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High Pressure Simple Cannon Plan help!!!

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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High Pressure Simple Cannon Plan help!!!

Unread postAuthor: jazzman56 » Thu Jul 21, 2011 5:46 am

Hi all i have recently been researching on how to make a high pressure cannon using a shock pump and have drawn up some plans. I need help to know what will work and what i can improve so have come up with a few questions.

Ammo: BB (9.5 mm)
Chamber: 90cm3 (is this right??)
Barrel: 1.5 meter by 1cm copper tubing
Fill: Epoxied in end cap schrader valve.
PSI: Any where from 200 psi upwards
Valve: (already have a ball valve 3/4 and a spring) Spring loaded ball valve (rated to 27 bar)

I feel like a total twit, i rushed writing this up and didn't look for how to post pics. :?


Can i Use Brass Fittings, the steel ones are really low quality??

Velocity ????? (have no idea, have downloaded GGDT but still confused how it works.

How large is the chamber need to be?

How to make a simple breech loading system?

What type of valve should i use (may have to take ball valve back as it's only rated to 27 bar)? If qev how would i incorporated it into this design?

Here are my pics of plans.(sorry drawn up quickly for the basic idea)

Image
Image

All comments welcome
Thanks Jazzman56
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Last edited by jazzman56 on Fri Jul 22, 2011 3:15 am, edited 2 times in total.

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Re: High Pressure Simple Cannon Plan help!!!

Unread postAuthor: MrCrowley » Thu Jul 21, 2011 6:19 am

jazzman56 wrote:Help How Do I Insert Pics?????????? SORRY

This topic is posted as a STICKY in Website discussion. Be sure to check all stickies in all forum sections at some point in the near future. :)

By the way, you should have posted this in your other thread.
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Re: High Pressure Simple Cannon Plan help!!!

Unread postAuthor: jackssmirkingrevenge » Thu Jul 21, 2011 6:22 am

jazzman56 wrote:Ammo: BB (9.5 mm)


Yes

Chamber: 90cm3 (is this right??)


It will cost you to pressurise this past 150 psi with a shock pump, reduce to 30cm<sup>3</sup>

Barrel: 1.5 meter by 1cm copper tubing


10mm internal diameter? Quite loose, you will have significant power loss and poor accuracy. Look for 3/8" pipe.

Fill: Epoxied in end cap schrader valve.


If done well, yes.

PSI: Any where from 200 psi upwards


400 psi!

Valve: (already have a ball valve 3/4 and a spring) Spring loaded ball valve (rated to 27 bar)


Rated to 27 bar, can probably take 50 bar without coming close to failing

Velocity ????? (have no idea, have downloaded GGDT but still confused how it works.


Can't help you from work.

How large is the chamber need to be?


See above.

How to make a simple breech loading system?


Hole in the barrel and sleeve.

What type of valve should i use (may have to take ball valve back as it's only rated to 27 bar)? If qev how would i incorporated it into this design?


"only 27 bar"? That's almost 400 psi, you'll be fine with a shock pump.

Help How Do I Insert Pics?????????? SORRY


Either post to photobucket or imageshack, or use the convenient spudfiles uploader.
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Unread postAuthor: Crna Legija » Thu Jul 21, 2011 7:17 am

go to the GGDT home page then click on the Usage tab then Main Window Input, there you can read how to use GGDT and what to put where, if you still don't get some of them ask us.

to hook up a qev into your gun you will need to remove the ball valve, connect the chamber(make it 30-40ml)to the bottom port of the QEV(2). Then you will need a valve to trigger the QEV to open(pilot valve) you connect it and a fill valve using a tee to the port labeld 1, and 3 is your barrel.
Image

you should read up on how piston valves work start, here
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Unread postAuthor: jazzman56 » Fri Jul 22, 2011 5:02 am

JSR: so my 10MM (millimeter)barrel is to large a bore for my 9.5MM (millimeter) steel ball bearings. So a 0.5MM gap is too large of a gap.
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Unread postAuthor: Crna Legija » Fri Jul 22, 2011 5:28 am

jazzman56 wrote:JSR: so my 10MM (millimeter)barrel is to large a bore for my 9.5MM (millimeter) steel ball bearings. So a 0.5MM gap is too large of a gap.


yes that is a massive gap, look at good BB barrels compared to the 6mm BBs they are like 6.03 and some are 6.01, you can use it for now but i would defiantly try get something better.
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Unread postAuthor: jackssmirkingrevenge » Fri Jul 22, 2011 5:38 am

The BBs should fit the barrel well enough to minimize leakage of air around the projectile (blowby) but not so tightly that friction is excessive. Even small differences in diameter can have significant effects on performance. An attempt to quantify this power loss was made in this experiment

Two 15 inch lengths of barrel tubing were used, one was aluminium with an I/D of 5mm, while the other was a straighted piece of coiled copper tubing with an I/D of 4.5mm. The barrels were hooked up to a blowgun attached to a compressor and used to fire lead BBs - with a nominal diameter of 4.5mm - at 100 psi through a chronograph. Over a 5 shot string, the 5mm I/D barrel averaged 242 feet per second, whilst the 4.5mm I/D barrel averaged 279 feet per second. With an average projectile weight of 8 grains, this gives a muzzle energy of 1.04 and 1.38 ft/lbs respectively - a significant power increase of 33% over the wider barrel.
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