Sturmey Archer AW 3SP Hub - Only Two Gears

[keithglos]

There is a position between the high gear and the "normal" where there is no drive. So you would be able to pedal the high gear and hear the pawls ticking, and see the wheel going round faster than the cog. So pull the chain past the first slipping, and you should have middle or normal gear, where the cog is turning the same speed as the wheel.
A further pull should engage low gear, which seems to be slipping, and it seems as if your pawls in the left hand end plate have stuck, or the pawl springs rusted away. You can take the LH cone off and remove the LH end plate to see this, it is left hand thread, and has 2 large flats on it. If you find the pawls are not working it would be better to take the hub apart from the other end, but a little oil while the end plate is off might work.

 

[iamrcb]

All the pawl springs are new. The ones near the planets spring back quickly, the others at the end (left) spring back slower due to oil resistance. These also have a chamfer on the top surface, that I think are facing the right way.

 

[keithglos]

Guessing a bit, the low gear pawls are not engaging, so must be the wrong way round, or the springs not in. It's probably well over 50 years since I had one apart, but I think the later AW was little changed.

 

[iamrcb]

Readjusted it from scratch.

I have high and middle gear. When I change to low (most chain pulled out) I just get freewheeling.

 

[iamrcb]

Which ones are the low gear pawls?

The ones nearest the planet cage or the ones at the other end (left side)¿

 

[keithglos]

so the pawls under the LH end plate are not engaging. If you take it apart from the right hand cog side, pull out the internals in one piece, then unscrew the left hand end plate (LH thread) and try it on the low gear pawls.
We always marked the RH end plate position against the hub as they were a 2 start thread, and if reassembled on the wrong thread the wheel would need retrueing. They might be more accurately machined now.

 

[keithglos]

If you think of it like this: the high gear drives the planet pins, and takes the drive from the gear ring, the low gear drives the gear ring and takes the drive from the planet cage. Planets being the 4 cogs, gear ring goes around the planets. On the axle the sun gear is always stationary.

 

[iamrcb]

I can remove the whole internal assembly, but the hub shell end on the left cannot be removed, its a one piece shell.

 

[keithglos]

All you can do is look at the ratchet system in the LH of the shell, and compare with the pawls, do the pawls look as if they will pick up the ratchet, or try the planet cage in the hub shell. It was always easier when I had them in my hands. Hope you can see it now, and get it going. Useful experience?

 

[iamrcb]

Keith, you are the SA saviour.

I have all three gears, all nicely adjusted.

I can now strip, reassemble and adjust an SA hub in minutes all because I've now done it so many times trying to get this bike right. No experience of this type of setup before.

What was wrong?

I foolishly put the low gear pawls in upside-down, hence no bite on low gear. Doh.

Test ride tomorrow.