This is an off the shelf electric ATV that had all its electronics removed and replaced with our own to make it remote controlled.
We used a linear actuator with potentiometer feedback to steer the ATV so the wheels return to center when the joystick is released. The main drive motor is controlled using a Sabertooth 2x32 and the batteries are 2 of our lead acid 12v 12 amp hour batteries wired in series.
To make the quad look realistic we added a mannequin with all the appropriate riding gear. We hid all the mechanical components inside it to make the head tilt up and down, and look left and right. The 'eyes' are LEDs and can be turned on and off remotely. There are strobe lights to make the ATV more flashy but they can be disabled with the remote if wanted. The mannequin also has a speaker in the helmet to broadcast whatever you want it to say via a remote microphone.
This is a bidirectional level shifter used to step down or up signals from 1.8V to 5V range.
Use these roll pins to fix sprockets to a shaft and keep them locked in place.