At 08:38 PM 4/21/2011, Mike wrote:
>Maybe, I could set up a bench rig using a variable speed Dremel motor with a

Dremel way way too fast.  Think 3/8 electric drill.  You need around
800 rpm, remember.

If you do some calculating you can figure out how many black spots to
put on your cardboard circle so the strobe effect of a neon light or
*single* fluorescent tube (not the CFL type which operate at high
freqs) will tell you when speed is correct.

Lessee...60 Hz = 120 pulses per second.  805 rpm = 805 / 60 = 13.42
rps = 360 x 13.42 = 4830 degrees per second / 120 = 40.25 degrees per
pulse.  So put your dots a fat 40 degrees apart and you should have
an 805-rpm strobe disk.

To operate the drill trigger, could use a band clamp; or for a 110
volt drill an SCR light dimmer (or a Variac if you have one around)
ought to do the trick.

Use a short length of speedo cable or other flexible drive to avoid
stressing the connection btw drill and gauge.

Yrs,
d