Bachmann 24/25: Preparing the Locomotive

Following the manufacturer's recommendations for running-in, ensure that the locomotive is performing smoothly and to your satisfaction generally. Deal with any issues now, especially those covered by warranty or your basic statutory rights as customer, before making any modifications.

Separate the body shell from the chassis of the locomotive according to the manufacturer's instructions. Store the body retaining screws safely away.

Make a note of the identification of the terminals on the circuit board to which the two wires leading to each bogie are connected. Note also to which side of each bogie they go. Disconnect the wires leading to the bogies. On some Bachmann locos the connections are soldered, on others the wires are passed through holes in the terminals and retained by plastic sleeves.

Select one of the bogies and undo the screw which retains the bogie pivot in the chassis block. Drop the bogie out from the bottom of the block. The cardan shaft joining the motor to the bogie will either come with the bogie or be retained at the motor end. Either way, remove it but note that the ears on each end of the cardan shaft are of subtly different shapes, so record which end is which.

Assign the bogie to one or other of your sets of etched bogie parts, marking the bogie drive, drive shaft and chassis block accordingly.

Similarly remove the other bogie.

Checking squareness of chassis Check that the chassis block is square. Use two straight-edges as shown and sight between them.

If there is any misalignment, check for obstructions, such as swarf, preventing the plastic undertray from fitting snugly up against the cast chassis block.

Suggested bogie pivot arrangement Bogie pivot components are supplied in the kit to mate with the M2 nuts fitted to the tops of the bolsters:

The diagram here shows the suggested pivot arrangement to which the following instructions apply. This arrangement is suitable for either conventional or 'American' pick ups (with which the bogie bolster is 'live'); the key attribute for the latter being that the outer brass tube, and therefore the loco chassis block, is electrically insulated from the bolster top. The arrangement also secures the bolster vertically, but allows some vertical movement to accommodate adjustments in ride height.

Other arrangements are possible; the epoxy glue can be omitted and all components can be shortened, for instance. If required, a thin insulating washer can then be placed on top of the bolster to prevent electrical shorting to the brass tube.

Test the 4mm OD tube for a free sliding fit through the pivot holes in the loco's chassis block. Open out the holes if and as necessary. Note that the fit is for the tube passing perpendicularly through the hole; pitch and roll movements of the bogie are not accommodated at this pivot.

Cut two sections of the 4mm OD tube about 4mm in length. Check that the nylon insulators supplied are a free fit through the tube, opening out the bore if necessary.

Remove the M2 x 5.5mm diameter washers from the main fret.

Select a flat surface, free of any twist, of about the same length as the locomotive. Place the bolsters on this surface, ensuring that their bases are straight and true such that they sit perpendicular to the surface.

Rest the loco chassis over the bolsters, with the central holes in the bolster tops aligned with the bogie pivot holes in the chassis, and the lower faces of the chassis resting on the 'shoulders' of the bolsters.

At each pivot, pass one of the 4mm tubes through the hole in the chassis to rest on top of the bolster. Withdraw it approximately 1mm and glue it in place with quick-set epoxy. To make sure it is aligned correctly, before the glue hardens pass the nylon insulator through the tube and screw in the M2 screw with 5.5mm washer.

Allow the glue to set, then mark the protruding length of the M2 screw threads. Remove the bolsters from the chassis and leave the glue to harden to full strength.

Trim the M2 screws so that they protrude no more than a thread or two below the nuts in the tops of the bolsters.