Small Motor Clamp

Ball Mill number 3, new motor housing to prevent slippage (see my other postings for details of the other printed parts used) As ever this is a work in progress...
Motors and rods are salvaged from old HP Deskjet printers, flexible drive shaft is some reinforced tubing.
https://www.youtube.com/watch?v=giaEPxpL8vg
Comments and suggestions for improvement are welcome