That’s ridiculous. 50mA can be lethal only if it’s applied directly across the heart. And also, if you’re going to measure what current the victim is receiving, you can’t just short your cap through an ammeter. Your body is not made of copper and will not conduct nearly as well as the meter. You need to measure the current through a very large resistor, anywhere from half a megaohm for moist or sweaty skin up to several megaohms for dry skin… let alone clothing!

Besides, they’re using photoflash caps from a disposable flash camera which are generally around 150uF and charge to about 400 volts. I’ve shorted my finger across these fully charged before and it did little more than burn the top of the skin (and tingle!).

Posted at 1:53 am on Jul 10th, 2008 by Satiagraha

Very impressive, at first I was not sure why anybody would want a spud style taser but after the explanation about the BPV being susceptible to this projectile I understand the application.

I am curious about why a school physics lab would allow the production of a weapon lethal or not.

Posted at 2:32 am on Jul 10th, 2008 by kain

For better spud guns, go here

http://www.xinventions.com/main/spud/home.htm

Posted at 4:43 am on Jul 10th, 2008 by IC BS

Their delivery system is terribly large and cumbersome. Since their projectile sticks out the end of the barrel, why is the barrel 3 feet long?
I know they are students but this is not a successful project. But probably a good learning experience.
Goal: replace the gun as a killing machine.
A gun is still easier and better to use= not successful.

Taser beat them: http://www.taser.com/products/law/Pages/XREP.aspx

Posted at 4:47 am on Jul 10th, 2008 by Mike

just a couple of things
1. this has been done, these guys could face serious patent concerns http://www.taser.com/PRODUCTS/LAW/Pages/XREP.aspx
2. in no way would a bullet resistant vest (no such thing as a bullet ‘proof’ vest) be suceptable to these, the kevlar weave is not only very tight but has multiple layers made to specificly cover the gaps in the previous layers weave, this on its own without even taking into consideration metal, ballistic plastic, or ceramic inserts would stop the penetration of the electrodes.

Posted at 4:52 am on Jul 10th, 2008 by revere

The exposure time to those Amps is also critical.
I do not have the diagramm in front of me, but you can derive it from electric discharge-diagramms with body-equivalent resistances in mind.
With skin-penetration you can simulate the resistance by about 50 Ohms (ionic current transportation).

1mA directly to the heart with right timing can already be lethal. Timing of low electric shocks is the critical distinction between fatal and non-fatal. If the heartmuscle-cells are relaxing (reloading) (so called p-part of an ECG) you can easily trigger fatal fibrillation.

A loaded capacitator can be lethal, but the discharge has to take place after penetrating the skin and at the right spot with the right timing and maybe orientation to the heart-axis.

Poisoning with cyanide would be way more efficient.

It takes much more to immobilise a person with one single shock than a simple capacitator. If a single DC puls is enough to take one down it can also be fatal – very unpractical. AC pulses are less critical but nevertheless can be fatal as well (tasers and zappers can kill).

(english is not my motherlanguage)

Posted at 7:16 am on Jul 10th, 2008 by Till

Idiots… This is a bunch of crap. If I would have known College would have been this easy, I wouldn’t have busted my ass for the last 6 years working late nights for terrible pay…

Instead, I would have been drinking until dawn and building potato guns for my final research project.

Posted at 9:22 am on Jul 10th, 2008 by Alexander

this is cool, but not real practical. You would have to be able to aim it fairly precisely, and you’ve got the big randomness factor of shooting the thing. Also, my friend and his dad (they are farmers) build a tater cannon and launched it across their yard at his dirt bike, and it was enough to knock it off balance and tip it over, so the sting of the taser would only be an after effect, the poor schmuck on the receiving end would have a nice bruise to show off too.

Posted at 9:49 am on Jul 10th, 2008 by mike

Are these physics students? And they were surprised when they blew an amp meter by discharging a high-voltage capacitor through it? There is absolutely nothing scientifical about this (and I think it was suposed to)!

Posted at 12:48 pm on Jul 10th, 2008 by crisr

unless i’m mistaken, taser already makes one of these. It gets fired out of a shotgun. In addition, they actually have a high voltage switcher circuit built into the shotgun projectile which constantly delivers high voltage pulses to a target (compared to a single shock, which is probably unsufficient to stop someone for more than a second or so, unless you actually kill him/her). It’s (supposed to be) non-lethal (honestly as long as if you can incapacitate (sp?) a subject long enough there is no use for a lethal projectile).

Posted at 1:11 pm on Jul 10th, 2008 by threepointone

Their potato cannon setup was less than stellar.
The projectile should have been plunger-ed down to the base of the barrel, not sticking out the end.

It’s been a while since i looked all this up for my cannon, but i vaguely remember the proper ratio being somewhere around 1.5:1 of Chamber Volume : Barrel volume for most efficient utilization of expanding gasses (combustion).

Also, i think most common propellants (propane being the ‘best’) need optimal ratio between themselves and oxygen in the chamber. (5:1 oxygen to propellant seems to pop into my head, not a random spray + cap)

Obviously, shooting in a dorm hall means they don’t want full power, and full power might be considered lethal (i’ve shot my cannon straight across campus from the dorms to the academic side when i was in school. Would never consider putting a human in front of that. ever. A paintball chrono’d @ 280fps will explode your eyeball inside the socket. A potato sized plastic projectile will cause serious serious injury @ similar speeds)

Plus, for something light that, pneumatic would be much smarter. More control over everything, plus pneumatic cannons can achieve much greater velocity/distance.

Posted at 5:01 pm on Jul 10th, 2008 by prophetnoise

revere: kevlar is meant to stop “blunt” objects from going through. If you fire a needle at it with the same force as a bullet, it is going through plain mesh armor. however, inserts are a different matter.

Like I have said, the easiest way to defeat this… would be to line the kevlar vest with a multilayer metal mesh. When the pins/prongs/needles went through the plain kevlar, the meshes would short them in just above a microsecond, discharging all current across the vest, leaving nothing but the prongs to do damage. If done on a commercial scale… the kevlar could be metal impregnated, allowing for all of the charge to be removed long before it got to the person.

Posted at 1:03 am on Jul 11th, 2008 by The_Truth

fucking stupid.

“amperage is the thing that kills you”

Posted at 10:51 pm on Jul 11th, 2008 by tom