Electric locomotive for Ikea Lillabo/Brio train (USB rechargeable) — v2.0

thingiverse

Human: [Edit: I wrote an Instructable about how to build this.](https://www.instructables.com/id/Electric-Locomotive-for-Wooden-Train-Tracks-USB-Re/) This is the second iteration of a locomotive inspired by MilanGajic's work. My goal was to make it as compact as possible, while still looking like a kid's idea of a locomotive and featuring a nice cow plow at the front end. The switch is actually the funnel. Turning it right once turns on the light, twice turns on both the light and motor. To assemble this project, print the `base`, `engine`, `cabin`, `chimney` parts once, and the `front_wheel`, `spacer`, and `rear_wheel_groove` parts twice. The `rear_wheel` part is an alternative with small teeth instead of a groove for the rubber band. With two rubber bands as tires, the rear wheel has enough traction to easily pull several Lillabo cars or even climb the bridge. Use `loco-rear_wheel_groove.stl` to attach a tire; use `loco-rear_wheel.stl` for the older version with less traction. The front wheels are intentionally "wobbly" on their axle, which helps keep the locomotive on track during curves. Assembling this part involves screwing the spacer onto M3 bolts, then attaching the wheel to the spacer and finally securing it to the base. Extra parts needed: * [small rotary switch](https://www.aliexpress.com/item/5pcs-lot-Band-Switch-Rotary-Switch-Gear-Change-Switch-1-Pole-5-Position-2-Pole-3/32976667211.html); I used a 2 pole, 3 positions switch (but should have ordered the 2 poles, 4 positions version instead). * one 5mm LED and a matching resistor (I used red and 200 Ω). * [T-shape DC motor](https://www.aliexpress.com/item/TT-Motor-Smart-Car-Robot-Gear-Motor-for-Arduino-Free-Shipping-Wholesale-for-Arduino-Motor-Smart/32642267017.html) * [small lithium-polymer battery](https://www.aliexpress.com/item/best-battery-brand-3-7V-lithium-polymer-061730-601730-MP3-wireless-mouse-Bluetooth-stereo-280mAH/32662741428.html) and [micro-USB charging module](https://www.aliexpress.com/item/5-pcs-Micro-USB-5V-1A-18650-TP4056-Lithium-Battery-Charger-Module-Charging-Board-With-Protection/32402397769.html) * [12mm ring magnet](https://www.aliexpress.com/item/10pcs-12-x-3mm-Hole-4-mm-Super-Strong-Ring-Loop-Countersunk-Magnet-Rare-Earth-Neo/1000007719690.html) and round-head 4mm bolt & nut * two M3 bolts for the front wheels (screw them through the spacer part first: this prevents the wheel from screwing or unscrewing the bolt) and a M4 bolt for the ring magnet. * solder and heat-shrink wrap for insulation. The LED is wired in series with the resistor, which is then wired in parallel with the motor. Photos of the rotary switch are included to show some of the wiring. The positive pole of the motor should be the upper one (this applies independently of the position of the motor). The wheels and spacer parts should be printed twice.