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Coilrifle accelerator-hybrid

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Hardraade

Sun Feb 12 2012, 11:34PM

Registered Member #4403 Joined: Sun Feb 12 2012, 10:23PM
Location:
Posts: 7

Hello. Ive been posting around for something similar to my.. "visionarities".. but no luck, Ive been adviced to give u guys a go:

Could a coilpowered ram-piston generate the same or higher compression of air as quickly and powerful as the inner piston of a break-barrel spring-powered airrifle? I need to generate a flux-induced force equivalent to 30 joules of mechanical force.
Does anyone know if someone already has given this concept a go?

I was also wondering if an airgun-mounted muzzle accelerator would create enough pull to further accelerate the projectile, considering the small diameter..
I got some ideas for improving the "Gaussian response" of my projectile, but need input..Im planning to fill a length of plastic tubing with powdered iron, washed in diluted phosphoric acid for minimizing the amount of FeO, neutralized while submerged in acid and totally freed from water by methanol.

When packed tightly in tubing, epoxy-resin would be introduced by syringe, and forced through the powder, fixating it. I believe that by "locking" the magn.field of each Fe-granule in an uneven fashion, would make it more responsive to the coils than a CNC-massive projectile.

1. What if i used powdered neod.earthmagnets for projectile-filling?
2.Considering the small diam. of the projectile; would lengthening be a alternative for adding to the mass?

PSCG

Mon Feb 13 2012, 02:48PM

Registered Member #3792 Joined: Sun Mar 27 2011, 06:07PM
Location:
Posts: 136

First of all, welcome to the forum Hardraade!

About your first question, there has been a discussion about propelling a projectile in this way (but not too much information, probably i'm missing some old threads). Take a look here.

For your second question: air guns are known to push the projectiles at velocities between 100 and 310 m/s. Accounting for projectile velocity equal to 200 m/s and a coil accelerator length of 50 cm, the flight time through the accelerator would be 0.0025 sec (2.5 ms). It is possible but considering the efficiency of a coilgun, it is not practical.

I do not know if anyone else has tried to make projectiles from iron powder (but i would be very interested to learn how this approach works for coilguns - saturation would still be a problem).

The Nd powder is not different from a solid Nd magnet. Because of the huge magnetic fields that are created by the coil, they end up demagnetized. See *link*.

Projectile mass can be increased by increasing it's length. In fact, it will help the projectile be more aerodynamic stable during the flight.

Forty

Mon Feb 13 2012, 08:40PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

I think the coil air piston would work pretty well. It's electrical to mechanical energy efficiency would likely be much higher because you could utilize a heavy armature with lots of iron, better coupling by having the armature on the inside and outside of the coil (as the page linked by PSCG shows), and little to no 'suckback' effect because the armature wouldn't have to move from one side of the coil to the other. The projectile could also be very small and light (because it wouldn't need the magnetic material) so very high velocities could be achieved.

I don't think the accelerator at the end of an air rifle would be very effective (as PSCG said)

the powdered iron projectiles should work rather well and they will also minimize eddy current losses in the projectile (they've been discussed many times but not many have been made.) The main problem I see with them, which is why I haven't made any, is that they would likely crack or fall apart when they hit a hard object. I like my projectiles to be relatively equal and easy to make so i bought a bunch of cheap solenoids and use their preshaped plunger pins (like the pins shown here but i got them for $2 each

another benefit of that is that the solenoids provide a perfect coilform, external iron enclosure, and a bunch of wire for other projects.

If you do opt for the powdered iron projectiles, I'd recommend putting a solid tip at one end to absorb some of the impact shock.

and to address your actual questions:

1. Earth magnet material might work alright (probably very high permeability but low saturation, I'd have to check, I'm sure the internet knows) but you would have to demagnetize it first by heating it up. If you didn't, the particles would clump together to form a single magnet and magnets are not good to fire from a coilgun because of extra suckback, possible backwards firing, and possible remagnetization of the projectile. Also you'd have to find out what conditions are used to initially magnetize the material (eg. application of a strong field, cooling in the presence of a field, etc) because you wouldn't want your coilgun to re-magnet-ize your projectile every shot.

2. Lengthening will add to the mass. more material=more mass after all. If you meant could lengthening be used to add more mass instead of increasing diameter, then yes, that'll work. The coil length should then also be increased to approx 1 +/- 1/3 ( or 67%-133%) times the projectile length (to my knowledge, the coilgun community hasn't really decided on the best ratio)

I hope that helps and I look forward to discussing future ideas. Welcome to 4hv

Hardraade

Tue Feb 14 2012, 08:43PM

Registered Member #4403 Joined: Sun Feb 12 2012, 10:23PM
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Posts: 7

Ive seen some paintball-grenadeshells that propels a bunch of .68 balls. Couldnt this be an initial thrust if loaded into the breech with the possibility of semiauto action?

Hardraade

Tue Feb 14 2012, 09:14PM

Registered Member #4403 Joined: Sun Feb 12 2012, 10:23PM
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Posts: 7

Or would a barrelmounted breakbarreled lenght of tubing functioning as a "blank cup" you can mount on a firearm loaded with blank rounds, launching footballs.
Just modified to fit a projectile fitted with seals,keeping the airpressure from seeping around,before reaching the coils?
*Bying a cheap one and cut the barrel,fitting the extended tubing with the coils attached.

Since the concept of placing the powerpack in the stock would the most non-bulky and practical design, I rather want to give the projectile the most powerful initial thrust as possible,reducing the battery-power needed for sufficient muzzle velocities. It also makes the weightbalancing of the rifle better, considering the weight of the coils resting on the muzzletip.

Hardraade

Fri Feb 17 2012, 03:43PM

Registered Member #4403 Joined: Sun Feb 12 2012, 10:23PM
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Posts: 7

Im curious if the demagn.of the projectile's powdered neodym.caused by discharging the accelerating-coil could be eliminated by giving the projectile's surface exposed to the EMP, an insulating layer of metallic mesh. Creating a Faraday-effect that in theory,would protect the earth magnets from being deGaussed from the huge EMP-discharge.

Turkey9

Fri Feb 17 2012, 05:05PM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

The net electric field inside of a conductor is zero, but not the magnetic field. In other words, your shield won't block the magnetic field. If it could, your projectile wouldn't feel any force from the accelerating coil!

Hardraade

Fri Feb 17 2012, 05:17PM

Registered Member #4403 Joined: Sun Feb 12 2012, 10:23PM
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Posts: 7

Are the flux-currents identical to EM-radiation?

Turkey9

Fri Feb 17 2012, 08:01PM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

I don't know what you mean by flux-currents. Flux is the measure of magnetic field passing through a surface. EM radiation, or electromagnetic waves, have a magnetic component, but it doesn't behave the same as a purely magnetic field. The accelerating coil in a coilgun creates a very large magnetic field, but it is not the same as an EMP.

Hardraade

Wed Oct 03 2012, 06:48PM

Registered Member #4403 Joined: Sun Feb 12 2012, 10:23PM
Location:
Posts: 7

Regarding the air-piston driven by coil-accelerator I initially aired in this thread; Would a quench-approach which surrounds the cylinder, or a serie of separate coils give the best results?

I intended to use the TAR-21 platform combined with the length of barrel in the Steyr-AUG.
Because of the huge compartments available for components, the non-exposed barrel except muzzle.
(so any visible coils dont compromise autenticity. )

And the railings that makes several hidden compartments for external components possible, like the AN-PEQ lasersystem, angled frontgrips each got enough space for a batterypack\capacit.wiring or just for heatsinking\whatever fits the weaverrailings.

Most importantly, the total length is suff. for the .177 cylinder and (Inner)barrel to fit within most of limits of aut.rifle

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