OPERATION

 
The layout of the sidings beyond the station at Little Bazeley is a variation of Alan Wright's Inglenook Sidings shunting puzzle. The choice of a very loose 1964-1969 modelling period, being the very last years of the British steam/diesel transition era, just about allows for comparatively short standard wheelbase stock of 10'-0" (3m). Scaled down to 4mm scale 00 gauge, this translates into goods wagons about 3,2" (8cm) long, i.e. short enough to allow for the capacities needed for an Inglenook Sidings setup within the given space of 4' x 1' (120cm x 30cm).
 

 
The warehouse setting is left fairly unspecific as to who exactly receives and ships what, further disguised by the very general signs reading "Sussex Storage". This also allows for a fair variety of freight stock to be used. The shunting puzzle is fully workable within the limits of the baseboard on the basis of the original Inglenook rules.
 

Shunting Order for Little Bazeley Sidings

1. Form a departing train consisting of 5 out of the 8 wagons sitting in the sidings

2. The 5 wagons are selected at random

3. The train must be made up of the 5 wagons in the order in which they are selected

 

Couplers

 

One essential aspect of operating a shunting layout is the choice of couplers and the uncoupling system to go with them. Since the late 1990s manufacturers have acknowledged the importance of reliably working couplers by either having their products factory-fitted with such couplers (as in the US, where magnetic couplers in the mould of the Kadee system are now almost standard fittings) or by providing coupler pockets in accordance with the NEM 362 norm, allowing modellers to substitute the factory-fitted couplers with a different coupler of their choice by simply plugging this into the pocket.

 

  Ever since developed by Tri-ang in the late 1950s, the tension lock coupler has been the standard device used on British 00 scale models. Consisting of a fixed loop bar and a raisable "fish-hook", they are foremost and above all designed to perform automatic coupling.

This is achieved by pushing the hook through forward motion over the loop of the next vehicule's coupler; once the hook drops again, the two items of rolling stock are securely coupled and, thanks to the barbed form of the hook, interlocked - in fact so much so that uncoupling becomes a major problem, even when taking stock off the rails.

 
In general, tension lock couplers are therefore regarded as being both unsightly and operations-unfriendly, and only suffered because ready-to-run UK models offer no alternative.
 
As can be deduced by the way a tension lock coupler works, uncoupling can only be achieved by way of lifting the hook sufficiently in order to allow the loop to pass under it again - and this will only work when the couplers are not under tension (hence their name), i.e. the rolling stock is standing still.

The "classic" way of achieving this is by using a sprung ramp between the rails. When a train passes over itp, the couplers are interlocked through the tension and depress the ramp. However, if the train stops, the ramp will lift the now loose coupling hooks, splitting the consist at this point.

The problem is that this works fine most of the time but not all of the time, and unwanted uncoupling increases as the speed of a train passing over the ramp decreases - as would be the case on a shunting layout such as Little Bazeley.

The answer to this problem is to have an uncoupling ramp which is not permanently "active", i.e. which is raised to push up the hooks only when rolling stock standing over it is intended to be uncoupled. A number of home-made systems, ranging from basic to highly complex, have been developed by numerous individuals, and there are even commercially produced motorized solutions which are push-button activated.

 


Peco uncoupling ramp (above), Gaugemaster uncoupler (below)

 
This allows for remote uncoupling, but only at the exact location of an uncoupling device, as tension lock couplers immediately recouple once the hook is no longer raised, making "delayed uncoupling" (i.e. pushing an uncoupled wagon to a point beyond the uncoupling device) impossible.

This is one of the major features and advantages of magnetic couplers working on the Kadee / MicroTrains principle - and (together with their much sleeker appearance) one of the reasons for their growing popularity with UK prototype modellers, further heightened by the now de facto standard of NEM 362 coupler pockets on 00 scale models which allow for easy swapping of couplers equipped with a swallow-tail end.

 

 

Unfortunately, the NEM 362 specifications are mostly adhered to by manufacturers with regard to the pocket and coupler shafts but interpreted rather loosely in terms of distance to the railhead (which NEM 362 sets out as 8,5mm with a tolerance of +/- 0,2).

The negative effect this can have on UK models fitted with Kadee couplers is illustrated here: two pieces of rolling stock from the same manufacturer (Bachmann UK) using the very same NEM 362 Kadee couplers provide no guarantee that the couplers will line up correctly.

The different heights at which the coupler pockets are located are clearly visible in this random example.

 
This results in a call for some major surgery in order to achieve reliable uncoupling as Kadees (as well as other magnetic buckeye couplers) tolerate little to no misalignment in height between two couplers.
 
One big advantage of the Inglenook concept as operated on Little Bazeley is that uncoupling moves only take place in one direction, as all of the sidings point the same way.

Given that delayed uncoupling is not necessary, I really could not be bothered with the major hassle of adjusting Kadee couplers even on as few as the 8 cars necessary for the Inglenook operation - even less so as Kadees are the most expensive option by far.

But turning back to the tension lock coupler, there is an additional alternative option to the "activated uncoupling ramp" approach.

 

 
First described by Brian Kirby in December 2008 on rmweb.co.uk, this method modifies the narrow Bachmann tension lock couplers (which feature a coupling hook made of non-magnetic material) by adding a bent iron staple to the hook. As the rolling stock passes over a magnet, the hook is pushed upwards as the staple is being drawn down by the magnet.
 
 

Putting the concept to the test using rather coarse staple samples (they are bent so that the inward leg rises back against the wagon floor in approximately a 45 degree angle) the setup nevertheless worked reliably, especially when using fairly large (i.e. thick) iron staples - finer examples took more finetuning until they were attracted downwards by one of the two magnets (one for each coupler) between the track.

In comparison to any self-made raisable uncoupling ramp (which can run into unexpected re-alignment difficulties when lowered back to in-between the tracks), the Kirby method has the advantage of working faultlessly once all the couplings are set up properly.

 
Adding the staples to the counterarms of the coupling hooks does take some time and effort, although routine does set in very quickly. It is also an extremely cheap solution which - especially if compared to the money spent on rolling stock or track - costs almost next to nothing. If thought of before laying track even the magnets could be hidden out of sight; at Little Bazeley they are visible, not precluding a later attempt at disguising them somehow. But again: the most important characteristic of the Kirby uncoupling method is its operational reliability.
 
 

 
 

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Page created: 07/JUN/2004
Last revised: 29/OCT/2013