Spinning a radius dish

[David Lehrer]

Does anyone out there have any idea how to hook up a radius dish on a spinner to a motor so that it will turn 50 RPM or so and I can lower a side assembly onto it and sand it even?

[Greg Robinson]

Hi David.

You'll need to use some sort of bearings to support the outer edges of the dish. You could use "Lazy Susan" bearings, or a series of castor/universal bearings around the perimeter.
In order to get the speed correct, you could use a belt and pulley system, with the outer perimeter of the dish used for the large pulley. If you correctly size your drive pulley on your motor, you could get the appropriate speed reduction without having to add any further reduction.
You'd need to harden up the edge of the dish (presuming you're using MDF dishes). CA glue should do the trick.

Good luck! And post back with your results if you can.

[David Lehrer]

Hi David.

You'll need to use some sort of bearings to support the outer edges of the dish. You could use "Lazy Susan" bearings, or a series of castor/universal bearings around the perimeter.
In order to get the speed correct, you could use a belt and pulley system, with the outer perimeter of the dish used for the large pulley. If you correctly size your drive pulley on your motor, you could get the appropriate speed reduction without having to add any further reduction.
You'd need to harden up the edge of the dish (presuming you're using MDF dishes). CA glue should do the trick.

Good luck! And post back with your results if you can.

[David Lehrer]

Hello Greg,
The type of drive belts that I am familiar with are V-belts which wouldn't work against the flat edge of the radius dishes. Do you have another type belt in mind? Or would it be possible to rout a V channel around the circumference of the dish that the belt would fit into?
David

[Greg Robinson]

You can use a router to form the v-groove. Remember that V-groove belts do not bear on the bottom of the channel, only on the sides. If you do not have the appropriate straight tapered router bit, you can use a small diameter straight bit and angle the router. You can flip the disk rather than re-jigging the router for the opposite angle for consistency too. This step would best be done when you already have the dish mounted on it's bearings so that you can rotate it easily and don't have to register the router off the edge somehow.

There are also flat belts available, these may be easier to use. Most of them are toothed, but don't worry about toothing the dish, you want it to be able to slip if anything goes wrong.

[David Lehrer]

Thank you so much.

[Dave Stewart]

I have a small buffer motor that slides out from under the tablesaw.
I attach a hockey puck, drop it iinto a leg vice & use that to drive the edge of a disc mounted on a lazy susan bearing. (I'll hand spin the disc & rotate it into the spinning motor.)

[David Lehrer]

Dave,
This seems like a simple solution. A couple of questions...How do you attach the hockey puck to the motor shaft? Have you reinforced the edge of the dish where it rubs against the hockey puck? Does it slip? Any idea what the RPM of the disc is?
David

[Mark Swanson]

Having an exposed motor and pulley is a bit dangerous, things can get hung up in there.
I don't think there is any better solution than Mario's, he posted photos and things a long time ago and put them in the Library.

[Mark Swanson]

Here it is- http://www.mimf.com/old-lib/mcknight_motorized_dish.htm