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Plague damage preview

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Plague damage preview

Unread postAuthor: c11man » Wed Jun 02, 2010 10:30 pm

so Plague is operational but not painted and pretty so i havent posted it yet. also i havent had a chance to take it anywere so i am stuck shooting only empty pop cans because i am in town. the following is a result of one of those shots
<a href="http://s696.photobucket.com/albums/vv321/c11man/New%20Plague/?action=view&current=104_9983.jpg" target="_blank"><img src="http://i696.photobucket.com/albums/vv321/c11man/New%20Plague/104_9983.jpg" border="0" alt="Photobucket"></a>
yes i managed to spit a soda can in half with minimal dage to the can.

now who can guess how i did it?
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Unread postAuthor: D_Hall » Wed Jun 02, 2010 10:37 pm

Not knowing anything about the cannon... I'll guess that you shot an empty soda can at an axe head or similar.
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Unread postAuthor: jor2daje » Wed Jun 02, 2010 10:39 pm

i think you filled it with water and shot the other side, hydrostatic shock sheared the can almost perfectly course dhalls idea makes sense too. Cant wait to see your cannon.
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Unread postAuthor: c11man » Wed Jun 02, 2010 10:44 pm

D_Hall wrote:Not knowing anything about the cannon... .


my bad :D
Plague is a 4inch piston, 3inch porting, 1800 cubic inch cannon and currently only a 10ft 2.5in sdr26 barrel, soon i will be up to a 15ft 3inch. so now you know a little more about the cannon
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Unread postAuthor: jor2daje » Wed Jun 02, 2010 10:58 pm

ah, then dhalls makes even more sense.
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Update.. Another possibility of how this was done.

Unread postAuthor: Technician1002 » Wed Jun 02, 2010 11:25 pm

Yea right! minimal damage to the can.. As far as I can tell, it's pretty much wasted for being able to hold anything now. :D

Nice job on the cannon. It's larger than my current build. :shock:

As far as a guess as to the source of the damage, it looks like it hit a steel wire. Was this shot through a fence?

The torn edge wobble and the damage on the bottom of the can seen in your other photobucket photos indicate the can impacted on the bottom first. Since cans tend to quickly rotate and fly sideways, I'm assuming this impact was within a few feet of the muzzle, ie point blank range.

An ax head would have tried to separate the can violently. I don't think a wide object did this. The force would have distorted the can. It hit something narrow such as a wire. The wrinkle in the edge of the tear and the upward tear on the bottom of the can indicate this was not a hydrostatic blowout from an impact of a projectile from the other side. something sliced the can. See my updated theory below the photo.

If it was hydrostatic tear, the impact was on the bottom of the can with a small object. The tear at the top makes me think this is not the case. The top of the can separation is not uniform, so I think it was cut with a wire and not simply hit with water pressure.

It is still possible this damage was just hydrostatic from a projectile launched into the bottom of the can. The can split on both sides and opened like a clam and tore the top as seen. A high speed video of this would have been great to watch.

This is the photo I examined for the other view.
Image

Update.. I think I may have the answer after thinking about it for the evening.

I think a can was loaded into the barrel empty with the top of the can going in first (top to the valve). On the shot, air blew into the can. The can pressurised in the barrel as it plowed air in the barrel along the way. Shortly upon exit (no chance for rotation) the can impacted something and split the bottom. Once the bottom split and tore to the sides, the internal pressure blew the can apart. This is my final theory and my final answer. The can on exit may have had as much as 30-50 PSI internal pressure.

Great puzzle and great forensics quiz. :wav:
I may try this theory to see if I get the same kind of result.

Air only seems to be a bust.. or I should have used the larger cannon and higher pressure? This test was with the marshmallow cannon with the 3 foot tennis ball barrel to test the ax theory.
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dull knife and pop can.
Last edited by Technician1002 on Thu Jun 03, 2010 9:05 pm, edited 1 time in total.
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Unread postAuthor: c11man » Thu Jun 03, 2010 2:24 pm

very nice ideas! and mostly correct except the target, the target was a the edge of a piece of 1/16inch thick steel that was not sharpened in anyway. other than that it is all correct, the can was loaded open end to vavlve, and the target was only a foot from the muzzle.

and tech you definely need the larger cannon with higher pressure, this shot was done at 60psi and speeds slightly over 1000fps
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Unread postAuthor: Technician1002 » Thu Jun 03, 2010 6:52 pm

:D I have a larger cannon. I'm working on an even larger one. I used the small one first for the photos so others would think. I got nearly the same results with the larger one. :D I didn't post it so others had a fair chance at discussing it. I didn't want to post a full spoiler, but post possible solutions.

If I can get an apple over 800 FPS with a 2 inch valve, I'm sure your numbers are close for the empty pop can.
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Unread postAuthor: c11man » Thu Jun 03, 2010 7:06 pm

well my 1000fps guess was bassed on the fact that i measured a can at 950fps at the same pressure and the 5ft barrel, and this shot was done with 10ft and i didnt want to be too optimistic.

did you get a clean split like i did or did it damge the can more? and was that a machete as your target?
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Unread postAuthor: Technician1002 » Thu Jun 03, 2010 7:38 pm

You got my target correct. I knew an ax would not be right. I have one and could test it.

I'm in town so I used lower pressure so I still mangled the can some, but with more pressure in the can, I got a better split than before. It got dark by the time I got that done so no photo at this time. I have to watch the noise in the neighborhood with the large cannon at pressure.
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Last edited by Technician1002 on Fri Jun 04, 2010 12:32 am, edited 1 time in total.
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Unread postAuthor: c11man » Thu Jun 03, 2010 7:45 pm

well i dont worry about nois as much as i should, i shoot my cannon at 60psi intown and no cops showed up yet,

and i was extremly supprised that a blunt peice of steel was able to cut the can so cleanly, i guess things realy change over 1000fps
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Unread postAuthor: Technician1002 » Thu Jun 03, 2010 8:18 pm

It's raining now. I grabbed the can and brought it in to grab a photo. Here is my can split with the 2 inch valve. My shot was at 65 PSI. It did hit the machete. The damage does look very much like your photo. The can was launched out of the 7 foot barrel. At higher pressure I might have gotten a cleaner edge. I posted the other picture as I liked the look of the can draped over the machete.

I've seen your valve. I'm waiting the posting of the entire cannon.
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Split60PSI.JPG
I did not take a picture and post this so I would not post a spoiler. This is why I chose my final answer.
Split60PSIa.JPG
Another view of the skinny slice.
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Unread postAuthor: c11man » Thu Jun 03, 2010 9:01 pm

realy still that rough even with the sharpened target? i figure that you would be able to get a cleaner slice than me at lower speeds becuase of the non blunt target.

100psi and you should get a very nice slice
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Unread postAuthor: Technician1002 » Thu Jun 03, 2010 9:09 pm

Due to the 2 inch valve and about the same pressure, my velocity was lower than yours. This damage is a cross between your shot and the marshmallow shot. Higher pressure would have made the clean slice. Due to noise I limited my pressure.
Mine really gets loud at high pressure.

I still feel good about getting speed near yours with only a 2 inch valve. :D
I have a 4 inch on the drawing board.
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Unread postAuthor: c11man » Thu Jun 03, 2010 9:27 pm

wanna redue the 2inch qdv vs mine with full soda cans? i have a feeling i might win :D
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