Neil Fraser

For the past decade I've been a software engineer at Google in California. In my spare time I've created a mélange of open-source software. I've also built some rather unusual hardware. On rare occasions I've even been known to write something interesting.

Wooden Pylons Tuesday, 20 November 2018

A year ago I made a wooden train crossing for Beverly. However, the resulting carnage has proved the need for proper grade-separation. Time to build some pylons that allow one track to pass over another.

The straightforward approach to cutting out the pylons from a 2x4 is to just stack them end to end, lengthways. However, the orientation of the wood grain would mean that the smallest pylons (the 1 cm and 2 cm tall ones) would certainly split into pieces. A better orientation is to rotate the pylons by 90°. One side benefit is that this orientation happens to be a more efficient packing solution, allowing a second 7 cm pylon to be extracted from the same block of wood.

The actual cuts weren't exactly as laid out in pencil above, since the saw-blade has a non-zero thickness. So the cuts were adjusted such that each pair of blocks would not be short-changed by a few millimeters. Rounding off the top edges using a belt sander helps the track sit better, since the track would be angled either up or down.

Each block is marked with its height using a laser engraver. The 1-7 pattern was created in SVG using Inkscape. Stacking the blocks allows the top surfaces to be at a constant height so that the laser can focus.

[Laser engraving numbers on wood]

The laser cut was much cleaner than I expected; I'd actually been hoping for more visible charing of the wood. So I painted the engraved areas black. The tolerances were too tight for the smallest brush I had, so I used a wire instead.

Painting numbers on all 16 pylons was rather tedious. Sierra offered to help and was really good at it.

The last step was to add some guide posts so that the rails wouldn't slide off the pylons when in use. I bought one foot of plastic fuel line, cut it into 32 small lengths, then screwed them into the tops of each pylon.

The pylons were popular with Beverly, she kept exclaiming "Over!" and "Under!" as she pushed trains around the layout.

As always, I'm thankful to be able to use Google's workshops for personal projects. Though everyone in the workshops who saw me building wooden train accessories assumed I had a son, not a daughter.

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