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Rockerbox Other Stuff Gearbox Summary

I stripped the gearbox this afternoon-I started writing this page 10 months ago. I thought I should strip the box and check the condition of the bearings; I was expecting some rust inside the box, when I changed the oil there was a lot of water in the oil. I think the water was probably due to recently being washed and the water entering the box thru the clutch cable fitting. I pulled the gearbox cover off and the inside was clean, everything was sparkly clean, but there was lot's of bronze dust in the bottom of the case. I pulled the gears out and realised every one of them was really badly worn. The bronze was from the selectors being switched, one has a bevel ground onto it to clear third gear and the gear has chewed it's own clearance in the other shifter fork. It looks like there is a spacer/shim missing from the layshaft, probably the so called wedding ring? There is a really chewed looking case hardened spacer in the kickstart assembly.


Figure 1. The gears meshed as installed.

Not such a good photo maybe a close up of a tooth would be better. The above picture shows the wear on all the gears, but needs to be seen in all it's glory at 1600x1200 really. Thats, third gear. I wonder if the box was professionally restored;-) I have everything, except a new layshaft spacer[BK82, 'badly chewed spacer'], to rebuild the box. I bought new gears, all the gears were beyond use, I didn't manage to get a new second but someone in the Velo owners club donated one[I keep meaning to mail him and say thanks]. I bought a new mainshaft, the old one was pretty worn. I bought another pair of selector forks, the wear on the bronze was acceptable but both had a lot of wear on the cam plate pins, I scored another pair of forks in better condition with good pins. The bearings all had to be replaced, I splurged the moolaha on RHP bearings, all those new gears I wouldn't take any chances with Chinese looking bearings. I was quite suprised RHP bearings only cost me a few quid more than brand with no name ones.

rockerbox2
Figure 5. One of the cracks in the cover, they run running radially outwards from the kickstart boss.

The gearbox lost all it's oil on my floor probably in a month or so, when I cleaned the case and cover the reasons became quite apparent. The cover had cracks radiating from the kickstart boss. One crack ran out through the level plug hole, another from the opposite upper kickstart bolt thru the oil filler boss and a small one through the bottom kickstart boss bolt hole. I welded them up, fingers crossed it's OK. I also replaced the oil filler plug, it was a pretty stainless part with barely any thread on it, nearly forgot I welded up the cracks in the filler boss and made brass plug to suite. The case was essentially sound, one thread was gone and it had cracked to the edge of the flange, so it had to be welded up and re-threaded. When I took the gearbox out is was apparent the gearbox adjuster slot was badly worn and the 'ear' on the engine plate that it bolts to was also worn badly. So I have made a new adjuster and engine plate, if the engine plate had snapped I wouldn't have been at all suprised.

Figure 2. Third gear driven gear, the double gear. Little bit of gear wear?