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Scalextric ARC ONE (Start) Controls – adding brakes

One thing I didn’t realize when I set about grafting the ARC ONE system onto my Carrera Go!!! track was that the controllers only had two wires, and thus no motor braking would be possible. The track is so short, and the turns so tight, you really do need the brakes, especially if the car has no magnets.

After a little searching, I found that these controllers could be purchased new for about 6 bucks. Cracking one open to see what it would take to add a braking contact and wire seemed pretty low risk.

Behold, a pretty basic wire wound resistor controller.

When the trigger is in the released position, it is held against a plastic stop that contacts the copper wiper. This is exactly what I was hoping for. Adding the brake contact could be accomplished by adding a piece of metal between the wiper and the stop, and running the wire out.

A quick measurement of the stop indicated a piece of 5mm OD brass tube could be cut to length and put into place.

In order to get a good bond via super glue, I crushed the tube down a bit.

Slip over stopper and add glue:

I opened up the exit from the handle to make sure the wires weren’t being crushed.

Reassemble, and add whatever connector to the new wire you are comfortable with. I like Anderson PowerPole connectors, although I haven’t totally decided how I’m going to implement these extra connections. This wire just needs to be connected to the ground on the low voltage DC side of the track set.

The only hang up I hit was that the two controllers I received were wired opposite of one another. In normal operation, it doesn’t matter where the two wires connect to inside the controller. One just needs to be on the wiper and the other on the resistor. However, once you want to ground the wiper, it suddenly matters which has 15Volts and which is just running out to the motor. You want the 15 Volt wire going to the resistor, and you want the other wire on the trigger/wiper. By luck, the first controller was wired as desired, and everything worked. I didn’t bother checking the second controller, and of course it was different. When I hooked everything up, the ARC ONE browned out, as the power supply was shorted to ground. So, I had to open the second controller back up and swap the wires in the handle. They are just attached with screws through eyelets, so this isn’t difficult.

I now have a completely functioning analog system with brakes along with computer timing and scoring for $40.

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Framing and Connections

I like the things I build to have robust connection points. In other projects, I’ve come up with small 3D printable pieces that allow me to “panel mount” Anderson PowerPole connectors as well as 5.5 mm barrel jacks. I reused these concepts here. I use three powerpole connectors for my controller wiring.

In order to give them something solid to be attached to, i framed the foam track with 1/16″ thick 1″ leg angle aluminum. I used Gorilla Glue to attach the aluminum to the foam.

I used a power drill and some files to create the square hole for the barrel jack to protrude through. I also made a little template to make it easy to drill the pair of mounting holes.

I didn’t want the aluminum to be directly in contact with the surface it might be sitting on, so I made 3D printed plastic corner pieces to cover up the corners.

To complete the project, I put a bead of grey caulk around the top edge of the aluminum and foam to fill the gap. I also purchased these variable voltage power supplies from Aliexpress, so it is easy to change the track voltage.

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Copper Tape

I’m using standard adhesive backed copper tape for the rails. I did order the tape with conductive adhesive, and I can report that indeed this stuff works very well.

The testbed oval track used 1/4″ wide tape. There was a lot of pleating and wrinkling in the turns, even though they were a pretty large radius. I asked some questions on the forums and had a very helpful discussion with Ed “HO RacePro” who suggested going to thinner tape. So, for the proof of concept track, i ordered 1/8″ wide tape.

There were a few difficulties. The tape applying tool I found on thingiverse worked quite well with the 1/4″ tape. It didn’t work as well with the thinner tape. The OD of the retainer was smaller than the OD of the roll itself, so the roll wanted to unspool over the sides. i ended up applying the tape by hand, which was tedious.

This is a still shot from a video I took of a car running. At this point, I just had the rails hooked up to a power supply.

The crossover took a little thinking, and in hindsight i wish I would have planned it a bit better.

I just drilled holes through the foam with a 5/32 drill bit and ran the tape to the underside of the foam to make connections. Most connections are just the tape stuck to itself. I did solder wires onto the tape where i would need to make connections to the power supply and controller.


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Slot surface improvements

On the proof of concept oval, I just used flat latex in the slot. This worked fine, and made it easy to judge if any wear was happening, but the roughness of it that is good for tire grip isn’t good for low resistance on the guidepin or flag. If you just pushed the car around the track with your finger you could feel the drag that just isn’t there in a plastic track.

So, I devised the following solution.

  1. go ahead and paint the slot and road area grey.
First coat of grey

This is necessary to blend the slot in with the road color.

2) Coat the slot and area where the car will run with Smooth-On Epsilon Pro Epoxy.

A quick snap in the middle of the process.

Repaint just the area where tires will touch, not down in the slot.

Now you have high hardness and some strength only exactly where you need it. And you have traction where you need it.

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Clean Up

The burning process will leave very long “hairs” of melted foam down in the slot. will be on the walls and some will be on the bottom. I used drill bits to break them out. They may or may not have actually caused a problem, but I didn’t want them coming loose in later steps.

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The Finer Points

The tip used in the soldering iron should be smaller than the slot desired. the tip is so hot, it will burn off the foam without actually touching it. This has a few undesired effects. The width of the slot varies a bit depending on how fast you move through the material. If you stop or hesitate to reset your feet, you’ll be left with a large defect at that point. I cut the slot in the pictures all in one go, as starting and stopping creates relatively large defects. Plan ahead and start and stop in straights, and make sure you wont have to reset your feet in a curve.

I started with a 40W fixed power iron, but that was too hot. I used my adjustable iron in the final iteration. I don’t have a lathe, so I just built up the cutting tips by nesting K&S brass tubing. I tested 2mm, 2.5mm, and 3.0mm diameter cutters and various wattages. I found that 2.5mm and 30 Watts was the best. I wanted the slot a little oversized, as I was planning on a few extra steps to be described shortly.

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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.