The article cited above is thorough and exhaustive. However I have the temerity, or ignorance, to make a couple of observations. Firstly, the idea that one can simply straighten brake shoe pivot pins should be distrusted. A brief inspection of an original steel plate must result in the conclusion that any bending will seriously compromise the fit of the pin and the integrity of the surrounding metal. As a second point,a recent experience with a friend's Twin illustrated that much cable movement was misdirected into flexing the backing plate, cam boss and probably the aforementioned pins. One must then ask; "how came the pins to be bent?" and the rhetorical reply is: "a design that could be improved coupled with the effluxion of time." There have been, as I and others have previously mentioned, several nifty wheezes for improving and making safer, the existing plates, and I repeat, some sort of bridging plate over the inner end of the pivot pins positively locating slightly thinned shoe eyes and being rigidly bolted to the existing backing plate is a plan worthy of consideration. I saw this done on an Australian machine some 30 years ago an apparently the brakes were brilliant. The above remarks also apply to the brake anchor pin which I personally wouldn't trust after 60 years of unknown use. Strengthening this component, the backing plates and the cam boss has been covered in "Forty Years On."As usual I await verbal blandishments and character assassination. F5AB/2A/7945 since 1970.
Max's Brake Tips
- Thread starter bmetcalf
- Start date
I kind of understand where you are all coming from, However.............what exactly do you suggest.....Do you think if a Vincent had a magnificent four leading shoe front brake like a Fontana or Gremica that setting up the brakes would be any different. If you reline the shoes oversize, and mount the shoes, cams etc on the backing plate and true it up in the lathe, then machine the linings down either using a shim under the cam face or simply machining the OD of the linings down 20 thou under the ID of the drum to which that backing plate assy belongs.....this will give good results. The pivot ends of the shoes from a good four leader may not be on a pin fixture of 360 degrees, as per a Vincent, but they are still anchored opposite the cams in a similar way, that is that they do not move around and realign themselves as to give a better servo action. They work well because they are big, and have lots of surface area. The bent pins and so on you describe, I think, are due to poorly fitting shoes. Say ones that have been relined, radius ground (like the shoes for a car) and then installed....perhaps into oversized drums....how can a brake work like this correctly, or else ( and this is reeeeeeeally common) grease has found it's way from the bearings to the lining surface, so the old handle bar lever gets a really good squeeze to try and stop the machine. The pins bend because they are the weakest link. The brakes on my Rapide work very well because I have all good components, and took the time to set them up as I described earlier, but how many owners go to this kind of trouble, or have a lathe to do so. Because a Vincent has small brakes, they need setting up carefully to get anywhere near good results...........Greg.
The Vincent brake design is of the 1920s make no mistake. The technology was there in the 50s, proof of that one would only have to look at the Norton Manx DLS stopper. My brake tip article was meant to improve what came on the bike not to modify with various means of bracing to keep things from moving around. The backing plate is about as simple as it gets, a plate two pivot pins, and a cam support tube . After a trip to the press, she's done ready for paint. Good idea to produce a part at a low cost , not a good idea to produce a good part.
MAX
MAX