Summary

Design

Lipo battery and brushless motors are not your thing? This low power, Bluetooth controlled car can run from solar panels. Using a pair of DVD motors, step down regulator, and a capacitor bank (40000 uF) this car can pass through shadows for several seconds.

Printed Parts

chassis x1
front x1
steerbar x1
steerknuckle x2, one mirrored (in the photos I printed them in wrong direction)
servoarm x1
frontwheel x2
rearwheel x2
gear1 x2
gear2 x2
engineframe x2, one mirrored

Additional Parts

SG90 or MG90 servo x1
DC motor from DVD player x2, driven separately
I made the rest of the car body using 2mm cardboard. Those are quicker to make.
Attach rubber strips on the wheels to increase grip.
M3 screws with various lengths are used. Several holes need to be threaded using a hand tap.
Holes on the gears may need to be drilled. 2 mm for gear1 and 3 mm for others. Add lubricant.
Install your favourite controller, here I used a not-Arduino-Nano (LGT8F328P), DRV8833 motor driver module, and HC-05 Bluetooth module mounted on perf board.
Capacitors are rated 16V, and the solar panels 12V. Use diodes (1N5819) on each positive terminal of the panels then join the cathodes on the capacitor. The voltage is then converted to 5V for powering the system. I have not tried supercapacitors. The capacitor voltage is measured by the controller to prevent brownout by reducing motor power when energy supply is low.