How will this design work? Need help with GGDT..

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Postby dt1028 » Mon Mar 21, 2005 1:57 pm

I am competing against other people in my college physics class. The project is to build a device capable of propelling a 2.5 inch-size projectile with out gunpowder (I already asked).

So long as your device can propel it a few feet you get a grade. However bonus points are awarded if you are the winner in the following categories.

Distance
Projectile Speed
Ingenuity

I want to win at least 2 of the categories, distance and speed.

Before I tell you what I need help with I wanted to let you guys know I have lots of experience with cannons of all sorts…(including breech loaded gun powder ones)

This will be my seventh air (or helium) based cannon so I understand the basic principles.

All of my previous air cannons have used a basic sprinkler valve modified.

Now since I really want to do well with the project I am going to use a Supha valve to dump the most air as possible.

The design I want to build uses the following:

6 inch diameter pressure chamber (SCH 40 PVC) 72 inches long
2.5 inch diameter barrel 72 inches long
Supha Valve Electronically controlled

I will be using regular compressed air at around 85-100 psi

The cannon will be on a mount.

Here is a picture of the proposed design

<img src="http://img55.exs.cx/img55/6205/plan11bj.jpg" />



Ok what I need help with:
Is this design far to large?
Should the reservoir be smaller?
Should the barrel be long or shorter?
What pressure should I run it at?

I attempted to answer these question my self with GGDT, but I am not sure what values should go in a few spots. Below is a screen of what I have it set to:

<img src="http://img109.exs.cx/img109/8972/help4jo.jpg" border="0" width="717"/>




The areas boxed in blue I am not sure what to put in this spot. Specifically the valve date for the Supha valve.
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Postby Baker9o9 » Mon Mar 21, 2005 2:08 pm

Wow it sounds like your going to have a big gun 6" chamber and a 2.5" barrel i think if the barrel is the same length as the chamber then you will not get the maximum performance, try using a shorter chamber or longer barrel, also i beleive the supah valves are rated at a max 150 psi but im not positive.
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Postby plasticex009 » Mon Mar 21, 2005 2:19 pm

To get a good approximation using GGDT you would need someone to give you the measurements taken from a Supah valve for these parameters. You could e-mail Joel or someone who has a valve and see if they would give you these measurements.

To figure out if your launcher is too large, you can use the gun optimization tool under the Tools menu in GGDT.
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Postby dt1028 » Mon Mar 21, 2005 2:25 pm

I plan to order my supha when I have the design finished. So if any one has the info for the valve could you please pm them to me.

BTW I noticed that I can only get 2.5 pvc at a max lenght of 4 feet or so from the website. Is there a way I can build the barrel so it breaks down into two pieces? This would help with transportation.
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Postby chewy » Mon Mar 21, 2005 4:06 pm

a 6 x 25" chamber is more than you need for a 2.5 x 72 " barrel. Supahs are rated at 100 psi MAX no higher. You will get a lot more performance with a air triggered supah then an electric, and no need for battery's. You will receive all the info on the valves when you get them. Joel has a system for adding sections to barrels. It can be done using couplers or threaded flange couplings. Personally i would go with a 4" chamber. Its stronger cheaper and lighter.
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Postby utcpyro » Mon Mar 21, 2005 5:53 pm

Ok, for longer pipe you can go to US Plastics, and they will ship up to 8ft segments of it. You'll have to buy 10ft of it, and they will cut it down to 8ft and send you a little peace of pipe with the big one. Item number 26508 is probably what you need there (2.5" SCH40, white).

Oh, and on GGDT, you'll want the "Inner Diam" to be zero. That box it only used if you have the barrel running through the chamber, and I don’t think you'll be doing that with a Supah valve.

I also agree with Chewy, you don’t need a 6" air chamber, and you don’t need it that long. It'll just make it harder to carry the thing around not to mention not be as safe pressure wise.
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Postby dt1028 » Mon Mar 21, 2005 10:24 pm

I have refined the design and I think this is what I will be going with...

BTW...I looked over the rules again and I says I can not uses a projectile over 2.5 inchs but it can not be smaller then 1.5 inchs.

Knowing this it looks to be much cheaper to build then I intended....

The design I want to build uses the following:

4 inch diameter pressure chamber (SCH 40 PVC) 52 inches long
1.5 inch diameter barrel 72 inches long
Supha Valve air triggered controlled

Here are the results I am getting from GGDT:

<img src="http://img56.exs.cx/img56/3974/help29uy.jpg" />

Gonna shoot joe an email to see if he can help me predict it with the valves meausments...
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Postby utcpyro » Mon Mar 21, 2005 11:00 pm

What do you plan on shooting out of this thing any way?
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Postby PotatoNick » Mon Mar 21, 2005 11:05 pm

a 2.5 inch projectile I think, lol
order the supah plus or mod a supah yoursekf
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