Anne POSSOZ on fri 16 nov 01
Hello there,
Although I don't follow the list anymore, I assume that it still
exists and I would like to share this with you.
Just after buying a small mill (5 and 1 liters jar), fixed rotation
speed, I wanted to compare the speed with books, web, etc.
As at first, it was inconsistent, I decided to compute it myself and
arrive at this (full detailed calculation for inetrested person):
F = .50 /sqrt(R) F : tour/sec
R : m
Or
F = 30./sqrt(R) F : tour/min
R : m
F : frequency of rotation
R : the inside radius of the jar (half the diameter)
Sorry, no feet or inches on this side of the ocean.
Full details:
------------
The critical speed should be when
the gravitational force == centrifugal "force"
Vc: critical speed at the outer radius inside the jar [ m/s ]
R : the inside radius of the jar [ m ]
G : gravitational constant = 9.81 m/(s*s) [ m/s2 ]
F : frequency of rotation [ /s ]
M * Vc**2 / R = M * G (1)
And knowing that omega = Vc / R = 2 * pi * F (2)
We compute:
Vc**2 = G * R (1)
Vc = 2 * pi * F * R (2)
Vc**2 = (2 * pi * F * R)**2 (2')
(1) = (2')
G * R = (2 * pi * F * R)**2
G = (2 * pi * R)**2 * F**2
So that :
F**2 = G/(2 * pi * R)**2
F = sqrt(G)/(2 * pi) * 1/sqrt(R)
F = .50 /sqrt(R) [s-1] = [m-1/2*s-1*m-1/2]
F : tour/sec
R : m
Or
F = 30./sqrt(R) F : tour/min
R : m
Cheers,
Anne (physicist, sorry)
--
Anne Possoz Service Informatique Central Tel : (41/21) 693.22.49
Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland)
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