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.

Handlaid Points

The latest project on my workbench is a No.6 left hand point.  This one uses Code 83 rail (equivalent to 82 lb/yd rail in S scale).

Construction follows the same techniques I have been using for well over 30 years, with real wood sleepers and gluing the rail down with Pliobond adhesive.

Although I usually use Northeastern 12" x 6" HO scale lumber for the sleepers, this time I used precut On3/On2½ "switch ties" by Mt Albert Scale Models in Canada (available from The Railcar near Newcastle, NSW).  The thickness of the Mt Albert sleepers closely matches the On2½ flexible track and points available from Micro Engineering.  Prior to construction, I stained the sleepers with potassium permanganate solution.

The sleeper size and spacing of the Micro Engineering On2½ flexible track and points are just about spot on for Sn3½ track, except that the sleepers are 4-5 mm too long, but that is fairly easily fixed by trimming the ends of the sleepers.  Micro Engineering only makes #5 points in the On2½ range, so handlaying is the only option for other types other than converting HO points "sleeper by sleeper".  They do make a "kit" for No. 6 points consisting of a cast metal frog and machined blades, which could reduce the time and skills needed for handlaying.

New source for Pliobond

Pliobond has been used for many years for handlaying track and building turnouts, but it is now virtually impossible to get in Australia other than in industrial quantities.

Thanks to eBay, I tracked down a source from the US in small tubes, which are a convenient size for modelling purposes. Here is the eBay link

It is actually a fishing tackle shop and they sell Pliobond for coating knots, etc.  The good news is that they are happy to send to Australia and it took about 2 weeks to arrive.  I would suggest NOT ordering more than 2-3 tubes in one go as a larger order may attract suspicion from postal authorities as many suppliers will not send glues and paints via airmail.

Each tube is 30 ml, compared the last batch I bought locally which were 50 ml.  The smaller tubes are actually an advantage as it does become more viscous after several years once opened.

As well as tracklaying, Pliobond is a useful adhesive for joining dissimilar materials such as wood to styrene, metal to styrene, and wood to metal.  It usually is used as a contact adhesive by applying a thin coat to both items, letting it dry a bit, then bringing the items into contact and clamping for a while.

For tracklaying, it is only necessary to coat the underside of the rail (flatbottom only) then let it dry for 15 min or longer.  When the rail is positioned on the sleepers (usually wood), heat applied from a soldering iron to the top of the rail softens the dried Pliobond and allows it to stick to the sleepers.  The great thing is that minor adjustments to track gauge, etc. can be made anytime later simply by heating with a soldering iron.  The rail can be precoated well in advance, and the Pliobond is no longer sticky once dry.  Rail precoated with Pliobond lasts indefinitely and can be used any time.