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expanding foam

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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expanding foam

Unread postAuthor: soap » Mon Aug 29, 2005 8:17 pm

im new here, so i havnt gotten aroudn to reading through all the post, though i have read many. i have yet to see anything about expanding foam being used to make sabot's. has any one ever tried this?

i plan on making pvc "rockets" (no propelent) with solid copper nose cones, and plastic fins. i then plan to put one of these in a short section (the length of the rocket) of 2" pvc pipe so that the rocket is standing up. then simply fill with expanding foam (the 2 part stuff) let that dry then cut it down the middle then cut the two halfs of foam into halfs again. i iwll then put the peices back together with the rocket back inside. wrap the whole thing in a few peices of very weak paper tape and then tape a small piece of round cardboard to the bottom.

i should then be able to fit this in my 2" barrel. when it shoots the foam will be ripped off by the air and the rocket will break free. a perfect fit for a projectile with fins.

any ideas? anyone ever try this? wil;l it work? in the future if this simple design works out, i plan on taking about 8" of 3/4" pipe and putting endcaps on both sides after filling it with some pyro mixture . drill a small hole in the center of one end cap large engouth to snuggly fit a shotgun shell primer... glue the primer in. glue a heavyduty normaly open spring on the endcap with the primer. attach a nail to the back of the copper nozzle, and glue the nozle to the spring. ad fins and i have a accurate explosive round... of course these would be used in non violent ways, on my property were no one will get hurt...
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Unread postAuthor: sergeantspud2 » Mon Aug 29, 2005 8:59 pm

the sabot sounds like a good idea. Mythbusters on discovery channel used a foam sabot for their chicken gun and it worked pretty well from what i could tell. i don't think you need paper to hold it together because the barrel would do that. where do you get the foam? and about the expolsive on the bottom i think thats against fourm rules
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Unread postAuthor: soap » Mon Aug 29, 2005 10:48 pm

oh sorry about the explosive idea, i did not realize that it was agains the ruels, in wich case i will not talk about that fantastic idea anymore.

the paper tape is to hold the sabot together while its not in the gun. the gun i am making is going to be a breach loader and id like to be able to reload rocket after rocekt after rocket without having to assemble each sabot first.

i bought the expanding foam at a store called TAP plastic here in the bay area, though im sure that there are hundreds of places to buy it online. yes its the same thing they use in mythbusters. 2 parts, you mix em they foam up in a matter of second and then it takes like 20minutes for it to dry
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Unread postAuthor: Weasel » Sat Sep 03, 2005 11:04 pm

that sounds so sweet lol i hope it works, and if not its still briliant!
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Unread postAuthor: boilingleadbath » Sun Sep 04, 2005 12:09 am

I didn't use expanding foam, but I have made a multi-piece paintball sabot. (lesson learned: multi-piece sabots are a pain to collect after a shot) Essentialy the same meathod; dremmled out a hemisphere, used razor saw to cut into quarters.

As to shooting heavier objects: Sabot collapse. It's bad. Basicaly, your projectile, due to the force caused by the acceleration, is pushed through the sabot... mostly a problem with heavy/pointy objects, but I'v had this happen with my (single piece; not the before-mentioned) [polysyrene foam] paintball sabot. (or more accuratly, that the sabot is forced into the projectile, damaging the sabot)

Something you might want to keep in mind.
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Unread postAuthor: Devilsmed98 » Wed Sep 07, 2005 5:57 pm

sounds like it can work. the chicken on myth busters launched just fine. I think that the rocket may be a bit unbalanced with the copper head.
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Unread postAuthor: Spudlightyear » Wed Sep 07, 2005 6:37 pm

yea the copper is a tad to heavy for this try aluimum light and sturdy
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Unread postAuthor: boilingleadbath » Wed Sep 07, 2005 6:56 pm

"may be a bit unbalanced with the copper head."
Ah... you may want to read up on some aerodynamics; no offence ment.

Basicaly, you want a heavy front if you want your dart to be stable. I'm being lazy, and am unwilling to go into the details of why, so just belive me... or use google or something. *yawn*

edit: on the other hand, copper is a bit expensive. I'd use steel or somesuch.
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Unread postAuthor: Devilsmed98 » Wed Sep 07, 2005 6:59 pm

boilingleadbath wrote:"may be a bit unbalanced with the copper head."
Ah... you may want to read up on some aerodynamics; no offence ment.

Basicaly, you want a heavy front if you want your dart to be stable. I'm being lazy, and am unwilling to go into the details of why, so just belive me... or use google or something. *yawn*

edit: on the other hand, copper is a bit expensive. I'd use steel or somesuch.


o i thought wrong i was thinking a slow home made missle in my mind going going then head first into the ground. but launching at high speeds would make it better because it would make it more stable. srry for the confusion
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