Throwing explosive fun

[Chris J Dixon]

Which reminds me about a test report written by one of my colleagues about 45 years ago.

They had built a prototype railway rolling stock dc chopper based on a string of thyristors. The assembly was placed on a substantial metal bedplate in the test area. It was connected to the power supply through a water fuse. This consisted of a plastic bucket filled with water, having a couple of submerged cable connectors and a thin wire between them. For safety, the bucket had a wooden lid with a heavy weight sitting on it.

When the inevitable fault occurred, the fuse blew with some force, creating a waterspout which lifted the lid high in the air. Unfortunately, on the way back down, the heavy weight was faster then the wooden lid, and it wedged itself between the cable connectors, re-making the circuit. This would have been bad enough on its own, but with all the water sloshing around on the bedplate, the supply was now both shorted and earthed.

I believe it took some time to get supplies restored, and there were no intact thyristors left.

Chris

[nothanks]

Brilliant! :-) Similar to Gerard Hoffnung's bricklayer tale

[Alan J. Wylie]

The "Things I Won't Work With" blog by Derek Lowe is always a good read, e.g.

"I'd call for all the chemists who've ever worked with a hexanitro compound to raise their hands, but that might be assuming too much about the limb-to-chemist ratio. Nitro groups, as even people who've never taken a chemistry class know, can lead to firey booms, and putting six of them on one molecule can only lead to such."

and (staying on-topic)

"the that latter two blew up so violently that they ruptured the pans on the apparatus while testing 1.5 milligrams of sample."

Also discusses highly corrosive substances, e.g.

"chlorine trifluoride" ... "It burned its way through a foot of concrete floor and chewed up another meter of sand and gravel beneath"

[Fredxx]

Breaking bad myth-busters suggest you need an awful lot more than a "tiniest" drop.

Where did you find this 'tale'?

[SteveW]

Back in school days, I attended an outside lecture on explosives. My chemistry teacher vowed to never carry out one of his demonstrations again, as the lecturer was missing some fingers from the same experiment.

<Snip>

Sounds like the blood in Alien.

[Cursitor Doom]

Sub tiniest drop. You cannot form a drop small enough to replicate this effect with a standard 1ml pippette. You would not believe it if you were not there. That's why they're so twitchy about anyone trying to acquire nitric acid (and especially nitric and sulphuric acid together raises the loudest of alarm bells).

[Cursitor Doom]

Haha! You jest. You're obviously too young to remember the power of the firworks of yesteryear. The crap they've been selling since about

1980 is a joke compared to what we had back in the early post-war period. So yes, galvanised bucket clean over the house. Back in those days, galvanised buckets where a common sight in every hardware store, along with a rack of shotguns and ammo. In the countryside anyway; not sure about the cities.

[John Walliker]

My experience of bangers and galvanised buckets started in the mid 1960s. I agree that later on bangers were made much less powerful. Nevertheless, I still don't believe that a 1d banger could propel a galvanised bucket any significant distance let alone over a roof -not even a single storey one. I did once manage to punch several holes in the sides of a thick-walled galvanised steel firebucket with a firework that used the gunpowder from several bangers combined with very strong containment, but the bucket stayed firmly on the ground. It was after that event that I decided things were getting too dangerous and I stopped trying to make ever better fireworks.

[Jeff Layman]

Agreed. In the 60s I once put a small amount of a well-known sugar mix at the bottom of a small metal empty Nitromors can (the type which was about 3" diameter and high, with a 3/4" screw cap). I drilled a 1/8" hole in the cap, and ignited the mix with a Jetex fuse. It caught fire and the jet of smoke through the hole in the cap got longer and longer. After ten seconds there was a loud bang, and the can was no longer there; well, the base of it was! Wondering where the rest was, I suddenly heard some clanging. It was the body of the can bouncing on a roof well over a 100 ft away!

[The Natural Philosopher]

A pyro friend and I used to get old pain tins and the like, add a few grammes of weedkiller and sugar mix, tamp the lids down, and place them on a tray on more weedkiller and sugar, light that, which cause the material inside to detonate, and we could easily get to gutter height.

We dint run, just stepped back.

Use more explosive?

[The Natural Philosopher]

I did the same with a 16 gauge aluminium tube, with a washer epoxied over the end to make a nozzle. Suspended from the washing line by two stirrups. The idea was to make a rocket, but I actually made a mortar round.

I found what was left of it a year later in the hedge - just twisted shrapnel. I got my hearing back after a few hours.

[Jeff Layman]

+1

A penny banger couldn't do that to a bucket. It might turn it over or blow it a foot or two into the air. It would need far more gunpowder to lift it dozens of feet. The cardboard casing is too weak to sustain the pressure build up needed. If you wanted a really big bang, you needed more gunpowder and a stronger case. In the late 60s I got an empty cardboard "tube" from a London bus conductor's ticket machine. It was about 2" long, with a 1/2" diameter hole. The important thing was that the cardboard was almost half an inch thick. I araldited a 1/4" of 1/2" dowel in each end, and drilled a hole in one just enough to take a penny banger fuse. It became a "6d" banger with the contents of six penny bangers. When it went off, the shock wave noticeably moved in a 6 x 4 ft pane of glass more than 30 feet away.

Agree about things getting silly. A friend's older brother made a "banger" out of a Sparklets bulb! Not sure if it was just gunpowder or his own mix, but it easily split a 6" wooden post. I didn't see the explosion, as I made sure I was round the corner of the house. Nobody else seemed to think that there might be some dangerous shrapnel flying around!

[John Walliker]

The containment I used was so strong that it took a few seconds to rupture after the gunpowder had been ignited. What really worried me was that it might have lasted a bit longer still and I might have gone back to inspect it. It had been ignited from a range of 100 yards which was just as well. John

[Vir Campestris]

My one was to put an old 7.62 cartridge case - loads of them lying around on army training areas - into the end of a bit of copper pipe, with the idea that when the banger powder in it detonated the case would take off with some velocity.

I never found the pipe.

Andy