DIY Electromagnet Start Gate
Posted: Sat Sep 28, 2019 1:05 am
I haven't really been satisfied with my jury-rigged solenoid start gate setup for my Micro Wizard Freedom track. I use that track use for about 15 Awana races a season. I just hadn't made the time to build something better. I've seen some gravity gates that some of the league guys have come up with. No springs or rubber bands to snap the gate open, causing a lot of vibration to the track, just gravity. I definitely wanted a new gate like that. Then I saw Chuy's electromagnetic gate that he posted about on the NPWDRL forum. I really like the design and especially the electromagnetic release. That inspired me to get off my duff and build myself a new gate.
After a bit of trial and error, I've got the mechanical part of the gate done (photos below). The MW track isn't as easy to attach things to, like the Best Track, with its hardware channels. So, I came up with my own hardware channels, using some leftover channel that I had in my workshop for making up various woodworking jigs. I mocked it up first on some 1/4" MDF. Then I made up a mounting plate with 1/8" x 3" aluminum plate, complete with clinch nuts to make mounting/unmounting to the track easy. I tried some off-the-shelf brackets to hold the start pins to the main rod, but those were too short. So, I got some 1/2" x 1/2" aluminum bar stock and made my own. Set screws hold the brackets to the main rod and hold the start pins.
The start pins are actually 8mm stainless steel straws which came with colored silicone tips. Those tips will hopefully keep the pointy nose cars from slipping off the start pins. Some lesser quality stainless you can stick a magnet to, but not to these, fortunately. So, no worries if someone ever decides to stick a magnet in their car's nose. I had started out with solid start pins, but was concerned about dampening the pendulum action, with more mass being swung around. Some dampening is necessary to keep the pins from swinging back through the holes in the track. We wouldn't want some car, that is really slow off the start (e.g. a bad wheel issue), get popped off the track by the pins swinging back and catching the bottom of the car. To dampen the swing, I used a memory foam ear plug. That works perfectly. Memory foam absorbs the impact quickly but rebounds slowly, making the dampening nice and gentle.
I tested out the electromagnet by rigging it to a power supply. I wasn't sure just how strong it would hold. A spec sheet doesn't really give much assurance that it will hold back 4 outlaw cars, weighing up to 1 lb each. I was quite surprised at how well a 5V electromagnet will hold, even with our heaviest cars loaded on it. It takes a good amount of hand strength to break the release lever free.
Now to work on the electronics. I'm going to use a small micro controller board from Adafruit, with a relay to power the solenoid. Just like with Chuy's gate, I'll have a key fob remote release. I'll also have a remote switch that can be plugged in, to be the backup triggering means.
I had to draw it out to make sure the pin swing would work out and figure out how long my pin holders and start pins needed to be.
Side view - latched
Side view - unlatched
Top view
Bottom view
Here you can see the purple memory foam ear plug. It is stuck in a hole of a little corner bracket. Easy to change out, if necessary.
After a bit of trial and error, I've got the mechanical part of the gate done (photos below). The MW track isn't as easy to attach things to, like the Best Track, with its hardware channels. So, I came up with my own hardware channels, using some leftover channel that I had in my workshop for making up various woodworking jigs. I mocked it up first on some 1/4" MDF. Then I made up a mounting plate with 1/8" x 3" aluminum plate, complete with clinch nuts to make mounting/unmounting to the track easy. I tried some off-the-shelf brackets to hold the start pins to the main rod, but those were too short. So, I got some 1/2" x 1/2" aluminum bar stock and made my own. Set screws hold the brackets to the main rod and hold the start pins.
The start pins are actually 8mm stainless steel straws which came with colored silicone tips. Those tips will hopefully keep the pointy nose cars from slipping off the start pins. Some lesser quality stainless you can stick a magnet to, but not to these, fortunately. So, no worries if someone ever decides to stick a magnet in their car's nose. I had started out with solid start pins, but was concerned about dampening the pendulum action, with more mass being swung around. Some dampening is necessary to keep the pins from swinging back through the holes in the track. We wouldn't want some car, that is really slow off the start (e.g. a bad wheel issue), get popped off the track by the pins swinging back and catching the bottom of the car. To dampen the swing, I used a memory foam ear plug. That works perfectly. Memory foam absorbs the impact quickly but rebounds slowly, making the dampening nice and gentle.
I tested out the electromagnet by rigging it to a power supply. I wasn't sure just how strong it would hold. A spec sheet doesn't really give much assurance that it will hold back 4 outlaw cars, weighing up to 1 lb each. I was quite surprised at how well a 5V electromagnet will hold, even with our heaviest cars loaded on it. It takes a good amount of hand strength to break the release lever free.
Now to work on the electronics. I'm going to use a small micro controller board from Adafruit, with a relay to power the solenoid. Just like with Chuy's gate, I'll have a key fob remote release. I'll also have a remote switch that can be plugged in, to be the backup triggering means.
I had to draw it out to make sure the pin swing would work out and figure out how long my pin holders and start pins needed to be.
Side view - latched
Side view - unlatched
Top view
Bottom view
Here you can see the purple memory foam ear plug. It is stuck in a hole of a little corner bracket. Easy to change out, if necessary.