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Post by Cybermortis on Nov 3, 2012 14:12:59 GMT
In gaming circles a 'Glass Cannon' is a unit or class that can cause a lot of damage, but which is itself fragile.
But can this be taken literally? Could you really make a working cannon out of glass?
On the face of it the answer is no, but investigation into the strength of various types of glass seems to show that this might not be impossible. Some types of high end glass show practical strengths equal to some types of cast iron, and these types of iron were used to create early European cannon.
So the important factor might not be the glass, but the gunpowder being used. This might allow you to build a glass cannon that would survive being fired...at least once.
Cannons, Mythbusters, the chance of a spectacular explosion and no clear cut answer....seems ideal to me.
Information and comments?
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Post by memeengine on Nov 3, 2012 14:19:38 GMT
Could you really make a working cannon out of glass? A key factor would be how many times it has to work? If it only had to fire once, it sounds entirely possible (if not particularly practical). |
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Post by Cybermortis on Nov 3, 2012 14:32:17 GMT
I'd say it only has to be capable of being fired once, although for some reason I suspect that if it works once it may be capable of firing two or three times before failing. (No idea why I think this).
Of course we all know they are going to test this thing to its destruction even if they get it to fire anyway....
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Post by flippons on Nov 3, 2012 14:52:41 GMT
Some time ago on TV, I saw a car (I seem to recall it having an approximate mass of 1 metric ton) being suspended from a glass rod. Obviously, that will involve different forces to being used as a cannon, but it's still pretty good for a piece of glass!
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Post by memeengine on Nov 3, 2012 15:11:10 GMT
While I'm thinking about it, would a glass pistol be sufficient as a proof of concept? I suspect that even a small glass cannon would be fairly costly to manufacture (especially if they didn't get it right the first time).
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Post by Cybermortis on Nov 3, 2012 15:39:32 GMT
I should have stipulated that 'Cannon' would not mean something 9 feet long and capable of firing a 18 pound iron ball.
I'm thinking more along the lines of a 14/1500's cannon or a swivel gun from the 1700's. These were about 3 feet long and fired one pound shot - much more manageable to create and move around. (Tori's 'cannon' is not a suitable design, its a carronade not a cannon).
They could test various designs out using other materials with known stress levels, as well as performing similar tests to work out the amount of pressure different types of powder produce, in small scale. They should also be able to do small scale tests with small glass cannons in the bunker before moving onto building the full scale cannon.
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Post by memeengine on Nov 3, 2012 17:30:27 GMT
I'm thinking more along the lines of a 14/1500's cannon or a swivel gun from the 1700's. These were about 3 feet long and fired one pound shot - much more manageable to create and move around. Just for the avoidance of doubt, I take it that a "working" glass cannon would be expected to have a muzzle velocity within the same order of magnitude as a brass or iron one of equivalent size? For example, it wouldn't be considered a success if the amount of powder that could be safely used only caused the ball to dribble out of the muzzle. |
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Post by Cybermortis on Nov 3, 2012 17:50:08 GMT
Probably be best to classify a successful test as one in which the cannon can fire a shot at a lethal velocity without being destroyed in the process.
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Post by chriso on Nov 4, 2012 4:13:44 GMT
Also should define glass. Fiberglass, for example, you could almost certainty make a cannon out of while crystal would be a more unlikely candidate. Don't know enough to offer a concrete definition though.
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Post by craighudson on Nov 4, 2012 10:26:17 GMT
So-called fibreglass is actually a composite material consisting of glass in a matrix, so it's not itself glass.
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Post by memeengine on Nov 4, 2012 11:10:10 GMT
I'd agree with craighudson that fibreglass is essentially as much plastic as it is glass so it falls outside the spirit of the 'glass cannon' idea. However, chriso does raise a valid question of exactly what type of glass we're willing to allow. The scientific definition of what can be termed glass is wider than its general public usage would suggest (which normally refers to soda-lime glass).
While the 'glass cannon' is usually pictured as an old fashioned smoothbore, the concept itself seems to be a comparatively recent one (growing out of wargaming) so from an 'authenticity' point of view there's no reason not to allow the latest in glass technology.
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Post by Cybermortis on Nov 6, 2012 19:39:30 GMT
I think in this case MB would need to talk to an expert in regards the properties of different types of glass to find what types may have comparable strength to cast iron. Apart from anything else they would need to know what types are likely to be available, and how much it would cost them to use.
Chances are they would be limited to what is available in the local or near-local area.
No reason they couldn't try for fibreglass I guess, although in this case (and with an eye for a potentially awesome visuals) I'd say that whatever they use has to be transparent so the inside of the cannon can be seen.
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bioLarzen
Demi-Minion
"I reject your avatars and substitute my own."
Posts: 86
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Post by bioLarzen on Nov 8, 2012 12:11:43 GMT
This is a test where the biggest difficulty might be the safety precautions. If a glass cannon exoplodes when fired, it would act like a ginormous frag grenade, sending potentially lethal glass shards in every directions, with alarming velocity and energy. I'm not at all sure the guys' usual safety screens would be enough to protect them...
But, I guess, this is an issue they can deal with if that's the only thing that would keep them from doing this myth.
bio
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Post by Cybermortis on Nov 8, 2012 14:04:17 GMT
Agreed on the safety aspect.
When I originally posted this I suggested that rather than use the bomb range, it might be safer if the tests were conducted indoors.
One of the reasons for thinking this was that large chunks of glass might prove a hazard on the bomb range if they get scattered over the road leading to their testing area.
It would be a lot easier to recover the glass shards if they are contained within a building - and they could always sell the bits on EBay for charity. (Who wouldn't want a chunk of glass cannon as a paperweight?)
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Post by trakmec on Nov 8, 2012 14:53:12 GMT
Well shouldn’t the amount of explosive propellant used give you a safe standoff distance? If it did have a catastrophic failure the mass or velocity of the glass shouldn’t be much different then fragments from other similar sized explosions they’ve done.
In fact I would expect the glass to fragment more producing smaller pieces in general. The ballistic shielding they use should be capable of dealing with it, at the appropriate standoff. Inside of a building you risk rebounding and secondary effects.
cybermortis: excellent idea auctioning off some of the fragments. There may be a small problem with it. I do not know about glass, but steel fragments are often wickedly sharp. If the glass produced similar edges they might hesitate to sell jagged razor blades to the general public, then again it may be a non issue.
I know I'd love to have something from one of the myths.
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Post by Cybermortis on Nov 8, 2012 15:19:01 GMT
Just because the cannon is inside a building doesn't mean the cast has to be.
The problem with glass fragments is that we have no idea what size they are likely to be. We don't know how thick the barrel is going to be and if the key to getting this to work really rests with using earlier gunpowder formulations we are adding in another unknown. I know that during filming of a British TV program on Guy Fawkes even the experts were surprised by how strong a blast they got from detonating a simple wooden barrel of powder.
Here we are dealing with both a powder and barrel who's interaction is going to be difficult to predict. Meaning that they would probably not be able to tell exactly how large an explosion they might get, or how the cannon would fail - it may shatter into millions of small pieces or a smaller number of large chunks.
The concern is not that these would prove dangerous to the cast and crew, but that they could end up with razor-sharp chunks of glass scattered over the access road to the testing area. This would make the location unusable by vehicles or people until or unless these chunks were removed - which could take days.
Indoor testing however means that all the glass would be confined to a known area regardless of the force of the blast, and could be swept up in an hour or less.
The point about the glass being razor sharp, and therefore unsuitable for selling on, might not be a problem as the sharp edges could be ground down before the are put up for sale.
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Post by The Urban Mythbuster on Nov 8, 2012 15:56:16 GMT
For the purpose of testing this. the modified shipping container they keep outside the building and have used for other ballistics myths should suffice to keep the people/surroundings safe.
As far as glass goes, I saw a documentary about the Presidential limo ("The Beast") which discussed the (over)engineering that goes into making POTUS safe. Part of that was an extra thick ballistics glass. I remember it was glass, not plexi or fiber. Perhaps that would be a start.
Though, there probably is a chance that the glass and it's construction is classified in order to keep the "wrong people" from obtaining and finding ways to defeat it. Possibly, the manufacturers would release some to the MBs for "scientific research."
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Post by the light works on Nov 8, 2012 15:58:06 GMT
or cast in resin - which would give a relatively uniform shape.
It is not the big chunks that would be the safety hazard - those could easily be hand picked - it is all the spalling that would occur, and as said, it would be much easier to sweep up an entire bunker than to risk having someone later on drop a knee (or a knee of a several hundred dollar safety garment) onto a missed fragment.
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Post by The Urban Mythbuster on Nov 8, 2012 16:45:03 GMT
One thing to take into consideration when thinking about making a glass (or ice) cannon would be the practicality of it. Essentially, the cannon might need glass walls that are six inches or greater thick. Even if it's only a 3 feet long, it would be a lot of weight. The greater the weight, the greater chance it is dropped, broken, and never actually tested.
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Post by Cybermortis on Nov 8, 2012 17:32:02 GMT
For the purpose of testing this. the modified shipping container they keep outside the building and have used for other ballistics myths should suffice to keep the people/surroundings safe. From the glass sure...but what about the cannonball - even a one pound shot would have no real trouble punching its way through the bunkers side and probably through the wall behind that. If they decide to do some small scale tests to find a usable design/glass before building the 'full-sized' cannon then the bunker would be fine. But considering that they once managed to put a hole through the back wall of M-6 using an air cannon, and if this works it would be several orders of magnitude more powerful than that, then testing in the bunker is a definite no-no. |
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