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Sunday, 8 November 2015

3D Print Experiments - Track Bases (FB rail)

Trying to get more accurate track bed dimensions in 00 I previously spent a lot of time spacing out individual sleepers on Peco code 75, which does gives a more authentic look but the sleeper lengths are still inaccurate.

Now with a 3D printer to hand I wondered how easy it would be to make my own track bases to slide on to the rail. This would be quicker than setting individual sleepers and separate chairs. I focused on flat bottom rail and decided to set the sleeper height same as Peco so that the track was compatible with their turnouts.

The photo shows the printed parts (grey) with correct sleeper size and spacing for 00 gauge. i.e. sleepers 32mm* long and 8.8mm pitch. The dark coloured sleepers are Peco.


The CAD design was relatively simple. The sleepers were designed as joined pairs with integral rail base plates.

Optimising the printer was the difficult part but after a whole day spent tweaking this and that it finally came down to three factors. First to design the rail base plates a little meatier than Peco so that this minuscule part was substantial enough not to be malformed due to plastic fluidity. Secondly to heat the PLA plastic to 185C instead of the default 205C to stop the plastic 'leaking' and causing malformation and thirdly to vary the plastic layer height. The default is 0.24mm, which I retained for the sleeper but reduced it to 0.1mm for the base plates. The base plate clips are very small and need to be built up in very small small layers to preserve their form.

This unkind macro photo showing the rail 'clip' makes it all look a bit rough. The roughness is far less noticeable at normal viewing distance and when painted the lines shown in the top photo will be less prominent too.

Providing the clips have formed correctly they slide onto the rail easily and and hold it firmly.

* Is a 32mm long sleeper correct to scale? Well NO. in 3.5mm scale (being correct for 16.5mm 00 track gauge) a modern 8.5 foot sleeper scales to 30mm and in 4mm scale it is 34mm. To compensate for the narrow look of 16.5mm track when modelling everything else to 4mm the distance from the outer edge of the rail to the end of the sleeper is scaled in 4mm instead of 3.5mm giving a sleeper length overall of 32mm. Visually it looks right even though it is not true to scale overall.

2 comments:

  1. Interesting. I've been wondering about using a Templot drawing to cut out the track base for turnouts

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    Replies
    1. Thanks for your comment. No experience of Templot sorry to say. I am now experimenting with 3D print sleepers with integral bullhead rail chairs. The oak keys are proving a design problem resulting in wayward prints.

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