replicating gun recoil

[jhony]

Hi there,

I am trying to design a pc gun controller that eumlates (somewhat) the recoil of a gun.

the preffered gun model is an m4a1.

the approach i am considering is to utilise a solenoid to act as a hammer.

i thought i can power it through a high power capacitor and and a portable car jumper lipo battery, 100,000 mah @12V

i cant figure out, how newton thirds law would behave: what system will generate a force that pushes on the player and wont cancel itself.

the design idea was to make a coil around a tube and to put a free metal rod inside as the hammer.

after the cap fires, and the rod hits a plate, a current in the opposite direction would flow, and return the hammer to its original location, where it will be held in place with a magnet, until it fires again

obviously, much less force is needed to reset the hammer....

the recoil is difficult to calculate because there is a recoil suppression system

but, from a quick search on wikipedia i got "free recoil" of 4.3 joules,(is this possible ?)

and i am curious how much BANG i can get SAFELY from such system.

Thanks everybody !

 

[hevans1944]

Recoil mainly occurs only after the projectile and expanding muzzle gases exit the barrel. neglecting the small amount of gas ported to operate the bolt after firing. This is the only time a transfer of momentum can occur. The time interval from cartridge ignition to bullet leaving the barrel is very small, but it is the momentum imparted to the bullet and expanding gases that is responsible for recoil. You cannot simulate recoil with a plunger/solenoid system because you are using a closed system that has no net momentum. And the solenoid wouldn't move anywhere near fast enough, even if it had something to push against that was separate from the "gun" producing the "recoil".

I would give up trying to "simulate" recoil and use real ammunition at a firing range. Note that even "hot" 5.56mm NATO rounds have very little recoil because the bullet is very small, compared to other, larger, shoulder-fired weapons. A PC-based system that "simulates" recoil has no practical training use, other than it wouldn't use ammunition and could be "fired" indoors instead of on a firing range. When I pull the trigger on an M4A1 I want to see a hole appear in something. Full-automatic firing is another hoss altogether. I find it impossible to control the point-of-aim under full-automatic fire... spray and pray. Plus it's a real PITA to reload a dozen or so 30-round banana magazines for just a few minutes of firing. Fun though.

 

[CDRIVE]

Hop, I must be loosing it because some of your description seems to defy Newton's law of every action has an equal and opposite reaction. As far as I know the laws of action-reaction hold true in zero atmosphere, IE does not need expanding gases to satisfy this law. A blank round is nearly recoil-less because little mass goes from rest to rapidly exiting the barrel. The only recoil felt is from the much lighter expanding gas molecules exiting the muzzle.

Chris

 

[Koen]

maybe you can investigate the working of this:

This is an Airsoft Electric Gun, and has a system that provides blowback (the recoil)
At the moment i only have non blowback rifles (exept my handgun, but that is not electric)

But maybe this system could help you to find out what you want

 

[CDRIVE]

I'll say again. Blowback has nothing to do with recoil. Even a slingshot has recoil. In fact if you fire a speargun out of water you'd best keep the butt end clear of your face! Ask me how do I know?

Chris

 

[hevans1944]

Hop, I must be loosing it because some of your description seems to defy Newton's law of every action has an equal and opposite reaction. As far as I know the laws of action-reaction hold true in zero atmosphere, IE does not need expanding gases to satisfy this law. A blank round is nearly recoil-less because little mass goes from rest to rapidly exiting the barrel. The only recoil felt is from the much lighter expanding gas molecules exiting the muzzle.

Chris

Sorry about that, Chris. You are right and I was wrong.

Primary recoil starts as soon as the bullet begins to move down the barrel, not when it leaves the barrel. The net momentum of the bullet is the product mv, where v is the muzzle velocity and m is the bullet mass. This is conserved by imparting an equal and opposite momentum, in the opposite direction of the moving bullet, to the much heavier weapon (and shooter if the butt is held firmly against the shoulder). While the projectile is moving down the barrel, propelled by hot expanding gasses, there are equal and opposite reaction forces on the bullet and the bolt. The force on the bullet imparts momentum to the bullet, the force on the bolt imparts momentum to the weapon and shooter.

There is a secondary recoil that occurs after the bullet leaves the barrel, but this is caused by the hot gasses venting from the muzzle.

I found a website that explains all of this correctly. I should have read this before I posted.

So, maybe it is possible to simulate gun recoil with a solenoid, a heavy weight, and some springs without anything leaving the gun. I just don't have sufficient imagination to know how to do that. Maybe an inspiration will come later. Meanwhile, the question posed by @jhony remains unanswered.

Maybe this can be considered a two-part problem: impart momentum to the gun first and delay the equal and opposite momentum to a later time. This reminds me of a proposed scheme for moving a row-boat without oars on the water. You toss an anchor from the bow to the stern. During the toss, while the anchor is in the air, momentum is imparted to the boat to move it forward. When the anchor lands at the stern, its momentum is transferred to the boat in the opposite direction but by then the boat has moved. Pick up the anchor from the stern and carry it back to the bow. Repeat until you reach your destination (if ever).

Not being a nautical-type person, I don't know if the anchor-toss method of row-boat propulsion will work, but I suspect that it will not. Of course, if you have an available supply of a LOT of anchors, you can make sure to toss them over the stern so they land in the water and transfer no momentum back to the boat. That should work. Otherwise, anchor-toss boat propulsion is right up there with machines that allegedly convert angular momentum to linear momentum with no external forces involved.

 

[KJ6EAD]

There are arcade game guns that have a solenoid, weight and return spring to add some realism. There are weapon simulators such as MILOS and Theissen use with their laser-based training systems that use CO₂ cartridges to drive a piston which moves the bolt or slide of a modified firearm. For a rifle, a solenoid, weight and damped spring such as a gas spring might be somewhat realistic.

 

[CDRIVE]

Hop, the anchor analogy had me in stitches. I've had boats all my life and must admit I never tried that. I guess because over the years I've found that my boats were more sea worthy without gaping holes in the hull! As far as throwing the anchor past the stern and into the water is concerned.. that won't work at all but I'm going to let you mull over why.

What I have seen many times which demonstrates equal and opposite reaction is people attempting to jump from a boat to a dock. Works OK with large vessels but not from a much lighter boat like Boston Whaler. In those cases things usually end with the jumper getting stitched up.

Cheers!
Chris

 

[hevans1944]

As far as throwing the anchor past the stern and into the water is concerned.. that won't work at all but I'm going to let you mull over why.

Why won't that work? Assuming you first remove the anchor rope (or chain)? Not that I think this is a viable row-boat propulsion method. Maybe better to erect a small sail and blow on it? After all, if you can tack against the wind, surely you can provide your own wind!

 

[CDRIVE]

Yes, if you throw a line-less anchor it should work. I can think of equally heavy but cheaper objects to throw though. Come to think of it I had a confrontation with a pedestrian today. I think he's just about the right weight!

Chris

 

[Gryd3]

Keep in mind the whole equal and opposite reaction thing happens twice if you want to 'emulate' recoil...

If a weight inside a prop is propelled in any direction, the prop will exert force on the opposite direction.
So.. if you want to make the weight hit a plate inside the prop to make it feel like recoil, the prop will feel as though it is pulling away from the shooter as the weight accelerates toward the butt of the prop. Then once the weight hits the plate, it will rapidly decelerate and the shooter will feel 'recoil'.
Alternatively, if you had a sudden 'burst' and propelled a weight toward the muzzle, the shooter will feel recoil, but the trick here is controlled deceleration of the weight so that the shooter does not feel like the prop is being pulled away as the weight decelerated and returned to it's resting spot.

This project will be more about the management of acceleration of the weight. Quick acceleration or quick deceleration will cause the shooter to feel a kick. Slow acceleration or slow deceleration will go mostly unnoticed.
This is why I think the only option is to rapidly move a mass toward the muzzle of the prop, then try to slowly dampen the motion to bring it to rest.
(A fun experiment you can do... Grab a Nintendo Wiimote and a bluetooth receiver. You can actually view and log the accelerometer and gyroscope sensor data. You will find that when you manually make the motion with a Wiimote or other g-force sensor, that there is a very large positive G-force exerted on the 'shoot' and a smaller negative g-force experienced as you return back to the original resting point)

Best of luck and have fun! (Perhaps compressed air would be a good thing to experiment with? Shoot it out the muzzle, or use it to propel the weight inside the prop into a spring)