# Steve NC, and other airgun gurus.......

Joined: April 1st, 2009, 3:18 am
Question regarding the Webley Paradigm piston design/theory.

The piston in said gun has a Belleville spring stack aft of the piston seal. The seemingly functioning design works by compressing under air charge, creating headspace. Once the gun is fired, the spring stack unloads towards the valve. The logic is that the single stroke charge of air pressure is maintained by this approach, by not suddenly dropping off due to transfer port passage.

My question:

If a gun has, say, .10cu/in valve volume (including induced piston headspace) with a transfer port passage volume of .035cu/in, the piston will need to move at least an equivalent volume of .035cu/in, right?

In single strokes, as we know, stored pressure differs from that of firing pressure. The transfer port passage in a single stroke can reduce pressure significantly. The Achilles heel of SSP.

With that said, the telescopic piston made for the SSP project, but now has a fixed piston, may experiment with it. Make it function like the Paradigm to see what happens.

Joined: March 28th, 2002, 6:54 pm
the piston has to weigh less than the air charge it's pushing.Otherwise it's lagging behind the pressure drop of the charge, and not doing much good. How likely is it you can build a piston/spring system that weighs about what your pellet does?

Joined: January 2nd, 2001, 4:27 am
Question regarding the Webley Paradigm piston design/theory.

The piston in said gun has a Belleville spring stack aft of the piston seal. The seemingly functioning design works by compressing under air charge, creating headspace. Once the gun is fired, the spring stack unloads towards the valve. The logic is that the single stroke charge of air pressure is maintained by this approach, by not suddenly dropping off due to transfer port passage.

My question:

If a gun has, say, .10cu/in valve volume (including induced piston headspace) with a transfer port passage volume of .035cu/in, the piston will need to move at least an equivalent volume of .035cu/in, right?

In single strokes, as we know, stored pressure differs from that of firing pressure. The transfer port passage in a single stroke can reduce pressure significantly. The Achilles heel of SSP.

With that said, the telescopic piston made for the SSP project, but now has a fixed piston, may experiment with it. Make it function like the Paradigm to see what happens.
scientist that i no of on any airgun forums.

Joined: May 12th, 2001, 1:29 pm
Question regarding the Webley Paradigm piston design/theory.

The piston in said gun has a Belleville spring stack aft of the piston seal. The seemingly functioning design works by compressing under air charge, creating headspace. Once the gun is fired, the spring stack unloads towards the valve. The logic is that the single stroke charge of air pressure is maintained by this approach, by not suddenly dropping off due to transfer port passage.

My question:

If a gun has, say, .10cu/in valve volume (including induced piston headspace) with a transfer port passage volume of .035cu/in, the piston will need to move at least an equivalent volume of .035cu/in, right?

In single strokes, as we know, stored pressure differs from that of firing pressure. The transfer port passage in a single stroke can reduce pressure significantly. The Achilles heel of SSP.

With that said, the telescopic piston made for the SSP project, but now has a fixed piston, may experiment with it. Make it function like the Paradigm to see what happens.
...mainly by taking advantage of the higher efficiency of a metal spring over a compressed air charge at giving back more of the energy invested in compression. This advantage arises from the fact that much of the work of compressing air is lost in heating the air, only to dissipate before the shot is taken, and thus wasted. Steel springs don't do that.

Consequently, by sharing the energy of the compression stroke between the air charge and a highly preloaded steel spring, more energy can be extracted from a given pump displacement volume, while simultaneously reducing the peak pressure of the charge. Hence more power from less effort: win-win.

The plot below simulates the result.

Last edited by pneuguy on December 7th, 2017, 5:44 pm, edited 1 time in total.

Joined: April 10th, 2010, 2:40 am
Question regarding the Webley Paradigm piston design/theory.

The piston in said gun has a Belleville spring stack aft of the piston seal. The seemingly functioning design works by compressing under air charge, creating headspace. Once the gun is fired, the spring stack unloads towards the valve. The logic is that the single stroke charge of air pressure is maintained by this approach, by not suddenly dropping off due to transfer port passage.

My question:

If a gun has, say, .10cu/in valve volume (including induced piston headspace) with a transfer port passage volume of .035cu/in, the piston will need to move at least an equivalent volume of .035cu/in, right?

In single strokes, as we know, stored pressure differs from that of firing pressure. The transfer port passage in a single stroke can reduce pressure significantly. The Achilles heel of SSP.

With that said, the telescopic piston made for the SSP project, but now has a fixed piston, may experiment with it. Make it function like the Paradigm to see what happens.
limited throw gas ram inside the piston assembly, sounds silly, But I cant see much else chasing the air charge. I know crosman sells them for 9 bux , and a few companies make smaller variants.The pressure could act on the face of the ram , keeping it energized and flush to piston face.. when the seal is broken , the ram chases the charged air out the Tp
Last edited by murphy29 on December 7th, 2017, 3:52 am, edited 1 time in total.

Joined: May 12th, 2001, 1:29 pm
scientist that i no of on any airgun forums.
It's of one of the beautiful red-shouldered hawks that help me clean up after each session of rodent-snuffing.

Joined: May 12th, 2001, 1:29 pm
the piston has to weigh less than the air charge it's pushing.Otherwise it's lagging behind the pressure drop of the charge, and not doing much good. How likely is it you can build a piston/spring system that weighs about what your pellet does?
...for kinetic energy. But the reason it works anyway is because the piston only moves about 1/200th as far as the pellet, therefore has an average speed only 1/200th as fast, and so (because kinetic energy goes as the square of speed) steals only (1/200)2 = 1/40000 as much energy for every unit of mass.

So even though the piston probably weighs ~200x as much as the pellet, it nevertheless robs less than 1% of the energy.

Joined: May 12th, 2001, 1:29 pm
limited throw gas ram inside the piston assembly, sounds silly, But I cant see much else chasing the air charge. I know crosman sells them for 9 bux , and a few companies make smaller variants.The pressure could act on the face of the ram , keeping it energized and flush to piston face.. when the seal is broken , the ram chases the charged air out the Tp
...a couple of 100lbs of force. A Paradigm type needs 2x or 3x as much.

Joined: August 22nd, 2001, 3:27 pm
Question regarding the Webley Paradigm piston design/theory.

The piston in said gun has a Belleville spring stack aft of the piston seal. The seemingly functioning design works by compressing under air charge, creating headspace. Once the gun is fired, the spring stack unloads towards the valve. The logic is that the single stroke charge of air pressure is maintained by this approach, by not suddenly dropping off due to transfer port passage.

My question:

If a gun has, say, .10cu/in valve volume (including induced piston headspace) with a transfer port passage volume of .035cu/in, the piston will need to move at least an equivalent volume of .035cu/in, right?

In single strokes, as we know, stored pressure differs from that of firing pressure. The transfer port passage in a single stroke can reduce pressure significantly. The Achilles heel of SSP.

With that said, the telescopic piston made for the SSP project, but now has a fixed piston, may experiment with it. Make it function like the Paradigm to see what happens.
and the weight and velocity of the pellet, before I gave any thought to the mechanics involved.

Joined: March 28th, 2002, 6:54 pm
...mainly by taking advantage of the higher efficiency of a metal spring over a compressed air charge at giving back more of the energy invested in compression. This advantage arises from the fact that much of the work of compressing air is lost in heating the air, only to dissipate before the shot is taken, and thus wasted. Steel springs don't do that.

Consequently, by sharing the energy of the compression stroke between the air charge and a highly preloaded steel spring, more energy can be extracted from a given pump displacement volume, while simultaneously reducing the peak pressure of the charge. Hence more power from less effort: win-win.

The plot below simulates the result.

would't the piston still have to lag behind the pressure drop, since it can't move until the pressure ahead of it drops below the spring stack pressure?