I have decided to lengthen the operating arm (by one inch) on the rear brake of my 1930 TT Rep, so that the rod runs free of the gearbox base tray ; the rod currently has to be bent to connect it to the operating lever and this creates a fair amount of drag on the rod against the gearbox base tray (and not allowing the arm to return easily).
So, I notice that most photographs of Scott rear brake units generally indicate that the operating arm is held in position against the brake cam with a nut (or perhaps a bolt).
However, mine seems to be a single arm/cam unit and the only removable item appears to be a grease nipple.
Does this sound correct? Should the arm actually lever off when the grease nipple is removed? Should the arm be sprung within (or without) the brake drum (mine is not)? Are longer arms available (photographs appear to indicate that this might be so)?
It is usual for the arm and cam to not be in separate pieces, but on some works bikes there are variations. It is of course an Enfield component, fitted to many different makes, including Brough Superior, Norton, Zenith, etc., as well as Royal Enfield. You will see different fittings on these different makes. Vintage and early 1930s Flyers and Reps with the right-hand side brake pedal had the gearbox tray with a groove milled into the side to give working clearance for the brake rod. When foot gear-change came in the brake pedal went to the L/H side, and so the gearbox trays no longer had the groove in them. Maybe you have a later tray that is causing the clearance issues ?
I should have added that if you fit a longer arm to the rear brake, this will in effect lower the rod, and it may then foul the frame lug at the back of the engine. You should really be looking for the correct gearbox tray with the groove milled into the side.
I obviously have the later tray ; it is a replacement for the previous (welded) tray that didn’t have a groove (obviously a replacement itself).
I checked the route of the rod with an extended arm and it clears everything when extended by exactly one inch.
However, even in this position, the operation seems to be slightly stiff (although each individual component works freely) and I wondered if there should be a spring somewhere to ensure that the arm/cam returns to the original position after use.
What I usually do is put a spring on the shackle at the brake pedal end of the rod, and then anchor the other end of the spring to the bolt that holds up the front stand, using a length of piano wire to extend the spring if necessary.
On closer inspection, it appears that I have a tray with the necessary groove. However, having used the ‘chunky’ SOC brackets to mount the tray, they do not leave sufficient room for the rod to run in the groove.
I could. of course, grind off a section of the inner half of the bracket but, as the brake arm is moving slightly in the brake plate (obviously a bit worn and requires a new bush), I will pull the lever unit out and extend it by an inch and fit a new bush.
Once I have the rod running free, perhaps new springs internally will ensure that the arm returns to the correct position after use.
After messing about with various springs, I settled on a 150mm long side stand spring off Ebay (No 1823 9588 8312).
This can be slipped over the brake rod, with the front hooked over the ‘c’ bracket at the brake pedal end ; the rear of the spring is then level with the first bolt of the footrest bracket.
A little right angle bracket fixed inside the footrest bracket and a rather neat job.
As the spring is just a bit larger than the brake rod, it fits over it nicely (so the rod runs inside the spring) ; the rear hook on the spring is bent out 90 degrees to fit the angle bracket.