"BR" wrote in message
...
I'm doing some casual experimentation at home and would like suggestions
on building a
rotary tank to study fluid motion. I have many questions and probably
could have gotten a
few of them answered on my own but what the heck. I have no experience in
metalwork,
though I have experimented with brushed DC motors and PWM controllers.


Don't sweat the small stuff.. For example, you had mentioned: i) The small
flat in the bottom of a mixing bowl. This would have very little impact on
your results. Get on with your stuff and don't worry about perfection until
everything else is working perfectly. ii) Back lash in the speed reducer.
That will have no effect at all except to introduce a very tiny time delay
in your direction reversals. Again, first make it work; then perfect it.

I did some very primitive experiments along these line using a phonographic
turntable. It worked fine. Try borrowing an AC signal generator and
driving a turntable with one of these. The variable frequency together with
the 78/33/45 gearing would give a pretty good range. 16 RPM versions also
exist. I would not recommend welding to the bottom of the bowl. I suspect
you will waste a lot of time trying to adjust it and it will never be quite
good enough.

I'd really love to see some of the pictures.

Walter.