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School T-shirt Cannon

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: rcman50166 » Mon Sep 21, 2009 9:03 am

New Update:

Realized the bushing does not fit into a pipe but rather fits in a coupling

Does anyone know if a female pipe adapter requires a coupling as well or does that slip over the pipe?
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Unread postAuthor: Technician1002 » Mon Sep 21, 2009 11:27 am

They both fit in a bushing most times. Sometimes you can find a female adapter that fits on the end of pipe. It is why I recommended visiting the plumbing store to see what parts sizes are.

As you can see from the collection of barrels in the photo below, most of the fittings are in a coupler. Two of the male fittings are directly on the pipe, the blue and white ones next to each other for example.

The launcher in the photo is my 2 inch 3 gallon launcher. It can toss shirts 350 feet.

An option after you get lots of experience with PVC is to make a custom bell on the end of the pipe so the coupler will fit directly into the pipe, or get a length of pipe with the bell already on the end. See second photo for the breech of the Mouse Musket where I put a female adapter directly into a pipe.
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launcher-12-5-08 009a.jpg
Most tubes use a coupler. A couple of tubes with male adapters attach directly to the barrel.
PICT226.JPG
Breech of the Mouse Musket with the 1.5 inch female adapter inserted into the end of the 2 inch pipe without a coupler.
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Unread postAuthor: rcman50166 » Fri Sep 25, 2009 12:02 pm

Hey guys I thought I'd just let you see our stand in cannon while this one is being built. It was an old broken cannon but has been revived. Unfortunately it is ball valve regulated but it seems, by the sound of it, it is opening most of the way before the t-shirt leaves the gun.

[youtube]http://www.youtube.com/watch?v=esuej_ZB5dU&feature=channel_page[/youtube]
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Unread postAuthor: Technician1002 » Fri Sep 25, 2009 12:17 pm

rcman50166 wrote:Hey guys I thought I'd just let you see our stand in cannon while this one is being built. It was an old broken cannon but has been revived. Unfortunately it is ball valve regulated but it seems, by the sound of it, it is opening most of the way before the t-shirt leaves the gun.


Did you measure off the range on the flat field? Since we can't be side by side, I would like to know the range you were getting. I overlaid the range of my little launcher on top of the field. Distances shown are horizontal distances with a shirt.
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stadium1.jpg
Little cannon range at Hillsboro stadium.
Rose_Garden_basketball_medium1.jpg
Range of the large cannon at 60 PSI at the Rose Garden Arena
Abby's B-day 069.jpg
Little launcher in action launching cross the field into the stands.
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Unread postAuthor: rcman50166 » Fri Sep 25, 2009 12:40 pm

Technician1002 wrote:
rcman50166 wrote:Hey guys I thought I'd just let you see our stand in cannon while this one is being built. It was an old broken cannon but has been revived. Unfortunately it is ball valve regulated but it seems, by the sound of it, it is opening most of the way before the t-shirt leaves the gun.


Did you measure off the range on the flat field? Since we can't be side by side, I would like to know the range you were getting. I overlaid the range of my little launcher on top of the field. Distances shown are horizontal distances with a shirt.


My temporary cannon has a range of around 160 ft at 70psi
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Unread postAuthor: Technician1002 » Fri Sep 25, 2009 1:37 pm

rcman50166 wrote:
My temporary cannon has a range of around 160 ft at 70psi


I think you will notice a considerable increase in performance. Enjoy.
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Unread postAuthor: rcman50166 » Fri Sep 25, 2009 2:00 pm

Proof that ball valves actually have a good use in potato guns.
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Shown here is the valve actually all the way open by the time the projectile leaves the barrel
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Unread postAuthor: Mr.Sandman » Fri Sep 25, 2009 2:06 pm

Not exactly proof. But ball valves do have their place in spudguns but as most say it is better to use a valve that has higher performance
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Yeah, it's that important.
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Unread postAuthor: Technician1002 » Fri Sep 25, 2009 3:01 pm

rcman50166 wrote:Proof that ball valves actually have a good use in potato guns.


Nice shot. Since acceleration is greatest early in the shot, performance improves by using an even faster valve. I designed to have a valve fully open before the shirt moves 2 inches in the barrel. I think you will notice this difference with a piston and larger valve seat for even greater flow when the valve is open.

For comparison, the Arlington team also captured a shirt launch photo. They put the shirt on the roof above the stands at PGE Park. Using ribbon as a kite tail, the shirts tumbled less went farther.

Flow and valve speed makes the difference between 160 feet on 70 PSI and 350 feet on 60 PSI.
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Shirt launched at PGE park. Dry Nitrogen was used so there is less condensation showing.
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Unread postAuthor: rcman50166 » Fri Oct 09, 2009 7:34 pm

I thought I'd just update my progress. The design still has to be approved. Long story though, check the "In the world of spuds today" thread to see it. I fooled around with a tail like the last post suggests. Here's a vid of it working, and rather well too. It detaches mid flight just like we wanted. The shirt is taped closed though, but it should work.

[youtube]http://www.youtube.com/watch?v=qFlCnHFDKII[/youtube]
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Unread postAuthor: rcman50166 » Sat Oct 10, 2009 5:46 pm

I'd also like to add this video. It's been modified to a 10 ft barrel at 92 psi and has a pvc rocket as ammo. Watch it dissapear... If you open it up in youtube and make it full screen, you can see it on its way down.

[youtube]http://www.youtube.com/watch?v=_ozHGTa3Z8k[/youtube]
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Unread postAuthor: rcman50166 » Sun Oct 25, 2009 7:33 pm

Ok new update: The design has been approved and so has the budget. I'm waiting for the parts order to come in now but while I wait I'd figured I'd make the Solidworks rendering of the cannon.

Also as I've mentioned before. This cannon will be modeled off of the Javelin Missile System. (FGM-148) However I can't find a practical way of dimensioning the command launch unit. Can someone help me find a set of dimensions or a picture I can use for scaling?
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T-shirt Gun (Solidworks).JPG
Here is the design. I didn't bother including threads so don't ask about them
T-shirt Gun (Solidworks).JPG (22.35 KiB) Viewed 316 times
T-shirt Gun (Solidworks) 2.JPG
T-shirt Gun (Solidworks) 3.JPG
T-shirt Gun (Solidworks) 3.JPG (26.31 KiB) Viewed 316 times
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