Shunting on the Sagatukett River RR

[Keith Addenbrooke]

I don’t think there’s a dedicated Forum for Shunting Puzzles on RMweb, but here would seem to be the natural home for this one: my “baseboard” is just 3 x A4 sheets of paper after all.  “Trains” are by Lego. ... and Micro Layouts and Shunting Puzzles do rather go together.
 

It’s strictly just for a bit of light relief - (I painted some baseboards for a layout project  this morning which are now drying).  I must admit though I’d love to model this one day...and I have referred to this puzzle in another thread elsewhere on RMweb recently.

 

Background: I first came across the track plan for the Sagatukett River RR in Kalmbach’s 1981 “58 Track Planning ideas from Model Railroader.” A reprint in a later 2010 Compendium (101 More Track Plans) identifies the original source as being MR March 1972 if anyone is interested (it’ll still be in copyright, so I’m quoting my source rather than copying anything).  The model is for a delightful little short line, bigger than a micro-layout, but the accompanying article includes a fiendish shunting puzzle for one end of the line that has had me stumped for years (note: the 2010 reprint omits this puzzle). With a bit of time on my hands I’ve drawn out the puzzle to see if the only solution I’ve come up with works - I think it took me 116 moves...

 

Let me take you to Equinox:

 

Trains arrive from bottom right passing a quarry 1/4 mile from the terminus before pulling into Equinox, a small town with a small station, and a number of small industries scattered around a triangular yard.  This is the puzzle:

 

A short train has arrived at the Station consisting of an Engine, 3 Box Cars (Wagons) A, B (behind the station T) and C, with a Caboose bringing up the rear.  The following shunting (or switching) moves must be completed before the train can depart - which it must do with the engine facing forwards to depart (having turned on the Wye) and with the caboose moved at the rear of the train:

 

Freight Cars D, G and I will be in the departing train (in any order).

Incoming car A is for the Warehouse Y, car B is for the Freight House U and car C is for the Woodenware  Works V.

Car E has finished stone to move from the Monument Works X to move to the Warehouse Y (it is too heavy to carry).

Car F is now empty and needs to return to the Quarry Z.

Car H has a load of stone to go to the a Monument Works X.

Here are the railroad operating rules:

 

Track capacity is given in brackets.  I have drawn the layout using Parker Quink Setrack pieces to help.
Additionally, a car can stop on a switch (point) or crossing if needed, but it will block the point.

Each time the engine starts, it is counted as a move.

The engine must stop before coupling, uncoupling or reversing.

All freight cars must be moved by the engine - no “fly shunting” using ropes, poles, rolling under gravity or any other means is permitted.
Cars can be spotted on the main line after or during moves: we are operating on a ‘one engine in steam‘ basis, though note this rules out a second engine coming to help.

 

The suggested first move is to either back the train, or to uncouple the engine for it to run forwards - as the Caboose is standing on a point other options appear limited.

______________________________
 

If you’d like to build this as a model, good luck - I haven’t tried mapping it to see if it can be done with the capacities shown, but the original author Robert Silas proposed it as a proper track plan.  Remember the wiring needed for a reversing Wye.

 

Have fun, Keith.

 

[Keith Addenbrooke]

An additional photo of the start position.  

 

 

After a recount, I believe I have a solution in 115 moves: I’d included a few uncouplings while stationary as engine moves, which saved a few, but I had the engine the wrong way round at the end so had to insert an extra trip round the wye in the middle of the sequence (when it was clear of cars).  Of course, were this real, that would mean predicting the end point about 30 or 40 moves before finishing to plan ahead.