Centrifuge projectile speed

[Simon Quellen Field]

The discussion was about 50,000 rpm, not 110,000 rpm.

But you are also making a physics error.

The speed of the projectile will not be the speed of the outer end of the tube.

It will be the speed of the center of mass of the projectile.

Another error is comparing the kinetic energy of a plastic tube to that of a

lead bullet. Rubber and plastic bullets are used in crowd control because they

are (in theory) non-lethal.

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On Wed, Mar 7, 2012 at 10:42 AM, Dan Wright <djwr...@gmail.com> wrote:

Assume spinning the end of the test tube makes a total diameter of 12.8 cm. = 5.04 inches /12 = .42 feet * 3.14 * 60 * 110,000rpm / 5280 =  1648.5 mph

A Colt .45  is just over 500 mph

Sent from my iPhone

On Mar 6, 2012, at 5:26 PM, mad_casual <ademl...@gmail.com> wrote:

I assume since you say eppendorfs, you're making an analytical ultra (as opposed to preparative). As someone gives below, the 5.56 NATO round is 11.8 grams of copper jacketed lead rifled at ~950 m/s. Assuming your 3.5 cm radius (assumed from 200,000G <-> 70,000 rpm), your eppendorfs will be ~1.2 g of plastic jacketed water travelling (tumbling) at ~250 m/s. About 1/3 the mass and 3X the velocity of a paintball. I wouldn't want to take one in the mouth, neck, eye, or groin unprotected, but with goggles and a lab coat I wouldn't be too worried about projectiles.

As others point out, the question is more about how quickly is your rotor going to wear out. I think with plastic, you should make an effective system for collecting the rotor pieces and consider them and consider them single use/disposable.

On Wednesday, February 29, 2012 9:49:14 AM UTC-6, Richard Proctor wrote:

im going to be working on cathals dremelfuge. ive found a US company
called Portescap who manufacture very high RPM brushless motors that
can hit in excess of 70,000 RPM or 200,000 G .

My main concern is whether the material in 3D printing can really deal
with those kind of forces.

The balance must be that the thing is light enough to not cause the
motor to lower its RPM but be stable enough to not cause eppendorf
bullets :-s

thoughts anyone....i'll be running FEA analysis on selection of
polymers in the next week.

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[Meredith L. Patterson]

Rubber and plastic bullets are also supposed to be fired at the ground
so that they bounce up and strike their targets, not fired directly at
people in crowds; furthermore they're supposed to be fired from at
least 10m away, according to the manufacturer's instructions. (Not
that cops tend to pay attention to this sort of thing.)

A direct hit from a rubber bullet to the eye stands a good chance of
killing you, and I expect an eppendorf at 50,000 rpm to the eye does
too.

--mlp

[Simon Quellen Field]

Indeed.

Don't do that. :-)

And you are likely to be standing close to the centrifuge when it fails,

so air resistance might not have much time to work on the plastic tube.

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[Dan Wright]

Ok let's use 50,000 rpm which is on the low end of an ultrafuge.  It would be 749 mph-- still much faster than a  Colt .45 bullet.  Oh the mid point of the mass of the test tube would be near the end of the test tube because the liquid would tend to be near the bottom.  (centrifugal force)  PSSC Physics

Assume the projectile is 1/7th the density of copper or lead.  It is at least the density of water, but encased in a hard plastic pointed case.  Human soft tissue is about the same density. Fat is less dense and thus floats.  A projectile of water encased in an eppendorf tube at anywhere in the several hundred mph range would penetrate soft tissue and could easily kill. 

Think of the IEDs using a less dense thin copper plate to destroy the most heavily armored tank. Think of a rail gun. Velocity kills. Be careful!

Assume spinning the end of the test tube makes a total diameter of 12.8

cm. = 5.04 inches /12 = .42 feet * 3.14 * 60 * 110,000rpm / 5280 =  1648.5

mph

Assume spinning the end of the test tube makes a total diameter of 12.8

cm. = 5.04 inches /12 = .42 feet * 3.14 * 60 * 50,000rpm / 5280 =  749

mph

Sent from my iPhone

[Daniel C.]

On Wed, Mar 7, 2012 at 11:54 PM, Dan Wright <djwr...@gmail.com> wrote:
> A projectile of water encased in an eppendorf tube at anywhere in
> the several hundred mph range would penetrate soft tissue and could easily
> kill.

Hardly. Getting punctured by a flimsy tube filled with water would
cause some lacerations, or a hole through your chest cavity at worst.
(Your heart is behind some pretty thick bone - no eppendorf tube is
going to get through that.) Neither of those would kill a person,
unless (as Meredith pointed out) you had the extremely bad luck of
catching it someplace where very little stands between it and your
brain. Anything less than brain or heart damage isn't going to kill a
person.

That's not saying you shouldn't be careful - just that a flying
eppendorf doesn't spell certain doom. You could still injure yourself
badly.

> Think of the IEDs using a less dense thin copper plate to destroy the most
> heavily armored tank.

You're talking about an EFP (explosively formed penetrator), which is
an apples to oranges comparison. An EFP uses an explosive charge to
turn a shaped copper disc into a jet of molten metal traveling at
extremely high velocities (8,000 meters/second or higher) to penetrate
armor. A centrifuge has a small, solid piece of plastic in it, at
roughly room temperature, traveling at (if we're to accept these
calculations) 1648.5 mph, which is about 737 meters per second.
Getting hit by one won't be comfortable - it may even cause a serious
injury - but the comparison to an EFP is not reasonable.

-Dan

[Patrik]

I'd be a lot less worried about getting hit by a high-speed eppendorf
tube, than by a sliver of metal shrapnel. Put enough unbalanced load
on a 50,000 rpm DIY axle, and something will give. And once a 50,000
rpm metal rotor or axle pieces start bouncing around inside the
centrifuge, metal fragments may spray in all directions.

I think it's entirely feasible to build a safe DIY armored enclosure
for an ultracentrifuge. But I'd much rather take myself out of the
line of fire in the first place, by putting the ultracentrifuge in a
hole in the ground.

On Mar 7, 9:26 pm, "Daniel C." <dcrooks...@gmail.com> wrote:

[Dan Wright]

Anything less than brain or heart damage isn't going to kill a
person.

a hole through your chest cavity at worst.

Neither of those would kill a person,

Good to know that you can only die from heart or brain damage. I will tell my carotid artery, femoral artery and aorta. Oh that sucking chest wound would bring extra oxygen to my lungs. 

Sent from my iPhone

[Daniel C.]

On Thu, Mar 8, 2012 at 1:52 AM, Dan Wright <djwr...@gmail.com> wrote:
> Good to know that you can only die from heart or brain damage. I will tell
> my carotid artery, femoral artery and aorta. Oh that sucking chest wound
> would bring extra oxygen to my lungs.

If you get hit in an artery, direct pressure or a tourniquet and
lactate ringer will keep you alive until you get to the hospital.
(Unless you're one unlucky S.O.B., in which case you're dead anyway.)
Battlefield first aid for sucking chest wounds is trivial. I'm
qualified to deal with any of those wounds, and I'm not even a medic.
But regardless, a flying piece of plastic isn't going to blast open a
major artery and cause you to bleed out :P I don't have the math
skills to calculate the probability of this is, but I'm quite certain
it's very low. We should focus on what's infinitely more likely -
that if someone tries to create an ultracentrifuge at home, they will
seriously injure themselves in some non-life-threatening way. "You
could die" is seldom taken seriously, while "you could seriously
injure yourself, likely badly enough to require hospitalization, and a
permanent and life-altering maiming is not out of the question" is
more likely to be heeded.

-Dan

[Nathan McCorkle]

> --

You could easily be blinded with an eppendorf (or part of the plastic
centrifuge rotor that was discussed much earlier in this thread), and
then knock stuff over (open flames,
chemicals which burn or explode or poison), which could result in
pretty bad things.

--
Nathan McCorkle
Rochester Institute of Technology
College of Science, Biotechnology/Bioinformatics

[Daniel C.]

On Thu, Mar 8, 2012 at 2:52 AM, Nathan McCorkle <nmz...@gmail.com> wrote:
> You could easily be blinded with an eppendorf (or part of the plastic
> centrifuge rotor that was discussed much earlier in this thread), and
> then knock stuff over (open flames,
> chemicals which burn or explode or poison), which could result in
> pretty bad things.

Yes. You could start an article of clothing on fire, and then
(because you've been blinded and can't see that it's burning) wear it
to a social gathering, and everyone there would start on fire from
your burning clothes, and then they would all go home and start their
houses on fire, and... man. That would be just as bad as the bad as
the freak gas fight accident that killed my friend and world-famous
supermodel.

All this thinking is making my head hurt. I'm going to get an orange
mocha frappucino.

-Dan

[John Griessen]

On 03/08/2012 12:36 AM, Patrik wrote:
> I think it's entirely feasible to build a safe DIY armored enclosure
> for an ultracentrifuge. But I'd much rather take myself out of the
> line of fire in the first place, by putting the ultracentrifuge in a
> hole in the ground.

The hole method stops so many people from wanting
that design -- it would be so inconvenient.

Concrete multi layered containers with steel and glass fiber reinforcement
seems a more productive path for conversation.

As far as worry and liability, the ones that will build will, and the ones that are afraid
of it won't have any fully assembled guaranteed ultracentrifuge to buy from me, that
is for sure. My first kit centrifuges will probably go to a whopping 200 RPM
as part of an incubator shaker function in a multipurpose modular
parallel liquid processing machine I'm dreaming up. But later? Why not a 5000 RPM version
and then more?

[mad_casual]

One of my favorites!:
http://www.youtube.com/watch?v=kOURLAgQT_8

[Nathan McCorkle]

Most tabletop microtube centrifuges go up to about 15000 rpm, using plastic rotors, so if you can come up with a good enclosure, I'd think you are on track

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[mad_casual]

Rubber and plastic bullets are also many times the mass of a typical lethal rifle or handgun cartridge and travel many times slower. They are meant to transfer their energy superficially and the 'skipping' is meant to induce tumbling (and visibly reduce liability on the part of the shooter(s)). A 'direct hit' and 'to the eye socket' reverses this. I wouldn't be surprised if a fair portion of people would be killed by direct fire from a paintball marker to the eye. Heck, it wouldn't surprise me at all to learn that someone could throw a pencil or framing nail hard enough to penetrate someone's eye socket.

I keep making the point that the OP SEEMED to be talking about an analytical centrifuge where the samples would be 1-2 mL (1-2 grams) rather than a preparative one where samples+containers can weigh 50g or more. I don't, in any way, mean to discourage people from wearing goggles in the lab or PPE (or masks on the paintball field, or helmets in a batting cage, etc., etc.). I just frown on the analogy between eppendorfs (terminal ballistics: abysmal) and bullets (terminal ballistics: gold standard) and would like to discourage people from digging holes or filling washing machines with concrete to prevent themselves from being "killed by an eppendorf".

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[Daniel C.]

On Thu, Mar 8, 2012 at 11:30 AM, mad_casual <ademl...@gmail.com> wrote:
> One of my favorites!:
> http://www.youtube.com/watch?v=kOURLAgQT_8

I'm pretty sure one of them was firing eppendorf tubes. Those things
look innocent when they're sitting quietly in their packaging
material, but secretly they hunger for the succulence of human brains.

-Dan

[Nathan McCorkle]

On Thu, Mar 8, 2012 at 11:30 AM, mad_casual <ademl...@gmail.com> wrote:

> One of my favorites!:
> http://www.youtube.com/watch?v=kOURLAgQT_8

One of my favorite childhood movies! This scene perfectly portrays how
an eppendorf could cause a major accident :D !!!!

[Daniel C.]

On Fri, Mar 9, 2012 at 7:12 PM, Nathan McCorkle <nmz...@gmail.com> wrote:
> One of my favorite childhood movies! This scene perfectly portrays how
> an eppendorf could cause a major accident :D !!!!

WE MUST NOT ALLOW AN EPPENDORF GAP!

[CrazyCarl]

I asked this a while back in the physics StackOverflow:

http://physics.stackexchange.com/questions/13899/calculating-ballast-needed-to-offset-wobble-of-a-1g-unbalanced-centerfuge-spinni

HTH