RC Catapult

I took inspiration from: https://www.thingiverse.com/thing:467807 this: https://www.printables.com/make/2223836 and this model: https://www.printables.com/model/214-catapult

This is a functional, mobile-controlled catapult operated via a custom Android app built using MIT App Inventor. It’s an engaging project that combines 3D printing, basic electronics, and app development, suitable for makers of all levels. The Catapult shoots Nerf RIVAL balls.

The catapult is powered by a servo motor and DC motors, controlled by an Arduino board connected to a Bluetooth module (such as HC-05). The Android app lets you control the launching and movement remotely via Bluetooth. The .aia source file is included in the zip file, so you can open and modify the app in MIT App Inventor as needed.

All parts were printed in PLA (PETG maybe be better) with three perimeters and 25% cubic infill. A layer height of 0.2 mm is recommended. Some parts require supports. The model is designed for easy assembly and reliable mechanical performance.

The electronics are powered by a single 18650 Li-ion battery through a 1S Li-ion to 5V boost converter module. The USB-A output connector has been removed, and the 5V output is wired directly to the circuit. Power is controlled using a standard on/off switch.

Electronics used in this project:

• 1× Arduino Uno 
• 1× HC-05 
• 2× L298N motor drivers (for dual DC motor control)
• 2× N20 DC motor
• 1× SG90 micro servo motor (for triggering the catapult)
• 1× Mechanical Endstop Switch
• 1× 18650 Li-ion battery
• 1× 1S Li-ion to 5V boost converter (USB module with USB-A port removed)
• 1× On/off switch
• 1x TT Gear Motor
• 1x 10K Resistor
• 1x Part of breadboard

Included in the download are all 3MF files, a wiring diagram and the mobile app source code. Feedback, remixes, and suggestions are very welcome.