they are pretty robust after all the design is British Victorian era .. almost Steam Punk..

from 1909,, AW3 is 1930's [ about when the last Brit won the Men's finals at Wimbleton]

Dan Burkhart has some tear down Videos , recent one on the NIG redesign..

1) the gear is not disengaged only the power application changes

AW3 is used as a 4/3 or 3/4 overdrive or reduction gear . the pawls are the shift between

like the pawls on a freewheel or freehub ..

5 speed is 2 ring gears planetaries have 2 sizes of gear one on each end.

[20% and 33%]

FWIW there is the S3X fixie 3 speed , ratios are the bottom 3 of a 5 speed .63, .75, & 1.. [1.33,1.6]

http://www.sturmey-archer.com/produc...4/specs/1.html

Shimano's are notorious on spare parts AW3 being made for ever is easy.