On Sat, 2 Jan 2010 16:22:44 -0800, "Steve B"
wrote:


"Prof Wonmug" wrote in message
.. .
I want to make some "spinners" with my granddaughter. These are disks
with various patterns that do interesting things when spinning. Some
change colors: yellow and blue wedges turn green, all colors turn
white. Some appear to spin backwards. Some are spirals. Benham disks
generate colors from black and white:

http://en.wikipedia.org/wiki/Benham's_top

These can be made with toothpicks like a top, but the best effects are
achieved with more controlled spin speeds. Most of them work best at
fairly low speeds (150-300 rpm).

I have an old Makita cordless drill, which works OK, but the speed is
difficult to control precisely and it's way overkill. I also have a
Dremel tool, but its slowest speed is like 2000 rpm, which is way too
fast.

Does anyone know of a simple tool, like a cordless screwdriver, that
has better speed control and goes down to 150 RPM?

Or does anyone have a better suggestion?

Is there some kind of simple turntable?

I need speeds of 150 to 1,000 rpm (I think).

How much trouble would it be to build a simple hand-cranked turntable
either gear or belt driven?

I would try to find a motor from an old sewing machine. Variable speed from
very slow to very fast. Should be easy to get pulleys and the drive belts
are like big O rings, and available cheap at sewing places. With some
ingenuity, it might be possible to stack pulleys, like a drill press, and
change from one to another quickly and safely. All on one shaft.

If you can find an old machine WITH the foot control, you got the motor AND
the variable speed control, and all for probably $10 at a yard sale. Maybe
buy one that's on the fritz, but the motor works. That's all you want
anyway. Then it would probably be only $5. Take the motor and speed
control, and use the rest for a boat anchor.

Another clever idea. Thanks.