SpudFiles

That lighter fluid can shot would be interesting to watch with a full can and a candle nearby

Pretty crazy speeds you got. Do the BBs fit firmly in the barrel, or do they roll?
Being a fan of D_Halls theory of compressed dead volume allowing supersonic speeds, I wonder what kind of results you would get if you put the BB something like 6" from the breech to give it some extra dead volume to compress.

Any idea why the chrony is objecting to the .12g

I'm hoping it's the sonic boom

A better question is, how much difference would it make?

Well, it's not just a question of the pressure difference, the projectile would be accelerating in an air-drag free environment. I know NASA have the barrels of their high speed launchers under vacuum, it might be an interesting route to try.

how are you using tape as a burst disk? can you demonstrate in any way?

very easy, in between the fittings I put a rubber washer and a disk of tape, I'll post photos when I'm home.

Have you tried using PBA Raptor pellets? 25% increase in velocity

Those pellets are a bit of a gimmick, they achieve high velocities simply by being lighter in weight.

That lighter fluid can shot would be interesting to watch with a full can and a candle nearby

Not in an urban environment hehe

Do the BBs fit firmly in the barrel, or do they roll?
Being a fan of D_Halls theory of compressed dead volume allowing supersonic speeds, I wonder what kind of results you would get if you put the BB something like 6" from the breech to give it some extra dead volume to compress.

They roll but they could be wadded. My problem right now is the chrony, I haven't gotten any further readings for 0.12 gram BBs, I'm pumping it till the disk fails (the gauge is fucked but it's well over 350 psi) and there's a distinct crack - I'll see if I can borrow and F1 style chrony for some actual data.

jackssmirkingrevenge wrote:

clide wrote:That lighter fluid can shot would be interesting to watch with a full can and a candle nearby

Not in an urban environment hehe

Now that's an idea. Hydraulic shock with a can full of petrol, with a lit blowtorch nearby...

I think that might need a fire extinguisher around though.

Now that's an idea. Hydraulic shock with a can full of petrol, with a lit blowtorch nearby...

Not before I'm living in the American midwest

In response to this earlier question:

how are you using tape as a burst disk? can you demonstrate in any way?

I attached a pic of the firing setup, with the rubber seal covered with the transparent tape disc between the barrel and the chamber.

I have to say this burst disk malarkey has caught my fascination, I'm looking into the possibility of making a bigger calibre launcher with a triggered valve.

Being a fan of D_Halls theory of compressed dead volume allowing supersonic speeds, I wonder what kind of results you would get if you put the BB something like 6" from the breech to give it some extra dead volume to compress

I've got 3 ci of dead space built right into the design of my next launcher, in the form of a small chamber in front of the valve. Hopefully that will help.

I have to say this burst disk malarkey has caught my fascination, I'm looking into the possibility of making a bigger calibre launcher with a triggered valve.

Jack, if you're thinking about a large bore burst disk gun, take a look at this video. On towards the end, as I fine tune it to perfection, the shots get pretty powerful, and this is only at 160 psi. I will make another video when I take it up to 350. *
*May not be suitable for indoor use
[youtube][/youtube]

''may not be suitable for indoor use''


oh boy that made me laugh, and awsome looking cannon Jack....and a scale up would be uber cool;)

Liking the Halo soundtrack. I prefer a valve that doesn't need reassembling after each shot, and is a little more predictable, but that's still some good shootin'.

I like the burst disk because of their power. Maybe you should come up with a design that would let you trigger the burst disk and make a rifle?
I still think you should try a 2x hybrid mix. Maybe it would boost the fps because of the pressure spike?

FeLeX wrote:I still think you should try a 2x hybrid mix. Maybe it would boost the fps because of the pressure spike?

I'll agree with DYI's views here:

Hybrids only complicate the matter, as you then need an ignition source, a fuel metering device, fuel, some accurate gauges, some means of venting the chamber, and a spark gap.

I prefer to use purely mechanical devices without the need for combustion.

DYI, I'm not too keen on going very large calibre (although I do have a 2.75 inch steel ball bearing that's crying out for a launcher), I'd be more interested in a high velocity 3/4" launcher, anti-material rifle style, with a small chamber at high pressure.

DYI wrote:

Being a fan of D_Halls theory of compressed dead volume allowing supersonic speeds, I wonder what kind of results you would get if you put the BB something like 6" from the breech to give it some extra dead volume to compress

I've got 3 ci of dead space built right into the design of my next launcher, in the form of a small chamber in front of the valve. Hopefully that will help.

I have to say this burst disk malarkey has caught my fascination, I'm looking into the possibility of making a bigger calibre launcher with a triggered valve.

Jack, if you're thinking about a large bore burst disk gun, take a look at this video. On towards the end, as I fine tune it to perfection, the shots get pretty powerful, and this is only at 160 psi. I will make another video when I take it up to 350. *
*May not be suitable for indoor use
[youtube][/youtube]

Nice gun
But do you think your house is the best backstop? lol

But do you think your house is the best backstop?

You'd have though he'd learnt that lesson already, but nooo...

jackssmirkingrevenge wrote:I'd be more interested in a high velocity 3/4" launcher, anti-material rifle style, with a small chamber at high pressure.

Sounds great - as long as you don't call it the anti-materiel rifle. There are far too many spudguns that get called that.
I quite like to think of launchers in that sort of calibre as more like shotguns rather than AMRs.

The thing is that they resemble modern AMRs more than anything else (since the latter tend to look like they were bodged together from plumbing supplies anyway) - they're certainly anti-material, but rifles, most of them ain't.

An 0.75" launcher is very comparable to a low powered 12 gauge shotgun in terms of performance and the sort of ammunition it can fire, the problem is that once you get to a certain barrel length for useful power, it loses that scattergun look.

DYI, I'm not too keen on going very large calibre (although I do have a 2.75 inch steel ball bearing that's crying out for a launcher)

If it weren't for the fact that you were in Europe, and the shipping would cost more money than I have to my name, I'd ask you to send it here so that I could shoot it a 350 psi out of a 3" barrel.

But do you think your house is the best backstop? lol

That building you see is my shed, not my house, and the only shots on that video that were done without a backstop were using a rubber ball as a projectile. I've only shot through a wall once, I learned from my mistakes after that.

DYI wrote:If it weren't for the fact that you were in Europe, and the shipping would cost more money than I have to my name, I'd ask you to send it here so that I could shoot it a 350 psi out of a 3" barrel.

Well I had made this to fire it but being a combustion performance was fairly dismal, I probably could have thrown it faster so there's still the pneumatic route to explore, I do have a couple of 10 litre fire extinguishers that would make lovely chambers and already have a threaded fitting, hmmm...