Self-balancing robot framework

This was originally just the lower base including motor mounts for a self-balancing robot.
Later, I added two versions of the upper level.
One holds an Arduino Nano and the other version holds an ESP32 C3 Super Mini.
Both attach to the bottom side of the upper level.
If necessary, there are pegs underneath for an optional rubber band or other strap to hold the controller in place.
Also attached underneath is a GY521 MPU6050 gyro/accelerometer, centered over the axles.
It is held in place with a snap-fit clip onto pegs.
Since this configuration behaves like an inverted pendulum, the two 18650 batteries are placed on top.

The motors are the typical 3 to 6 volt DC motors available online for this small class of bot.
200RPM with 1:48 gear ratio
Mine were purchased here: https://shorturl.at/pbPaD
The motors fit snug vertically and additional platforms can be added using the four 1/4 inch holes in the corners of the base.

I also added a mid-level platform for possible future accessories.