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Ragnarok

Wed May 16 2007, 02:16PM

Registered Member #659 Joined: Fri Apr 20 2007, 09:14AM
Location: SW Hertfordshire, UK
Posts: 75

I guess at least someone will be interested in this, so I'll post it here for you to look at. If a mod thinks it should go somewhere else, then my apologies, you are welcome to move it.
I was torn between using "General Science" and "Projects", but I guessed "Projects" is more for things directly related to the forum.

I've tried to avoid confusing you with spudding terms, but if I've messed up and said something that isn't clear, just ask and I'll try to explain it better.
And you can click on any image for a larger picture.

H.E.A.L.
(High Efficency Air Launcher)

LINK TEMPORARILY REMOVED

HEAL is a semi-advanced pneumatic spudgun. It's about 130 cm long (Approx 52") from muzzle to stock (with the short 1m barrel), and masses in at 3.8 kg (Approx 8.5 lbs). It has a 20.30 mm (0.80") bore, (interestingly, approximately equal to what a 9-gauge shotgun would be) which I use mostly because it's my preferred bore size - rather than for huge power (Higher bores would increase power, but the ammo costs significantly more).

The whole cannon is capable of working effectively at pressures from 1 bar up to 21 bar (15-300 psi), which allows it to be pretty powerful.
All things counted, it cost about Â£130 in UK money, (Approx $250 US at the current exhange rate) which isn't that bad.

The main valve is a custom built barrel sealing type piston valve, which opens very fast (1 to 2 ms), and provides excellent air flow. This is piloted (or opened) by a Quick Exhaust Valve (QEV) to get optimum opening time and performance from it.
If you want a visual explanation of how a piston valve works, then this is a very good forum thread to give you an idea. QEVs operate very similarly to this.

The design took into account most of the suggestions made on spudgun forums about my last spudgun, so that has made this launcher my best yet - pretty damn powerful for it's size, and good visually (I plan to polish up the copper later on today to get it looking it's best).

The muzzle velocity obviously varies significantly based on pressure and ammunition mass, but muzzle velocities over Mach 0.9 should be possible with some projectiles.
Muzzle energy could potentially reach about 350 J from the short barrel with heavy rounds.(Closer to 500-550J could be achieved from rather longer barrels.)

Primary testing was done on Monday, and everything is working perfectly so far, catapulting loosely wadded paintballs well into a nearby crop field at fairly low pressures. (They are bio-degradable, in case you're concerned by that)

The design uses my universal twist-lock fittings to allow various muzzle attachments to be used, to either improve accuracy and range, or dampen the firing sound.

As you may be able to tell from this, my pneumatic skills are a quite a bit more advanced than my electronics (but I am endeavouring to learn better electronics). Hope you like it.

This is the main piston valve and it's pilot valve:
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The valve arrangement shown here is possibly one of the most powerful ever used on an amateur cannon of this bore diameter. Some people use valves less powerful than this on cannons of about 63mm bore.

The pressure gauge and safety valve:
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The safety valve is just a basic ball valve, which can be shut to prevent the air from the chamber from entering the barrel, which totally prevents accidental firing.

With the breech closed, and the trigger/fill setup:
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The red slide valve visible in that image under the copper chamber is the main trigger. The ball valve immediately in front of that is a 2nd safety valve (I take safety seriously when using something as potentially dangerous as this, unlike some other spudgunners I could mention).
There is also a non-return valve immediately behind the red slide valve to prevent any air losses when filling.

Breech opened:
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The breech is almost totally airtight with no real loss of power, rather unlike my last one, which had some tendency to leak.

I also took a couple of silly images while I was out, which can be seen below.

1st person shooter style image:
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Sometime, I'll take a better picture and put a HUD on it for a laugh.

1st person shooter image 2
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And a photoshopped image of me in a bullet time dive:
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Yes, I am wearing safety goggles. Again, it's a important piece of kit for spudgunning.
I was on a table that I then edited out. I did try doing actual dives, but after a few failed attempts which blurred a lot, my shoulder started to hurt, so I cheated.

Well, I hope I haven't bored you senseless - what do you think?

EDIT: Apologies, I've removed all of the links because the site I used to use was a bit dodgy. I'll replace them eventually, but for now, look here at a much newer and better version of the launcher: http://www.spudfiles.com/forums/heal-320psi-20mm-copper-cannon-t11453.html

Wolfram

Wed May 16 2007, 03:36PM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

Sounds very interesting, but the pictures seem to be missing.

Ragnarok

Wed May 16 2007, 06:14PM

Registered Member #659 Joined: Fri Apr 20 2007, 09:14AM
Location: SW Hertfordshire, UK
Posts: 75

Oh dear. That's not a good start.
I'm surprised at that, because both computers I've checked the thread on have the pictures working fine.

Are the pictures back yet? The hosting might possibly have been down for a few minutes...

If not, I'll seek different hosting.

Steve Ward

Wed May 16 2007, 06:57PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

Pictures worked fine for me. Nice work! Funny about the table thing, i thought it looked odd, but didnt immediately think it was faked.

Bjørn

Wed May 16 2007, 08:39PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

The pictures were missing for quite some time but they are back now.

Nice work. I would like to know how much air goes into it, what pressure and the exact weight and velocity of the projectile.

Ragnarok

Thu May 17 2007, 09:23AM

Registered Member #659 Joined: Fri Apr 20 2007, 09:14AM
Location: SW Hertfordshire, UK
Posts: 75

BjÃ¸rn BÃ¦verfjord wrote ...

Nice work. I would like to know how much air goes into it, what pressure and the exact weight and velocity of the projectile.

The chamber is about 650 cc in volume. And I can use any pressure from 1 bar (the minimum valve seal pressure), up to 21 bar (the maximum I feel happy using).
That of course translates as an air volume from 640cc at minimum pressure, up to 13.4 litres of air at maximum.

There is no exact weight and velocity of the projectile, because I use so many different ammos - paintballs, potato slugs, 20mm steel ball bearings, loads of plastic BBs - this thing is very versatile in what it will accept.
So far, the range of my projectile masses has roamed from 0.8g up to 50g.

I can't give you exact velocities, but the velocity of a 25g potato slug is predicted as being in the 160-170 m/s range.

Billybobjoe

Thu May 17 2007, 07:46PM

Registered Member #396 Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176

Very nice - good to see another spudder on here. I like the use of the slide valve for a pilot. What are the pressure ratings on the valve? All the QEV's I've seen max out at around 125 PSI - obviously they differ in the UK.

Do you frequent the Spudfiles forums? I used to spend a lot of time on the Spudtech forums but they doesn't exist anymore. Have you heard of GGDT

? It can give a fairly accurate estimation of muzzle velocity with accurate inputs.

Tesladownunder

Fri May 18 2007, 01:08AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Nice work.
My website rated quite highly in the spugun webring for a long time. This was because I incidentally made a spud gun from my railgun injector. It is fired by a 240V solenoid (no idea what type) and runs to 40psi.

Recently, I needed a length of copper pipe to make a high current coaxial resistor so I removed about half the barrel length. This means that I now have a sawn-off spudgun!

TDU

Ragnarok

Fri May 18 2007, 09:31AM

Registered Member #659 Joined: Fri Apr 20 2007, 09:14AM
Location: SW Hertfordshire, UK
Posts: 75

That particular QEV is rated for about 150 psi, but they've been tested way past that, and it's generally accepted that they're more than safe at 300.

I do read spudfiles, and did read spudtech, but never actually posted there.
And yes, I do use GGDT - most of the muzzle velocity figures are estimated from there.

Moving on, I was wondering about using something like this as a railgun injector at some point. This could chuck out something suitable for use as a railgun projectile at about Mach 0.5, which as far as I understand, should be sufficently fast enough to avoid the currents welding the projectile in place.

Bjørn

Fri May 18 2007, 10:25AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

Your first step is to be able to measure the velocity of your projectile. Without that you are working on assumptions that might be completely wrong.

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