Page 2 of 2

Posted: Thu Apr 26, 2012 5:26 am
by pneumaticcannons
what sort of pressures
DYI pressures :D

Im curious as to how you plan on filling it with light gas in the future... Through the barrel?

Posted: Thu Apr 26, 2012 7:51 am
by inonickname
warhead052 wrote:Ok, what sort of pressures are you planning on using? I don't see any failure points now that you have told me that.
Not as much as he should be... There's millions of PSI right under you nose DYI, you know how to get them :wink:

Posted: Thu Apr 26, 2012 8:08 am
by Zeus
warhead052 wrote:Ok, what sort of pressures are you planning on using? I don't see any failure points now that you have told me that.
Yeah, when DYI builds something, everything can be a failure point.
inonickname wrote: Not as much as he should be... There's millions of PSI right under you nose DYI, you know how to get them :wink:
Ino, thing is, DYI can find millions of PSI, and the RCMP love finding DYI using millions of PSI.

Posted: Thu Apr 26, 2012 8:27 am
by Petitlu
great job DYI !

Posted: Thu Apr 26, 2012 11:37 am
by DYI
Not as much as he should be... There's millions of PSI right under you nose DYI, you know how to get them :wink:
Despite the inherent interest of high explosives and notwithstanding the interest various agencies would have in catching me producing them, I prefer the electric gun as a concept. The thing is, if I wanted to and had the funds, I could generate millions of PSI in an electric gun. It would have an identical lifespan to an equivalently high pressure HE gun (one shot), and perform significantly better. I'm well aware that there are some very fascinating methods out there to use the aforementioned millions of PSI to achieve very high speeds, but they're all inherently single use. What I'm pursuing is reusability and practicality (oh hush, I'll figure it out eventually :lol: ) while still achieving unusually high speeds. I'll leave the Voitenko compressors to others :wink:

Although I find it hard to believe myself, I've actually stopped seeking more pressure. It is becoming increasingly odious to contain, and is currently on the verge of exceeding the capabilities of the available materials (not counting maraging steels as available due to lack of heat treating facilities and lack of money). It is becoming increasingly attractive to pursue more constant projectile base pressure profiles without increasing the initial pressure.

To answer the other questions:

1. Design operating pressure is 800MPa, which presents a bit of a problem for the barrel - using my recent correction to btrettel's yielding pressure formula, the barrel's ID is guaranteed to plastically deform somewhat if I use normalized 4340. I have a variety of ideas to combat this, including the obvious solution - heat treating. I'll be doing some testing with an unmodified barrel first, to see which of my solutions is more appropriate.
The fill pressure for the light gases I mentioned would range from 3000psi to 10000psi.

2. I would actually be filling through the central electrode. Please don't ask for specifics as to how I'm actually going to accomplish that - I really do need to study today

:roll:

Posted: Thu Apr 26, 2012 11:54 am
by warhead052
I've got nothing then. 10,000psi is more that I could ever get my hands on right now, so I wouldn't know the failure points. I would suggest layering it in a few sand bags, possibly firing from a separate room though, just to be safe.

Posted: Thu Apr 26, 2012 4:49 pm
by DYI
Warhead, 10 000psi is the fill pressure, which is quite easy to contain with proper materials. It's the expected ~100 000psi during the firing which will cause problems, if there are any.

Also, for future reference, when launchers like this fail, they don't do so explosively. They either eject their internals (like the central electrode, for example) along the long axis of the gun, or they plastically deform on the inside (not on the outside, unless you're really trying to wreck the thing, as mentioned below). The sort of rupture you're thinking of wouldn't be achieved by anything short of packing the internals with a good HE. In the case of the thicker chamber section, there's a chance even that wouldn't break through (I'm guessing this by comparing the diameter ratio here to that of the Trauzl lead block test, but I digress...).