SpudFiles

Can't you just make a slimmer pump and top it up with that?

I could, but the next size down of reasonably priced pipe would be too small. There are pipes in more appropriate sizes, but they cost many times more.

And with an altered compressor, I don't need to pump - it's all good.

Ragnarok wrote:With the extra pressure and the changes, HEAL should be able to give a lot more than it already does. I'm still a long way short of 4 figure muzzle energies, but to get 1000J (let alone 1000 ft-lbs.) with a hand-held cannon in a low bore size would be nigh on impossible.

With a long enough barrel and chamber you could conceivably go at least 75% of the way using a lead slug weighing several hundred grams...

Good luck with the improvements. Also i am interested in what you are going to do to mod a copressor to give it higher working pressure.

on another note, you say you want more power, could you maybe do this by using a different gas to obtain higher velocities? helium maybe?

have you considered shooting some kind of dart with this gun? I wouldnt know if they could handle the high pressure, due to my lack of experience in that area.
And very nice gun, this is probably the gun ill be thinking about when i hear the words efficiency and power

As suggested above, one way of boosting performance without altering the launcher or pressure is by experimenting with lighter gasses such as helium, as well as altering the ammunition. as the warring factions in the second world war discovered, the use of saboted ammunition was an easy way of extending the useful life of an otherwise obsolete design.

@JSR: If I were to cast a 100g lead slug, that would come out at about 610 J from the 125cm barrel assuming I make all the changes.
Very respectable for a "small" spudgun, but quite a lot short of the targets.
Longer barrels can change that of course, but within practical lengths, 1000+ J isn't possible.

Still, I have a 300g length of 20mm steel rod around. I plan to use it in the next video... from a 200cm barrel, almost 900J would be possible.

@ALIHISGREAT: Surely almost everyone wants more power!
I could use a different gas, I've been assessing that. I don't know I want to get into that complication just yet, and if I were doing that, I could combine both the improvements and the helium/hydrogen/whatever - a double pronged attack of sorts.

I'm not directly doing anything to the compressor, I'm boosting the pressure after the compressor. It uses a spool valve (a favourite in my recent designs) for controlling a pneumatically driven pump.
It's a little more complex than that, but that's the basic idea.

@hyldgaard: Darts are something I'll be experimenting with at some time. Not immediately though.

Ragnarok wrote:@JSR: If I were to cast a 100g lead slug, that would come out at about 610 J from the 125cm barrel assuming I make all the changes.
Very respectable for a "small" spudgun, but quite a lot short of the targets.
Longer barrels can change that of course, but within practical lengths, 1000+ J isn't possible.

Still, I have a 300g length of 20mm steel rod around. I plan to use it in the next video... from a 200cm barrel, almost 900J would be possible.

@ALIHISGREAT: Surely almost everyone wants more power!
I could use a different gas, I've been assessing that. I don't know I want to get into that complication just yet, and if I were doing that, I could combine both the improvements and the helium/hydrogen/whatever - a double pronged attack of sorts.

I'm not directly doing anything to the compressor, I'm boosting the pressure after the compressor. It uses a spool valve (a favourite in my recent designs) for controlling a pneumatically driven pump.
It's a little more complex than that, but that's the basic idea.

@hyldgaard: Darts are something I'll be experimenting with at some time. Not immediately though.

what sort of performance would you be getting if you used helium with the 100g lead slug that JSR suggested? and the compressor pump thingy idea sounds good i look foreward to hearing more about it.

With helium, 640 J. A ~5.1% increase.
With hydrogen (as good as it gets), 645 J. About 5.9%.
For heavy (and slow) projectiles, changing the gas doesn't help as much as it does at higher velocities.

The booster is something I'll be parading later. Should be quite cool when I'm done.

Do you really need to quote the entire post?
I'm not ranting at you, but there are a lot of people responding to the post above, and quoting large chunks of it.

Do you really need to quote the entire post?
I'm not ranting at you, but there are a lot of people responding to the post above, and quoting large chunks of it.

no, but its just easyier and quicker for a lazy guy like me 8)

I plan to get over 4000 ft/lbs from my BB gun with a .957" barrel only 60" long, so it certainly is achievable. Not particularly easy though, and certainly not as practical as your design.

From what I have gleaned after looking into options for propellant gases, you will have a very difficult and/or expensive time getting either helium or hydrogen to the pressures you need on the output to make them useful. The highest output helium reg I could find was 0-200 psi, and cost over $300. I never really looked into hydrogen, but it certainly is a viable option for a copper gun (unlike steel, which it embrittles over time). CO2 is far too dense, and HPA is kind of pointless, since you can get that with a pump. Nitrogen is cheap and has cheap regulators available, but offers very little density advantage over air. H or He regulators with high outputs are rather uncommon equipment. You could, of course, build a massive gas ram to compress useful quantities of helium to high pressure, but then you run into the cost problem again.

Now, for what *could* be a viable solution to your problem:

This air driven pump that you are talking about must suck air from the atmosphere around it, and use a piston driven by the compressor air, probably large diameter on the compressor side and small diameter on the output side, to push the atmospheric air that it sucks in into the chamber. Now, what you could do very cheaply, to obtain a source of high pressure helium, would be to simply buy a low pressure regulator, and set it up to feed into the intake for the pump, thus, the pump would pump in helium rather than air.

Now, all of this assumes that my idea of how your compressor driven pump works is at least somewhat correct.

Mostly correct, but it uses compressed air as an input, not atmospheric air. Means it pumps 9 times as much air with a stroke.But that could still be adapted to accept a helium input.

I don't know what helium would cost me. Perhaps I should nose around a bit, but I don't think I'll actually get hold of any. Sounds like it could be expensive, and it might be best to keep things subsonic. Sonic booms in a back garden tend to get noticed.

I know, the energies are logically achievable (take just about any rifle you'd care to name), but not on pressures I am comfortable with using and without significantly resizing HEAL. However, for now, 500 to 600 joules is more than enough fun - a good 30 to 40 times what even a powerful air rifle (for the UK, so 16.3 J) will do.

A 0-100 psi helium regulator wouldn't be terribly expensive, and the tanks cost MUCH less to buy/lease than most people would expect. $56/ year for my 90 cubic foot nitrogen tank.

As far as I can tell, sounds from subsonic gas releases and projectiles seem loud up close, but dissipate quickly at range. My house is surrounded on 3 sides by neighbours, and I fire the SCTBDC in the back yard every once in a while, with no complaints. Detonations and large supersonic objects seem to be noticed a lot more, so I keep below Mach 1 for back yard shooting. I've never really been incredibly interested in breaking the sound barrier with a projectile just for its own sake. I certainly could if I had the inclination.

The BB gun won't get built until spring, mostly because I don't feel confident machining the valve myself, and it will cost a small fortune to get a machine shop to do it. That, combined with the cost of about 18" of 6" steel bar stock and some 1.5" hydraulic tube and fittings means that I'll need to save a fair bit of money before I start it. But 24mm ball bearings at 1500 fps will make the whole thing worth it.

DYI, is this a normal .33 gram, .177" BB we're talking about sabotted in a .957 barrel? Or a ball bearing?

A .33 gram BB would have to be traveling at over 3.5 miles per second to end up at 4000 ft-lbs. That's getting into the domain of those big "hybrid" guns that NASA uses to simulate meteorite impacts

That sounds a reasonable price, but it still increases operation costs, and complicates things a bit.

I still think it would probably be best to keep things subsonic in my garden (about the only place I ever get to shoot), so the idea will need to wait.
I'd love to go supersonic, it would be pretty awesome, but I don't know when I'll be able to.

Subsonic still leaves a nice mess though.