SpudFiles

This started as a simple test, as stated in this topic.
http://www.spudfiles.com/forums/surpris ... 21307.html

The gun is quite simple, a 1''x1' pipe as a chamber, and a 1/2'' ball valve, spring loaded opens into a copper AA battery barrel.

This gun surprised me with its performance.


I will warn you, the stock on this gun is not pretty, as it was intended to simply work, and no time at all was put into the stock (2x6)

without further ado, here is a video.
Edit:( youtube kind screwed the sound quality. you can hear the sound "peak" in every shot. a few of the shots were felt in my chest.)
[youtube][/youtube]

What do you think about the power? all shots in the video other than the one noted, were 550 psi. the ball valve is held closed by a sear, and released with a trigger.

A few shots, like the 650 psi one, were made with "aerodynamic" aluminum slugs. shaped like this. "=>"

Batteries at that speed do not survive hitting the sand pile. they usually are flat after every shot.

The sound of the shot is interesting, is it like that in real life ?

I never used my spring loaded spudgun past 390psi, I'm tempted to rebuilt it now.

There is something about spring loaded action that makes the whole thing better.

Very impressive, have a look here - no firearm bullets from a range of weapons penetrated more than 6 inches of sand.

One up for spring loaded ball valves

jackssmirkingrevenge wrote:One up for spring loaded ball valves

:occasion5:

al-xg wrote:The sound of the shot is interesting, is it like that in real life ?

I never used my spring loaded spudgun past 390psi, I'm tempted to rebuilt it now.

There is something about spring loaded action that makes the whole thing better.

It is similar to like that, only, it sounds a little less like a microphone peaking out.

The sound is much fuller in real life, and if you notice, on the 650psi shot, the lap top wobbles. the muzzle was about 15-20 feet from the laptop.

jackssmirkingrevenge wrote:Very impressive, have a look here - no firearm bullets from a range of weapons penetrated more than 6 inches of sand.

One up for spring loaded ball valves

Haha you forgot something, one up ball vales...AND HIGH PRESSURE.

That sand test is interesting. I am going to assume that the pine dowel was able to penetrate more, because it was not blown to pieces. It must have worked much like an arrow.

Well, i machined a few aluminum bullets, so i may have to do some sand penetration tests with those.

Upon investigation, i did find battery chunks quite far into the sand pile.

While I'll not deny that's respectable performance, ultimately, if you put that kind of pressure behind anything, you'd have to be doing things very wrong not to get something out of it.

Ultimately, this debate is not going to be solved with assertions of "I was surprised by the performance". It needs two otherwise identical launchers - one with a valve generally accepted as high performance, and one with a "fast" ball valve - to actually be put to the chronograph.

jackssmirkingrevenge wrote:Very impressive, have a look here - no firearm bullets from a range of weapons penetrated more than 6 inches of sand.

That doesn't really mean much. If you look, the lower velocity but heavier pistol bullets actually outpenetrated the rifle bullets (partly because they didn't disintegrate). And in many mediums, similar things will happen.

Take Joerg's slingshot crossbow. For only 53 Joules, that will put its projectile through 16" of ballistics gel. That's about the same penetration you'd normally expect out of a 9mm FMJ with roughly ten times the energy.
In most mediums that can be roughly treated as an incompressible fluid, slow and heavy can do a lot more than you expect.

So, in this case, the relatively low velocities and high sectional density of the pine dowel mean I'm far from surprised.

Well rag, what do you suggest that i do as a proper test?

jhalek90 wrote:Well rag, what do you suggest that i do as a proper test?

Proper test of what, exactly?

I've already talked about what is actually needed to get solid comparisons between valves - two otherwise identical launchers being chronographed. Ideally, you'd then test them at different pressures and barrel lengths to see how that affected things.

I guess it would also be nice to see some stroboscopic photography (or high speed video, either would work) of the ball valve mechanism actually opening so you could actually get an opening time for the valve as well. However, that's obviously a little more demanding.

Haha you forgot something, one up ball vales...AND HIGH PRESSURE.

Very true may I suggest some more challenging targets (domestic appliances, rows of water bottles/soda cans etc.) with the camera closer to the target?

Ragnarok wrote:That doesn't really mean much. If you look, the lower velocity but heavier pistol bullets actually outpenetrated the rifle bullets (partly because they didn't disintegrate).

Fair point, it's not an accurate comparison in scientific terms but I was trying to illustrate the point to jhalek on the awesometer

Ragnarok wrote:And in many mediums, similar things will happen.

Think it will happen with this one?

From you of all people! Shame!

Ragnarok wrote:I guess it would also be nice to see some stroboscopic photography (or high speed video, either would work) of the ball valve mechanism actually opening so you could actually get an opening time for the valve as well. However, that's obviously a little more demanding.

1000 fps should be enough, surely someone on the forum can oblige. Calculating the actual flow at T=x would be rather complex given the shape of the opening at any given time.

Surely it would be easy enough to compare a 3/4" QEV to a 3/4" spring loaded ball valve, given the same barrel and chamber at the same pressure.

jackssmirkingrevenge wrote:From you of all people! Shame!

My dictionary says mediums is a perfectly acceptable form of this meaning of medium. Frankly, I would rather say "media", but that to most people means "the press".

1000 fps should be enough, surely someone on the forum can oblige.

Probably, although it would ideally be the same person as is doing the tests.

Calculating the actual flow at T=x would be rather complex given the shape of the opening at any given time.

Calculating the size of the opening is basic calculus. However, actually calculating the flow is a bit more complicated, because the flow path and turbulence would change pretty quickly.

However, that could be determined experimentally. Not that I imagine anyone wants to.

Ah, but we're not most people

We're not most people, but it is still quite a bit of work.

Practical reasons mean it would probably be better determined with water as the fluid medium.
You'd need two accurate pressure gauges, a flow meter (of sorts, at least*), and quite a bit of patience, retesting the valve's Cv every 5 or 10 degrees of "open". Then you'd need to convert that back into flow efficiency.
*Could be as simple as timing how long it takes to fill a 10 litre bucket or something.

However, ultimately, if done, that information could be fed back to D_Hall if he wanted to put the ball valve as an option in GGDT.

interesting.... JSR do you have any idea where a guy in Michigan, USA, could rent/ borrow for cheap/free a high speed camera??

Being over 4,000 miles away from Michigan, USA, I am possibly one of the worst people you could ask. You can buy a new Casio EX-FC100 for less than $200 though, not really that expensive for a very good camera.

jhalek90 wrote:interesting.... JSR do you have any idea where a guy in Michigan, USA, could rent/ borrow for cheap/free a high speed camera??

Casio EX FS10 now $89