Triangles glued, body painted.

Shunting Dice for Operating Sessions

The operation session which a good friend of mine and I are planning is approaching. It’s going to be a premiere in more than one aspect: we haven’t done joint operations for a long time; it’s also been a long time since we did some shunting; and we’re going to try and let children participate.

So the question stands: How can we combine interesting operations with as few rules as possible and as little preparations as possible? Enter *drumroll* the shunting dice.

While rummaging Rik’s Weblog I stumbled across a post dealing with managing freight on the railway. Rik utilizes a self-made database program which generates trains using a random number generator. That made me think: there’s another type of random generator, namely dice. It’s an easy principle: each time when one is approaching a train station, one throws the dice. It will tell wether to connect or disconnect waggons. It might also point out wether one or – say – two waggons are to be handled. And finally, which end of the train is about to gain or lose waggons. One can either fulfil the task – or one cannot, for instance because the station doesn’t hold enough waggons to connect. In the latter case the train simply proceeds to the next station. So it comes down to 2³ options. 2 x 2 x 2 = 8 possible dice throws require a D8, AKA an Octahedron.

Triangles cut, symbols engraved and painted.

Triangles cut, symbols engraved and painted.

Sounds easy, doesn’t it? One simply cuts eight equilateral triangles, chamfers them 30° each, glues them togehter… wait a minute, it won’t fit. Of course, an octahedron consists of two pyramides and a pyramide naturally has got right angles at its base. So it’s going to be 45° chamfer… won’t fit either. That’s what can happen if one simply jumps at it.

Wikipedia reveals to the kind student that an octahedron comprises dihedral angles of about 109.5°. So the triangles have to be chamfered by half that angle, that is 57.25°. My original octahedron, measuring 8 cm edge length, with a lot of re-measuring and manual labor, was brought down to 6 cm edge length and accurate angles.

All eight faces were furnished with symbols for the possible combinations: roman numerals for the number of waggons, triangles pointing left or right for the front or rear end of the train, and a line or up-pointing triangle for connecting or disconnecting. To make them stand apart, each symbol got its own colour, too.

Triangles glued, body painted.

Triangles glued, body painted.

The chamfered edges can be quite easily glued using tape: connect to outer edges with a length of tape, apply a little(!) glue into the resulting groove, fold and fixate it – done. As soon as the glue has cured, the body can be filled and painted. The end didn’t become quite as pretty as I had hoped, but it’s just a first try.

If on the upcoming operation session the concept proves persuasive, I will try and make a better-done dice and then I will tell about it, too.

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