Monday, 5 July 2010

Servicing the Sturmey-Archer S3X hub

Servicing the Sturmey-Archer 3-speed fixed gear hub

Follow these instructions at your own risk - Sturmey-Archer have not published any official workshop instructions for the hub as yet. However, I have stripped and rebuilt lots of SA hubs including this one and had no problems (except when I tried to mix incompatible parts or something else stupid)

Tools required: sprocket lockring spanner (the same as a Shimano
external BB spanner), cone spanners, small circlip pliers, tyre lever,
hammer, punch, vice and (ideally) the SA ball ring spanner.

Materials required: rags, solvent, small paintbrush, detergent
(washing-up liquid), gear oil, SA internal hub grease, lithium bearing
grease.

1. For easier cleaning, remove the lockring, sprocket, spacers and
external dust shield from the hub. Make a note of their order, or your
chainline will be affected. For reference purposes, the chainline is
45mm with the sprocket outside the two spacers. I have found it is
possible to stretch this to 46mm with an additional 1mm spacer and still
give the lockring plenty of thread to bite on.

2. Remove the locknut(s), spacer(s) and cone from the LH side of the
hub.

3. Using the ball ring spanner, unscrew the internals from the shell.
They will not be super-tight and you should be able to do this without
resorting to a mallet. If you don't have the correct spanner, SA permit
the use of a hammer and punch on the two semi-circular cutouts, but this
will normally mark the finish. As soon as the mechanism starts to move,
you will find it can easily be unscrewed the rest of the way by hand.

4. Withdraw the internals from the shell and wipe away as much grease as
possible.

5. Remove the RH locknut, any spacers and the cone.

6. Lift off the driver, clutch spring cap, clutch spring, ball cage,
ball ring, gear ring and clutch.

7. Remove the circlip and withdraw the axle from the planetary gear
unit, which is riveted together and cannot be further disassembled.
Likewise, the compensating spring and axle key cannot be easily removed
from the axle.

8. To remove the ball cages from the driver and the shell without
damaging them, insert a tyre lever between the metal dust seal and the
ball cage as if you were about to prise out the seal, but don't - this
will damage it. Holding the tyre lever in place, strike it from inside
out using the hammer and punch. This should pop out the seal cleanly
after a few blows. A slight warping is OK and will disappear when
refitted, but you must avoid denting or creasing the seal. New seals
are available if necessary.

9. Clean all parts, including the inside of the shell, in solvent. The
planetary unit and axle assemblies will need to be soaked for a while
and very thoroughly cleaned with a small brush, since you can't
disassemble them properly. You may wish to replace the bearing balls,
which are 1/4" and 3/16". Treat the plastic ball ring seal/ball cage
with care, as this is a SA-specific part.

10. Wash in strong detergent to remove any traces of solvent. Rinse
with clean water and dry the metal parts in a warm oven at about 75 deg
C as quickly as possible to avoid rust. Ensure the shell and the
plastic parts are thoroughly dried - use a hair dryer to be absolutely
sure.

11. Inspect all parts for wear or damage. Typically the most wear is to
the LH dog of the axle key, which is what locks the sun gears in
position for gears "1" and "2", and to the axle slot where the key
slides. It is highly unlikely that there will be any wear to the clutch
or to the planetary unit. If possible, replace any rounded-off parts;
hopefully SA will make the axle assembly available as a spare.

12. Replace the axle ball cages, ensuring that the solid ring of the
cage is facing outwards. Grease the cages with normal lithium bearing
grease. Fit the dust seals with the open end of the "U" shaped channel
facing outwards. These will usually require tapping into place using
the hammer and a suitable flat plate - the handle of the ball ring
spanner works well. It is permissible to fill the "U" shaped channel of
the dust seal with grease to better repel dust, although this *may*
allow water to creep in by capillary action - your choice.

13. Oil the planetary unit, paying special attention to the axles on
which the planets turn. Also run oil down the middle of the axle to
ensure the compensating spring is well lubricated. The oil is necessary
because grease smeared on the outside might not penetrate for a long
time, allowing rapid wear of unlubricated surfaces. Wipe any excess oil
off the surface to avoid diluting the grease which will follow.

14. Stir the special hub grease to mix in any free oil and smear all
parts, except the outer face of the ball ring and its cage, ensuring
that the gear teeth and the slot in the axle are especially well
treated. Pay special attention to any areas which have been polished
silver by use, since these are the internal bearing surfaces.

15. Insert the axle into the planetary unit and secure it by fitting the
circlip.

16. Replace the other parts in the reverse order of (6). Use normal
lithium bearing grease on the large ball ring race.

17. Screw in the RH cone by hand until it stops. back it off exactly
half a turn then, holding the LH flats of the axle in a vice so it
cannot turn, ensure that the cone does not move with a cone spanner and
do the locknut up tightly against it. This sets the internal clearances
and ensures all the internal parts can rotate freely against each other.

18. Grease the threads of the ball ring and screw the mechanism into the
shell, tightening it firmly with the ball ring spanner.

19. Refit the LH cone, spacer(s) and locknut(s) and adjust the bearings.
You should aim for a just-perceptible amount of sideways play at the rim
when the wheel is fitted in the frame. Do not eliminate the play
completely, and do not make any adjustments at the RH cone.

20. Refit the outer dust shield, spacers, sprocket and lockring then
refit the wheel to the bike (recommended 20Nm on the axle nuts), grease
and insert the indicator spindle then connect and adjust the cable as
per the instructions. Test ride.

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