I bought a Cowan extracting line this year and have had some trouble with the DC
drive.  Phone calls so far have not solved my problem and I decided to redesign
the drive.  It's been over 30 years since I sat in my first year engineering
class and learned the forces associated with revolving objects, and I could not
remember: does centipetal force vary with the diameter -- or the *square* of the
diameter???

Well, I remembered we had talked about this and to check the BEE-L logs.

Lo! and behold!  I found this:

>>>Centrifugal force for an extractor can be calculated with the formula
f=mv²/r where f = force in newtons, m=mass in kgs, v=velocity in
metres/second, and r= radius in metres.

In practice an extractor with a diameter of 1.2 metres (from frame
centre to frame centre) at 150rpm will develop 14.8 times the force of
gravity and this works for semi radial extractors (one speed only).
If these are full depths, there will be around 12.3 Gs on the bottom
bars and 17.3 Gs on the top bars.  The difference in centrifugal force
between top and bottom bars is greater in smaller extractors.

The following implications are also important::

2X RPM and force goes up 4X.
3X RPM and force goes up 9X.
I.e. RPM has an exponential effect on force.

2X diamter and force goes up 2X.
3X diameter and force goes up 3X.
I.e. Increases in Diameter have a linear effect on force.

It's important to get the RPM right!
<<<

What a fantastic resource this is.

And thanks to Peter Bray who originally posted this info.

And I also read this:

>>>FWIW, we run our Kelleys up to 200 to 240 RPM maximum speed
depending on the amount of comb breakage we are experiencing.  This in
turn depends on the thickness of the honey.

The reel diameter is 56 inches in diameter, so a formula to determine a
good trial speed for another diameter would be:

S = 220 X 56 / D

Where S is the speed in RPM and D is the diameter of your extractor reel
(not tank) in inches.<<<

I can thank myself for that one.  How easily we forget what we know!

allen

-----
See if your questions have been answered in over a decade of discussions.
BEE-L archives & more: http://listserv.albany.edu/archives/bee-l.html
Search sci.agriculture.beekeeping at http://www.deja.com/