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Post by PK on Nov 14, 2012 20:55:34 GMT
I'd imagine that even with a "wall of ice" (aka, the side of the block you drilled into) it wouldn't be particularly difficult to drill a touch-hole to insert the igniter through. Even if they didn't have a drill long enough, a heated rod of the proper diameter would do the trick. It might take some time and reheating, but it'd get there without much in the way of weakening the block.
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bioLarzen
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Post by bioLarzen on Nov 14, 2012 22:15:18 GMT
Couldn't the gunpowder be ignited the way it is ignited in a handgun's cartridge - not by a burning fuse, but by hitting it suddenly and hard enough? I mean, not the powder of course, but a sort of primer - but this way only the space around the primer and the powder should be kept dry - and I guess it would be an easier task than keeping the thing dry around a burning fuse...
bio
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Post by Cybermortis on Nov 14, 2012 22:35:50 GMT
You mean a percussion-cap system?
Copying the hammer system from a handgun would require building a metal mechanism, then drilling a large hole in the back of the gun. This would be a needless waste of time and money, as chances are not only would be be a great way to ensure the breach is going to fly apart it is likely to destroy the mechanism at the same time.
This would be eye wateringly dangerous. No explosives expert is going to put any amount of impact sensitive explosives inside a bag containing gunpowder - drop the bag and the resulting explosion is going to put someone in the hospital (ICU or Mortuary depending on how their luck holds). It is also dangerous because you'd end up with two projectiles - the shot and the mechanism, which will be flying out of the back of the gun at high speed.
Last there is the question as to how you'd trigger the system. Running wires or cables down the barrel is a none-starter. Apart from the it getting in the way of the shot there is a risk that yanking the cable is going to twist the gun away from what you were aiming at.
That means that the cables would have to run through the barrel wall, which would involve...drilling a hole in the barrel.
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Post by trakmec on Nov 15, 2012 2:43:09 GMT
Ok, think I might be able to help here. Eight years as a Sapper and a little bit of time playing with demo.
What they can use is a Non electric detonating system and whatever kind of firing system they want. Basically you have a predrilled hole in the breach of the cannon big enough to fit a blasting cap thru. When they’re ready to fire they place a powder bag and projectile down the muzzle, and then insert a nonelectric blasting cap already crimped and sealed onto a length of detcord into the firing hole. As long as it's touching the powder bag it'll set it off
From there they can connect a fuse and a cap for an initiating system, or tie into an electrically wired cap allowing for command detonation.
Safe, simple, no water issues, nothing unnecessary in the weapons bore, and if it misfires it’s easy to fix.
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Post by silverdragon on Nov 15, 2012 7:43:45 GMT
Ok, I have a "better" idea then... (the one I was thinking on anyway)...wired, drill a hole through the cannon at the back end, and feed the wires from the cartridge through that whilst loading, then attach to the switch gear...
I am presuming the cartridge will be loaded through the muzzle POST freezing and just before firing.
I wasnt thinking on a R/C detonator, but that does have its merits?...
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bioLarzen
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Post by bioLarzen on Nov 15, 2012 12:28:58 GMT
You mean a percussion-cap system? Copying the hammer system from a handgun would require building a metal mechanism, then drilling a large hole in the back of the gun. This would be a needless waste of time and money, as chances are not only would be be a great way to ensure the breach is going to fly apart it is likely to destroy the mechanism at the same time. This would be eye wateringly dangerous. No explosives expert is going to put any amount of impact sensitive explosives inside a bag containing gunpowder - drop the bag and the resulting explosion is going to put someone in the hospital (ICU or Mortuary depending on how their luck holds). It is also dangerous because you'd end up with two projectiles - the shot and the mechanism, which will be flying out of the back of the gun at high speed. Last there is the question as to how you'd trigger the system. Running wires or cables down the barrel is a none-starter. Apart from the it getting in the way of the shot there is a risk that yanking the cable is going to twist the gun away from what you were aiming at. That means that the cables would have to run through the barrel wall, which would involve...drilling a hole in the barrel. OK, it was just a thought, no need to kill me over that  bio |
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Post by Cybermortis on Nov 15, 2012 15:39:43 GMT
Sorry Bio, that came over as a little more aggressive than was intended.
Ultimately how the charge is ignited would have to be decided by the MB, probably after discussion with their explosives expert. However it is likely that they would pick the simplest option - which is just to use a spark to ignite the powder. All they would need is a long metal tube with two wires that will create a spark between them when an electrical circuit is completed. Simple, effective and above all safe. (It is more or less the principle behind electrical detonators, some of which use gunpowder)
My comments about damp powder were meant to warn MB about a problem that could occur if the powder is left to sit in the barrel for any length of time.
In all of the cannon myths they have tested to date they have never had to worry about leaving a loaded gun in place while they set up a shot or deliver lines to camera. Here they would need to be aware that they will need to fire the gun as soon after the fuse goes in as possible to reduce the chance of a misfire.
This is an issue both for safety and for their filming schedule.
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Post by The Urban Mythbuster on Nov 15, 2012 16:30:26 GMT
Could we put one provision on the ice cannon that would not be made of ice? Would it be permissable to put a small metal sleeve through the insertion hole for the fuse (on the cannon), as to lessen the chance of the fuse/powder getting wet?
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Post by PK on Nov 15, 2012 16:38:07 GMT
I may be mistaken, but I believe the electronic ignitor that they have used in the past comes in its own metal tube.
Is there any reason that they couldn't package the black powder in a zip-top plastic bag before placing it in the barrel? It would be a bit more difficult to pierce than the usual foil packing they usually use, but it seems like it would be workable and would go a very long way towards protecting it from the damp.
That way, they wouldn't need to be rushed to get the cameras set up, film the dialogue, etc. The only thing that would need to be done "last second" would be to insert a rod to pierce the bag, then insert the ignitor.
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Post by Cybermortis on Nov 15, 2012 16:48:47 GMT
Could we put one provision on the ice cannon that would not be made of ice? Would it be permissable to put a small metal sleeve through the insertion hole for the fuse (on the cannon), as to lessen the chance of the fuse/powder getting wet? I think that would be perfectly acceptable, in fact I think they used metal tubes in some cannon for the priming powder. |
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bioLarzen
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Post by bioLarzen on Nov 15, 2012 22:08:53 GMT
Could we put one provision on the ice cannon that would not be made of ice? Would it be permissable to put a small metal sleeve through the insertion hole for the fuse (on the cannon), as to lessen the chance of the fuse/powder getting wet? Well, I think an ice barrel would make an ice cannon, so some steel insertions that would not contribute to the ice barrel's strength and durability wouldn't do any harm. bio |
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Post by the light works on Nov 16, 2012 2:10:48 GMT
I would think a metal insert would count as firing mechanism, not cannon.
I'd drill a hole in the bottom of the breech, too - to let any meltwater drain.
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Post by Cybermortis on Nov 16, 2012 2:19:14 GMT
Not really, as I said I think cannon used a hollow metal tube filled with powder as a primer - a way to ensure that the power wasn't blown away and that the trail of power into that cartridge wasn't broken.
Standing water in the base of the breach shouldn't be a problem as long as the powder is contained in a waterproof bag/cartridge and the touch-hole is on the upper part of the breach. The problem would be the hole that needs to be punched into the cartridge to allow the powder to be ignited. This could allow moisture to seep into the powder, which in turn might render the powder inert - worse is that this would be happening with the powder around the fuse - meaning that the gun isn't going to fire.
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Post by blazerrose on Nov 16, 2012 2:55:38 GMT
It was posted two or three times on Disco, but seems to have been one of those good ideas that got missed or misplaced. And Blazer - What makes you think the researchers haven't already spotted this? As a Disco-posted idea they can use the basic idea as is. Covering all of my bases. ;D |
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Post by trakmec on Nov 16, 2012 5:20:57 GMT
Cybermortis: I really do think a nonelectric cap, or even better a demolition knot of some kind would do this job very well. Detonation cord with a standard demo knot like a Uli, triple roll, or double overhand in the end of it could be treaded thru the bore and out of the cannons vent.
It would not be affected by moisture and by its design the Det cord is stable and shock resistant until set off by a blasting cap. Once the crew was ready the cap could be connected to the Det cord just prior to firing, keeping the whole rig safe.
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Post by silverdragon on Nov 16, 2012 7:46:22 GMT
I have this idea,
Worth a think through, perhaps we can make it practical for them?...
I drive "The fridge" now and again, sometimes called Refers, bur Refrigerated wagons?...
Adam and Jamie have used one before, the Ice Boat.?
They do get rather cold. Minus 32degC comes to mind for one that I drove recently...
I am suggesting keeping the cannon INSIDE the container....
A few reasons, first, you can keep it at minus "something" to prevent melting, second, it will be an excellent "Blast shield" if the barrel suffers terminal failure?....
Thirdly it will prevent damage whilst unloading?...
I am thinking that why bother taking it out, open the doors, aim at something not important, and its going to be remotely fired anyway with a long firing cord or however they do it, so why NOT just leave it inside the container?...
Either that, or head to Canada in the cold season?.... Alaska even?....
I bet hiring a Refer van for a week is cheaper than the airfare to Alaska for the build team.
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bioLarzen
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Post by bioLarzen on Nov 16, 2012 12:00:40 GMT
I have this idea, Worth a think through, perhaps we can make it practical for them?... I drive "The fridge" now and again, sometimes called Refers, bur Refrigerated wagons?... Adam and Jamie have used one before, the Ice Boat.? They do get rather cold. Minus 32degC comes to mind for one that I drove recently... I am suggesting keeping the cannon INSIDE the container.... A few reasons, first, you can keep it at minus "something" to prevent melting, second, it will be an excellent "Blast shield" if the barrel suffers terminal failure?.... Thirdly it will prevent damage whilst unloading?... I am thinking that why bother taking it out, open the doors, aim at something not important, and its going to be remotely fired anyway with a long firing cord or however they do it, so why NOT just leave it inside the container?... Either that, or head to Canada in the cold season?.... Alaska even?.... I bet hiring a Refer van for a week is cheaper than the airfare to Alaska for the build team. That would be a great idea - if they can ley their hands on a fridge truck that they wouldn't mind risking destroying. If the cannon fired inside the fridge cabin explodes, I reckon it could render the cabin useless. But the guys have shown from time to time that they're good at finding equipment on the cheap, so, why couldn't they find a fridge truck that's OK to potentially destroy? bio |
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Post by Cybermortis on Nov 16, 2012 15:34:04 GMT
Cybermortis: I really do think a nonelectric cap, or even better a demolition knot of some kind would do this job very well. Detonation cord with a standard demo knot like a Uli, triple roll, or double overhand in the end of it could be treaded thru the bore and out of the cannons vent. It would not be affected by moisture and by its design the Det cord is stable and shock resistant until set off by a blasting cap. Once the crew was ready the cap could be connected to the Det cord just prior to firing, keeping the whole rig safe. The problem is that using a detonating explosive will increase the pressure in the breach, worse its going to be producing this pressure right within and around the weakest part of it - the touch-hole. Testing in a cold climate was put forward a few pages back. Firing from within a truck is a problem for the following reasons; The hope is that they will be able to build more than one cannon, possibly several out of different types of ice or at least so they have spares and could test fire the three types of propellent that could be used. If you are using the transport as the firing platform you could only use it to move a single cannon at a time, as if the gun does fail it will destroy the others if they are also being carried inside. And if you remove the spare guns they would start melting - which sort of defeats the reason for using a refrigerated truck in the first place. No one but no one who owns a large refrigerated truck (or large refrigerator) is going to let MB fire a gun within it. The chances of the unit being damaged in the process is far too high. Setting the gun up in such a confined space runs into a lot of problems. The foremost is safety - if anything goes wrong the only way to check the gun is to walk in front of it. The other major problem is the limited space in which to place camera equipment, and the real risk of that equipment being damaged or destroyed. The problem with the camera equipment is a significant one, as it not only means they risk loosing expensive equipment, but they may not get usable footage. |
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Post by silverdragon on Nov 17, 2012 9:54:45 GMT
Ok, TWO trucks..... one for storage, one for setting up and firing....
Old trucks need to go somewhere to die.
I am sure a "Second hand" sold-for-spares type fridge van could be sourced from somewhere....
Two trucks makes unloading on site easier... tail to tail is the same height and doesnt need a fork-lift?....
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bioLarzen
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Post by bioLarzen on Nov 17, 2012 12:21:52 GMT
... or, a regular container - the kind they destroy every now and then, like in the Hitler's assassination episode - could perhaps be turned into a freezer cabin temporarily with the use of a lot of ice?
bio
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