No.55 DMUs – Close coupling and corridor connectors for Bachmann Types

January 30, 2013

Following my posts dealing with Collett and Hawksworth coaching stock I am moving forward a few years to talk about Bachmann DMUs, Class 108, 105 and Derby Lightweight.

Location – location!!!

When I acquired my first Bachmann Class 108s I immediately set about closing up the gap between the units. The Bachmann 108s have sprung buffers and it is possible to draw the two coaches together such that the moulded corridor connections are almost touching yet still allowing the unit to negotiate relatively tight curves.

As bought (bottom) modified (top)

The solution that I adopted was to replace the Bachmann couplings by a plain bar filed down from a 30mm long piece of code 100 nickel silver rail.

Original Couplings (top), modified coupling bar (middle), 30mm length of Code 100 nickel silver rail

The nickel silver rail is filed down so that it is a force fit into the original Bachmann Coupling Pocket. The 30mm length works on my layout with Peco Medium Radius points. If the curves were smaller radius then the units would need to be gently eased further apart. If the minimum radius was larger then conversely the rail could be pushed further into the coupling pockets. This modification is straight forward and totally reversible should the units need to be sold.

The Bachmann Cravens (Class 105) also have sprung buffers and the same approach can be used.

Class 108 (bottom) Derby Lightweight (top)

When Bachmann introduced their Derby Lightweight Units I tried the same approach – however I missed the fact that the buffers were not sprung. As can be seen in the above picture, replacing the couplings with a fixed bar still leaves a massive gap if the units are still to negotiate 36 inch curves.

27mm high, folds at 8,8,10.5,13,13,13,10.5,8,8mm and indents 2.5mm top and 1.5mm bottom

One solution is to fill the gap with corridor connectors. My first attempt was to make connectors to the dimensions I used earlier for the Bachmann Collett coaches. This was not a good idea. The moulded plastic connectors on the Derby Lightweight units are relatively narrow. I have suggested some more appropriate dimensions beneath the picture above.