What is Double recoil

[playu72]

Hello what is the double recoil of spring airguns?

[Gavlar]

I think, and I stand to be corrected as I know almost nothing about springers, the first recoil is when the spring and piston goes forward, pushing the gun backwards, the second is when the spring and piston come to a sudden stop at the end of their travel then bounce back, pushing the gun forwards.

[Jesim1]

Laws of motion - every action has an equal and opposite reaction.

You cock the gun and compress the spring giving it potential/kinetic energy.

You then pull the trigger and release the spring and the gun reacts to that energy in the opposite direction by pushing backwards.

The spring then hits the stop and is fully extended, but both it and the piston have momentum, so it pulls the gun forward, hence double recoil, one back and one forward - it plays hell with cheap scopes and those not meant for springers.

James

[Shed tuner]

I think we may need to refine the q.... but very roughly, the firing cycle consists of rearward recoil, then forwards surge, followed by a much smaller recoil, then a tiny surge, any tiny recoil, until it settles as the piston is pushed forwards by the spring, then bounces back somewhat on a cushion of air.. In most cases only the recoil-surge-recoil is significant.

Have a look at this thread:

http://www.airgunbbs.com/showthread....er-Data-Thread

also the linked pix on the first page here show what's happening;
http://www.airgunbbs.com/showthread....le-of-two-guns

[playu72]

Oh thanks! I could imagine something like this.

Sorry my bad english

[zephyr]

A bad joke

BOOM BOOM

[Steyr]

My understanding was that the piston flies forward with corresponding recoil compressing the air but then the air cannot go through the transfer port fast enough so the compression of the air slows or stops and the piston flies forward repeating the process several times in the firing cycle. Then the piston hits the end of the cylinder for good measure.

I am not a springer man and I seem to recall this was the way it works from the late, great Gerald Cardew.

That is why an air rifle springer recoil is so harsh compared to the single kick of a powder burner.....

[ptdunk]

When the piston is released the spring expands, pushing the airgun backwards, then when the piston hits the end of the cylinder it pushes the airgun forwards.

I did a YouTube vid on how recoiless springers try to compensate for this, with a cutaway firing demo at 0:40 and a cutaway recoiless firing demo at 1:40

https://youtu.be/1tyDTwpEDLg

Matt

[averageplinker]

When the piston is released the spring expands, pushing the airgun backwards, then when the piston hits the end of the cylinder it pushes the airgun forwards.

I did a YouTube vid on how recoiless springers try to compensate for this, with a cutaway firing demo at 0:40 and a cutaway recoiless firing demo at 1:40

https://youtu.be/1tyDTwpEDLg

Matt

Great vid. Thanks for making it and posting a link.

[Black Beard]

The piston shouldn't hit the end of the cylinder. If it does, you get horrible recoil and less power. If you've got your gun set up correctly the piston is stopped and sent backwards by the compressed air in the cylinder a bit before it hits the end of the cylinder. The air in the cylinder acts on the front face to make the forward recoil. Since air compresses in a non-linear way this force is harder than the initial spring force/recoil but for a very short time.
If the piston does hit the end of the cylinder the forces are huge and will trash scopes quite fast.

BB

[ptdunk]

The piston shouldn't hit the end of the cylinder. If it does, you get horrible recoil and less power. If you've got your gun set up correctly the piston is stopped and sent backwards by the compressed air in the cylinder a bit before it hits the end of the cylinder. The air in the cylinder acts on the front face to make the forward recoil. Since air compresses in a non-linear way this force is harder than the initial spring force/recoil but for a very short time.
If the piston does hit the end of the cylinder the forces are huge and will trash scopes quite fast.

BB

Of course, I fettle my vintage springers to try to stop the piston slamming into the end of the cylinder, as it's noticeably harsh if they do.
I should have said 'when the piston reaches the end of travel'

Cheers,
Matt.

[BTDT]

Of course, I fettle my vintage springers to try to stop the piston slamming into the end of the cylinder, as it's noticeably harsh if they do.
I should have said 'when the piston reaches the end of travel'

Cheers,
Matt.

Pistons don't ctash into the cylinder end at the end of the compression stroke, Matt.

I once managed to engineer such a crash. I tried first by shooting with no pellet in the breech, but that didn't work, so I tried again with an empty breech and no seal on the piston, and that did the trick. It wasn't as calamitous as many imagine, because the piston does not crash into the cylinder wall - what happens is two systems (the rifle, and the piston/spring)) with equal and opposite momentum collide with each other. The rifle is not jarred forward, it just comes to a very sudden stop; from 15M/s to a standstill in 0.24 ms. Then all hell breaks loose, because the mainspring starts boinging about like TonyL the night before a boinger bash.

Wouldn't do a scope much good.

The harshness you mention is not a crash - it's something else.

[TonyL]

[ptdunk]

Pistons don't ctash into the cylinder end at the end of the compression stroke, Matt.

I once managed to engineer such a crash. I tried first by shooting with no pellet in the breech, but that didn't work, so I tried again with an empty breech and no seal on the piston, and that did the trick. It wasn't as calamitous as many imagine, because the piston does not crash into the cylinder wall - what happens is two systems (the rifle, and the piston/spring)) with equal and opposite momentum collide with each other. The rifle is not jarred forward, it just comes to a very sudden stop; from 15M/s to a standstill in 0.24 ms. Then all hell breaks loose, because the mainspring starts boinging about like TonyL the night before a boinger bash.

Wouldn't do a scope much good.

The harshness you mention is not a crash - it's something else.

I only meant rifles I’ve acquired with seals so deteriorated they don’t hold air, or they have bolts that stick out proud of the piston seal.
The metallic ‘crack’ they produce on firing is soon eliminated with renewed piston seals and a clean & relube. In the end they always shoot sweetly.

That’s about as advanced as my fettling gets!

Matt