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".
On Wednesday, March 7, 2012 1:04:33 PM UTC-6, mlp wrote:
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
On Wed, Mar 7, 2012 at 6:53 PM, Simon Quellen Field <sfield@scitoys.com> wrote:
> 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 <djwrister@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 <ademlookes@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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