Re: C4 Racing from Newbury - 2 horses *electrocuted*

But would almost certainly be wearing rubber wellies, not steel shod feet directly on the wet grass like the horses.

Reply to
Dave Liquorice
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As long as you have enough resistance you'll be OK

Reply to
Donwill

Titanium shoes on race horses I think.

Reply to
The Natural Philosopher

The Sun has a theory.

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"The two which died were shod in steel whilst the survivors were wearing less-conductive aluminium."

I suspect that someone at The Sun does not understand conductivity values.

Reply to
ARWadsworth

I'm ashamed to admit that we've been cheerfully piling on the crassness in another part of this thread. :-/

Reply to
Angus Rodgers

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Aluminium oxide is both an excellent insulator, and very hard.

Whilst breadboarding a circuit which used power MOSFETs to switch mains, I temporarily clamped the two MOSFETs to the same aluminium heatsink with a pair of bulldog clips. I knew it was live (didn't bother with insulating kits whilst breadboarding), so kept clear of it when powered up.

When recovering the components to build the final thing, it only then dawned on me that the two MOSFET tabs had mains voltage between them. The layer of aluminium oxide on the heatsinks had withstood that, keeping the tabs insulated from the heatsinks (well, at least one of them had, and possibly both), or there would have been a big bang and fried MOSFETs.

Reply to
Andrew Gabriel

[snip war story]

While this is true, I would have expected that aly shoes would be constantly being scratched, thus exposing fresh aly and allowing current to pass.

I know the fresh aly oxidises fairly quickly but I don't know the timescale.

Reply to
Tim Streater

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Perhaps it was a magnetic field inducing currents in the iron, but not the al :-)

Reply to
The Natural Philosopher

My theory is the two which died stood facing towards or away from the power line; the survivors stood more-or-less parallel, so electrically each animal was a pair of bipeds with little current in the torso.

Fliss

Reply to
Felicity S.

Yes, of course. I also read what Greenaum wrote.

Fliss

Reply to
Felicity S.

Nah - it's ley-lines, innit. The whole area's lousy with 'em. Probably find they got tangled up in the exotic energy field that surrounds the course.

Proper tin-foil hats (and in their cases skid-trays) and they'd have been fine.

Reply to
Skipweasel

On Sun, 13 Feb 2011 12:51:15 -0800 (PST), zoe rothwell sprachen:

Modern tasers (stupid scifi name! "electrocuter" would do nicely) fire a probe with wires attached to it. It would be simple enough to find the culprit at the other end of the cable.

They're fired by a blank shotgun shell, which would make a lot of noise.

I *suppose*, if you were a really big-time horse nobbler (remember them ultrasonic nobble-binoculars in the 80s?), you could adjust the cartridge to fire at sub-sonic speed, so there wouldn't be as much of a bang. Possibly fit a mechanism to retract the wire quickly. But it's hardly the ideal crime.

You could bury some sort of electric "mine" in the ground, but it'd be found quickly.

Apart from that, there's been research into wireless tas^H^H^Helectrical life-riskers. You use an ultraviolet laser beam, a pair actually, to heat the air into an ionic plasma. In this state, it conducts. So you point your twin laser "plasma-wires" at your target, and send a voltage down.

The air heating makes an explosive "CRACK!", the lasers are the size of a bench, and it needs a large-scale power supply. Not discrete enough yet.

If it was a nobbling, probably the best way of finding out would be traditional detective work. Trace who was betting on what, the horses' owners, etc etc. Still, I think a freak accident is much more likely. Who was it said something about not blaming things on malice that could be put down to simple incompetence?

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"hey let's educate the brutes, we know we are superior to them anyway, just through genetics, we are gentically superior to the working class. They are a shaved monkey. If we educate them, they will be able to read instructions, turn up on time and man the conveyor belts, sorted." #

Reply to
greenaum

Sounds like an ideal investigation job for Dick Francis's Sid Halley!

Reply to
Mortimer

Some malicious person, probably.

As it involves following the money trail, I was thinking of Detective Lester Freamon from /The Wire/ - but we don't want any more bad puns.

Reply to
Angus Rodgers

Apparently some racing plates are made of anodized aluminium, which is definitely harder to make conductive. I just tried using the sharp probes on my multimeter on a piece of anodized Al - no current. In contrast, I could get close to a zero ohm reading from a sheet of ordinary aluminium with just touching the probes on to the surface.

Francis

Reply to
Francis Burton

On Mon, 14 Feb 2011 23:35:05 GMT, "Felicity S." sprachen:

You could be right. It's about volts-per-metre in this sort of scenario.

Aluminium has virtually the same conductivity as steel, particularly when compared to dirt and horseflesh. Stupid Sun. Who told them they could have an opinion.

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"hey let's educate the brutes, we know we are superior to them anyway, just through genetics, we are gentically superior to the working class. They are a shaved monkey. If we educate them, they will be able to read instructions, turn up on time and man the conveyor belts, sorted." #

Reply to
greenaum

On Mon, 14 Feb 2011 15:22:39 +0000, Tim Streater sprachen:

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"hey let's educate the brutes, we know we are superior to them anyway, just through genetics, we are gentically superior to the working class. They are a shaved monkey. If we educate them, they will be able to read instructions, turn up on time and man the conveyor belts, sorted." #

Reply to
greenaum

On Mon, 14 Feb 2011 15:03:04 +0000 (UTC), snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) sprachen:

The tiny thin layer of it on aluminium is. But you can still conduct current easily through aluminium foil, or metal. The oxide layer in practice is too thin to insulate electrically.

The layer of oxide forms in just a few seconds on pure aluminium. I've seen it happen on TV, it forms before one's very eyes. Same as when you slice through Sodium.

It's too thin to make a difference. I imagine in your MOSFET case, either one of them wasn't making proper contact or, more likely, the FETs were tougher than you thought. Electronics, and power electronics particularly, can take a lot more than they're rated for, before they actually blow.

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"hey let's educate the brutes, we know we are superior to them anyway, just through genetics, we are gentically superior to the working class. They are a shaved monkey. If we educate them, they will be able to read instructions, turn up on time and man the conveyor belts, sorted." #

Reply to
greenaum

On Sun, 13 Feb 2011 23:36:51 GMT, "Felicity S." sprachen:

It's a giant "depends". Depends on the individual's body, the quality of contact they make, time period, all sorts of ethereal factors.

You could come up with a minimum deadly, and maximum survivable voltage. But within 5 minutes somebody would appear who'd survived worse, or died from less.

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"hey let's educate the brutes, we know we are superior to them anyway, just through genetics, we are gentically superior to the working class. They are a shaved monkey. If we educate them, they will be able to read instructions, turn up on time and man the conveyor belts, sorted." #

Reply to
greenaum

But when they blow, you know about it...

At university we had a project to develop a switched-mode power-supply in which a thyristor is switched on and off at a constant frequency but with a variable mark-to-space ratio to keep the output voltage after smoothing constant with a varying load.

We were warned that the thyristor that we'd been supplied with was rated to carry a certain current, but only when it was being switched and not when it was permanently turned on.

It was only a matter of time before one of the teams suffered a loose wire between the thryristor and the switching circuit while the PSU was carrying full load...

Within a matter of about two seconds, there were five distinct sounds: a cry of "shit!" from the person who had accidentally disconnected the oscillator, a yell of "duck!", a scraping of chairs on the floor as everyone took cover, a VERY loud bang like a shotgun, and a gasp of "F**k!" as everyone reacted to the bang.

The end had blown off the thyristor and embedded itself in the ceiling - thank goodness it went upwards instead of into someone.

Reply to
Mortimer

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