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Penetration contest

A place to ask general spud cannon related questions.
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Number of sheets of 3/4" plywood

0-2
1
6%
3-8
4
25%
12-15
1
6%
15-20
0
No votes
20-30
3
19%
30+
7
44%
 
Total votes : 16
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Penetration contest

Unread postAuthor: pat123 » Tue Aug 04, 2009 10:00 pm

How many pieces of plywood do expect to shoot through with your competition gun?
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Unread postAuthor: Technician1002 » Tue Aug 04, 2009 10:39 pm

LOL.. If I was entering and built the gumball machine gun, I would have to vote 0-2 as I would only be shooting a single sheet.

For PVC the votes cast is impressive.. Well done if you make it.. I'll be looking for the proof videos. 30+ is quite a punch.
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Unread postAuthor: paaiyan » Tue Aug 04, 2009 10:47 pm

Is over 9000 an option?
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Unread postAuthor: Technician1002 » Tue Aug 04, 2009 10:52 pm

paaiyan wrote:Is over 9000 an option?


Yes.. You will just click 30+ and it's right there. The plus sign includes it. :D Looking forward to seeing your proof video. :shock:
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Unread postAuthor: paaiyan » Tue Aug 04, 2009 10:54 pm

About that video.... Is there any way we can extend the contest deadline? Say, until I become a millionaire? That's not too much to ask right?
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Unread postAuthor: D_Hall » Tue Aug 04, 2009 11:35 pm

I might be able to do 30+ inches of concrete. :)

(but I don't imagine i'll be signing up for the contest)
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Unread postAuthor: jrrdw » Wed Aug 05, 2009 12:13 am

Interesting, 6 votes. Good, that means we have at least 6 entries. :D Shhhhh, don't say who you are or what your using :twisted: .
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Unread postAuthor: Gippeto » Wed Aug 05, 2009 12:14 am

Anyone know just how much energy it takes to punch a 2" hole in a sheet of 3/4" plywood?
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Unread postAuthor: jackssmirkingrevenge » Wed Aug 05, 2009 2:38 am

Gippeto wrote:Anyone know just how much energy it takes to punch a 2" hole in a sheet of 3/4" plywood?


That's very subjective, it depends on the shape and hardness of the projectile. However generally it's a hell of a lot more energy than one would need to punch a 0.5" hole if you catch my drift.
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Unread postAuthor: inonickname » Wed Aug 05, 2009 3:24 am

I'm not doin none of this PVC rubbish..

Has anyone considered 1/2" sch. 80? The burst pressure (yes, PVC) is around 3600 psi. If sleeved in the next size or two, 3000 psi hydrogen could be used with a burst disk and hardened dart..

Or even 800 would be impressive with a fridge compressor and H2 inlet (from NaOH + Al..)
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Unread postAuthor: jackssmirkingrevenge » Wed Aug 05, 2009 3:32 am

I'm giving this a miss, it basically boils down to who can make the biggest launcher, and if I had the space then I would not be able to afford the amount of plywood I need :roll: The projectile will doubltess begin to deviate off course as soon as it hits the first sheet, so keeping it in line until it reaches the last one its going to penetrate means big sheets in a big space, all things I don't have.
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Unread postAuthor: CpTn_lAw » Wed Aug 05, 2009 5:00 am

It would be interesting to make a study about energy loss when impact on plywood, because a 2" projectile is likely to be much heavier than a 1/2" one, and given a certain muzzle velocity, the initial kinetic energy of a 2" projectile would be much much bigger. So, considering it loses energy when impacted, would the loss of energy be a linear function of weight , speed and width ?
If such a study were to be made, we could probably find the ideal mass/size projectile.
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Unread postAuthor: jackssmirkingrevenge » Wed Aug 05, 2009 5:21 am

CpTn_lAw wrote: If such a study were to be made, we could probably find the ideal mass/size projectile.


For pure depth of penetration the ideal is simple, maximum mass and minimum size. The higher the sectional density, the easier its going to be for the projectile to penetrate and the harder it will be for the projectile to lose velocity.

This is why the best penetrators in the world have a tiny cross sectional area but are relatively long and made of the densest materials available ;)

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Unread postAuthor: Gippeto » Wed Aug 05, 2009 12:23 pm

I'm out too. :( (4" Sched 120 pvc is TOO much $$$ locally)

Jack, do you REALLY think a dart is going to win this ??

I predict that the winning projectile will be more...old fashioned. :)

We'll have to wait and see.
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Unread postAuthor: jackssmirkingrevenge » Wed Aug 05, 2009 1:10 pm

Gippeto wrote:Jack, do you REALLY think a dart is going to win this ??

I predict that the winning projectile will be more...old fashioned.


I'm actually rather taken aback that someone of your background doesn't agree. The fact that all the world's major armies rely on saboted darts as projectiles when penetration is the requirement should be proof enough of the benefits of high velocity resulting from low projectile weight as well as high sectional density.

It may be counter-intuitive, one would think that at the same velocity a 1" ball bearing will penetrate more than a 1/4" dart becaust it's heavier, but the fact is that per unit of projectile contact area, the dart has a lot more mass pushing it through the target medium.

Don't you remember the coin challenge? You don't need a lot of ft/lbs to push a dart-like projectile through a seemingly hard target, it's the reason why bowhunters can take down such large prey with relatively low muzzle energy behind their arrowheads.
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