Springer anti bounce experiment

[BTDT]

To put into context, simply doubling the pellet friction is worth about a 25% reduction in piston bounce...

Doubling the piston seal friction surely, Jamie?

[Loki_79]

Doubling the piston seal friction surely, Jamie?

No it is pellet friction! In my model the pellet friction is one of the most dominant factors by far (apart from TP diameter). Probably because the transfer port flow equations assume flow based on an orifice plate model. 10N of (constant) piston seal friction is completely negated by an extra few mm of spring compression.

If the release friction for the pellet is too low (~1N) then the pellet will move before any significant pressure has built up in the chamber (or barrel).

For anything around 1 to 10N I can get fairly reaslistic behaviour, but it is effectively controlling the barrel expansion volume (flow is still limited by the TP port).

If the pellet friction is extremely high (~200N), then we have the equivalent of a closed piston and get damped simple harmonic motion of the piston.

[BTDT]

Gotcha. Pellet release pressure is indeed a dominant factor but, as it's determined by both friction and deformation of the pellet as it conforms to the rifling, I think of it as just release pressure.

[Black Beard]

The sliding weight in itself won't make much difference to the feel of the recoil. You mainly feel the forces from the spring and the compressed air in the cylinder. The interaction between the piston and the air in the cylinder is not felt by the shooter.

BB

[Shed tuner]

The sliding weight in itself won't make much difference to the feel of the recoil. You mainly feel the forces from the spring and the compressed air in the cylinder. The interaction between the piston and the air in the cylinder is not felt by the shooter.

BB

nah, but the effect of the piston bounce is felt when it lands afterwards...

[Loki_79]

The sliding weight in itself won't make much difference to the feel of the recoil. You mainly feel the forces from the spring and the compressed air in the cylinder. The interaction between the piston and the air in the cylinder is not felt by the shooter.

BB

You may not feel the weight actually sliding, but if it doubles the mass of the piston then you are going to notice for sure!

[Black Beard]

No. The energy put into the piston is the energy in the spring and it becomes the energy in the air in the cylinder. You can't feel what the piston does unless it is attached to the cylinder. Most of what you feel is the force of the spring pushing back and the air pressure pushing forward. The spring is still having to accelerate the mass of the piston and weight. The air is still having to stop the piston + weight. The recoil is going to be very close to a airgun with a piston that is the same mass as the complete piston + weight.

You get a similar thing if you have a really heavy spring with little preload. The recoil curve looks a bit wavy but it is essentially the same where it matters.

BB

[Desmond.22]

Bit late to the party but just reading these ideas I'm seriously impressed.

Some seriously clever and experienced lads on here and glad to see the springer still priority for some shooters.

[Loki_79]

No. The energy put into the piston is the energy in the spring and it becomes the energy in the air in the cylinder. You can't feel what the piston does unless it is attached to the cylinder. Most of what you feel is the force of the spring pushing back and the air pressure pushing forward. The spring is still having to accelerate the mass of the piston and weight. The air is still having to stop the piston + weight. The recoil is going to be very close to a airgun with a piston that is the same mass as the complete piston + weight.

You get a similar thing if you have a really heavy spring with little preload. The recoil curve looks a bit wavy but it is essentially the same where it matters.

BB

I'm not sure what you are trying to argue, but the piston will always come to rest in contact with the action as Jon said already. I.e. the second piston impact is always heavy without any air to cushion the landing.

The oscillations that you describe are the typical 'boing' in boinger, and even if you think you can't feel them you can certainly hear them. The amplitude is directly proportional to piston (and spring) mass though.

And "The recoil is going to be very close to a airgun with a piston that is the same mass as the complete piston + weight." is almost what I have been saying since my first post on this thread, but to have any effect on the friction whatsoever the sliding mass will have to be *at least* equal mass to the piston (and I suspect a lot more). So assuming that the piston is already as light as possible, the new mass of the combined piston+weight is going to be *at least* double the mass of the original piston.

If you want to check my working, I put the whole model here:
https://www.dropbox.com/s/l05r4i6b5x...model.rtf?dl=0

[TonyL]

There's a superb article on piston bounce by Jim in this month's Airgun World, tinkery people..

And enlightening information about the magnitude of the forces involved. Wow!

For anyone who might not usually buy the magazine, it's worth it for this article alone if you're interested in spring gun mechanics.

[Weasle]

There's a superb article on piston bounce by Jim in this month's Airgun World, tinkery people..

And enlightening information about the magnitude of the forces involved. Wow!

For anyone who might not usually buy the magazine, it's worth it for this article alone if you're interested in spring gun mechanics.

My first 'go to' read when the Mag falls thru the door - Good old Jim rescues rescues my sanity regularly.

Cheers Steve

[Born Again]

If you want to check my working, I put the whole model here:
https://www.dropbox.com/s/l05r4i6b5x...model.rtf?dl=0

A chartered engineer I work with says "If you can't put numbers on it you don't understand it". So well done, I wish I could.

[BTDT]

There's a superb article on piston bounce by Jim in this month's Airgun World, tinkery people..

And enlightening information about the magnitude of the forces involved. Wow!

For anyone who might not usually buy the magazine, it's worth it for this article alone if you're interested in spring gun mechanics.

My first 'go to' read when the Mag falls thru the door - Good old Jim rescues rescues my sanity regularly.

Cheers Steve

Thank you kindly, young Sirs.

The article was inspired by this thread, as it happens.

[TonyL]

Thank you kindly, young Sirs.

The article was inspired by this thread, as it happens.

With pleasure, Sir.. And, in your case, Jim, the "Sir" title should really mean just that and you should receive a knighthood for your services to airgunnery. Maybe this New Year, eh?

Your articles are always the highlight for me. So rammed with information, practical, pragmatic and thought provoking. And that's not taking away anything from the many other contributors who do a brilliant job and make the magazine what it is.

When IS that book coming out, by the way?

Re this article, I did wonder as to whether this thread had anything to do with it. Take a bow, Nick.

And it's amazing to think how superbly many springers shoot when there are forces at work inside to this magnitude. I appreciate that it's all over so quickly but it's huge testament to this system which can provide this level of performance and refinement combined with longevity.

Keep the excellent work coming, Jim, and I'll have five signed copies, please.

[Shed tuner]

Jim, did I conclude correctly that using a lighter lathe will reduce piston bounce ?