Even though the pinewood derby is a cub scout thing, our boy scout troop decided to have one as well. For a challenge, my son and I decided to make a car powered by an electric ducted fan.
You need to pick a brushed motor and use a simple switch, or use a brushless motor, which requires electronic controls. We chose a brushless motor because of its high performance, and because I already had the necessary electronics from my RC hobby. We chose to just control the fan remotely for safety. That way we could shut it off at the end of the track.
For this setup, you need the following parts. I am linking to similar items to what I used. The project would definitely make the most sense for someone who already has some RC gear.
- brushless electric ducted fan unit – $20
- brushless RC electronic speed control – $8
- Li-po battery – my EDF supports 2S or 3S batteries – $15
- Li-po charger – $30
- RC transmitter and receiver – $53
If you buy the parts linked, you’ll just need connectors for the charger and to hook the battery to the JSC. The linked battery uses a JST connector. You could certainly get cheaper parts if you shop carefully on AliExpress or Banggood. All I had to buy was the fan unit, because everything else was for a plane I was building.
If you don’t want to radio control the motor, and instead want it to start with the gate, you could use a servo tester. The ESC needs a PWM signal to run the motor at the right speed, so you can’t just hook it up to the battery like you could with a brushed motor.
If you’re not familiar with how to wire these electronics, start by connecting the 3 colored wires from the ESC to the 3 wires from the brushless motor. I had to solder on mine, since my motor didn’t have bullet connectors. Connect the servo connector from the ESC to the throttle port on the receiver. Finally, connect the red and black power cables from the battery to the ESC, preferably by soldering a connector to the ESC that matches the one on your battery. If the motor runs backwards, just swap any two of the wires to reverse it.
To mount the EDF to the body of the pinewood derby car, we quickly modeled a 3D printed part. The EDF unit press-fits into the ring, and the mount attaches to the wood car body with a couple of small screws.
Hopefully you’ll spend a little more time on nicely mounting the electronics to your car or making it look cool, but ours worked well! Here’s a video. On the last run, my son put it on the track backwards to see if it’d climb back up the hill. He reported it would, but he backed off the throttle to avoid wrecking it.