SpudFiles

An interesting take on the "valveless" design (where the projectile seals the chamber) in this patent.



The red lever pushes the green pin with moves the purple projecile enough for air to get behind its base, the resultant pressure difference launches the projectile.

I believe there had been a similar design made on spudtech. The inconvenience is the need for a perfect seal and a rigid projectile.

I have come up with this (rough) deisgn a few years back on the same principle, actuated by a piston valve instead of a mechanical rod:

Hmm.

I had an idea similar to the patented design for a chain of projectiles fed into that position in semi-auto where the projectile immediately behind is the breech seal.

Too complicated to actually make.

However that design looks fine. As long as you were certain the whole system sealed perfectly.

Otherwise, as there is no safety mechanism at all, once air gets behind the projectile it fires


Incidentally jack, doesn't your sketch look like an unneccesary complication of a coaxial piston cannon?

I bet you wouldn't even need a piston. You could just use a blowgun to give the projectile a "tap", and full flow would kick in as soon as it started moving forward.

It would be the equivalvent of a piston valve with zero opening time and maximum flow, so if it's performance you're after then it's not an unnecessary complication.

so could i shove a projectile down the barrel and over some orings and then use somehting to push it forewards and it would be just like that design or is it a bit more complicated?

Looks too inconvenient to warrant constructing. Also does not look like any performance increase would be had by this design. A novelty at best.

Oh and it is a valved design! Note: piston and exhaust valve.

benstern wrote:Oh and it is a valved design! Note: piston and exhaust valve.

Ignore my design, the patent shows the projectile simply pushed forward by a lever to expose its base and fire it.

The performance advantages could be tremendous, because unlike a piston valve which is still opening after the projectile has started to move, once the base of the projectile passes the end of the barrel its the equivalent of a piston that has moved back to maximum flow in zero time.

so could i shove a projectile down the barrel and over some orings and then use somehting to push it forewards and it would be just like that design or is it a bit more complicated?

Pretty much, but getting it airtight in the first place might be a little tricky.

Have a look at the diagram, the red lever pushes the green pin with moves the purple projecile enough for air to get behind its base et voila, whoomph!

The performance advantages could be tremendous, because unlike a piston valve which is still opening after the projectile has started to move, once the base of the projectile passes the end of the barrel its the equivalent of a piston that has moved back to maximum flow in zero time.

but surely the time it takes for the ammo to move past the brach of the tee is the opening time but i suspect it will be significantly less than a piston's opening time. the one major problem i can think of for us spudders is that regular ammo would be needed, i was thinking about cylindrical air rifle pellets?

but surely the time it takes for the ammo to move past the brach of the tee is the opening time

This is irrelevant, because in a piston launcher this movement doesn't exist - the actual time of firing is when the base of the projectile is in line with the breech, and unlike a piston launcher at this point the valve is already fully open. On the contrary you should get even more power, because the projectile is already moving when in a piston launcher it would be starting from a stop, you would have effectively lengthened the barrel slightly.

With a bit of work it could be made with an ammunition feed to give multiple shots, though there'd be a lot of wasted air:

what if you had a projectile with a groove cut into it so that it could be latched into place in the barrel, up against a o-ring (similar to how a quick connect works). then when the projectile is unlatched, it fires. this would make it much easier to get a perfect seal, right?

hyperspaz wrote:what if you had a projectile with a groove cut into it so that it could be latched into place in the barrel, up against a o-ring (similar to how a quick connect works). then when the projectile is unlatched, it fires. this would make it much easier to get a perfect seal, right?

Have a look throughthis thread

did you ever continue your experiments with a quick disconnect? it seems like a perfect option- there is no flow restriction. Obviously you're limited in your projectile size, but still. 9/16" can do some damage.

what if you had a projectile with a groove cut into it so that it could be latched into place in the barrel, up against a o-ring

yeah why not, but there would be quite a lot of force acting on the latch...

I don't think there is any need to waste air with this design.... you just have to build a system that sends air into the chamber when the gun is loaded
Sounds complicated but in fact it isn't. You don't even need electronics to control that, you might as well use a simple pneumatic circuit

POLAND- are you still referring to the quick connect design? Couldn't you simply just make a chamber like a normal gun, fill via a ball valve or similar, and then fire it by sliding the sleeve back? Perhaps I'm on the wrong topic, but i dont see why youd need anything complex.

POLAND_SPUD wrote:you just have to build a system that sends air into the chamber when the gun is loaded
Sounds complicated but in fact it isn't. You don't even need electronics to control that, you might as well use a simple pneumatic circuit

Blow forward bolt

did you ever continue your experiments with a quick disconnect? it seems like a perfect option- there is no flow restriction. Obviously you're limited in your projectile size, but still. 9/16" can do some damage.

Not my experiments, LeMaudit's