Click images below to see the P.D.F files. Left is front dynohub - Right is the geared rear version.
Proceed as follows:
Remove the dynamo-side locknut and washers, making a note of their arrangement so that they can be replaced in their original positions.
Remove the four magnet-fixing nuts and lock washers from the back of the hub drum, and then remove the four magnet-fixing screws.
Hold the wheel, with the dynamo downwards, just above the work-bench. A few light taps with a mallet on the end of the spindle will cause the dynamo unit to drop out complete.
The magnet spacing ring can now be lifted out of the hub drum.
Unless it is essential to do so, the armature and magnet should never be separated. If they are to be separated, a keeper ring is absolutely necessary, because the magnet will lose some of its magnetism unless there is always iron inside it. Even a moment's separation will cause loss of magnetism, and a spanner placed across the magnet is useless as a substitute for a keeper ring. To separate the magnet and the armature, hold the dynamo unit in the left hand, with the terminal plate against the palm. Then fit a keeper over the armature and lightly tap the keeper with the palm of the right hand. The magnet will slide off the armature and on to the keeper. At this stage it is wise to test the armature with a test meter. If there is no reading on the test meter there is a break in the winding. If a test meter is not available, a battery and bulb may be connected as shown in the diagram, and if the bulb does not light a break in the armature winding is indicated. A second test is to disconnect the lead from one of the armature terminals and touch the outer edges of the armature with the bare lead. If the bulb lights, this indicates a short circuit.
Remove the cone locknut on the left-hand side and unscrew the left-hand cone.
The channel-section dust cap is just a press-in fit and can be prised out with a wide screwdriver (to avoid damage). The ball cage may be lifted out for examinationof the hub bearing surface. If a new ball retainer and balls have to be fitted, it is usually best to fit a new dust cap as well. Both hub cups are part of the hub shell and if either is worn a complete new shell must be fitted.
The spindle may now be pulled out from the dynamo side, together with the right-hand cone. If the bearing surface is in good condition and the spindle threads are sound, there is no need to remove the cone.
The ball cage may be lifted out for examination of the hub bearing surface.
SPECIAL NOTE. - GH6 hubs prior to 1952 had the adjusting cone on the dynamo side. This cone is extended to pass through the armature body and is flatted at the outer end to take (K428) notched adjuster washer, by means of which the cone may be turned. Dismantling instructions from 1 to 5 remain exactly the same as for the current model. For paragraph 6 read 'Unscrew the dynamo-side cone and lift the ball cage out of the hub shell. The spindle may now be pulled out from the other side, together with the fixed cone.' All further comments apply equally to all GH6 hubs.
Proceed as follows (see notes at end if hub was supplied before April 1952):
Fit the ball cage with the ball-retainer ring facing outwards, into the cup on the left-hand (the smaller) end of the hub shell. If a new ball-retainer is being fitted, the dust cap also should be new.
Fit the dust cap, with the channel facing outwards, and press it home (or tap lightly with a hammer).
If the dynamo-side cone has been removed from the spindle, replace it (LB357AZ) on the spindle and screw it up tight against the shoulder on the spindle.
Fit the ball cage, with the ball retainer ring facing outwards, into the cup on the dynamo-side of the hub shell.
Insert the spindle into the hub shell from the dynamo-side.
Fit the left-hand cone and adjust the hub bearings as described in The Fitting and Adjustment of Strurmey-Archer Hubs. (A correctly adjusted wheel must have a slight trace of play at the rim.)
Fit the cone locknut and screw it up tight against the left-hand cone.
If the magnet and armature have been separated, take the magnet and keeper ring in the left hand and, with the right hand, lay the armature alongside it.
While holding the magnet with the chamfer facing outwards, push the armature and the keeper through so that the magnet slides from the keeper on to the armature.
Fit the card disc (carrying patent numbers) inside the cover plate, with Its notches opposite the magnet notches.
Fit the cover plate over the magnet, chamfer inwards, making sure that the four holes in the cover plate are in line with the notches in the card and the magnet.
Fit the metal spacing ring into the hub shell.
Fit the shim washer over the cone.
Push the complete dynamo unit into the hub shell, making sure that the holes in the cover plate are in line with those in the hub shell.
Fit the magnet fixing screws, washers and nuts.
Fit the spacing cup, washer (if any) and dynamo cone locknut in the arrangement noted when dismantling.