Magnetic couplers for diesel multiple units in N gauge
Graham Farish class 108 DMU. The coach on the left has a steel bar (part of paper clip) while its pair has a magnet as a coupler.
The quality of n gauge models today is much better than in the early days, but it seems a shame that the large and ugly Rapido coupling at each end is still the standard offering. I have long wanted to use an alternative that was less obtrusive and hopefully more reliable. It also had to be easy to make and implement.
I have been doing some experiments with using tiny magnets to provide coupling on some wagons built from Peco kits together with a class 04 shunter. The results were very encouraging. I need to do more development along those lines and hope to report on that later. In the course of that work, it occurred to me that a useful application would be to link coaches in a diesel multiple unit where coupling is more important than uncoupling. This article describes how I converted class 108 and 101 units to magnetic coupling.
I bought Neodymium disc magnets 2 x 0.5 mm from ebay (Spider Magnetics). They can also be purchased from their own website. They are not very expensive and whole trains can be converted at little cost.
They are supplied in a stack sellotaped to a card. My recommendation is to leave them on the card and remove one at a time as needed. With a modelling knife, you can cut through the sellotape to slice off the end magnet; with any luck, it will be found attached to the knife as you remove it.
Class 108 DMU
Graham Farish Class 108 DMU with original Rapido couplings
The same unit with magnetic couplers
This model has Rapido couplers with NEM pockets. I wanted to use the NEM attachment with my conversion so that, if necessary, I could put back NEM Rapido couplers, The couplers just pull out.
As shown in the photos above, one coach has a magnet as a coupler and the other has a steel bar (cut from a paper clip). As the two coaches are pushed together, the magnet attracts the steel bar and forms a strong coupling.
The actions needed to convert the NEM couplers are shown in the diagram (non-NEM coupler shown). The loop of the Rapido is cut off leaving a T-bar. The magnet is superglued to the face of the T-bar and on the other one a length of wire cut from a paper clip is glued. The magnetic coupler can be further trimmed to remove more of the plastic.
It is important to get the gap right to prevent the buffers locking on sharp curves. Tests showed that the original arrangement was too close, so I spaced them further by adding a second magnet on top of the first. It need to be superglued on top of the original.
The photos above show some of the advantages. It is less obtrusive and allows closer coupling, but the real joy is in setting up and dismantling the DMU. Pushing one coach near the other leads to the magnet taking over to hold the other. To separate them at the end of a running session, just grip the two coaches and gently pull them apart.I have tested the DMU around an oval of track with 9 inch radius curves and I am very happy with the results.
It should be possible to paint the steel bar and magnets to make them less obvious.
An earlier article described some modifications to an early Graham Farish class 101 DMU. In that, some change to the coupling between the two coaches was made. A hook of paperclip wire was epoxied into the coupling box of one of the coaches and this engaged with the loop of the Rapido coupling on the other coach. To convert to magnetic coupling, the hook was bent up to provide a near horizontal bar. The coupling on the other coach was converted as above to add a disc magnet.
The hook and magnet have both been painted black although it looks as though another coat of paint is in order,
A simple magnetic coupling between coaches in a diesel multiple unit is less obtrusive than the Rapido coupling and allows closer coupling between the coaches. The joining together and disassembly of the train is also much easier. This is a concept that will be explored in other directions.
Article dated: 30/05/2017