> > >>>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.
>
> > 2X RPM and force goes up 4X.
> > 3X RPM and force goes up 9X.
> > I.e. RPM has an exponential effect on force.
>                   ^^^^^^^^^^^
> Good post Allen! But please use the correct mathematical terminology:
> RPM does NOT have an exponential effect on force -- the force varies
> with the SQUARE of the speed ie RPM as in the formula you quote above.
> Exponential implies that the "magical" number "e" = 2.71828.... appears
> in the formula raised to a power that is dependant upon the RPM: if this
> were so the force would increase with RPM much more dramatically than
> indicated above!

You are right of course, but the above quote is from Peter Bray, not me.

That is not to say that I did not make an error in the portion following.  The
second quote was from a previous post by me and the error was kindly picked up
by another ham radio/engineering type, Wade Troyer who wrote me:

>>>>Interesting analysis for the extractor force, diameter, speed relationship.
Are you
certain the proper end relationship is S = 220 x 56 / D   ??

Could it actually be S = 220 x ( 56 / D )^.5  ?? This is assuming that force is
to be
kept constant and that mass remains constant. I used the relationship F = m x
V^2 / r
and substituted V = pi x D x S to convert velocity into speed in RPM's and r = D
/ 2 to
convert radius into diameter. Next I set D1 x S1^2 = D x S^2 where
S = New Speed, D1 = 56, S1 = 220, D = New Diameter
Solving for S gives S = 220 x ( 56 / D )^.5 <<<<

He is correct of course, and I implied his result in my original post, but
somehow did not get it right in my formula.  I am indebted to you both for
pointing out the oversights and I hope we have it correct now.

> > What a fantastic resource this is.

> Absolutely! But what a shame we can't remove some of the dumb posts we
> sent in ignorance or in haste: they all are there for future searchers
> to find and shake their heads over!

That's the truth, and some of mine are kinda dumb.  I only hope anyone reading
has the sense to read all the way through a thread or a search result to get to
the correct conclusion.

Actually, the logs could conceivably be edited and we have discussed this.

However it is a huge job, and also we are not sure any one of us is wise enough
to decide what will go and what will stay.

Real time oderation is accomplished by a panel of moderators who work
independantly. Approval by any one of them gets any post accepted.  Ie. if any
*one* of the four votes for a post, it goes through to BEE-L.

Editing that way would be cumbersome, if not imposssible.

allen