Tuesday, March 24, 2015

3D-Printed Sn3½ Flexible Track


As an experiment, I recently tried 3D printing some sleepers for correct-scale Sn3½ track, using a similar principle to commercial flexible track.  I used the Makerbot Replicator printer which we currently have at home on loan, using a chocolate brown filament so the basic colour is about right.

It seems to work fairly well, although it would be a bit time-consuming printing sleepers for a basement-size layout.  For a modest layout, though, it appears to be a feasible proposition.  

The photos show the track with Code 70 rail (weathered, from MicroEngineering) but code 83 would fit too as the dimensions of the base of the rail are the same.  The tops of the sleepers have a textured finished from the printing process rather than the fake woodgrain on commercial track.

3D printed track with handlaid track in the background.
Note: I don't recommend use of unsupported MDF as trackbed
as it will inevitably sag - this is just a temporary arrangement.
The longest length which will fit in the printer is 18 sleepers @ 12 mm spacing which equates to 216 mm of track, so about 4 lengths would be required for a yard of track.  Printing each length takes just under one hour.  It may well be possible to print several lengths at one time side-by-side which wouldn't save much time but would save on trips back and forth to the printer.
Computer rendering of the sleepers.
As for cost, the cost of the plastic material works out to about $6 per yard, plus the cost of the rail of course (not including any costs for the 3D printer itself).  As a comparison, the NorthEastern scale lumber which I have used in the past for handlaid track costs about the same.

I also 3D-printed a jig to make it easier to insert the rail by keeping the sleepers parallel to each other so the rail slides in relatively easily.  So far, I have made about 1.5 metres of track.  

The 3D design could be changed to print straight track or fixed curves of any desired radius rather than having "flexible" track.  For example, if laying parallel tracks in a yard it could be easier to lay lengths of straight track to avoid the inevitable "wobbles" with flexible track.




4 comments:

  1. Ive attempted this before both as my design printed at home and including ordering some from shapeways using WSF as the media (there is a NZ Sn3.5 concreate design someones done), my main issue with its use is that the "clip" that holds the track to the sleeper is easily broken, what has your experience been? Maybe my attempt was not well designed.
    On another note another clever use with your curve idea, is designing in a banked track slope, other wise its very difficult to do on bench. or you could consider just printing a wedge of plastic to go under the ballast/track.

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  2. The rail fixings seem pretty strong so far. The PLA/PLA material is pretty tough but flexible - not dissimilar to the plastic material used for commercial flexible track.
    Printing curved track with superelevation has the disadvantage that the tops of the sleepers would not be horizontal, so the stepping effect from the 3D print layers would be prominent. The same would apply for concrete sleepers if the top surface is concave.
    As an aside, did you know there are some easily accessible concrete sleepers in the car park of TBE bike shop in Nedlands?

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