Post questions and info about things you have launched or thought about launching. No posts about explosive projectiles!

Postby Navigator7 » Fri Jan 19, 2007 3:21 pm

Very nice BLB! Good job.

What happens when this mixture sets in the sun.

I'm not stupid....Just asking.

Also...what is your opinion .....if instead of pulp, shredded plastic bags like the kind at the grocery produce department were substituted for pulp?
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Postby Mr.Plow » Fri Jan 19, 2007 3:29 pm

<blockquote id="quote"><font size="1" face="tahoma,verdana,arial" id="quote">quote:<hr height="1" noshade id="quote">
Also...what is your opinion .....if instead of pulp, shredded plastic bags like the kind at the grocery produce department were substituted for pulp?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
perhaps answered by:

<blockquote id="quote"><font size="1" face="tahoma,verdana,arial" id="quote">quote:<hr height="1" noshade id="quote">I doubt it would make much of a difference using non-porous materials, simply because frozed water does not have the adhesive properties of dried concrete...<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
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Postby boilingleadbath » Fri Jan 19, 2007 4:42 pm

Nav, the pycrete (well, the ice portion of it) eventualy melts, leaving a lump of very soggy paper pulp which is entirely unsuitable for use as a projectile.
This is a bit slower than the melting of pure ice, but it happens just the same.

(if you where refering to the unfrozen material... well, it gets warmer, and a bit drier. Pretty boring.)

...and I've never tried it, but Mr.Plow's prediction is probably correct - and anyways, HDPE is pretty stretchy, so I wouldn't expect it to add much strength.
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Postby benstern » Fri Jan 19, 2007 5:03 pm

I remember pykrete being mentioned as projectiles for spudguns...
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Postby userjjb » Fri Jan 19, 2007 10:56 pm

It would seem to me that using sawdust like originally suggested would yield the best results. Pykrete is a composite material with a dispersed phase of cellulose and a matrix of ice, a so-called particle reinforced composite.

Ice by itself is a brittle material with limited tensile strength and passable compressive strength. However with the addition of particulate cellulose (sawdust), a reinforcing effect is achieved as the dynamic or static loads are distributed evenly by the ice matrix onto the particulate.

The wiki says that pykrete has an estimated compressive strength of 21 MPa, some comparisons:

Pykrete 21 Mpa
Concrete 14-42 MPa
Steel 250 MPa
Wood 5 MPa

Of course for the use as a projectile impact strength is more important, however I can't find any data for that. One intereting thing to note is that ice can deform plastically under dynamic loads despite it's brittleness, which would make for some interesting impact results I think.

Some links I found useful:
<a href=""></a>
<a href=""></a>

I think I'll have to do some experiments. I'd be interested to compare ice, pykrete, and a pseudo-pykrete using long hydrophillic fibers (hemp/cotton). I think the pseudo-pykrete while more difficult to make might be more resillient than traditional pykrete.
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Postby spuzi14 » Fri Jan 19, 2007 11:17 pm

Cool, I have a crapload of I just need a new spudgun.
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Postby BewareOfDog » Fri Jan 19, 2007 11:41 pm

fmj, you're brilliant! 8)

For the past several days, I've been wondering about the construction of a "bowling ball" mortar. - Trouble is:

<li>Where to find 8-1/2" pipe?</li>
<li>Cost/Availability of bowling balls</li>

Now, I can easily make some 6" <b>pycrete</b> balls and take advantage of this cold weather out here. - Thanks again, for bringing this up!
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Postby jimmy » Sat Jan 20, 2007 12:12 pm

DR, remeber <a href="">this</a>?
I love the prose;
<i>Three ounces of Pyrodex, an old garage-sale-special bowling ball, an old chair and some sewer pipe... Fire in the hole!
I'll be over here where it's safe...
He's not running, but he ain't dawdling either! Let's see, the fuse burns at about one minute per foot, there's about six inches there... dum da dum... carry the three...
Let's do that AGAIN!</i>

Here's <a href="">another</a>.
I didn't realize there was a "<a href="">World Championship</a>" for chucking bowling Balls. Heck, it's even close to where I live.
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Postby benstern » Sat Jan 20, 2007 2:29 pm

Hmmm, seems that most of them are simply gas cylinders with the end cut off.

here are some topics mentioning pykrete: ... IC_ID=9466 ... IC_ID=7487
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Postby Duodec » Sat Jan 20, 2007 5:37 pm

There was a story about one of the supporters of the project. In front of a group of naysayers who were dubious about pycrete's strength, he wheeled in 2 carts, one with a block of ice and the other a block of pycrete. To the astonishmet of those gathered, he then brandished a pistol from his coat and fired two shots, one into each block. The ice block shattered and the second bullet bounced off the pycrete block.

It sounds like a Mythbusters episode, but if thats the kind of strength it has it would be ideal for ammo, spitballs on steroids!
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