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TIBS Launcher (New Piston)

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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TIBS Launcher (New Piston)

Unread postAuthor: userjjb » Fri May 04, 2007 1:16 am

<div align="center">
<img src="http://www.spudfiles.com/uploader/uploadFiles/2inchFULL2.jpg">



<a href="http://www.spudfiles.com/uploader/uploadFiles/2inchPILOT1.jpg"><img src="http://www.spudfiles.com/uploader/uploadFiles/2inchPILOT1mini.jpg"></a> <a href="http://www.spudfiles.com/uploader/uploadFiles/2inchPILOT2RR.jpg"><img src="http://www.spudfiles.com/uploader/uploadFiles/2inchPILOT2mini.jpg"></a> <a href="http://www.spudfiles.com/uploader/uploadFiles/2inchPISTONsideRR.jpg"><img src="http://www.spudfiles.com/uploader/uploadFiles/2inchPISTONsidemini.jpg"></a> <a href="http://www.spudfiles.com/uploader/uploadFiles/2inchPISTONtop.jpg"><img src="http://www.spudfiles.com/uploader/uploadFiles/2inchPISTONtopmini.jpg"></a>
<a href="http://www.spudfiles.com/uploader/uploadFiles/1qPISTONbottom.jpg"><img src="http://www.spudfiles.com/uploader/uploadFiles/1qPISTONbottomMINI.jpg"></a> <a href="http://www.spudfiles.com/uploader/uploadFiles/1qPISTONside.jpg"><img src="http://www.spudfiles.com/uploader/uploadFiles/1qPISTONsideMINI.jpg"></a> <a href="http://www.spudfiles.com/uploader/uploadFiles/1qPISTONtop.jpg"><img src="http://www.spudfiles.com/uploader/uploadFiles/1qPISTONtopMINI.jpg"></a>
</div>
The Two Inch Barrel Sealer (TIBS), a name I came up with so the title for this guy was less bland, heh. Originally completed a year or so ago, it was posted on Spudtech.

With the coming of spring weather I decided to improve upon several things that had been bothering me about this launcher. The chamber is 3" by 2 feet, the piston is housed in a 2" tee and is actuated by a 3/4" QEV, in turn piloted by a blowgun. It has a 1 1/2" female threaded adapter outlet, which is normally connected to my golfball barrel.

The piston was originally 2" Ultra-High Molecular Weight Poly-Ethylene (UHMWPE) rod, which worked beautifully. It has a coefficient of friction equal to Teflon, while being 10 times more impact resistant then bulletproof glass. The last 2 pictures on the top row show a top and side view of this piston.

Never being fully content, I decided to make a lighter air-tight piston using an o-ring and check valve. After some experimentation the final incarnation can be seen on the 2nd row of pictures. The piston is two 1 1/4" endcaps on a short length of pipe, with an o-ring sandwiched in between. The sealing face is a 2" 1/16 thick neoprene washer held on by a 1 1/4" fender washer and machine screw. Plumbed into the rear of the picton is my homemade check valve. Between the sealing face and o-ring are 3 equalization holes drilled into the side of the piston.

I had some trouble finding an appropriately sized o-ring because the gap between 1 1/4" and 2" pipe is fairly large. I eventually found one at NAPA auto parts, size 136 for those looking to build a similiar piston.

Likewise, I found it difficult to find a small spring check valve. I eventually ended up making one out a 1/4" male-male NPT-compression adapter, 1/4" female cap, 3/16" ball bearing, and a small spring
<div align="center">
<img src="http://www.spudfiles.com/uploader/uploadFiles/checkvalve.JPG">
</div>

The result? Previously I could only actuate above 25 psi, the old piston had too mush leakby and all the air would just rush out the blowgun. Now I can actuate all the way down to about 3 psi. Thanks to the o-ring and check valve, I can actuate the valve with something as puny as a blowgun, or even through the schrader I fill it through!

I'm extremely happy with this launcher, according to GGDT it can put a GB weighted to 180 grams at 125 psi and a 10ft barrel out half a mile. The only time I've found a GB fired out in my fields was at 20 psi, unweighted, and with only half my barrel on, and that was 500ft out.
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Last edited by userjjb on Fri May 04, 2007 2:13 am, edited 1 time in total.

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Unread postAuthor: hi » Fri May 04, 2007 1:41 am

wow, very very nicely done. it kinda looks like mine, but with a bigger chamber and a much nicer piston. very nice cannon.
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"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
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Unread postAuthor: mega_swordman » Fri May 04, 2007 5:13 am

Wow! That is really clean. I see this is your first post here, but I take it this isn't your first cannon. Clean, weel put together, and certainly pwns the cannon I made. Welcome to the forum and a job well done :thumbup:

By the way, for anyone who cares, I am trying to finish up a cannon here so I should be able to post it soon. However, I am isolated here (in Switzerland) and don't have a good supply of parts. One summer rolls in I should be able to roll out with some more cannons.
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"Never tell people how to do things. Tell them what to do and they will surprise you with their ingenuity." George S. Patton
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Unread postAuthor: demilus » Fri May 04, 2007 5:41 am

I really like your piston check valve. I have just been using a flap of old bicycle pump rubber to cover up my equalization holes :D Hmmmmm..... time to update the ol' piston....
Thanks for the idea and great cannon!
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Unread postAuthor: Juicey » Fri May 04, 2007 9:24 am

Wow, good looking cannon. Great job with the piston and the check valve. Plus the aesthetics of this cannon are great. Welcome to the forums.
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Unread postAuthor: spanerman » Fri May 04, 2007 3:51 pm

the only thing i would change, would be to have a 1/4' check valve instead on the BV on the filling portion..
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Unread postAuthor: userjjb » Fri May 04, 2007 4:05 pm

Thanks everyone for the compliments :)

spanerman wrote:the only thing i would change, would be to have a 1/4' check valve instead on the BV on the filling portion..


I suppose I could have put a check valve there, but I like having the ball valve to be able to control the fill speed. When I'm filling with a large compressor it can be difficult to fill to a specific pressure, especially if I'm trying to get repeatable results with my chrony. Also, I don't have to disconnect from my air source to stop filling, which makes reload cycles quicker.
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