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The Improved Pen Gun

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 Improved Pen Gun

Unread postAuthor: rcman50166 » Tue May 13, 2008 11:12 am

rcman50166's Pen Gun


First I want to say that this is not to show up JSR's pen gun. As a matter of fact, if it wasn't for him building it I probably never would have.


Improvements
JSR's pen gun was good but there were several things I saw that could be improved. The first was the piston. My pen gun has a smaller, lighter piston made from a small nylon spacer. The inside of the spacer was injected with hot glue and then shaped to make the barrel seal. This brings me to the second improvement. JSR's pen gun had the seal attached to a barrel bracket. This restricts air flow from the chamber to the barrel, potentially lowering efficiency. My pen gun has no such bracket so when the piston is in its exhaust position there is nothing blocking the chamber to the barrel, allowing for maximum efficiency. This again leads to the next improvement. JSR's pen gun has epoxy (I think) sealing the foreward end of the gun. Mine uses an o ring partnered with the top of a pen to seal the front which also stablizes the barrel allowing for no bracket on the other end as mentioned before. The pen is shortened to simulate the length of a regular disposable pen. The shrader valve is also vented by the pen cap which has a rod in it which looks like a click button.

Features
The barrel is at the same diameter as a pen's ink tube which, convieniently, is also the diameter of my ammo. It shoots pencilt tips. This is ideal because you can sharpen the tips and even rifle the round. Graphite also is known as a dry lubricant so as you shoot the pen, the round lubricates the barrel for the next shot. All together the pen gun costs $6.

Downsides
The downside of my particular design is that unless lubricated periodically, the valve may stick. Also, since there is no bracket to stablize the barrel, the barrel doesn't always line up with the seal. I personally fixed the problem on my pen gun. But the problem will be unique to every one built. Another potential problem, depending on the power desired, making the gun shorter makes the chamber and barrel shorter, a problem that can plaugue a pneumatic if extreme enough. However, I'm happy with it's performance overall.

Performance
Once all the kinks were worked out, my pen gun became very reliable, only requiring lubrication about every 100 shots. It has been tested with a small ball/bike hand pump, which I would guess to be around 50PSIG. I plan to test it at 250 PSIG this weekend. At 50PSIG (with the small pump), I was able to shoot through two pieces of paper even while the round tumbled into it sideways. I can shoot through one layer of a small plastic sandwich bag. It is plenty accurate only straying off with light ammo. However, the piston tended to stick when orange peels were loaded in. There are no apparant leaks when it is put through its paces in the underwater test. It can make someone bleed. I brought it to school to test its undercover capabilities and no one recognized it as a weapon, only the occasional "cool gold pen".

[youtube]http://www.youtube.com/watch?v=JG2ednTuGtA[/youtube]

Click here to see jackssmirkingrevenge's pen gun.
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Attachments
Rifled Ammo.jpg
Rifled Ammo.jpg (11.94 KiB) Viewed 4729 times
Pen Gun 8.jpg
Pen Gun 7.jpg
Pen Gun 5.jpg
Pen Gun 6.jpg
Pen Gun 4.jpg
Pen Gun 9.jpg
Pen Gun 9.jpg (33.08 KiB) Viewed 4729 times
Pen Gun 10.jpg
I almost forget, here is a cut away of my pen gun. Compare it to JSR's to see the difference.
Pen Gun.gif
Animated Theory
Pen Gun.gif (11.25 KiB) Viewed 2635 times
Last edited by rcman50166 on Thu Sep 03, 2009 1:46 pm, edited 8 times in total.
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Unread postAuthor: Carlman » Tue May 13, 2008 11:30 am

first off i dont think you should name the thread 'improved pen gun' if its not your gun to be improving on then you can call the thread that aye.

anyway sounds good to me mate!

cant wait for videos and pics :D
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Unread postAuthor: SNDM » Tue May 13, 2008 11:49 am

I think the title puts tribute to the original pen gun.
Keep it.

Yup, similiar thoughts, videos and pics!!!
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Unread postAuthor: rcman50166 » Tue May 13, 2008 12:27 pm

I wrote improved because that is exaclty what it is. Improving it doesn't necessarily mean the design is mine originally.
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Unread postAuthor: psycix » Tue May 13, 2008 4:23 pm

Well, I wont make any judgements before I saw your pics :wink:
Dont keep us waiting too long!
How small is it?
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Unread postAuthor: Sticky_Tape » Tue May 13, 2008 4:32 pm

psycix wrote:Well, I wont make any judgements before I saw your pics :wink:
Dont keep us waiting too long!
How small is it?

He said it was the lenth of a disposible pen. I think you should try a marker gun next definently more power to be found in marker guns.
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Unread postAuthor: rcman50166 » Tue May 13, 2008 5:18 pm

Ok Pics are up :D Videos are still to come (I'm working on it now)
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Unread postAuthor: Sticky_Tape » Tue May 13, 2008 5:33 pm

The diameter of the barrel is probably the same as JSR'S Pengun but if it is different could you tell me? Where did you get the barrel I don't know where to get small diameter tubing it's pretty frustrating.
EDIT: I have an Idea so you can easily get more ammo fast burn the pencil the grafite can take the heat I found a pencil in my grandfathers boat that was half burn't and the grafite was still together.
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You can tell how awesome a cannon is by the pressure used.
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Unread postAuthor: pizlo » Tue May 13, 2008 5:47 pm

Sticky_Tape wrote:The diameter of the barrel is probably the same as JSR'S Pengun but if it is different could you tell me? Where did you get the barrel I don't know where to get small diameter tubing it's pretty frustrating.


And you didn't read the first post why???
Cmon man he says the chamber and barrel are the same diameter, its all one tube.
rcman50166 wrote:
The barrel is at the same diameter as a pen tube which, convieniently, is also the diameter of my ammo.
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Last edited by pizlo on Tue May 13, 2008 5:48 pm, edited 1 time in total.
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Unread postAuthor: rcman50166 » Tue May 13, 2008 5:48 pm

Well I got the barrel at True Value. They come in 1 foot sections. As far as its diameter I'm not really sure. I know it has the same exterior diameter as a pen tube from a bic disposable pen (the one that's shown in the comparison). The interior diameter is just large enough to fit a pencil. Sorry I don't have numbers. I actually didn't plan for pencil tips to fit. I was looking for two different size pipes to fit on a specific o ring (also sold at True Value).

BTW the video should be up in the next 15-30 min.

Edit: sorry, it says that the diameter is the same as the pen tube but what I meant to say is it is the same as the ink tube :oops:
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Last edited by rcman50166 on Tue May 13, 2008 5:49 pm, edited 1 time in total.
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Unread postAuthor: pizlo » Tue May 13, 2008 5:49 pm

BTW: looks great RCman.
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Unread postAuthor: Sticky_Tape » Tue May 13, 2008 5:52 pm

pizlo wrote:
Sticky_Tape wrote:The diameter of the barrel is probably the same as JSR'S Pengun but if it is different could you tell me? Where did you get the barrel I don't know where to get small diameter tubing it's pretty frustrating.


And you didn't read the first post why???
Cmon man he says the chamber and barrel are the same diameter, its all one tube.
rcman50166 wrote:
The barrel is at the same diameter as a pen tube which, convieniently, is also the diameter of my ammo.

Sorry pizlo but how the hell could he shoot the rifled pencil grafite ammo through a 6mm barrel? I don't think pencil grafite is 6mm in diameter cmon. and what would the piston seal on?
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http://www.spudfiles.com/forums/high-pr ... 12803.html
xnt rnm ne z ahtbg
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Unread postAuthor: psycix » Tue May 13, 2008 5:52 pm

Ah pic are up.
Man that looks clean and smooth!
It really looks like a real pen :D

Good job!
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Unread postAuthor: rcman50166 » Tue May 13, 2008 5:58 pm

Sticky_Tape wrote:
pizlo wrote:
Sticky_Tape wrote:The diameter of the barrel is probably the same as JSR'S Pengun but if it is different could you tell me? Where did you get the barrel I don't know where to get small diameter tubing it's pretty frustrating.


And you didn't read the first post why???
Cmon man he says the chamber and barrel are the same diameter, its all one tube.
rcman50166 wrote:
The barrel is at the same diameter as a pen tube which, convieniently, is also the diameter of my ammo.

Sorry pizlo but how the hell could he shoot the rifled pencil grafite ammo through a 6mm barrel? I don't think pencil grafite is 6mm in diameter cmon. and what would the piston seal on?


no no no! don't fight. I made a mistake! It's my fault! I meant to say pen ink tube not pen tube.
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Unread postAuthor: Sticky_Tape » Tue May 13, 2008 6:05 pm

Guess what rcman I looked and looked but I had problems finding anything wrong with your gun but I found somthing I like being nit pickey.
EDIT: I think Pizlo owes me a apologie.
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Last edited by Sticky_Tape on Tue May 13, 2008 6:09 pm, edited 1 time in total.
You can tell how awesome a cannon is by the pressure used.
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xnt rnm ne z ahtbg
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