Inglenook Sidings Shunting Puzzle

The challenge of fulfilling the Inglenook Sidings Shunting Puzzle is linked to the fact that some advanced thinking is required – because there is limited space available to juggle around the rolling stock, as determined by the lengths of the individual sidings and the headshunt on the layout.

What looks like a simple task can thus provoke quite a bit of head-scratching. And since the number of possible combinations regarding the positions of these 8 items of rolling stock amounts to about 40,320, it should take a while before a feeling of “oh yes, I know this one” grabs the operator.

Inglenook Sidings Shunting Puzzle – Rules & Operation

The full rules can be found here, however the gist is:

  1. Form a departing train consisting of five (5) out of the eight (8) wagons sitting in the sidings.
  2. The five wagons are selected at random.
  3. The train must comprise the five wagons in the order in which they are selected.

The layout has a specific number of pieces of rolling stock that can be placed on each siding.

Diagram showing the arrangement of the Inglenook Sidings Shunting Puzzle track and initial rollingstock arrangement,
Diagram showing the arrangement of the Inglenook Sidings Shunting Puzzle layout and initial rollingstock arrangement,
  • A shall be one locomotive and three rolling stock items long
  • B shall be five rolling stock items long
  • C and D shall both be three rolling stock items long.

There is an online discussion about a solver here.

32 mm gauge rolling stock

32 mm model railway gauge of wheels. showing main dimensions.
32 mm model railway gauge of wheels. showing main dimensions.

I have chosen a 32mm gauge (SM-32) layout as it is a fairly common “narrow gauge” modelling gauge, with a scale of 14 mm to 1 foot. (1:19 scale – 32 mm is two-foot), with a 6-foot-tall person being about 96 mm tall.

32 mm is the spacing from the inside of one running rail to the inside face of the other. LocoRemote has several sets of 3D-printed tracks available.

I need to make up at least eight items of rollingstock with dimensions of 103 mm wide, 195 mm long body, 230 mm over the couplings, and a rail to-roof height of less than 136 mm—as well as a locomotive.

Coupling and uncoupling

Each item of rolling stock will need independent control over its A and B end couplers so that it can make and break its connection on demand to adjacent stock. This will need to be fully automated so that the challenge can be made to work.

I suspect that the easiest way to do this will be with magnets. However, I want to investigate Buckeye couplings as well.

I will look at using small RC servos as the coupling actuators, with a local microcontroller for control. this microcontroller will also manage location detection and other functions as required.

Localisation and Detection

Location detection may take the form of some kind of Fiducial markers or Barcodes on the track, IR LED beacons in the “four foot”, and or friend/foe detection of adjacent stock.