Updated Root-Ball Tumbling Device
No longer relying on sawhorses supporting the center axle — took a different approach, better suited to a friction drive. I can actually motorize it with a cordless drill motor, by pressing the keyless chuck against the skateboard wheels and spinning it. But it doesn’t quite have the necessary friction under full load to actually turn the tumbler cage as-is.
But it’s a big improvement all around; and a great new feature is the ability to just lift out the tumbler cage separate from the roller base. I figure if I have a way to spin both the skateboard wheels instead of just one, it should tumble fine.
No video yet, but it’s getting close !
I’ve got a cylindrical roller I fabricated from galvanized pipe pressed up against both of the polyurethane scooter wheels, so they’re both linked thru that and turning at the same rate on either side of the tumbler cage. Also visible in dark green is the motor hinge arm, which pivots downward away from the roller; which will use the motor’s weight to pull the flat belt (pending) tight.
Planning to use that repurposed 1/2hp washing machine motor to drive the flat belt. It doesn’t have a start capacitor - so I’m hoping that throw-starting with the tumbler in either direction will provide sufficient torque/speed in lieu of that. The roller spins pretty quick when turned manually so it could work. Otherwise I’ll need to dig around to see if I can’t find a suitable 50цf - 60цf cap laying around. I had one somewhere 
That hadn’t occurred to me; it’s at about 90%, and I’m fairly confident I’ll be able to get the belt drive to do what it’s supposed to. Might get done sooner with Pervitin - but alas, no hookups within a hundred miles or more, I’m sure 😆