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The Log Splitter, finally...NEW VID/PICS

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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The Log Splitter, finally...NEW VID/PICS

Unread postAuthor: Daltonultra » Fri Mar 06, 2009 8:28 pm

After a couple early test shots followed by a long run of nasty weather, I've finally got the Log Splitter fully operational. A few of you might remember my plan to split a chunk of 10x10 wood beam with a giant blowdart? Scrapped. I did it with a POTATO. :shock:

Chamber volume=1507 cubic inches
Firing pressure=120psi
Barrel= 2"x10' PVC
Valve=Rainbird PGA-200
Pilot valve=3/8" brass gas-cutoff ball valve

Image
[youtube]http://www.youtube.com/watch?v=CoTrWhWkJmA[/youtube]

I did two quick test shots a while back. As you can see, since these shots I've removed the long rear pipe and made a small frame up front to support the barrel. I need to make a much beefier frame for it, though. The barrel flex is out of control.

Dry fire, no projectile, still flipped the 2.5" thick cake of ice almost 25 feet.
[youtube]http://www.youtube.com/watch?v=hFPO4kyznfU&feature=channel[/youtube]
[youtube]http://www.youtube.com/watch?v=VTz26qKiNBU&feature=channel[/youtube]



NEW VID AND DAMAGE PICS!!

(the black thing hanging off the barrel is a set of hearing protectors. It wasn't as loud as expected, so I just hung them there.)
[youtube]http://www.youtube.com/watch?v=3JQSLSePjkw[/youtube]

I wish I'd gotten a vid of this shot, but I forgot to switch the camera to video, so I just took a useless picture of ground instead of thrilling footage of vaporizing potato and tree bark... :banghead:
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Image
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Last edited by Daltonultra on Sun Mar 08, 2009 12:48 am, edited 3 times in total.
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Unread postAuthor: Carlman » Fri Mar 06, 2009 9:55 pm

nice work mate!!

i used a free 2" sprinkler on a TB gun i made was quite the performer. I still have my 220psi 3" to use though :twisted:

I wanna see some plywood shots man!
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Unread postAuthor: psycix » Sat Mar 07, 2009 10:42 am

Looks good.
Beware with that barrel flexing, this is a big failure hazard.

Though I do think that that valve doesnt let full flow through. Again, I recommend, the piston valve for MOAR power.

Speaking about the valve, whats with the chamber sticking out the back end?
That valve has two inputs, one output and a pilot doesnt it?
Maybe you could improve the flow by fully using both of the two inputs instead of one and the other not really alot.
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Unread postAuthor: suburban spudgunner » Sat Mar 07, 2009 1:57 pm

SO...MUCH...POWER!!!

Guess you don't need an axe to split that firewood anymore. This is a beautiful thing.
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Unread postAuthor: kiwi of nitro » Sat Mar 07, 2009 5:23 pm

Did you modify the 2" sprinkler to make it pneumatic?
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Unread postAuthor: Daltonultra » Sun Mar 08, 2009 12:37 am

psycix wrote:Looks good.
Beware with that barrel flexing, this is a big failure hazard.

Though I do think that that valve doesnt let full flow through. Again, I recommend, the piston valve for MOAR power.

Speaking about the valve, whats with the chamber sticking out the back end?
That valve has two inputs, one output and a pilot doesnt it?
Maybe you could improve the flow by fully using both of the two inputs instead of one and the other not really alot.


Well, I fixed the barrel flex today, strapped a 2x4 under the barrel, joined to the barrel support. It seems to have completely eliminated both the flex, and the tendency of the gun to hop from the recoil.

The weird chamber on the back was a temporary thing. I couldn't find a 2" to 1/2" threaded adapter for the fill valve, so I threw that piece from a junked cannon on it just so I could take the test shots. I found that threaded adapter a couple weeks back, so now the back port has a 1/2" brass elbow, a ball valve, and a compressor fitting on it.
As for the two inputs, I don't think it would improve anything to use both. The diaphragm itself probably isn't flowing as much air as the bottom port is already giving it.


Kiwi, yes, it's modded. I took out the flow control knob and tapped the opening for 3/8"NPT and added a ball valve. I may replace that with a QEV and pushbutton valve later. For now, though, my next step is to put together a carriage for this thing. Right now, it takes two people to move it from the garage to my firing area out back of the house.



BTW, there's a new vid and damage pics up top.
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Last edited by Daltonultra on Sun Mar 08, 2009 1:06 am, edited 2 times in total.
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Unread postAuthor: SpudsMcGee » Sun Mar 08, 2009 12:52 am

Recoil much? That thing slid back a good two feet before it hit your friend's (Peter's) knee.
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Unread postAuthor: Daltonultra » Sun Mar 08, 2009 1:23 am

lol, yeah, it's a bit of a rocket.

BTW, interesting phenomena on one shot. We were curious as to distance, so we propped it up at about a 40* angle and launched a chunk of potato out through a hole in the tree line along the creek. Well, it definitely got some serious distance, but about 150-200 feet out, the shot suddenly veered left, then went ballistic, curving upwards till it was climbing almost straight up. It finally topped out somewhere around 300 feet and corkscrewed like mad the whole way down. The thing must have been spinning like mad. God only knows what kind of ground distance it covered, because there's no way we could have found it, but it was almost invisible when it went below the trees.
The next shot splattered in mid-air about 50 feet out. I can only guess it tumbled and the aerodynamic stress tore it apart.
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Unread postAuthor: psycix » Sun Mar 08, 2009 2:36 pm

Spuds have the tendency to spin faster and faster. With my combustion it usually goes like:
BLAM --- Split second pause --- WHIIRRRRRRRRRRRRRRRRRrrrrrr...(disappears in the distance)
This is normal for any cylindrical or spherical projectile (I believe it is for any shape). It always has a small spin in a random direction. As air rushes past, the spin becomes more and more intense. The more spin, the more the magnus effect (I believe it was called that) will pull it out of its default trajectory.
To stop this, you can either rifle your barrel or make sure the center of drag lies somewhat BEHIND the center of mass.
You can move the center of drag to the back by adding a tail (duct tape or a piece of rope for example.) And you can move the center of mass to the front by hollowing out the back of the projectile (effectively creating a tail) or have an extra heavy nose on the projectile (effectively using the whole rest of the projectile as a tail).
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Unread postAuthor: suburban spudgunner » Sun Mar 08, 2009 2:52 pm

Holy $#!+!!! (sorry if I've offended anyone's virgin eyes, but what more can I say?)

Those new damage shots are amazing! I don't believe I've ever seen a potato do that to a tree...
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Unread postAuthor: Daltonultra » Mon Mar 09, 2009 3:51 pm

The tree is actually a stump about 2 feet tall. If I did that to a living tree out there, my Mother would perform the Death Of a Thousand Cuts on me....
I think most guys on here don't shoot at trees much, or you'd see a lot worse.
Of course, once Dad finishes the ramp on the far side of the bridge, he has to clear a trail back through the trees to get the truck and tractor back into the meadow. I'm gonna see if he'll let me try blasting one of the locust trees down with the cannon...after I figure out how to fire it remotely...

BTW, tip for anyone that wants to use the same brand/type of valve that I'm using here, if you modify it as I did, make sure to cement the flow-control plunger back into the upper chamber in the valve to provide a bump-stop for the diaphragm.
You can see the glued-in plunger in the center here:
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