pykrete cannon?

Here’s one for y’all; could a functional cannon be made out of newspaper pykrete??

(First off, let me say that this thread is NOT meant for anybody to get the bright idea to actually try this. It is meant to just stimulate discussion.)

That being said, here is some info I found online. The first two I would need somebody a whole lot smarter than me to interpret, but it looks like pykrete is pretty tough. The printed material kind of supports it (I think).

http://www.researchgate.net/publicat...ow_temperature

http://w.andreasbastian.com/pykrete/...nal_report.pdf

Ballistic History: Bullet Resistant Barriers From Ice And Sawdust
SEPTEMBER 25, 2012 BULLET RESISTANT BARRIERS
During WWII Geoffrey Pyke–a somewhat eccentric British journalist and inventor–had what, at first glance, was a crazy scheme: To supplement the British Navy with floating, bulletproof iceberg islands.
Allied navies and merchants were sitting ducks for advanced German submarines. Pyke envisioned “berg-ships” up to 4,000 feet long, 600 feet wide, and 130 feet deep, made from forty-foot blocks of ice. They’d be slow-going ships, but their extremely thick, naturally buoyant hulls could endure lots of bullets and torpedoes. And, unlike steel vessels, they’d be floating in a sea of raw material ready for repairs or expansion.
THE CHALLENGES OF BUILDING BULLET RESISTANT BARRIERS FROM ICE
Of course, there were a few hitches in this plan. Obviously, icebergs–even enormous ones–don’t hold up well as they travel south, and even a very large burg can be steadily chiseled away by a concerted barrage. Worse yet, ice is a very unpredictable building material; it fails at loads ranging from 5 to 35 kilograms per square centimeter (kg/sq-cm).
But Pyke had stumbled on a possible solution. He’d discovered that by adding impurities to water–such as sawdust–he could significantly improve the material qualities of the finished ice.

2 Million Ton Pykrete Aircraft Carrier In WW2 – The most popular videos are a click away
BULLETPROOF BLOCKS OF ICE
Through grueling hours working in an undercover meat-locker laboratory, Pyke and a team of military researchers discovered a mixture of water and sawdust that, when frozen, was as strong as concrete, could be preformed as easily as ice cubes, and could be worked with hand tools like blocks of wood. One scientist on the project, Max Perutz (who would later go on to win the Nobel Prize for Chemistry in 1962) wrote:
“Blocks of ice containing as little as four percent wood pulp were weight for weight as strong as concrete; in honor of the originator of the project, we called this reinforced ice ‘pykrete.’ When we fired a rifle bullet into an upright block of pure ice two feet square and one foot thick, the block shattered; in pykrete the bullet made a little crater and was embedded without doing any damage.“
Pyke ultimately settled on a mixture of 14 percent sawdust and 86 percent water (by weight). The sawdust significantly lowered the material’s thermal conductivity, which meant that once the outer layer melted slightly and went mushy, it functioned as an insulating jacket, helping to keep the pykrete core frozen solid. These opaque, tan blocks consistently held loads of 70 kg/sq-cm, and were almost uncrushable (a one-inch column could easily support an automobile). A bullet resistant barrier made from pykrete performed as well as brick against small arms fire, and even high-powered rifles. But the real selling point: Not only was pykrete easy to make and form with conventional tools, it was cheap.

PYKRETE BULLET RESISTANT BARRIERS
As is the case with conventional bullet resistant barriers–like steel and DuPont™ Kevlar® fiber–the secret to pykrete’s power is in its tensile strength, which is nearly three times that of poured concrete, and five times that of conventional ice. A 7.69 mm rifle bullet fired at pure ice will shatter most blocks (due to the material’s brittleness). Even if you had one of Pyke’s 40-foot blocks, a rifle shot would still burrow more than a foot into the ice. That same bullet fired into pykrete won’t make it more than six inches.

A six-inch thick ice-wall might seem a little inconvenient–especially if you’re building a bank in Georgia–but it’s hard to beat the price. And don’t worry if you don’t happen to live near a lumber yard willing to part with hundreds of pounds of sawdust: In 2009 MythBusters Jamie Hyneman and Adam Savage experimented with “super pykrete” made with newspapers instead of wood pulp. It performed even better than Pyke’s final formula.

ISTR that they tried leather cannons (actually, a piece of thin copper tube reinforced with layers of leather) back in the thirty-years war; but that the disadvantage of limited durability more than outweighed their advantage in maneuverability. But hey, if all you need is a single shot, go ahead! :slight_smile:

I don’t think so. Tensile strength to prevent bursting is what counts in cannons. The tensile strength of Pykrete is only 700 psi. Steel used for a cannon would have a tensile strength of tens of thousands of psi at a minimum and modern ones use steel like 4140 approaching 100,000 psi.

Now Pykrete made from carbon fiber might work if the fibers were long enough.

Dennis

The original Mythbusters did ice, leather, bamboo and wood cannons. All worked to the extent that it would fire a projectile, but the ice cannon failed when they increased the powder charge to get the projectile fast enough to cause damage to the target. Only the wood cannon was considered strong enough to withstand multiple firings and they finally got it to fail by plugging the barrel.

As mixdenny stated, the key is tensile strength. Pycrete may be as strong as concrete, but it’s still far below steel or iron. You can break shatter concrete or pycrete with a hammer, but properly tempered steel or iron will just dent.

But wouldn’t the longer fibers of the newspaper be stronger than regular pykrete? I know there wouldn’t be any chance of regular sawdust/woodchip pykrete surviving, but I’ve seen newspaper pykrete take a .30 cal hit and not shatter.

The Mythbusters did it again! They made a boat of newspaper pycrete because it was much stronger than regular sawdust pycrete. Drop test video here: https://www.youtube.com/watch?v=UMKis4FPykw

As I think about it, why not a fiberglass or paper mache cannon made with newspaper? Interlacing the newspaper horizontally and vertically (switching the grain of the paper), would increase the strength dramatically. Strong enough to be a multiple use cannon? Probably not.

Oh…just remembered, they did a duct tape cannon too. As I recall, it survived multiple firings.

You can overcome a deficiency in material strength just by making it thicker. Of course, you’re not gaining anything in affordability or maneuverability, but if you’re just trying to show that it can be done, it should work.

What could be cheaper than old newspapers and water? The real trick would be what to mold the newspapers around to form the barrel? PVC pipe with something sprayed on it as a release once the thing’s frozen would probably do it??? A long skinny nail in the pipe to form a fuse hole would also work I suppose. Wrap the thing in saran wrap to hold its shape while freezing. Have I missed anything?

Make a thick enough barrel wall and it will fire at least once. How many times is questionable because even if it can contain the pressure the interior wall of the barrel may degrade rapidly.

Newsprint doesn’t have long fibers. Most any kind of woven cloth should do better.

The explosive used makes a difference. Cast iron cannons were mostly fired with black powder, steel was needed for higher order explosives. Give it a long barrel and and just some fuel like propane or gasoline and you’ll end up with much lower pressure in the barrel than explosives.

Kind of like a potato gun, sure. But if it were me, I’d want to give it a try with black powder. As for a projectile, I’d probably want to start with a golf ball (I always hated golf anyway). I’d give it a good long fuse so I’d have enough time to get behind something good and solid before the thing went off of course. I’d have to get a good camera to record the event. Man, my wife would have a fit!