Perhaps you could use a servo motor from an old 51/4" floppy drive. These
are build on an aluminium frame and have good bearing. There is also a hub
to mount the bowl to. Some old turn tables used servo motors also.
Tom
"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.
Kalliroscope is a type of rheoscopic fluid used to study fluid motion.
For example:
http://www.kalliroscope.com/matisse/index.htm
click on Kalliroscopes / Revolving Kalliroscopes
A circular tank about 6-8" diameter by 3-4" deep, is mounted to a shaft
supported
by a suitable bearing block assembly. It will be filled with water and
kalliroscope or
other particulate matter, driven by a PC controlled reversible DC motor.
The tank could be
a cylinder, but prefer a hemiphere. The problem is finding a hemiphere
that can be mounted
accurately to a shaft. Perhaps a metal spinning co. might have some
leftover I could work
with, however haven't yet asked around. If I had to have one built, what
would be the ~
cost of a hemiphere, aluminum or stainless steel, 6" dia x 3" height with
an additional
1" height vertical wall section, with a boss or mating surface at the
bottom that would
allow accurate placement on a flange or shaft? I imagine the less TIR, the
more expensive.
Wall thickness can be whatever is necessary given it only has to contain
water. If it's
stainless steel then it can be similar to a kitchen mixing bowl. Max speed
is around 200
rpm or whatever that doesn't cause the water to be thrown out of the tank.
Coupling the motor to the tank. Should it be belt driven, or direct using
a flexible
coupler? Thinking of low speed DC servo motors in the ~300-550 rpm range
at
www.surpluscenter.com and perhaps they can be direct coupled? Or should I
consider a
higher rpm motor and reduce the speed thru a belt drive? Since tank
rotation will be
reversed frequently, I'm concerned with backlash of a coupler. I've seen
zero backlash
couplers but would then have to adapt shaft sizes, unless there are some
available with
different sizes on each end. But I guess it depends on what the motor
shaft and tank shaft
diameters happen to be. Now if I had one of those 7x12's...
Another thought (though seems insane) was using something like this:
http://www.etech4sale.com/commerce/c...roduct_id=1308
but the max rpm was I believe 63 rpm for this model. Other models go to
about 220 rpm or
so but were not on sale. However I'm not at all familiar with servo
actuators, and if it
would be worth it/too much trouble to adapt. The controller is expensive.
Seems like
overkill at 25 lbs. and they refer to it as compact, which kinda strikes
me funny. Of
course what am I thinking - I'm talking about a 6" diameter tank on my
desktop. Will a
servo actuator of that type allow for programming a smooth change in
velocity without much
trouble? What other smaller servos with bearings suitable for direct
mounting would be
reasonable for this application? A surplus servo and controller would be
ideal but I need
help in finding the right one that won't cost an arm. Having one that can
take the tank
directly would save a lot of work.
All this just to have the ability to repeat the rotary motions in case a
particular fluid
pattern interests me.
I appreciate your help.
Ben
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