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Making a SLOP track

Emboldened by the initial experiment, I decided to pursue a more complete example. I had read about Single Lane Open Proxy tracks and decided this would be a great testbed.

I use Alibre Design for my CAD work, and I set about modelling a layout that would be interesting. Some eagle eyed readers will figure out what real life track I modeled this after and also immediately spot the mistake I made in the geometry. I printed the layout on 20 some odd sheets of regular paper on my printer, and had to put them together like a puzzle.

Overall sheet size is 27″ x 48″

The tedious bit was going around and cutting the slot out of the pattern, so I could mark it with a permanent marker on the foam.

With everything traced, I removed the pattern, and did my best to freehand the slot with my soldering iron router.

Everything “Routed”
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Initial Testing

To evaluate the slot, I “routed” a simple oval, with a 9″ radius on one end and a 10″ radius on the other. I then painted the slot and area where the car would run with flat latex paint, as is common practice.

Finally, the track was taped with 1/4″ wide copper tape and directly connected the rails to my adjustable power supply. I printed this handy tool from thingiverse, which worked great.

https://www.thingiverse.com/thing:2008389

I grabbed a car and set the power voltage to where the car would just stay in the slot and let it run for several hours at a time, accumulating almost 15 hours of running.

The slot showed no wear, however the motor in the car clearly didn’t like all of the continuous operation.

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Light weight slot car track, proof of concept

Having built a 4×8 “traditional” construction slot car table (which must weigh over 100 pounds), I have decided there must be a better way to go about constructing a track. Some search of the usual forums led to discussions of routing a track in XPS foam. This is the dense pink or blue foam (depending on which hardware store you go to).

I did some experiments with cutting a slot in this material. I tried a few different bits in my rotary tool, and while this worked, the remaining surface wasn’t great. The material wanted to tear and ball instead of cut.

I did some testing with a few different hot wire cutters, and decided the simplest solution was to just put a custom tip in a soldering iron and use that to burn the slot in. The burned in slot has nice smooth surfaces, with a bit of a hard “face” to them.

To make this process manageable, I designed a fixture to hold the iron perpendicular to the track surface. The whole fixture is 3D printed, and in the end looks a lot like a router.