using both induction and reluctance for coilgun
Maz, Mon Apr 17 2006, 12:23AMis it possible to almost double the efficiency of a coil by making the projectiles out of three parts?
the back, a ferrous material, to be sucked into the coil.
the middle, up to the center of the coil. something that isn't affected either way. I'm thinking epoxy cast.
and finally, aluminum. to be pushed away from the center of the coil.
for some reason this seems way too easy but if it works, it should be of great benefit.
Re: using both induction and reluctance for coilgun
Electroholic, Mon Apr 17 2006, 12:41AM
u mean you want to pulse the same coil twice?
never heard of anything like that,
it should work, in theory. don't know about efficiency, tho.
Electroholic, Mon Apr 17 2006, 12:41AM
u mean you want to pulse the same coil twice?
never heard of anything like that,
it should work, in theory. don't know about efficiency, tho.
Re: using both induction and reluctance for coilgun
Simon, Mon Apr 17 2006, 05:58AM
Using two principles doesn't equal doubled efficiency, in fact, it sometimes means compromise efficiency. I suggest you try it and see what happens but I doubt you'll get much benefit. The epoxy will just be dead weight.
Simon, Mon Apr 17 2006, 05:58AM
Using two principles doesn't equal doubled efficiency, in fact, it sometimes means compromise efficiency. I suggest you try it and see what happens but I doubt you'll get much benefit. The epoxy will just be dead weight.
Re: using both induction and reluctance for coilgun
evilgecko, Mon Apr 17 2006, 08:47AM
I think he means that you but the bullet at the center of the coil so that you pulse it once and half the bullet is attracted and the other half repelled and the same time
evilgecko, Mon Apr 17 2006, 08:47AM
I think he means that you but the bullet at the center of the coil so that you pulse it once and half the bullet is attracted and the other half repelled and the same time
Re: using both induction and reluctance for coilgun
FastMHz, Mon Apr 17 2006, 05:26PM
Fascinating idea! You should definitely try it. Has anyone ever tried firing an all-aluminum slug from a CG?
FastMHz, Mon Apr 17 2006, 05:26PM
Fascinating idea! You should definitely try it. Has anyone ever tried firing an all-aluminum slug from a CG?
Re: using both induction and reluctance for coilgun
Bjørn, Mon Apr 17 2006, 06:53PM
Except in special cases the efficiency will be worse than the best of the two.
If you have a very efficient coil gun and the projectile is about to saturate, then you can reach higher powers more efficiently by adding reluctance than by increasing the current for the coil gun.
Bjørn, Mon Apr 17 2006, 06:53PM
Except in special cases the efficiency will be worse than the best of the two.
If you have a very efficient coil gun and the projectile is about to saturate, then you can reach higher powers more efficiently by adding reluctance than by increasing the current for the coil gun.
Re: using both induction and reluctance for coilgun
Madgyver, Tue Apr 18 2006, 07:15PM
Why should a Mag. field, strong enough to repell Aluminium not attract the iron too? unless your Epoxy spacer is VERY long.
Madgyver, Tue Apr 18 2006, 07:15PM
Why should a Mag. field, strong enough to repell Aluminium not attract the iron too? unless your Epoxy spacer is VERY long.
Re: using both induction and reluctance for coilgun
..., Tue Apr 18 2006, 10:37PM
That is the idea, you have the Fe being attracted to the coil while the Al is being repelled, doubling? you eficiency
..., Tue Apr 18 2006, 10:37PM
Madgyver wrote ...
Why should a Mag. field, strong enough to repell Aluminium not attract the iron too? unless your Epoxy spacer is VERY long.
Why should a Mag. field, strong enough to repell Aluminium not attract the iron too? unless your Epoxy spacer is VERY long.
That is the idea, you have the Fe being attracted to the coil while the Al is being repelled, doubling? you eficiency
Re: using both induction and reluctance for coilgun
Self Defenestrate, Wed Apr 19 2006, 12:08AM
I bet tuning the thing would be terribly hard. Seems like an interesting idea though. I'd give it a go.
Self Defenestrate, Wed Apr 19 2006, 12:08AM
I bet tuning the thing would be terribly hard. Seems like an interesting idea though. I'd give it a go.
Re: using both induction and reluctance for coilgun
Xyth, Wed Apr 19 2006, 01:55AM
I guess this isn't too bad of a place to make my first post...
I've been messing around with this idea for a little while recently. Using a 2 section bullet, front being aluminum and the back being steel (I was calling it a "Hybrid" bullet, since it's pretty accurate and sounds cool). I haven't had much luck so far, alot of it being because of how many variables seem to come into play. Such as the length of the aluminum bullet, the length of the steel section, distance between the two, how far each one was put into the coil, etc. There also seems to be the inherent problem of the ideal firing conditions for a reluctance coilgun are different from that of an induction coilgun. Since with a reluctance CG you need a slightly longer pulse since it has to be pulled into the coil and more slowly accelerated, where with induction you want a very fast pulse to dump as much energy into the projectile before it is pushed to far.
Anyway, I haven't done a whole lot of testing with the idea, espically since I don't have a chronograph currently (Though it is coming in the mail!) and have had to judge power by eye.
Also, not totally sure why this is, but the bullet had a tendancy to break apart. I was first just using tape to hold the two sides together, and they would rip off of each other pretty frequently. They survived a few more shots after I started super glueing them however. Im not totally sure whether this has to do with the eddy currents on the aluminum repelling the steel, or just the shock of the impact jarring the pieces... As well as the overall results seemed to point to a lower efficiency then with just a steel projectile.
Well, I look forward to seeing what kind of results you come up with.
Xyth, Wed Apr 19 2006, 01:55AM
I guess this isn't too bad of a place to make my first post...
I've been messing around with this idea for a little while recently. Using a 2 section bullet, front being aluminum and the back being steel (I was calling it a "Hybrid" bullet, since it's pretty accurate and sounds cool). I haven't had much luck so far, alot of it being because of how many variables seem to come into play. Such as the length of the aluminum bullet, the length of the steel section, distance between the two, how far each one was put into the coil, etc. There also seems to be the inherent problem of the ideal firing conditions for a reluctance coilgun are different from that of an induction coilgun. Since with a reluctance CG you need a slightly longer pulse since it has to be pulled into the coil and more slowly accelerated, where with induction you want a very fast pulse to dump as much energy into the projectile before it is pushed to far.
Anyway, I haven't done a whole lot of testing with the idea, espically since I don't have a chronograph currently (Though it is coming in the mail!) and have had to judge power by eye.
Also, not totally sure why this is, but the bullet had a tendancy to break apart. I was first just using tape to hold the two sides together, and they would rip off of each other pretty frequently. They survived a few more shots after I started super glueing them however. Im not totally sure whether this has to do with the eddy currents on the aluminum repelling the steel, or just the shock of the impact jarring the pieces... As well as the overall results seemed to point to a lower efficiency then with just a steel projectile.
Well, I look forward to seeing what kind of results you come up with.
Re: using both induction and reluctance for coilgun
Electroholic, Wed Apr 19 2006, 04:56AM
Care to Explain more?
What is the bullet placement? before or after the coil?
Which is head, which is tail?
Steel / Alu?
How do you pulse the coil? single / multi pulse?
If you are using only single pulse,
while bullet placement is behind the coil,
with steel as head, Alu as the tail.
I would imagin that when the steel part got pull into the coil, the alu part will be repelled.
You will lost energy and break your hybrid bullet.
the only way for it to work is like Madgyver have said.
longer spacer.
and you still have to pulse it twice.
still don't think efficiency would increase tho.
Electroholic, Wed Apr 19 2006, 04:56AM
Care to Explain more?
What is the bullet placement? before or after the coil?
Which is head, which is tail?
Steel / Alu?
How do you pulse the coil? single / multi pulse?
If you are using only single pulse,
while bullet placement is behind the coil,
with steel as head, Alu as the tail.
I would imagin that when the steel part got pull into the coil, the alu part will be repelled.
You will lost energy and break your hybrid bullet.
the only way for it to work is like Madgyver have said.
longer spacer.
and you still have to pulse it twice.
still don't think efficiency would increase tho.
Re: using both induction and reluctance for coilgun
evilgecko, Wed Apr 19 2006, 06:58AM
If you had iron to the left of the center of the coil, and then aluminium to the right, then both forces would be in the same direction, accelerating the bullet to the right.
evilgecko, Wed Apr 19 2006, 06:58AM
If you had iron to the left of the center of the coil, and then aluminium to the right, then both forces would be in the same direction, accelerating the bullet to the right.
Re: using both induction and reluctance for coilgun
Electroholic, Wed Apr 19 2006, 07:06AM
Oh!
I'm dumb. 
humm...I bet suck back is serious issue there then.
Then middle section will have to be tuned to the pulse length...
Electroholic, Wed Apr 19 2006, 07:06AM
Oh!
I'm dumb. humm...I bet suck back is serious issue there then.
Then middle section will have to be tuned to the pulse length...
Re: using both induction and reluctance for coilgun
FastMHz, Thu Apr 20 2006, 08:56PM
I just took one of my good CG coils and put an aluminum nail in it and fired it...nothing happened whatsoever...which surprises me, since my induction launchers work so well...maybe it cancels itself out and firing a non-ferrious slug from a cylindrical coil just won't work.
FastMHz, Thu Apr 20 2006, 08:56PM
I just took one of my good CG coils and put an aluminum nail in it and fired it...nothing happened whatsoever...which surprises me, since my induction launchers work so well...maybe it cancels itself out and firing a non-ferrious slug from a cylindrical coil just won't work.
Re: using both induction and reluctance for coilgun
GimpyJoe, Fri Apr 21 2006, 02:53AM
Have you tried playing around with the projectile starting position?
GimpyJoe, Fri Apr 21 2006, 02:53AM
Have you tried playing around with the projectile starting position?
Re: using both induction and reluctance for coilgun
WaveRider, Fri Apr 21 2006, 08:48AM
Starting position is important. Remember that the induction coilgun relies on repulsion of the armature instead of attraction, as in a reluctance coilgun.
Generally, a coilgun designed as for use with ferrous armatures will not work very well with non-ferrous materials. Induction guns need firing pulses at least an order of magnitude (two orders are better) shorter than reluctance guns. As a consequence, higher coil currents are required to generate the proportionally higher instantaneous forces over these short times...this means high voltages and high currents, e.g. kV and 10s of kA, typically. (The dynamics are similar for can-crushers and ring launchers.)
The pulse times must be short enough that the currents induced on the surface of the armature do not have time to penetrate and decay significantly during the firing pulse. Once the currents decay and the magnetic field fully penetrates the armature, the forces vanish.
You can get an order of magnitude idea of the relationship between penetration depth and pulse time from the "skin-depth" formula
where x_p is the desired penetration depth (which should be a small fraction of the armature radius), t_p is the permissible pulse duration, mu_0 is the vacuum permeability (4e+07 * pi H/m in SI units) and sigma is the armature conductivity (3.767e+07 S/m for aluminium in SI units).
Ferrous armatures do not have this built-in pulse time limitation. It's enough to switch off the current before the slug starts to exit the coil.
There may be room for building a "linear induction motor" that uses windings on a ferrous armature.....Hmmmm <scratches head....>
WaveRider, Fri Apr 21 2006, 08:48AM
Starting position is important. Remember that the induction coilgun relies on repulsion of the armature instead of attraction, as in a reluctance coilgun.
Generally, a coilgun designed as for use with ferrous armatures will not work very well with non-ferrous materials. Induction guns need firing pulses at least an order of magnitude (two orders are better) shorter than reluctance guns. As a consequence, higher coil currents are required to generate the proportionally higher instantaneous forces over these short times...this means high voltages and high currents, e.g. kV and 10s of kA, typically. (The dynamics are similar for can-crushers and ring launchers.)
The pulse times must be short enough that the currents induced on the surface of the armature do not have time to penetrate and decay significantly during the firing pulse. Once the currents decay and the magnetic field fully penetrates the armature, the forces vanish.
You can get an order of magnitude idea of the relationship between penetration depth and pulse time from the "skin-depth" formula
x_p = sqrt{t_p / (mu_0 * sigma)}
where x_p is the desired penetration depth (which should be a small fraction of the armature radius), t_p is the permissible pulse duration, mu_0 is the vacuum permeability (4e+07 * pi H/m in SI units) and sigma is the armature conductivity (3.767e+07 S/m for aluminium in SI units).
Ferrous armatures do not have this built-in pulse time limitation. It's enough to switch off the current before the slug starts to exit the coil.
There may be room for building a "linear induction motor" that uses windings on a ferrous armature.....Hmmmm <scratches head....>
Re: using both induction and reluctance for coilgun
TheMerovingian, Fri Apr 21 2006, 09:58AM
I think that the two approaches cannot be used at the same time. For a simple reason:
Induction coilgun needs fast rise/fall rates (since it relies on eddy currents). The iron part of the projectile is also conductive and will be repelled. Probably less than the other side due to the skin effect as you have stated but still present, reducing the advantage. Other problem is that coilguns don't work very well with fast pulses, because if higher inertia of the projectile (alu is lighter). And you risk the current falling way before the projectile reaches the critical point wasting power. Another risk is the detachment of the two sections since the forces are not the same (in the rise-phase of the pulse the alu-section will be repelled more that the attraction of the iron core).
I'm don't saying it is impossibile, just overcomplicated and overdangerous (High voltages, no semiconductor switching, difficulty to multistage it etc)
TheMerovingian, Fri Apr 21 2006, 09:58AM
I think that the two approaches cannot be used at the same time. For a simple reason:
Induction coilgun needs fast rise/fall rates (since it relies on eddy currents). The iron part of the projectile is also conductive and will be repelled. Probably less than the other side due to the skin effect as you have stated but still present, reducing the advantage. Other problem is that coilguns don't work very well with fast pulses, because if higher inertia of the projectile (alu is lighter). And you risk the current falling way before the projectile reaches the critical point wasting power. Another risk is the detachment of the two sections since the forces are not the same (in the rise-phase of the pulse the alu-section will be repelled more that the attraction of the iron core).
I'm don't saying it is impossibile, just overcomplicated and overdangerous (High voltages, no semiconductor switching, difficulty to multistage it etc)
Re: using both induction and reluctance for coilgun
FastMHz, Fri Apr 21 2006, 06:18PM
Yes I tried putting the AL nail in every position I could with no effect. I used the same cap bank I used for my induction launchers, and the CG coil is the same length of the same wire that I made my pancake coils with - so the pulse length should be similarly short. The nail doesn't even budge, not even by a hair...I hope somebody else tries it to see if the results are the same...there's really no point in making a dual induction/repulsion lanucher if aluminum can't be fired from a CG.
FastMHz, Fri Apr 21 2006, 06:18PM
Yes I tried putting the AL nail in every position I could with no effect. I used the same cap bank I used for my induction launchers, and the CG coil is the same length of the same wire that I made my pancake coils with - so the pulse length should be similarly short. The nail doesn't even budge, not even by a hair...I hope somebody else tries it to see if the results are the same...there's really no point in making a dual induction/repulsion lanucher if aluminum can't be fired from a CG.
Re: using both induction and reluctance for coilgun
Quantum Singularity, Fri Apr 21 2006, 07:30PM
Got to be a problem with your setup fastMHZ...
Not sure if I have an answer why yours isnt working... maybe its just so far out of tune? And I know you probably tried this but as far as start position the projectile should probably be entirely to one side off center of the coil, if not further out. I would think if very much of the projectile crosses center than it will cancel out.
For the original poster... my 2 cents on the combo gun would be that it is an interesting idea and would be unique however I would think the efficiency would be less for sure. The two types are too far apart to be used together efficiently. It would be more efficient just to make an optimally designed cg that used 2 stages rather than a compromised cg that used 1 stage but 2 different forces. Remember the reluctance gun can utilize more of a steady state current through the coil to draw the projectile in (the limit being when the projectile reaches center) and the induction/repulsion utilizes fast rise times to induce eddy currents (which is what creates the force). Thats just a simplistic view of the differences but shows just how different they are.
Quantum Singularity, Fri Apr 21 2006, 07:30PM
Got to be a problem with your setup fastMHZ...
there's really no point in making a dual induction/repulsion lanucher if aluminum can't be fired from a CG.Pulslaser (and others too) made a pretty awsome induct/repulsion cg that I beleive fired both solid and hollow aluminum rounds. It is down the list a little ways:http://4hv.org/e107_plugins/forum/forum_viewtopic.php?2913
Not sure if I have an answer why yours isnt working... maybe its just so far out of tune? And I know you probably tried this but as far as start position the projectile should probably be entirely to one side off center of the coil, if not further out. I would think if very much of the projectile crosses center than it will cancel out.
For the original poster... my 2 cents on the combo gun would be that it is an interesting idea and would be unique however I would think the efficiency would be less for sure. The two types are too far apart to be used together efficiently. It would be more efficient just to make an optimally designed cg that used 2 stages rather than a compromised cg that used 1 stage but 2 different forces. Remember the reluctance gun can utilize more of a steady state current through the coil to draw the projectile in (the limit being when the projectile reaches center) and the induction/repulsion utilizes fast rise times to induce eddy currents (which is what creates the force). Thats just a simplistic view of the differences but shows just how different they are.
Re: using both induction and reluctance for coilgun
FastMHz, Sat Apr 22 2006, 12:53AM
Interesting...I'll go do more experimenting...maybe my barrel being copper is a problem or something, so I'll try one of my coils on PVC with the AL nail and see what happens. I don't think I tried putting the nail entirely out of the coil either. I'll post back after I do some more testing.
FastMHz, Sat Apr 22 2006, 12:53AM
Interesting...I'll go do more experimenting...maybe my barrel being copper is a problem or something, so I'll try one of my coils on PVC with the AL nail and see what happens. I don't think I tried putting the nail entirely out of the coil either. I'll post back after I do some more testing.
Re: using both induction and reluctance for coilgun
Quantum Singularity, Sun Apr 23 2006, 01:39AM
Hmm, if your barrel is conductive that could very well cause the problem. Seems like it would have the effect of shielding the projectile inside from the forces, and if the pusle was strong enough might crunch the barrel like a can crusher. I may be getting beyond my knowledge in this matter but I would think as the pulse started to grow, the flux lines would first intersect the barrel and induce current to flow around the barrel. As more flux lines pass more current is induced in the barrel and therefore a strong magnetic field begins to form that repels the flux from the coil. I am not sure how completely this would repel but my guess is very little if any magnetic flux would make it through the opposing field around the barrel and induce a significant amount into the projectile. Anyone else agree or have a different/better explanation?
Quantum Singularity, Sun Apr 23 2006, 01:39AM
Hmm, if your barrel is conductive that could very well cause the problem. Seems like it would have the effect of shielding the projectile inside from the forces, and if the pusle was strong enough might crunch the barrel like a can crusher. I may be getting beyond my knowledge in this matter but I would think as the pulse started to grow, the flux lines would first intersect the barrel and induce current to flow around the barrel. As more flux lines pass more current is induced in the barrel and therefore a strong magnetic field begins to form that repels the flux from the coil. I am not sure how completely this would repel but my guess is very little if any magnetic flux would make it through the opposing field around the barrel and induce a significant amount into the projectile. Anyone else agree or have a different/better explanation?
Re: using both induction and reluctance for coilgun
FastMHz, Sun Apr 23 2006, 05:21PM
Thanks for the info Tristan - I do have slits cut into the side of the copper barrel to eliminate eddies to some degree, and regular steel slugs shoot out of it with lethal power...but no matter what I tried with the aluminum it just wouldn't move. I got it to budge about a mm once, but I think the coil itself jumped when I pulsed it...I haven't tried my pvc barrel yet 'cause I've been a bit busy with building my electric bazooka
Maz - I still think you should try it anyway and see what happens...it might be hard to tell if the AL part is working at all though since the steel part will work regardless...
FastMHz, Sun Apr 23 2006, 05:21PM
Thanks for the info Tristan - I do have slits cut into the side of the copper barrel to eliminate eddies to some degree, and regular steel slugs shoot out of it with lethal power...but no matter what I tried with the aluminum it just wouldn't move. I got it to budge about a mm once, but I think the coil itself jumped when I pulsed it...I haven't tried my pvc barrel yet 'cause I've been a bit busy with building my electric bazooka
Maz - I still think you should try it anyway and see what happens...it might be hard to tell if the AL part is working at all though since the steel part will work regardless...
Re: using both induction and reluctance for coilgun
Maz, Sun Apr 23 2006, 11:19PM
This is basically what i was thinking. quick paint job to get a visual. i wish i could say that i have tried it but i do not have the setup for reluctance to i look forward to seeing others results!
Maz, Sun Apr 23 2006, 11:19PM
This is basically what i was thinking. quick paint job to get a visual. i wish i could say that i have tried it but i do not have the setup for reluctance to i look forward to seeing others results!
Re: using both induction and reluctance for coilgun
Reaching, Fri Nov 24 2006, 10:05PM
grabbing this thread out, cause im on the search for new ideas for my big multistage coilgun.
so why not combine reluctance and induction but with 2 coils? a reluctance cg needs a longer pulse and a induction cg needs a short pulse. so i thought about it. i made a hybrid projectile with 2 sections. the head is a 3cm long 8mm steelrod the tail is a 2cm long 8mm aluminium rod held together with a iron screw inside.
why not use a simple reluctance cg coil to accelerate the projectile, then it passes a fotogate which switches the second coil on for pushing the projectile forward via induction. if it works fine it is very good for multistage coilguns cause you can use both principles. while the steel is saturating after beeing magnetized from a coil the inductive part can accelerate the whole thing. the steel part has more time to demagnetize(dont know the right word).
i hope there are no open questions, the picture is self explaining
Reaching, Fri Nov 24 2006, 10:05PM
grabbing this thread out, cause im on the search for new ideas for my big multistage coilgun.
so why not combine reluctance and induction but with 2 coils? a reluctance cg needs a longer pulse and a induction cg needs a short pulse. so i thought about it. i made a hybrid projectile with 2 sections. the head is a 3cm long 8mm steelrod the tail is a 2cm long 8mm aluminium rod held together with a iron screw inside.
why not use a simple reluctance cg coil to accelerate the projectile, then it passes a fotogate which switches the second coil on for pushing the projectile forward via induction. if it works fine it is very good for multistage coilguns cause you can use both principles. while the steel is saturating after beeing magnetized from a coil the inductive part can accelerate the whole thing. the steel part has more time to demagnetize(dont know the right word).
i hope there are no open questions, the picture is self explaining
Re: using both induction and reluctance for coilgun
Marko, Fri Nov 24 2006, 10:22PM
As it was discussed, when you try to launch this bullet using reluctance effect will be cancelled by attraction to iron. Maybe if you used very long projectile, with non-conducting part, or etc, but I still don't see any advantage versus using one of techniques solo.
Marko, Fri Nov 24 2006, 10:22PM
As it was discussed, when you try to launch this bullet using reluctance effect will be cancelled by attraction to iron. Maybe if you used very long projectile, with non-conducting part, or etc, but I still don't see any advantage versus using one of techniques solo.
Re: using both induction and reluctance for coilgun
Reaching, Sat Nov 25 2006, 02:18PM
ok, you dont understand what i was trying to explain.i want to use to seperate coils on 2 seperate coilforms to accelerate the iron part via reluctance and the aluminium part via induction. the first coil switches on and the iron is sucked into the coil, when the iron reaches the middle of the coil the first coil is turned off. the projectile leaves the first coil and passes the second coil and activates a fotogate that is placed on a calculated direction so that only the aluminium part of the projectile is in the second middle of the second coil so the aluminium part is repelled by the magnetic field of the second coil which is turned on with the fotogate. so you combined both principles. the advantage i see is that the iron part of the projectile has more time to demagnetize but still increase its velocity by the inductive part
Reaching, Sat Nov 25 2006, 02:18PM
ok, you dont understand what i was trying to explain.i want to use to seperate coils on 2 seperate coilforms to accelerate the iron part via reluctance and the aluminium part via induction. the first coil switches on and the iron is sucked into the coil, when the iron reaches the middle of the coil the first coil is turned off. the projectile leaves the first coil and passes the second coil and activates a fotogate that is placed on a calculated direction so that only the aluminium part of the projectile is in the second middle of the second coil so the aluminium part is repelled by the magnetic field of the second coil which is turned on with the fotogate. so you combined both principles. the advantage i see is that the iron part of the projectile has more time to demagnetize but still increase its velocity by the inductive part
Re: using both induction and reluctance for coilgun
mike0t4ever, Sat Nov 25 2006, 08:55PM
if you have a one coil for inductive acceleration and one coil for reluctance acceleration
then really all you fave are 2 coilguns in one your efficiency will never be the sum of efficiencies but rather the average efficiancy of each gun on its own
mike0t4ever, Sat Nov 25 2006, 08:55PM
if you have a one coil for inductive acceleration and one coil for reluctance acceleration
then really all you fave are 2 coilguns in one your efficiency will never be the sum of efficiencies but rather the average efficiancy of each gun on its own
Re: using both induction and reluctance for coilgun
Reaching, Sat Nov 25 2006, 11:20PM
yeah, and whats the problem? with a simple multistage cg you also have the average efficiency of both stages not the sum of both. i have to try it. the problem with a multistage cg based on reluctance is the saturation of the projectile. with a second coil based on inductance you have a chance to depolarize the projectile cause both parts of the projectile are connected electrically. so the projectile is no longer saturated , just a thought, but somewhere you have to start and why does everyone mean trying new techniques is wrong?? why not combine two techniques and use the advantages of both. for a reluctance based multistage cg the time is very important and the saturation rate of the projectile. so why do you mean it is wrong to accelerate the projectile via inductance to get a little more time for the iron part of the projectile to desaturate?? that would mean that you can add more kinetic energy in the following stages, increasing efficiency, not too much but better than nothing,
Reaching, Sat Nov 25 2006, 11:20PM
yeah, and whats the problem? with a simple multistage cg you also have the average efficiency of both stages not the sum of both. i have to try it. the problem with a multistage cg based on reluctance is the saturation of the projectile. with a second coil based on inductance you have a chance to depolarize the projectile cause both parts of the projectile are connected electrically. so the projectile is no longer saturated , just a thought, but somewhere you have to start and why does everyone mean trying new techniques is wrong?? why not combine two techniques and use the advantages of both. for a reluctance based multistage cg the time is very important and the saturation rate of the projectile. so why do you mean it is wrong to accelerate the projectile via inductance to get a little more time for the iron part of the projectile to desaturate?? that would mean that you can add more kinetic energy in the following stages, increasing efficiency, not too much but better than nothing,
Re: using both induction and reluctance for coilgun
mike0t4ever, Tue Nov 28 2006, 01:36AM
i'm not saying it's wrong to try
what i am saying is that the additional complexity of not only the gun but also the projectile makes this a very difficult tuning problem
also an electric connection between the ferrous and Al/Cu part of the projectile will do nothing to reduce magnetic saturation problems.
it may actually increase the eddy losses on the ferrous part by giving the eddy currents a more conductive path.
i think by saturation you meant hysterisis
the only way you can reduce it is if the ferrous and conductive parts of your slug have a fair amount of coupling between them (which will reduce the efficiency of the reluctance based acceleration due to eddy currents)
mike0t4ever, Tue Nov 28 2006, 01:36AM
i'm not saying it's wrong to try
what i am saying is that the additional complexity of not only the gun but also the projectile makes this a very difficult tuning problem
also an electric connection between the ferrous and Al/Cu part of the projectile will do nothing to reduce magnetic saturation problems.
it may actually increase the eddy losses on the ferrous part by giving the eddy currents a more conductive path.
i think by saturation you meant hysterisis
the only way you can reduce it is if the ferrous and conductive parts of your slug have a fair amount of coupling between them (which will reduce the efficiency of the reluctance based acceleration due to eddy currents)
Re: using both induction and reluctance for coilgun
WaveRider, Tue Nov 28 2006, 04:27PM
In my mind, there would be little benefit to using reluctance and induction effects in the same coilgun. The problems that you need to overcome are different for each.
Reluctance coilguns operate over relatively long timescales compared to induction guns. Example: Current on- times for most reluctance-based hobby coilguns: 0.5-3ms. Coil currents: 100A - 1000A. Capacitor voltages: 100-450V.
All of this is doable with readily available, relatively inexpensive SCRs, IGBTs, capacitors.
Contrast this with an induction gun: Current on-times < 10-100us. Coil currents: 5000-50000A, Capacitor voltages: 5000-25000V.
At this point, we see that given the need to switch kA currents and multiple kVs puts high levels of stress on the switching elements. It is more complicated. Switching time scales must generally be an order of magnitude shorter than for reluctance guns to reduce field penetration into the projectile (to get good force acting on the projectile).
Induction guns can generate tremendous forces (far more than reluctance guns). So if you go to the trouble of building a proper induction gun, in my opinion, it's not worth the trouble to tack on a reluctance gun...
My 2c...
WaveRider, Tue Nov 28 2006, 04:27PM
In my mind, there would be little benefit to using reluctance and induction effects in the same coilgun. The problems that you need to overcome are different for each.
Reluctance coilguns operate over relatively long timescales compared to induction guns. Example: Current on- times for most reluctance-based hobby coilguns: 0.5-3ms. Coil currents: 100A - 1000A. Capacitor voltages: 100-450V.
All of this is doable with readily available, relatively inexpensive SCRs, IGBTs, capacitors.
Contrast this with an induction gun: Current on-times < 10-100us. Coil currents: 5000-50000A, Capacitor voltages: 5000-25000V.
At this point, we see that given the need to switch kA currents and multiple kVs puts high levels of stress on the switching elements. It is more complicated. Switching time scales must generally be an order of magnitude shorter than for reluctance guns to reduce field penetration into the projectile (to get good force acting on the projectile).
Induction guns can generate tremendous forces (far more than reluctance guns). So if you go to the trouble of building a proper induction gun, in my opinion, it's not worth the trouble to tack on a reluctance gun...
My 2c...
Re: using both induction and reluctance for coilgun
Maz, Thu Nov 30 2006, 10:17PM
i dont think i have been here since febuary because some people were jerks and turned me off to the whole notion of posting my ideas. (sounds like einstien, tesla, and the like.) so i bid you adiou. no harm done, you can find an ass anywhere, there just seems to be a lot of them here.
Maz, Thu Nov 30 2006, 10:17PM
i dont think i have been here since febuary because some people were jerks and turned me off to the whole notion of posting my ideas. (sounds like einstien, tesla, and the like.) so i bid you adiou. no harm done, you can find an ass anywhere, there just seems to be a lot of them here.
Re: using both induction and reluctance for coilgun
Steve Conner, Fri Dec 01 2006, 12:17AM
Fine, be like that. The Information Unlimited forums are waiting for you. Next off-topic post gets this locked.
*edit* PS: I get the idea that Maz got browned off by people moaning at him that he should have used Google instead of asking questions here. He's not the only person who got annoyed by this kind of hostile sniping. In fact we banned it: check out the new rule F here
I'd also like to remind folks that if you have an induction gun with a solenoid pre-stage to get the projectile moving, you are using both induction and reluctance after all.
Steve Conner, Fri Dec 01 2006, 12:17AM
Fine, be like that. The Information Unlimited forums are waiting for you. Next off-topic post gets this locked.
*edit* PS: I get the idea that Maz got browned off by people moaning at him that he should have used Google instead of asking questions here. He's not the only person who got annoyed by this kind of hostile sniping. In fact we banned it: check out the new rule F here
I'd also like to remind folks that if you have an induction gun with a solenoid pre-stage to get the projectile moving, you are using both induction and reluctance after all.
Re: using both induction and reluctance for coilgun
Maz, Wed Dec 06 2006, 02:50AM
enjoy, jerk.
Maz, Wed Dec 06 2006, 02:50AM
enjoy, jerk.
Re: using both induction and reluctance for coilgun
ragnar, Wed Dec 06 2006, 03:04AM
lock, please..
ragnar, Wed Dec 06 2006, 03:04AM
lock, please..
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