2BA, 1/4" and 5/16" BSW spanners; circlip pliers; screwdrivers; small hammer; vice; adjustable spanner; toothbrush!
New contact pins (maybe), a little grease, washing-up liquid, time, patience, paint. Possibly circlips to suit.
Remove the actual handle - the dome-head nut and bolt, plus another bolt hidden under the plastic knob. Turn the whole thing upside down, and undo the four corner nuts, plus the six bolts (three pairs) holding in the 'innards'. Also undo the lock-nut and large screw - there is a ball bearing behind this to catch before it disappears onto the floor. The bottom casting should now be free, although gentle persuasion with the small adjusting tool may be required to budge it. Tap each corner in turn gently or it will jam up against the corner posts; these can be unscrewed next.
Unbolt the retainer which holds the springs which bear against the rocker arms, and retrieve these springs. They have a habit of flying off in all directions! The fixed contact assembly and terminal board can also be unbolted; retrieve the springs and washers off the two plungers on the rocker shaft. The rocker assembly is then pulled out - but don't pull too hard on the arms as they are plastic and may break. Wiggle it from side to side whilst pulling gently.
Now unbolt the clamp at the bottom of the gear cams, and the gear cam assembly will slide off (or drop off in kit form). Withdraw the gear shaft assembly from the top, retrieve the ball bearing between the gear and direction selectors, and then remove the direction cam assembly too.
I've not had any success dismantling the gear shaft from the casting it appears to be screwed into; it seems to be screwed together rather well! There is a small brass washer between the two cam assemblies, and a large brass washer above the direction one. Finally, unbolt the large brass casting to release the direction selector itself.
Picture 1 - gear cam assembly (left) and direction cam assembly (right). Note how these fit together - it's very easy to get them wrong!
The rocker assembly is perhaps the most important - at least, most troubles seem to be the rockers not moving freely. It is easily dismantled with a pair of circlip pliers, except that the brass bushes are often loose in the arms and / or rusted onto the shaft. If necessary, remove the offending arm first, and then support the brass bush in order to tap the shaft out of it. (tricky if there are several stuck - use your ingenuity!)
Clean everything up with copious quantities of washing-up liquid and toothbrush - it works surprisingly well, and doesn't seem to attack anything. The shaft itself can be de-rusted with a rotary wire brush. Make sure the rollers on each of the rocker arms do in fact roll, and if not grab them with large pliers and gently work them loose. I tried to avoid lubricating these on the basis that it will only attract dirt over the years, but gave in eventually and applied a little oil. The two plungers which provide the 'notches' usually need a little exercise to free them up too. Once dry I used a little superglue to hold the brass bushes in the rocker arms, and then reassembled it all with just a little grease in each bush. Make sure it's back together right though!
Picture 2 shows the overhauled rocker assembly and fixed contacts.
The fixed contacts can be replaced if burned - the renewable bit is just a tiny little thing, similar in shape and size to a drawing pin. If grabbed with a solid pair of pliers it can be twisted loose and pulled out; the replacement can then be pressed in with a soft-jawed vice (i.e. ordinary vice and two lengths of aluminium angle) Make sure you're not trying to pull the whole metal insert out though - only the silver tip! The moving contacts are also renewable - undo the two 4BA bolts to release it and a small spring - but I've not had chance to investigate sources for these yet.
The assorted other components benefit from stripping down, cleaning up and reassembly. With the two cam assemblies, make sure to note which cam is is which before starting - draw a picture. Picture 1 shows how they go back together; note the position of the flat on the end of the right-hand shaft. The cams themselves have a small 'pip' which (helpfully) isn't visible here; all of these should line up within each set of cams - but beware, not all seem to have these. The position of the ratchet (which gives the 'notches' for the gears or directions) is also important.
I shotblasted the various steel and aluminium bits, with the visible parts being powder-coated and the remainder treated to a few coats of spray-on silver Hammerite. I also replaced all the electrical screws and bolts - they're 2BA (see picture 2 above).
Picture 3 - the top casting cleaned and painted ready for reassembly to begin. The ball bearing interlocks gear and direction selectors.