> > >>>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