best starting point to build a homebrew centrifuge?

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.

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.

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

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

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

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

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.

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

It would help a lot if you described what you were doing. Are you separating materials by forcing them through a sieve, or what.

On Thu, 27 Oct 2005 10:21:22 +0100, with neither quill nor qualm, "Dave Baker" quickly quoth:

Are you sure, Dave? The forces at such a larger radius and such a larger mass at 300 RPM would seem to have a lot more energy than an average IC engine could put out. (I'd like to see figures on both for S&G. Throw in 1,500hp funny car/dragster engine figs, too, please.)

My truck's V-8 engine is spinning at an angle which would not slice and dice me if it blew. (Although the new small cars with transverse engines have their radial mass trajectories (what's the correct term for this?) "aimed" more toward you, they have considerably less mass to throw atcha.)

LJ--who doesn't recall hearing the term "centripetal" before this newsgroup and has zero college math under his belt.

-- SAVE THE PARROTS! Eschew the use of poly! ----------

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 -P.

I was going to say somthing about how yours must be REALLY good home-brew... ;-)

When you get to making ones own stil let me know.... :)

It depends on the size of the 'fuge. With a 10 ft dia 'fuge, tangential velocity at 300 RPM is 157 ft/sec or about 107 mph with about 150 G's on the load -- so the 220 lb mass is straining to leave the bucket with 33,000 lb of force if I did me sums right.

I once saw a $20K (1966 dollars) electrostatically-suspended gyro fly thru the 'fuge housing, go about 30 feet and then thru a brick wall. There were no pieces larger than a nickel left. I think that one only went up to 100 G's.

"Dave Baker" writes in article dated Thu, 27 Oct 2005 10:21:22

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.

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

Nick

What's wrong with a bucket on a rope?