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2.5 inch QDV build

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: CpTn_lAw » Sun Oct 25, 2009 4:54 am

I love to see work in progress! Looks very very promissing :D
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"J'mets mes pieds où j'veux, et c'est souvent dans la gueule."
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Unread postAuthor: Willdebeers » Sun Oct 25, 2009 5:04 am

Wow. This will definatly have some kick to it! Good luck with filling it though.
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Unread postAuthor: dewey-1 » Sun Oct 25, 2009 12:03 pm

Here is a possible method for the piston stop.
Use a thread sealant to seal the screw. SHCS = socket head cap screw

Click to enlarge.
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piston-stop.png
SHCS for stop
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Unread postAuthor: Technician1002 » Sun Oct 25, 2009 2:22 pm

dewey-1 wrote:Here is a possible method for the piston stop.
Use a thread sealant to seal the screw. SHCS = socket head cap screw

Click to enlarge.


I was thinking more along the lines of simply drilling a pair of holes and putting in a cut piece of chain. I can get cut links free where they cut chain at the hardware store. The ends on the inside would provide the piston stop and the outside would provide a connection point for a shoulder sling. It would be welded or brazed onto place.

Nice graphic by the way. Nice job. It looks like something I would build. :D
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Unread postAuthor: Technician1002 » Thu Oct 29, 2009 4:39 pm

Willdebeers wrote:Wow. This will definatly have some kick to it! Good luck with filling it though.


Bumped for the update.

I expect it to kick like a mule, but filling it will be no problem. It's about the same size as my 2 inch.

This weeks update for today. The sanding is finished. I finished off with 320 grit sandpaper which left a nice shiny and smooth surface. A golf ball is in it to provide a reflections and light background so the detail of the remaining pipe seam can be seen. It's almost completely gone. Click to enlarge and see the remains of the pipe seam.
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SizeComparison.JPG
Size comparison with my 2 inch 3 gallon.
Sanded.JPG
Nice and shiny. Only minor rust pits remain and spots of the weld. For comparison, the pipe on the left is what this was cut from.
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Unread postAuthor: Brian the brain » Thu Oct 29, 2009 4:47 pm

That'll do just fine.
Looks just like the inside of Mr.Porters piston housing.

But your design depends highly on O-ring seal.Make that soley ( sp?)

You could use some epoxy filler to bring up those pits.
I would not have chosen that particular pipe..
It looks like it was part of the RMS Titanic.
:roll:
Great name for the cannon btw..
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: dewey-1 » Thu Oct 29, 2009 4:49 pm

Tech;

If you get a chance, make measurements of the tank and the piston sleeve and I can create some 3D drawings to post on this thread.
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Unread postAuthor: Technician1002 » Thu Oct 29, 2009 5:33 pm

@ Brian, This is my 4th QDV. Getting the rings to seal will be no problem. The 2 inch has a fairly deep weld groove. I did epoxy fill it. In places the epoxy is starting to come lose. I am going to try to avoid filler at first. With all the edges rounded the o ring will seal. My other 3 are the Cellular Core Test Cannon (apple cannon) the T Shirt Cannon (2 inch QDV) and the Marshmallow Cannon (1 inch QDV)

dewey-1 wrote:Tech;

If you get a chance, make measurements of the tank and the piston sleeve and I can create some 3D drawings to post on this thread.


Thanks Dewey. I'll get them for you.

It's cold and wet today. I'll probably wait for nice weather to get good photos to mark up. I'm planning on cutting the ports tomorrow or Saturday. If I do, I'll be sure to get good photos to mark up. I have a benefit of the way I cut the tank. I can easily measure the tank thickness.

Edit; Nice halloween math class.. I wish I had this guy as my math teacher. He's fantastic.
[youtube]http://www.youtube.com/watch?v=XKviYiZhtZY[/youtube]
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tank threads.jpg
Tank thickness can be measured from the edge of this piece.
Last edited by Technician1002 on Mon Nov 02, 2009 6:21 am, edited 1 time in total.
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Unread postAuthor: rikukiakuchiki777 » Thu Oct 29, 2009 8:46 pm

Looking good tech. Can't wait to see damage pics :twisted:
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This Week's update Nov 5

Unread postAuthor: Technician1002 » Thu Nov 05, 2009 1:46 pm

I got the measurements for Dewey-1. So everyone can see the parts measured, I took photos. Sorry for the more than 6 photos in one post.

Edit; adding to my last post instead of bumping the same day.. I got the ports cut. :D Photos below.
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Attachments
Measurement1.jpg
Thickness of the bottom of the tank. 2.21 mm
Measurement2.jpg
Length of the pipe is 16-9/16ths inches long.
Measurement3.jpg
ID of the polished pipe is 2.491 inches.
Measurement4.jpg
Piston is 2.684 inches long. I get to turn it down this weekend on a lathe. No need to measure the current diameter. It's too big.
Measurement5.jpg
OD of the pipe is about 2.872. My calipers didn't quite reach from the side or end. I'll remove paint off the other piece and measure it later.
Measurement6.jpg
Tank length overall after cutting the ends and beveling them in. 12.75 inches.
Measurement7.jpg
Tank diameter is 9 inches. The weld around the middle is slightly larger.
Measurement8.jpg
This piston diameter gets fixed this weekend.
Measurement9.jpg
Length of threads.
Circumference.jpg
Distance is measured with a piece of paper.
Circumference thirds.JPG
Divided into thirds by folding.
Drilling.JPG
Pattern transfered by drilling the lengthwise cuts.
Marking Cuts.JPG
The other sides are marked with a hacksaw.
1st opening.JPG
First piece is removed.
Ports Done.JPG
Port cutting is finished. A little de burring and edge rounding will finish the job.
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Unread postAuthor: c11man » Thu Nov 05, 2009 6:10 pm

that looks great tech. now you get the fun job of rounding all those edges :shock:
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Unread postAuthor: dewey-1 » Thu Nov 05, 2009 8:24 pm

Tech;

What are the sizes of ports and width of ribs before filing?
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Unread postAuthor: Technician1002 » Thu Nov 05, 2009 8:28 pm

dewey-1 wrote:Tech;

What are the sizes of ports and width of ribs before filing?


The ports are 1.5 inches tall. The ribs are .5 inches wide.
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Unread postAuthor: theBOOM » Sat Nov 07, 2009 2:49 am

Tech how heavy is the obsolete tank yor using?
Give us pictures of the piston once its finished :o
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The good, the bad, and the ugly.

Unread postAuthor: Technician1002 » Mon Nov 09, 2009 4:31 pm

theBOOM wrote:Tech how heavy is the obsolete tank yor using?
Give us pictures of the piston once its finished :o


For this weekend update, I have good, bad, and ugly news.

The good, the piston is done. The port rounding is done.

The bad, I depleted my camera batteries at the event I attended over the weekend so when I got to the lathe, the batteries were flat, so no turning pics.

The ugly, my computer had a fan failure on the graphics card while I was gone. It smoked. I'll have to get a new card next weekend before I can download and edit the photos to websize. I have to borrow time on my wife's computer, so time in chat from home will be severely curtailed until I get my graphics card replaced.

To answer the above questions, the modified tank is 10.5 lbs. The tank with the pipe in it is 17 lbs. (on my bathroom scale)

Some info on the piston, to get the maximum performance, the piston was shortened to the bare minimum. The o rings will seal right on the edges of the port. This will limit the area I need to polish leak free for the rings as well as cut the piston mass to the minimum. The ring at the front is very near the front edge so when the piston unseats, the nose of the piston will be out of the way. The nose of the piston is also rounded to help this. The rear is a little thicker so the edge doesn't get broken from hard landings in the bumper.

For those taking measurements, the recess in the front of the piston extends in so only 1 inch of material remains at the rear of the piston. I didn't take measurements yet of the overall new length or the diameter of the hole in the front. The hole was enlarged with a home made boring bar. Sorry I didn't get pictures. The boring bar is made from a valve stem from a car engine. The valve head was cut off. The end bent over with a torch and then ground to a side cutting round nose boring bar. It worked like a champ.

The piston slides freely in the pipe without o rings with barely any sideways wiggle room.

I'll put some pics on a flashdrive and see if I can get a few posted tonight at work.
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