Re: DC power on Tesla secondary (was 20 joules at 100 bps vs 4 joules at 500 bps)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 06:08 PM 8/12/2005, you wrote:
> Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>
>
> Hi,
>
> A Gerret +P 44 caliber magnum round (about the max any normal human 
> would fire from a hand gun) is about 2000 joules.
>
> The original AK-47 round is 1400 joules.
>
> The 30-06 round is about 3600 joules...
>
> At say 10 feet, the "bang" from 20kJ would knock your right off your 
> feet and probably unconscious!!!

Only if all the energy is transmitted into you.

I've done quite a lot with exploding wires in that energy range, and 
while you feel it (standing some small number of meters away), it's 
not that bad.  Compare it to standing next to someone firing an 
elephant gun.  You feel the shockwave, but clearly the energy or 
momentum isn't being dumped into you.


> Be careful, 20kJ is definitely in the "not at all funny" 
> category!!  It is important to note the a 20kJ spark happens in 
> microseconds so the energy effect is a giant shock wave.  The 
> dropping car is spread out into a nice "soft" hit over tens of milliseconds...

See http://home.earthlink.net/~jimlux/energies.htm for a discussion of this.


> For 20kJ sparks, you would have to be uncomfortably near so sand 
> bags, very good ear protection, eye protection (very bright flash)....

Ear and eye protection sure.. Sand bags only if there's some sort of 
shrapnel likely.


> A KKK fire work (those Big single air bangs at public 4th 
> celebrations - 1/4 stick of dynamite) are about 70kJ...

I'd think a bit more energy, if it's really a 1/4 stick of 
dynamite.  1 Lb of HE is about 2 MJ, so a 1/4 stick would be more like 500 kJ.

BUT... sound and perceived impact is more a function of the time 
course ("whump" vs "bang" vs "crack") and how far you are from the 
source (i.e. are you getting a shock wave with an instantaneous 
pressure rise, or has it relaxed into a pulse)


>   You could probably easily hear 20kJ ten miles out...  If you are 
> within 15 miles of civilization, expect cops to show up....

I developed a semiautomated system to replace theatrical maroons 
(which are essentially large electrically fired firecrackers) using 
methane/oxygen explosions in a 6"x2foot chamber fired by a computer 
(drum pad hit generates midi signal, midi decoder generates pulse to 
electronic ignition, firing sparkplug, etc.).  I forget the actual 
energy release (several tens of kJ?), but, after we were testing in 
the parking lot, the guys from the SWAT team who showed up said it 
sounded a lot bigger than regular automatic weapons fire from several 
blocks away.

The sound (and perception of what it is) greatly depends on a lot of 
things (atmospheric conditions are one).

The real problem I found (after a day of testing many thousands of 
shots at a rifle range in the foothills) was that my whole body was 
sore from taking repeated small shock wave impacts all over.


> Be careful there friend :-)  If you do set that thing off, try to 
> get a tape video for us >:o))  But don't become a Darwin Award 
> =:O  Bill's 7.5kJ thing blew up the electronics in three of his 
> neighbor's houses too and much just from the "electrical" shock wave!!!...




> Cheers,
>
>         Terry