SpudFiles

i just want to put it out there for consideration. i'm thinking about building a springer someday but with a pop-off. the air will burst quicker than it would with the spring alone. if it is successful i hope to integrate this into an airsoft gun. the way i see it the resistance of the pop-off would be adjust as easily as the hop-up if it was built right. it'll be pretty sweet if one of you guys did it first. i'm pretty sure that a simple pop-off will make springers way better especially airsoft sniper rifles.

Technician1002 wrote:As a physics nut and general science junkie lets get on the same page for the terms used.

I'm sure you don't take me as an idiot... (Well, perhaps as far as electronics are concerned, maybe.)

While we're here, can we only quote the parts of posts we're actually referring to? (Except where it's essential I don't, I always cut down quotes to simply keep myself in the habit of it)

Accelerating from 0-50MPH requires the same force as accelerating from 50-100MPH.

Assuming it's happening in the same time (and obviously, neglecting air resistance).

But either way, I'm assuming no change in barrel length (as I believe our OP was), and under those circumstances, 1000 fps takes 4 times the force that 500 fps does.

As you say, force times distance. Same distance for four times the energy, must mean four times the force. (And assuming that calibre is the same, consequently, four times the pressure)

Hence, nothing I said was in error, apart perhaps from not stating the "for the same barrel" part, but I assumed that could be taken as read. Obviously not.

Ragnarok wrote:
But either way, I'm assuming no change in barrel length (as I believe our OP was), and under those circumstances, 1000 fps takes 4 times the force that 500 fps does.

Force = Mass X Acceleration

To accelerate in the same distance something that is already moving will require applying 4 times the force in 1/2 the time for the same distance and twice the speed.

In reverse, this is the way the springers get high force on a small projectile. The end of the piston stroke is short but the force is high.

Technician1002 wrote:Force = Mass X Acceleration

Yes, as I have been aware for half my life. But still, force times distance is the more useful here.

Then again... perhaps v² = u² + 2as would be an even better choice.

@ I-will:
I believe the popoff will destroy your efficiency rating. Think of pump action pneumatic guns. Their efficiency is very low because you are pumping air by hand. Most of the energy transfer in a springer is due to air flowing from the chamber cylinder to the barrel. Having the wall of a popoff there will effectively suck up the energy so to speak.

My design uses an o-ring sealed piston. The whole rear part of the gun is a big air chamber. The cylinder is pulled back by a cocking handle out the side, and the air cylinder seals against the main chamber wall behind the hole where the handle comes out. At full rear stroke, the rear of the piston is caught by a hook (Well its a little more complicated but suffice to say the piston catches) Then the chamber's air pressure pushes the cylinder forward into firing position. When the hook is released by the trigger, the piston is thrust forward by the air pressure. The good thing is I can up the pressure as far as the strength of my arm and comfort's sake will allow.

And as long as we're getting into semantics...

"Force = Mass * Acceleration" is only true if mass is constant. That equation does not hold true if mass varies (as it does for rockets).

Been thinking about this..( to bypass local laws)
How about using combustion ( metered or otherwise) to power the piston.

A little like a light gas gun...but reusable and slightly slower..
Since propane is cheaper than bottled CO2 for instance..it might be a good choice.

As I am no combustion guy myself and know little about the subject..but it seems like a large ( combustion side) surface piston driving a smaller one ( pneumatic side) could very well pack a punch...without too much effort.

And of course shock heating might get us over SOS.

Ragnarok wrote:

Marco321 wrote:To get 2000fps+ you would need like solid propellant...

...or a hybrid. There are two I can think of that have recorded 2000 fps+ velocities.

Possibly one or two others as well.

I would also note that one of the fastest projectiles I know of at 110,000 fps (not a typo) didn't use a combustible propellant.

Similarly, at a more leisurely 8,000 fps, the US Navy railgun doesn't use solid propellant.

yeah I know what you mean, there are plenty of ways to do it, but they would all be very hard to do, and posibly dangerouse if you don't know what your doing lol.

take a look at this page.

http://www.boltsniper.com/BS-8/BS8.htm

95% PVC construction. springer powerfull air gun.

Well hes getting around 100-200 fps so thats not very useful. I dont thats really what i would call powerful i could make something more powerful with a ball valve.

Yes but he is using nerf darts which are far heavier.

Heavier than what? I can outdo that with a ball valve, 1 inch pipe, some superballs and ten minutes. Sure, he could neck it down to 6mm and shoot a BB out of it at a decent speed, but then you have one freaking huge piston in relation to the rest of everything.

SEAKING9006 wrote:Heavier than what? I can outdo that with a ball valve, 1 inch pipe, some superballs and ten minutes. Sure, he could neck it down to 6mm and shoot a BB out of it at a decent speed, but then you have one freaking huge piston in relation to the rest of everything.

True.

All i meant to to was to show a design that was similar to what to OP was talking about. Not to showcase the design's "Raw power" ahhhahaa

Any ways, springs and pistons simply are out of the question of the AVERAGE builder on these forums who is looking for power.

Now, for pure coolness factor.... you must admit... that is one kick *insert other word for butt* nerf gun. lol

I have tried, and failed many times to make a springer than can even begin to compare to something as basic as a simple pop-bottle/ball valve cannon.

It would be interesting to see a combustion powered piston gun where the spring is replaced by a fuel/air mixture. That would certainly ease the problem of having to hold back a powerful spring and make the concept more accessible to home builders.