I'm neither an engineer or a machinist, but let me offer a few corrections to some your points here.classen":3i8lxv2r said:The original WTB rollercams had brass bushings press fit into the brake arms and came with a stainless steel cap that fit over the brake post. I'm no engineer, but as far as I can tell this had two benefits.
1. The tolerance between the brake post cap and the brass bushing could be very tight fit since both pieces were provided with the brakes. No need to rely on a good fit between the brake and brake post (likely some variability between frame/fork manufacturers). The brake post cap essentially becomes part of the bike.
2. The cap over the brake post has larger diameter than the brake post/boss reducing lateral compliance (back and forth jiggle). i.e. larger diameter rotating axis provides better stability.
halaburt":21o9d436 said:- 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).
halaburt":21o9d436 said: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.
At first I couldn't figure out what this 30deg problem you were talking about was... I thought you might mean the posts weren't quite perpendicular to the seat stays (no where near 30deg angle there though). Then I realized you meant the "shoulder" on the brake stud itself, right?classen":14k90id2 said: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.