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High-Velocity Damage/Hybrid ROF Discussion

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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High-Velocity Damage/Hybrid ROF Discussion

Unread postAuthor: saefroch » Sat Nov 06, 2010 11:58 am

Firing a 11/32" diameter low-carbon steel ball through cedar 1"x4" at about 750fps (says GGDT). Can anyone explain why there seems to be no clear hole in the target? I'm betting it has something to do with elasticity, but I'm rather lost. :?

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Last edited by saefroch on Thu Nov 11, 2010 9:21 pm, edited 1 time in total.
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Re: High-Velocity Damage????

Unread postAuthor: jackssmirkingrevenge » Sat Nov 06, 2010 12:07 pm

saefroch wrote:I'm betting it has something to do with elasticity, but I'm rather lost. :?


That's basically it, as a fibrous material wood can "spread" to allow the bearing to pass without necesarily being removed, and the round shape of the projectile facilitates this. Were you to fire a cylinderical projectile you would likely see a much cleaner hole.

Incidentally, this is the point why target shooters like wadcutter "flat head" style projectiles, as they leave clean discernable holes in paper targets as opposed to tears, because the edge shears off the marerial instead of pushing it aside.
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Unread postAuthor: saefroch » Sat Nov 06, 2010 12:12 pm

Sheet metal time, I guess.
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Unread postAuthor: jackssmirkingrevenge » Sat Nov 06, 2010 12:17 pm

Amen, sheet metal and clear acrylic are certainly the most satisfying targets in my book :D
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Unread postAuthor: SpudFarm » Sat Nov 06, 2010 1:09 pm

I know someone that almost got a 3/8" BB through a 1/4" steel plate from a 2" long barrel :P

Try to beat that one!

Some other fun targets is clay, wax, water, fruit and gel
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Unread postAuthor: saefroch » Sat Nov 06, 2010 1:13 pm

2" barrel? I think not... At least not from a pneumatic. Just picked up some 1/16th inch steel plate. Hopefully some vids today, but I don't know how much my poor ears can take.
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Unread postAuthor: DYI » Sat Nov 06, 2010 3:21 pm

2" barrel? I think not... At least not from a pneumatic.


Pneumatics are for the weak :P

As to the issue with the less-than-impressive penetration: Wood is a terrible target material. As Jack mentioned, it tends to spread out of the way without forming clean holes. This issue can be partially mitigated if you increase the impact speed to something like 20 times what it currently is :wink:

Why sheet metal and acrylic? The finely detailed craters and deformations formed in thicker plates (1/4" +) are far more interesting to look at than a simple hole ripped through a thin sheet with minimal required effort. As spudfarm mentioned, clay also makes a very interesting target, due to its low SOS and mechanical strengths. Those cause it to show effects that wouldn't be seen without very high speed impacts in other materials.

Also, the topic title is rather misleading. 750ft/s isn't even trans-sonic, much less "high velocity" for a gas gun.
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Last edited by DYI on Wed Nov 10, 2010 8:10 pm, edited 2 times in total.
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Unread postAuthor: Ragnarok » Sat Nov 06, 2010 4:00 pm

saefroch wrote:I don't know how much my poor ears can take.

You DO know what I'm going to say, right?
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Unread postAuthor: saefroch » Sat Nov 06, 2010 4:10 pm

Ragnarok wrote:You DO know what I'm going to say, right?

Ear infection.
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Unread postAuthor: Technician1002 » Sat Nov 06, 2010 11:18 pm

I have found that faster rounds make cleaner holes as the high KE is imparted to the wood which exits the rear. At lower speeds, it simply moves out of the way with high amounts of attached splinters which re-close the hole. Softer wood that has less brittle and more spring tends to close the holes more than dry crisp wood.
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Unread postAuthor: Selador » Wed Nov 10, 2010 8:03 pm

saefroch wrote:Hopefully some vids today, but I don't know how much my poor ears can take.


Quit shooting yourself in the ear.

;)

DYI wrote:Pneumatics are for the weak :P


And for those who like the lack of ongoing expense for volatile fuel...

;)

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Unread postAuthor: DYI » Wed Nov 10, 2010 9:07 pm

And for those who like the lack of ongoing expense for volatile fuel...


A hybrid can perform similarly to a helium pneumatic in the lower velocity ranges, while requiring only a tenth of the starting pressure. Even if helium is used as the buffer gas in the hybrid to reach very high speeds, hybrids are still vastly less expensive to operate than pneumatics because, when compared on a cost per kilogram basis with bottled gases suitable for use in pneumatics, propane is practically free. Only at the *extremely* low performance end of the spectrum can pneumatics compete cost-wise with hybrids.

When I first switched to hybrids, it wasn't mainly because of the potential for higher performance. It was mainly because I could shoot what was essentially the same cannon ten times more often for a fifth of the original cost.
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Unread postAuthor: velocity3x » Wed Nov 10, 2010 9:33 pm

The nitrogen for one of my pneumatics costs .79¢ per shot and the 1.250" ball bearing projectiles cost about $3.75 per shot.
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Unread postAuthor: saefroch » Wed Nov 10, 2010 10:15 pm

Ah, but for a pneumatic you can use free fuel, the air, if you're not too lazy to use a multi-stage pump. Currently, I'm at about $0.03 per shot for ammo, ignoring build costs.
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Unread postAuthor: Crna Legija » Wed Nov 10, 2010 10:31 pm

idk how much the electricity costs for my fridge for 90sec but i get 800psi out of it takes some time but i don't mind its to loud to shoot more then 5 time a day.
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