extendable gearbox with ball bearing embedded Free 3D print model

The gear ratio is 3:1 each unit. It is easy to extend by simply add another unit to it. I add a DC mini 130 motor case which you can change to another motor.
I design this extendable gearbox for convenient daily use. It is easy to make and use using 3D printed parts and ball bearing. Hope you will like it.Detail information on YoutubeHow to make an extendable gearbox with ball bearing embeddedLink to this video：https://youtu.be/HwFrASPbZB0