Magnetics and airsoft applications

[Able]

Hey guys,
For a while ive been hearing people say that we should use a EM system to eliminate the gearbox (magnetic coil to propel the piston forward. Having lots of time on my hands and taking electrical engineering ive been thinking about how to do it. Its been attempted before but now with stronger batteries and better tolerances in electronic I believe it would be possible to generate large enough energy to make this work. I have a few different ideas on how to make it work but need some help, and want to know if people would actually want to use such thing.

[Doc]

...What?

[pestobanana]

Would the magnetic pulse not damage other electronics that airsofters may be carrying? Wouldn't the FPS fluctuate depending on power levels? Wouldn't full auto be really sketchy?

Also what would the benefit of this be? Would it really be more power efficient? For reference, well built airsoft guns are typically 20-25% efficient in fully automatic (I have not calculated efficiency in semi automatic).

[-=ArchAngel=-]

If im not mistake, RealSword has been attempting for a few years now to make this concept viable, without any updates in almost a year or so.

[RainyEyes]

Originally Posted by Able

Hey guys,
For a while ive been hearing people say that we should use a EM system to eliminate the gearbox (magnetic coil to propel the piston forward. Having lots of time on my hands and taking electrical engineering ive been thinking about how to do it. Its been attempted before but now with stronger batteries and better tolerances in electronic I believe it would be possible to generate large enough energy to make this work. I have a few different ideas on how to make it work but need some help, and want to know if people would actually want to use such thing.

You're thinking about a gauss rifle concept but for airsoft. If you can make a compact design that propels a metal piston back and forth to compress air, go ahead. It's innovative but this is all ground breaking inventions. You have the floor.

[Magnumb]

It would of course be fascinating and remove almost all moving parts.

I have a few ideas in my head from a design perspective. To speak to an earlier posters concern about magnetic interference. Electromagnetic energy could be used in a pulse to push a piston. However this doesn't mean there is an EMP involved so you need not worry about that.

In my mind, a floating piston makes sense, a return spring would be too slow and frankly I think a electromagnetic push needs to activate the piston and and magnetism needs to draw it back. So there would be significant challenges cycling a capacitor fast enough to dump pushing the piston, and recharge in the time (and at the same time) you reverse the electromagnet to pull the piston back.

The neat thing about a design like this is if you can make sure the system knows where the piston is at any point in its stroke, you can stop the piston short (causing lower chamber pressure) to allow for adjustment of FPS for indoor or outdoor use. Obviously in Canada that's tricky as it needs to be above 366fps to be legal, but if you could have a selector to allow 370fps (indoor) 390 to 400 and 450 long range. You would have one hell of a flexible system.

Air volume is important (in chamber), however volume can be sacrificed if you can increase velocity, this could allow for a shorter stroke. A system like this should be simple. I wouldn't get over excited and design it like a rail gun, but rather figure out how to use electromagnetism to provide the motive effort, and attraction to draw the piston back any time you like in its compression stroke. The piston can be light. It's how it's driven that matters. Lighter the better IMHO.

In my minds eye, I see a backend loaded system with the majority of the propulsive and attractive force acting on the back of the bolt (or in this case, slug) high voltage, High C rated Lipoly and an aggressive cutoff so as not to diminish its ability to "recall" the bolt or charge and dump the capacitor.

Anyhow. No motor, no gear case, no momentary electronic contacts. All digital with simple user programability.

My 2 cents (or half cent if I'm not very clear in my presentation)

[pestobanana]

Originally Posted by Magnumb

Electromagnetic energy could be used in a pulse to push a piston. However this doesn't mean there is an EMP involved so you need not worry about that.

So you can use a pulse of electromagnetic energy but there is no electromagnetic pulse involved? wut.

[Able]

Ya Magnumb we are on the same page. I have some concepts worked out using sim software but its on the electrical side, not the mechanical side, of which im not to well versed.

an issue im having is trying to find out how fast the piston head has to move forward to create enough pressure to get the fps, then converting that using the weight and perm of material used in piston head. Also, with the simulations ive ran, I experience aprox 81% efficiency.

The charge level wouldn't matter so much if it were lipoly as they maintain a fairly steady charge. The issue with the capacitors charging speed is also one I have been working on, I believe by either adding a bank of smaller ones to equal the larger amount required.

The field strength does not even need to be too larger as 1J is not hard to reach.

[Magnumb]

Originally Posted by pestobanana

So you can use a pulse of electromagnetic energy but there is no electromagnetic pulse involved? wut.

Good question: let me explain...

An Electromanetic Pulse is different than an EMP. EMP will kill any live circuit. It's high energy radiation. It's like comparing chicken noodle soup to Molten Lava, yes, they are both sorta liquids.

Does that make sense? An Electromagnetic pulse requires physical constituents, power source, electromagnetic coil and other acting parties. It's only being referred to an electromagnetic pulse because it's using an instantaneous discharge of a high voltage cap or bank of caps to cause a high energy pulse, it just so happens to act through an electromagnet in this instance.

They sound very similar, so any confusion around that is understandable.

[Magnumb]

Originally Posted by Able

Ya Magnumb we are on the same page. I have some concepts worked out using sim software but its on the electrical side, not the mechanical side, of which im not to well versed.

an issue im having is trying to find out how fast the piston head has to move forward to create enough pressure to get the fps, then converting that using the weight and perm of material used in piston head. Also, with the simulations ive ran, I experience aprox 81% efficiency.

The charge level wouldn't matter so much if it were lipoly as they maintain a fairly steady charge. The issue with the capacitors charging speed is also one I have been working on, I believe by either adding a bank of smaller ones to equal the larger amount required.

The field strength does not even need to be too larger as 1J is not hard to reach.

I think you will have to run a much higher than operating voltage on the LiPo, they would need to be very high C as a cap can draw a lot of current. I imagine you would step down the voltage and increase the amperage to pump as much juice into the cap bank as possible. But you will need to cycle the piston back as fast, if not faster than it's going forward. So if it's not doing so against load (not pushing air) it can return fast with less energy required to accomplish that. Ohhhhh, could go really simple and as the piston slides forward it completes a circuit at the end of its forward travel causing a cap dump into a smaller electromagnet to force it back.

I freaking love this stuff....now if I was only smart enough to use big words to explain it.

You please me Able

[AnthonyG]

Sounds cool.

[dmitril]

I've done some math on this concept albeit with recoil action and hit an issue of too high power requirements to maintain 12rps. The problem is motors are ~80% efficient, while making a liner motor in this manner that is 10% is already great.
I haven't considered providing enough energy to propel the bb only, this might actually be realistic.
Another solution to this is to use neodymium magnets with a large surface area piston and short stroke but this is unlikely to fit into v2/3 form factor.

[ThunderCactus]

FYI you'll also need enough current to have that piston generate up to 80psi

And keep in mind, the piston body doesn't need to be there, only the piston head. So you could just use a long chain of solenoids with a rod that has the piston head on the front.
If you run out of room in the mechbox, remember you can always extend back into the buffer tube.

Multiple segmented solenoid with a segmented rod in order to up the pressure. Don't know how well that will work given then length of the stroke though.

Stroke will shorten as the barrel gets shorter: shorter barrel = shorter cylinder
With electrical power you should be able to accelerate fast enough in a very short distance, and all the power to generate initial pressure is going to be applied electrically instead of by momentum.
So you're going to need some capacitors lol

[Able]

yes, the issue is not with semi fire, it would be easy if it were semi only as you allow time for charging caps. a few concepts I have as semi working models are (wont go into to many details) an electro magnet that changes polarity to propel a neo mag net piston head forward, then switching polarity with less power (reg circuit) to pull it back. and judging that magnetics forces are uncomparibly stronger then most other forces this should not take to much to power through for the required fps.

an issue that arrises then is that is someone applies different battery you are not affecting the rof anymore its the fps that will be affected, which can be good and bad, allow for cqb to field levels by connecting dif battery.

also full auto draws too much current. with these currents the gun would also need isolation and short protection as it could range into danger territory quickly.

[Magnumb]

Originally Posted by Able

yes, the issue is not with semi fire, it would be easy if it were semi only as you allow time for charging caps. a few concepts I have as semi working models are (wont go into to many details) an electro magnet that changes polarity to propel a neo mag net piston head forward, then switching polarity with less power (reg circuit) to pull it back. and judging that magnetics forces are uncomparibly stronger then most other forces this should not take to much to power through for the required fps.

an issue that arrises then is that is someone applies different battery you are not affecting the rof anymore its the fps that will be affected, which can be good and bad, allow for cqb to field levels by connecting dif battery.

also full auto draws too much current. with these currents the gun would also need isolation and short protection as it could range into danger territory quickly.

Yes, very similar to what I was thinking. It (electromagnetic motor ) needs to do both jobs for sure. I agree with the above poster that the piston needs be only the bare minimum.

You make a valid point BTW, the electromagnetic force is one of the strongest there is period. It's 10 (to the 39th power) more powerful than gravity. (Funny how the standard model of cosmology completely discounts the possibility of its roll in the cosmos....but that's another topic all together.