|
|
Post by ironhold on Jul 24, 2014 15:17:58 GMT
This one's come up before, including at least one "Roadrunner & Coyote" cartoon and Twisted Sister's video for "I Wanna Rock".
The set-up is as follows:
Someone is looking to plant dynamite in order to take someone out. For some strange reason, however, they have the dynamite wired up to the detonator before attempting to plant it.
While they are gone, a butterfly or moth lands on the plunger. The weight of the insect is just enough to cause the plunger to start sliding down into the detonator. The detonator triggers, causing a nice, big "Boom!" with the someone getting blasted instead of their target.
But could an insect so light be enough to cause a properly-maintained plunger to drop?
I figure that a detonator box could be rigged up to something like a light bulb if it's the kind to generate an electric current. The team could then use a rig of some kind to carefully lower weights onto the plunger until they cause it to either slide in on its own or get pushed down by the weight.
|
|
|
|
Post by the light works on Jul 24, 2014 16:07:33 GMT
This one's come up before, including at least one "Roadrunner & Coyote" cartoon and Twisted Sister's video for "I Wanna Rock". The set-up is as follows: Someone is looking to plant dynamite in order to take someone out. For some strange reason, however, they have the dynamite wired up to the detonator before attempting to plant it. While they are gone, a butterfly or moth lands on the plunger. The weight of the insect is just enough to cause the plunger to start sliding down into the detonator. The detonator triggers, causing a nice, big "Boom!" with the someone getting blasted instead of their target. But could an insect so light be enough to cause a properly-maintained plunger to drop? I figure that a detonator box could be rigged up to something like a light bulb if it's the kind to generate an electric current. The team could then use a rig of some kind to carefully lower weights onto the plunger until they cause it to either slide in on its own or get pushed down by the weight. you are correct that the plunger style detonator has a small electric generator in it - which leaves me dubious that a butterfly could generate enough current to set off the cap. it also means that it has good potential to be on the show. I think it needs to have something a little more positive than just a light bulb, though. I'm thinking along the lines of the rig for toaster in the bathtub myth - something that fires off at the correct amperage, but small enough to use in the shop. |
|
|
|
Post by Cybermortis on Jul 24, 2014 16:54:09 GMT
From what little I can tell, it seems that the plunger type detonator had to be charged up by rotating a small wheel to create the charge that set off the explosive. This step seems to be ignored in a lot of films/TV shows, although I seem to recall some cowboy films correctly having the user wind the handle at the side before using it.
I'd guess that later versions might well have used the downwards movement of the plunger to create a charge on its own.
If they wanted to test this I think that rather than just using a lightbulb of some type, they could instead have the ends of the wires leading into a small amount of blackpowder in a bin-lid. If it works they would get a small 'poof' and a cloud of smoke which would be more visually interesting.
Isn't there a related trope where this type of detonator is dragged by the cables until it catches on something that results in the plunger being depressed?
|
|
|
|
Post by ironhold on Jul 24, 2014 17:57:19 GMT
This one's come up before, including at least one "Roadrunner & Coyote" cartoon and Twisted Sister's video for "I Wanna Rock". The set-up is as follows: Someone is looking to plant dynamite in order to take someone out. For some strange reason, however, they have the dynamite wired up to the detonator before attempting to plant it. While they are gone, a butterfly or moth lands on the plunger. The weight of the insect is just enough to cause the plunger to start sliding down into the detonator. The detonator triggers, causing a nice, big "Boom!" with the someone getting blasted instead of their target. But could an insect so light be enough to cause a properly-maintained plunger to drop? I figure that a detonator box could be rigged up to something like a light bulb if it's the kind to generate an electric current. The team could then use a rig of some kind to carefully lower weights onto the plunger until they cause it to either slide in on its own or get pushed down by the weight. you are correct that the plunger style detonator has a small electric generator in it - which leaves me dubious that a butterfly could generate enough current to set off the cap. ...unless, perhaps, the detonator was poorly-maintained and so was worn enough that any weight would cause the plunger to fall down. |
|
|
|
Post by GTCGreg on Jul 24, 2014 18:03:23 GMT
Those plungers are pretty hard to push down as they do turn a small generator so I doubt anything short of a very large bird would move it. That said, why connect it to a light bulb? Come on, this is Mythbusters after all. Connecting to nothing short of a dozen sticks of dynamite is what's called for.
|
|
|
|
Post by OziRiS on Jul 25, 2014 0:07:21 GMT
From what very little I've had to do with these plungers, I seem to recall that some of them even require you to first pull the plunger up a couple of inches before pushing it back down.
Can anyone confirm that?
|
|
|
|
Post by the light works on Jul 25, 2014 0:10:06 GMT
you are correct that the plunger style detonator has a small electric generator in it - which leaves me dubious that a butterfly could generate enough current to set off the cap. ...unless, perhaps, the detonator was poorly-maintained and so was worn enough that any weight would cause the plunger to fall down. but you still have the counter EMF of the generator. |
|
|
|
Post by c64 on Aug 4, 2014 16:31:13 GMT
Those "plunger type detonators" work just like those inexpensive dynamo torches.  The up and don action drives a cogwheel into one direction. A series of more cogwheels transform torque into speed which is then stored in a flywheel and using another gear to speed up even more fed into a generator. This is the electric motor in this case. Inside the a classic detonator, the same happens, just with a much longer bar driving a cogwheel. here the torch has the flywheel, the old detonators had a huge, heavy but for modern standards very weak magnet. The magnet rotates inside a coil and creates an AC current. The AC current then feeds a light-bulb like filament inside a blasting cap filled with a very sensitive explosive. When enough electric energy is fed into the blasting cap heating it up just enough, the cap explodes which in turn ignites the actual explosives meant to do business. That's why those blasting caps are in fact much more dangerous than the actual explosives. Unlike the actual explosives, they are meant to blow up easily. And they have a very big blasting potential them self. On July, 7th in 2005, terrorists tried to blow up a bus. Fortunately, they failed to build a decent bomb and the blasting caps were unable to ignite the actual explosives. But the blasting caps them self were potent enough to destroy the bus:  Pressing don the plunger converts mechanical energy into electrical energy. The potential energy of the plunger itself and a butterfly are nowhere close to the energy required to activate the blasting caps. You need to press the plunger dwon real hard and fast in order to heat up the blasting caps enough to ignite them. Slowly lowering the plunger won't create any significant amounts of electric energy. Remember, magnets back then were very weak and bulky. You need a decent RPM to induce a good current. And to reach this RPM, you need a lot of torque on the first cogwheel which requires a lot of pressure on the plunger. For the early plunger detonators, you had to lean over it and push down with as much of your body weight as possible to make sure it works at the first try. I am no expert for those things, but from playing with one, I'd estimate that you need at least 30LBS of pressure to generate a decent amount of electric energy in time. That's why more modern systems use a clockwork spring to ease operation. And even this wasn't really good enough since you had to crank up the spring for a long time to set the detonator. That's why modern systems charge a capacitor to release a lot of electric power all at once to make sure it works. |
|
