Bachmann 'Peak': Cosmetic Bogie Frames and More Rolling Tests

This section deals with fitting the moulded plastic bogie frames to the etched brass Bolsters. Buffer height checks and on-track towed or pushed testing can then be done. Illustrations are of both Peak and Class 40 models: some details differ but principles are the same.

The sideframes are fitted to the Bolsters because the real locos do not have secondary suspension. It is therefore correct for the sideframes to swivel about the pivots without any 'pitch' or 'yaw' with respect to the body. This means that you do not have to artificially increase the gap between sideframe and body, and that you can fully detail the items in the space between the two.

Marking outriggers of bogie moulding Take the Bolster and the moulded sideframe/undertray moulding for one of the bogies. Offer the moulding up to the Bolster, engaging the two central pairs of outriggers in the slots in the etch. Mark the plastic outriggers for cutting, flush with the inside faces of the Bolster's legs.

Cut through the two central pairs of plastic outriggers at the marks. Cut through the outer outriggers closer to the inside faces of the sideframes. Leave the inner cross member in place for now.

Undertray separated Cut through the two vertical square pillars joining the inner cross member to the undertray, thus separating the undertray from the rest of the moulding. Discard the undertray.

Clean up any flash, lumps or bumps from the inside of the sideframes.

Remove the tension lock coupling from the NEM socket: squeeze its tails together and pull it from the socket. Reduce the projection of the NEM socket to no more than 2mm from the inside face of the buffer beam, or remove it altogether.

Jackson mount We fitted a Jackson coupling. This was mounted in a piece of brass micro-tubing secured in a hole drilled through two pieces of PCB sleepering fixed at right angles. Initially we made the transverse piece the full width of the bogie…

Coupling inside view …but then realized that it might interfere with the Pony wheels, and obstruct access to a body fixing screw, so reduced its width as shown.

Coupling outside view A rectangular aperture was cut in the buffer beam to house the vertical part of the coupling mount. The vertical position of the coupling was jigged off the buffer centres (13.8mm, coupling height 10mm).

Sandpipe and axle end detail Modify the shape of the sandpipes. The sideframes are fitted around the wheelsets from above when the Bolsters and Subframes are bought together, so the sandpipes need to be brought slightly outside and/or away from the wheels. Bending them as shown is a reasonable approximation to prototype arrangements, and gives the required clearance.

If you have modelled the extended ends of the carrying axles, cut away the moulded versions.

We drilled 0.8mm in each corner of the aperture, and used a piercing saw to cut between the holes.

Peak Bolster/Pivot Frame fitted Fit the Bolster into the loco. Fix the Pivot Frame in place with the 2mm screw, and secure the bolster, flat against the floor of the loco, with tape or Blu-tak.

Peak sideframes fitted Fit the sideframe moulding on to the Bolster. Refit the body to the loco. Determine the position which gives the required clearance between the floor of the loco and the top of the moulding.

Peak sideframe glued in place Apply adhesive to the mating surfaces between the Bolster and plastic moulding and clamp the joints. As well as the vertical positioning, check that the centre axlebox on each side is correctly aligned fore-and-aft with the Bolster centre.

There is some leeway, fore-and-aft, in the housings for the stubs of the outriggers, as we found that, in the original bogie assemblies, the axleboxes were not particularly well-aligned with the axle centres.

When the adhesive has set, dismantle the Bolsters from the loco.

Reassemble the Bolsters on to the Subframes and fit the bogies back into the loco. Repeat the static and rolling tests (you now have buffers and couplings to enable pushed and pulled on-track testing). Check the height and alignment of the bogie frames with respect to the wheelsets and the loco body.

The kit has been designed to give a ride-height which places the top of the loco at the correct distance above the railhead. Variations in manufacture and construction may cause the ride height of your model to be slightly different.

Ride height is normally set to give a nominal buffer height of around 13.8mm above rail level. You may well find that there is a variation in the order of 0.5mm over the four buffers, just in the way that they've been fitted to the loco. You might also wish to check for maximum height overall, and then reflect on whether the manufacturer has got the buffers in the right place. Ultimately, working to tenths of millimetres, it will be a judgement call as to exactly where the correct ride height lies.