Modifying the Bogie Drive

This section describes the operations involved in modifying the drive unit for one bogie.

Removing sideframe/undertray moulding Using a small screwdriver, gently unclip the bogie sideframe/undertray moulding from the ends of the bogie drive unit. Take care not to damage the brake shoe and step detail. Put the moulding safely to one side for now.

Unclip the two wheelsets from the drive train moulding and put them to one side.

Unscrewing bogie pivot Undo the two cross-headed screws retaining the bogie pivot to the tops of the two pivot towers …

Bogie pivot removed … and remove the pivot. These parts are not required for the converted bogie.

Removing pickups Undo the cross-headed screws which retain the metal pickup strips on the side of the drive train moulding. Remove the strips and, with a sharp knife, the moulded pips which locate them. Put the pickup wires and strips to one side for reuse.

Removing idler axles Gently press out the three idler axles. We found that the axles are a tight fit in one side of the moulding only so, once you have removed the first one and thereby determined which side that is, press them out from the tight side and, when the time comes, replace them from the loose side.

When removing the idler axles, support the moulding on a hard surface with some kind of slot or hole to receive the axle.

Idler axles and gears removed Remove the gears that were retained by the idler axles and put them to one side for later.

An amount of dust and swarf is generated by the following operations. It is possible to remove the worm and its bearings. However, we found that, on refitting, it is tricky to align them correctly to regain their original free running and so feel that, on balance, it is better to leave them in place and clean them thoroughly once the following operations have been completed.

The drive unit moulding and your fingers will by now be thoroughly lagged in lubricating grease. Take time out to clean up and remove the grease.

Drive unit with extraneous parts removed Referring to the illustrations here and above, and using your favoured combination of razor saws and craft knives or burrs, cutting discs and grinders in a mini electric drill, remove the following items from the moulding:

pivot support towers,
wire retaining lugs
and bogie frame retaining clips at the ends.

Take them right down flush to the surrounding faces of the moulding. Exercise some care as, in spite of being somewhat 'soft' and 'soapy', the plastic can crack in a brittle manner if overstressed. Take great care at all stages not to damage the retaining lugs for the main axle bearings.

Remove one of the worm bearing retainer etches from the fret.

Worm bearing retainer, fold 1 Make the first fold as shown and reinforce it with a small amount of solder.

Worm bearing retainer, fold 2 Make the second fold as shown.

Worm bearing retainer, side folds Fold in the side ears of the retainer.

Worm bearing pillars truncated Returning to the drive unit, cut off the triangular lugs from the top parts of the plastic pillars which rise either side of the inner worm shaft bearing.

Worm bearing retainer in place Fit the worm retainer in place as shown, aligned vertically with the plastic pillars and with its curved lower edge resting on top of the worm bearing. Use the holes in its ears as a guide to mark the centres of holes to be drilled in the plastic pillars. The ends of the shortened pillars should come no higher than the top edges of the retainer.

Use a 1mm drill to make a dimple at the location of the hole.

Drilling worm bearing pillars Remove the worm retainer and, ensuring the assembly is well supported, as shown, drill out 1mm holes (to clear 14BA) in the pillars.

Worm bearing pillars drilled Work gently using a hand pin chuck and take care that the drill does not wander and break through the edges of the pillars.

Give the drive unit assembly a thorough wash and degrease to remove all traces of swarf and dust.

Worm bearing retainer secured Refit the worm gear retainer and secure it in place with one of the 14BA screws and nuts supplied.

Re-assembled drive unit Refit the idler axles and gears to the drive unit.

Note that the inner wormshaft bearing is shown here secured by a 14BA bolt alone, without the etched retainer. If, for any reason, such as variation in manufactured dimensions of the drive unit, the etched retainer can not be fitted, this is a perfectly serviceable arrangement. The holes are drilled such that the shaft of the bolt is in contact with the top of the bearing.