the limitation of the stock fork design he hoped we'd all just plan ahead when stopping is involved..
"bloody hell! this geezer goes on..." I hear you say...