Every time they demolish a building by implosion, all the top experts are called in to use the most hi-tech gadgets & latest explosive charges. Recently it was a sports stadium somewhere as shown on the evening news. The first screen shot was the man pushing the plunger & then cut to the shot of the stadium falling in on itself.
The only thing can come up with is that the mechanical action of the plunger starts a small generator spinning that produces the current needed to set off the charges. But why not just use a battery, or local power?
Isn’t the plunger a romantic image of days gone by? You’d think they could just push a button or something. Heck, why not go back to lighting a mile-long fuse, or a trail of gun powder a la Bugs Bunny.
Another WAG, the plunger is just for the cameras since that’s what people expect to see. I thought the safety factor was handled by not hooking the wires up to whatever switch that is used until just before detonation. Also IIRC someone won a contest and got to push the plunger on the sports stadium (you are talking about the Kingdome, right?), pushing a plunger is a little more dramatic than flipping a switch.
Northern Ontario is largely rock (Canadian Shield), and any time we put a pipeline in the ground there, we have to blast the trench for it. Use of electric detonators was discontinued years ago because of the fears of stray electrical charges (static, etc.) setting off the charges prematurely. What we use now is called primer cord, which is essentially a very thin tube filled with explosive/flammable powder (I assume it’s gunpowder, but frankly I’m not a blasting hand so I can’t be sure.)
I don’t know why building demolition is still done with electric detonators. You’d think there’d be more stray charges from radio broadcasts, etc. flying around the city. I’d guess that part of the reason for still using the plunger is because it looks better on film (more romantic.)
When it’s a contest winner, the plunger often isn’t even attached to anything. There’s a guy from the demolition crew standing next to the real box somewhere else who flips off the safety and presses the switch at the same time as the winner pushes the plunger. No one knows the difference.
I think it was the sports (baseball/football) stadium in Pittsburgh, whatever it was called.
I was bummed out when they imploded the Arlington County Courthouse (Arlington, VA). My apartment was only two miles away, and atop a ridge, as was the courthouse. I didn’t realize the demolition was impending, but I was up reading at 7 am on a Saturday. Then at what must’ve been exactly 7, I heard a distant rumbling, like a train being coupled or a thunderstorm.
Later in the day, I had the county information channel tuned on the TV (text messages mixed with pictures and jazz playing in the background). They showed two or three pictures in a row of the courthouse as it went down. They also had a timestamp on it, so then I realized what I’d heard. If only I’d known, I would’ve driven over to watch. :(:(
Just had a WAG myself - maybe the plunger is more of a pump, and the wire is actually a thin length of tubing. This setup removes everything electrical from the detonation circuit, reducing the likelyhood of stray magnetic fields or static charges being picked up by a mile-long conductor will set off the charge by accident.
Something like the squeeze-bulb used by photographers to trigger the shutter on a camera that is several hundred feet away (used to have one myself).
