Calcualting Motor Torque

abbeyg@umich.edu wrote:

You're spinning a liquid. If the drum has no internal vanes, The liquid
will come up to its speed with much delay. The starting torque --
friction aside -- will be little more than for an empty drum.

Jerry
--
Engineering is the art of making what you want from things you can get.
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You could obtain a worst-case answer of the torque during the pullout period
by assuming that the drum and contents are solid. The result will be
somewhat greater than the case where the fluid slips, but is that an issue?
If you design with too small small a margin you're likely to find that the
setup lacks grunt, at least at times.

Without knowing much about your application, it looks like the pullout
torque requirement would be a lot higher than the running torque if your
mechanics are good, so sizing for pullout is probably going to be OK.

This also depends on your drive type. Fixed frequency AC induction motors
aren't happy for long at speeds significantly below their synchronous speed,
so if you're considering such a drive you'll need to ensure that it can pull
out fast enough. There's plenty of information on the web on motor
protection.

abbeyg@umich.edu wrote:


Eh?  You're describing an 8 gallon tank.

How quickly does the thing need to spin up?  What sort of bearing drag
do you expect?  What do you define as "a decent speed" -- all of these
things make a significant difference in your answer.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google?  See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

Tim Wescott wrote:

   ...


I feel silly for not picking up on that. 36*16*pi/231 = 7 5/6 gallons.
That comes out to about 65 pounds; just over a cubic foot.

   ...

Jerry
--
Engineering is the art of making what you want from things you can get.
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Jerry Avins wrote:

When I started working at my Dad's shop one of my jobs involved rolling
55 gallon drums around.  I couldn't tell you just how big they are in
inches, but I can close my eyes and see one, and feel just how much heft
it takes to tip a full one up on it's rim to roll it around.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google?  See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

Tim Wescott wrote:

Have you ever dealt with one filled with CCl_4. That stuff is *dense*.
About 1.6 * water.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯