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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / November 2005best starting point to build a homebrew centrifuge?
i have in mind a project which would require some medium amount of centrifuging batches of materials. Industrial centrifuges are too expensive. I thought to start with a washing machine, it's a decent volume of spun space, and they are relatively cheap. Anything even better? Willing to spend as long as results/incremental-dollars margin is positive. > i have in mind a project which would require some medium amount of > centrifuging batches of materials. Industrial centrifuges are too [quoted text clipped - 5 lines] > Anything even better? Willing to spend as long as > results/incremental-dollars margin is positive. You might be surprised how cheap a 'real' centrifuge can be had. I bought a couple large ones at a Silicon Valley auction for $20 for the pair. I sold them for more than that, but ebay has all kinds of them for pretty cheap. About what you'd pay to setup a washing machine that won'yt realy spin at a very good speed. http://search.ebay.com/centrifuge Cheers, - JJG >> i have in mind a project which would require some medium amount of >> centrifuging batches of materials. Industrial centrifuges are too [quoted text clipped - 12 lines] > won'yt realy spin at a very good speed. > http://search.ebay.com/centrifuge That's true. A friend of mine has picked up four for nothing from science labs recently. I think 3 out of the 4 worked okay. They were scary 10,000 rpm machines, too, but only had a fairly small capacity. Chris > i have in mind a project which would require some medium amount of > centrifuging batches of materials. Industrial centrifuges are too [quoted text clipped - 5 lines] > Anything even better? Willing to spend as long as > results/incremental-dollars margin is positive. What on earth do you want a centrifuge for w.r.t. homebrewing? I've done it for years without ever seeing the need, and we have two boutique breweries around, one in the valley and one in the village and neither of them ever owned a centrifuge (nor do the large commercial German breweries I've visited)?!? -P.  Signature========================================= firstname dot lastname at gmail fullstop com I don't think he was going to use the centerfuge for making beer. "Homebrew" seems to be used as a synonym for homemade. > > i have in mind a project which would require some medium amount of > > centrifuging batches of materials. Industrial centrifuges are too [quoted text clipped - 13 lines] > > -P. > I don't think he was going to use the centerfuge for making beer. > "Homebrew" seems to be used as a synonym for homemade. Oh dear. A blonde moment ?!? Lol, -Peter Signature========================================= firstname dot lastname at gmail fullstop com >>I don't think he was going to use the centerfuge for making beer. >>"Homebrew" seems to be used as a synonym for homemade. > > Oh dear. A blonde moment ?!? > > Lol, -Peter I was going to say somthing about how yours must be REALLY good home-brew... ;-) > What on earth do you want a centrifuge for > w.r.t. homebrewing? [quoted text clipped - 5 lines] > the large commercial > German breweries I've visited)?!? We had two, 100 Hp centrifuges at a brewery that I worked at In Sydney. We used them to spin out most of the yeast before the beer was filtered. It save a significant amount of money in diatomaceous earth filter powder as well as saving on the disposal costs of used filter medium.. They frightened hell out of me. The rotor weighed about 100 Kg and spun at 300 rpm. . They used an eddy current drive to get it up to speed. It took over an hour to get to operating speed from cold start. I did a "back of an envelope' calculation with regard to the stored energy in one of these things,and avoided them like the plague ever since. Tom Miller > > What on earth do you want a centrifuge for > > w.r.t. homebrewing? [quoted text clipped - 24 lines] > > Tom Miller That's a lot less energy than an average IC engine spinning at 6k rpm so I'm not sure what you are so frightened about. -- Dave Baker "Dave Baker" <Pumaracing(NoEmails)@aol.com> writes in article <43609c15$0$41142$14726298@news.sunsite.dk> dated Thu, 27 Oct 2005 10:21:22 +0100: >> They frightened hell out of me. The rotor weighed >> about 100 Kg and spun at 300 rpm. . They used an [quoted text clipped - 13 lines] >-- >Dave Baker Tom didn't give us enough numbers to calculate energy. The energy of a spinning hollow cylinder is (1/2)*mass*(radius*angular_velocity)^2. What was the radius of the rotor, Tom? The mass of the moving parts in a car engine is much less than 100kg, and the radii are probably also much less -- radius of the crank and cam, and half the stroke length for the pistons, which is a high-ball estimate because the pistons only move at (radius*angular_velocity) in the middle of their stroke. -- spud_demon -at- thundermaker.net The above may not (yet) represent the opinions of my employer. >> > What on earth do you want a centrifuge for >> > w.r.t. homebrewing? [quoted text clipped - 30 lines] > -- > Dave Baker Wouldn't that depend a lot on the rotor diameter? The further out you move that 100Kg from the center the faster it will be moving at 300RPM. It seems to me like we could be talking about a LOT of energy. Especially considering it takes a 100HP motor over an hour to spin it up! Bob >...we could be talking about a LOT of energy. Especially considering >it takes a 100HP motor over an hour to spin it up! 100HPx746Wx3600s = 3 billion joules. How much is that in dynamite? :-) Nick >>...we could be talking about a LOT of energy. Especially considering >>it takes a 100HP motor over an hour to spin it up! > >100HPx746Wx3600s = 3 billion joules. How much is that in dynamite? :-) > >Nick I believe it is a couple hundred sticks of the stuff, maybe a whole ton of it. Although, it is the frissance of the dynamite, not the energy that makes it dangerous. Your typical chocolate chip cookie contains more chemical energy than a stick of dynamite. About the only way to fully realize this is to notice how flour, with an incendiary trigger, can make an adequite fuel air explosive. > Your typical chocolate chip cookie contains > more chemical energy than a stick of dynamite. Which is just the say the cookie not only tastes great, it has less filler >> What on earth do you want a centrifuge for w.r.t. homebrewing? >> I've done it for years without ever seeing the need, and we have two [quoted text clipped - 14 lines] > > Tom Miller Is this RPM right? 220 lbs. at 300 RPM just doesn't seem all that dangerous to me. How much weight was spinning when it was loaded? Garrett Fulton > We had two, 100 Hp centrifuges at a brewery that > I worked at In Sydney. We used them to spin out > most of the yeast before the beer was filtered. It > save a significant amount of money in diatomaceous > earth filter powder as well as saving on the > disposal costs of used filter medium.. </rant on> That's more or less what I had in mind when I asked. Where I come from, you don't use either centrifuges nor diatomaceous earth filters. You don't use finings, you don't use uv to age the beer (you bloody well age it in the tank first, and in the bottle second - 3 months minimum for the latter before the bottles are allowed out the gate). I know very well that the 'brewers' down here can't be bothered with that, and that's why I won't buy DB or Lion or Foster etc ... I drink my own or imported European beers. I stopped drinking Tuborg and Stella the moment they started making it in NZ under license, because I can taste the difference. :-( At times I have the feeling they use cats' kidneys in the filtration process, that's why they have to drink it ice cold: so they can't taste it. Brewing beer should be an organic process, i.m.o. and not a chemistry experiment. Patience pays off. Of course, that only applies if you take pride in the product rather than just chasing the dollars. Guess I'm just an old fusspot </rant off> -P. Signature========================================= firstname dot lastname at gmail fullstop com Depends upon what you expect from the centrifuge. If you intend to clean up waste vegetable oil with it, you might look for a cream separator as used in a dairy. If you project can be solved by filtration, it might be cheaper and easier to fabricate from available junk. > i have in mind a project which would require some medium amount of > centrifuging batches of materials. Industrial centrifuges are too [quoted text clipped - 5 lines] > Anything even better? Willing to spend as long as > results/incremental-dollars margin is positive. It would help a lot if you described what you were doing. Are you separating materials by forcing them through a sieve, or what. When you get to making ones own stil let me know.... :) >i have in mind a project which would require some medium amount of >centrifuging batches of materials. Industrial centrifuges are too >expensive. > >I thought to start with a washing machine, it's a decent volume of spun >space, and they are relatively cheap. What's wrong with a bucket on a rope? >>...we could be talking about a LOT of energy. Especially considering >>it takes a 100HP motor over an hour to spin it up! >100HPx746Wx3600s = 3 billion joules. How much is that in dynamite? :-) About 1530 pounds, ie 1.5 kilotons. Nick >>>...we could be talking about a LOT of energy. Especially considering >>>it takes a 100HP motor over an hour to spin it up! > >>100HPx746Wx3600s = 3 billion joules. How much is that in dynamite? :-) > > About 1530 pounds, ie 1.5 kilotons. ??? > Nick >>>>...we could be talking about a LOT of energy. Especially considering >>>>it takes a 100HP motor over an hour to spin it up! [quoted text clipped - 6 lines] > >> Nick .75 kt Gunner "Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules. Think of it as having your older brother knock the sh.t out of you for torturing the cat." Gunner >>>>>...we could be talking about a LOT of energy. Especially considering >>>>>it takes a 100HP motor over an hour to spin it up! [quoted text clipped - 8 lines] >>> > .75 kt that's wrong too i > Gunner > [quoted text clipped - 5 lines] > Think of it as having your older brother knock the sh.t out of you > for torturing the cat." Gunner >>100HPx746Wx3600s = 3 billion joules. How much is that in dynamite? :-) > > About 1530 pounds, ie 1.5 kilotons. > ***** > Nick Come again Nick ? a ton is 2000 pounds. ...lew... >>>100HPx746Wx3600s = 3 billion joules. How much is that in dynamite? :-) >> [quoted text clipped - 4 lines] >Come again Nick ? a ton is 2000 pounds. > ...lew... Small kilotons :-) One site says 100 grams of dynamite is 0.43x10^6 joules. Nick >>100HPx746Wx3600s = 3 billion joules. How much is that in dynamite? :-), > About 1530 pounds, ie 1.5 kilotons Erm, it would doubtless be "killa" if you were standing nearby at the time of an uncontained failure but it isn't "kilo" (1.5 kT = 3 million pounds, said of the blast aspect of nuclear weapons in broad comparison to TNT). I also think the amount of time needed to spin it up is irrelevant to a calculation of how much rotational kinetic energy it has when done (though perhaps highly relevant to how much energy will drain out of you when you get the electric bill!); and that's the key fact for safety. BTW, I think the energy use is 268 MJ, not 3 GJ, if you run a 100 hp (input) motor for an hour. Check my logic... A horsepower is 745 W. A watt is a joule per second, so if you do that for 3600 seconds you get 268,200,000 joules. See for instance http://www.newton.dep.anl.gov/askasci/phy99/phy99x45.htm and (one of the most eminently bookmarkworthy and explorable sites around) http://hyperphysics.phy-astr.gsu.edu/hbase/rke.html --Joe "Whatever the numbers, centrifuges are built strong, and operated according to safety instructions, for a reason" Chew >>>100HPx746Wx3600s = 3 billion joules. How much is that in dynamite? :-), >> >>About 1530 pounds, ie 1.5 kilotons > Erm, it would doubtless be "killa" if you were standing nearby at the > time of an uncontained failure but it isn't "kilo" (1.5 kT = 3 million [quoted text clipped - 11 lines] > A watt is a joule per second, so if you do that for 3600 seconds you > get 268,200,000 joules. Assuming you lose nothing to friction during that hour of the giant heavy drum spinning. - Logan Sure enough... that's why I took the liberty of specifying "100 hp (input"). That may not have answered quite exactly the question asked, but lends itself to doing a finite-envelope model without having to look around in the bottom drawer for another envelope. Accounting for real-world efficiency, the actual power usage curve, and other things you'd want to tease out if you were designing or specifying equipment, rather than just getting a quick calculation onto the right order of magnitude, makes for big equations with a lot of moving parts. Cheers, --Joe > Accounting for real-world efficiency, the actual power usage curve, and > other things you'd want to tease out if you were designing or > specifying equipment, rather than just getting a quick calculation onto > the right order of magnitude, makes for big equations with a lot of > moving parts. Agreed. I was just trying to imply that an hour's worth of friction might change the energy by an entire order of magnitude. On the other hand, if it truly takes an hour to get up to speed, then maybe friction is only a small part of the battle... - Logan >> Accounting for real-world efficiency, the actual power usage curve, and >> other things you'd want to tease out if you were designing or [quoted text clipped - 9 lines] > > - Logan There is no friction.An eddy current drive would be magneticly coupled. >>> Accounting for real-world efficiency, the actual power usage curve, and >>> other things you'd want to tease out if you were designing or [quoted text clipped - 10 lines] >> - Logan >There is no friction.An eddy current drive would be magneticly coupled. The energy difference between what the motor supplies and what the load absorbs is dissipated as heat in the eddy current clutch. Just like a friction clutch would except that there are no wearing surfaces. At the instant of startup, the drive is dissipating all the power and the load is absorbing none. At the instant of full speed, the load is absorbing all the power and drive is dissipating none. (This assumes no electronic ramp drive to the eddy current clutch) The actual solution to the stored energy problem is a nice little calculus problem but one can approximate by assuming that half is dissipated and half absorbed by the load. That's a spit-load of energy! I'd certainly not want to be in the building if the rotor disassembled itself. John --- John De Armond See my website for my current email address http://www.johngsbbq.com Cleveland, Occupied TN |
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