I've slowly been accumulating parts to modernize my Moulton F frame. One of my purchases is a set of Tektro R556 brakes, as they are about the only long reach dual pivot brakes on the market. Unfortunately, the rear suspension bushing housing interferes with the brake. What are other people using for brakes on old Moultons?
I have done the same mod with another brand brake and had to put a spacer in (I used the two semicircular spacers that come with the brakes, one on top of the other ) ie it lifts the brake enough to clear the bushing. I have done this on three F frames with Allongha long reach brakes. You may need to buy those threaded cylindrical nuts to reach the bolt from a bike shop, they are used on other brand brakes instead of a regular nut.
1940s Fothergill, 1959 Allegro Special, 1963? Claud Butler Olympic Sprint, Lambert 'Clubman', 1974 Fuji "the Ace", 1976 Holdsworth 650b conversion rando bike, 1983 Trek 720 tourer, 1984 Counterpoint Opus II, 1993 Basso Gap, 2010 Downtube 8h, and...
It's a problem, for sure. My first choice would be a hub brake, such as the roller brake with a Shimano Nexus hub. Instead I put a SA 8 hub on the rear, and a SA dynamo/drum hub on the front; that freed up the front brake, so I put that on the rear with long spacers as Edd suggested. The result was an excellent front brake and.... Well, at leasst there was a brake on the rear, and it worked after a fashion... but it was mainly decorative.
got to look at the welding on the swing arm...might need redone
If the swing arm is straight its a Series 2, shouldn't be a problem.
There is only a problem if it's a Series 1 with the slender, tapered, curved blades. Especially if it was made at Kirkby. There should be a number on the left side of the seat collar. K66 means it was made at Kirkby in 1966.
It's not nearly as simple as re-doing the welds. Especially if there is already some cracking.