Thanks for all the useful information and the clarifications. I truly appreciate your insights.
- The prototypes and earlier WTB models used approximately 0.375" OD x 0.75" tall brake studs. When Suntour licensed Cunningham's design, they established a new, smaller stud size of approximately 8.9mm OD by 16.5mm. That Suntour size became the de-facto industry standard for rollercam (and U-brake) studs. Some Cunningham and Potts bicycles continued to use the original larger (and arguably superior) size studs. Later WTB rollercams included the stainless cap you refer to simply to convert from the Suntour size studs back to the original WTB size (which the WTB's bronze bushings were sized for).
This makes complete sense. The odd thing with the Merlin rear brake studs is the 30 degree angle at the base. This makes it difficult to get the brakes setup without jiggle between the arms and the frame.
The other thing I'd observe in your drawings and photos is that original WTB bronze bushings don't have a step in them. They are a very tight press-fit and the fact they don't have a step allows the arm to be moved slightly up/down in relation to the mounting to allow for arm clearance on frames and forks where the brake stud isn't mounted exactly perpendicular and/or to allow headset clearance, etc.
This also makes sense. I think my powers of observation are severely lacking
. Now that I go back and look at various pictures of the DKG rollercams and the few that I have of Charlie's new roller/toggle cams I see that the brass bushing does not have a step. My rational for putting the step in was to keep the brake arm from sliding up and down on the brass bushing (which was a slip fit in my original prototype).
Now the brass bushing is press fit, but I still retained the step. Other than adding a little extra weight, and not allowing me the adjustability that you refer to, I think it will work quite well.