Circular railgun?
BigBad, Wed Jan 21 2015, 02:05AMI was toying with the idea of making a circular railgun. I figure if you bend the rails around in a near circle, and used a ball bearing for the projectile it could get up to a fair speed.
It might be possible to do it in the bottom of a jam jar and use aluminium foil for the contacts. You need rigid sides to minimise rolling resistance.
If there's a scoopy thing, perhaps I could use an electromagnet to time the release and fire it out the scoop when it reaches top speed by sliding it over a bit maybe.
Re: Circular railgun?
Sulaiman, Wed Jan 21 2015, 09:02AM
the principle sounds workable
but in a glass jar ?!
how about something like
model railway track glued to the inside of a pvc pipe?
Sulaiman, Wed Jan 21 2015, 09:02AM
the principle sounds workable
but in a glass jar ?!
how about something like
model railway track glued to the inside of a pvc pipe?
Re: Circular railgun?
DerAlbi, Wed Jan 21 2015, 10:06AM
A railgun is a device that is particulary known for its wear and tear of its rails. I do not think that you could use aluminum foil for contacting. the movement alone will produce plasma/arcs that will consume your foil in no time, dont you think?
Even with just placing a ball on 2 parallel wires will make the thing practically questionable. It will kind of float on its plasma and since the ball is not restrained down with pressure the contact will be horible. I dont know if you ever watched a trams wheels on the rails.. even with that pressure you sometimes see it arcing.
But yeah: interesting idea. you are practically limited by radial forces only and you could have a quite long acceleration distance in a good form factor. the increase of speed will actually put some pressure on the rails... hmmh.
First electromagnetic accelerator with an inherently spinning projectile
haha
DerAlbi, Wed Jan 21 2015, 10:06AM
A railgun is a device that is particulary known for its wear and tear of its rails. I do not think that you could use aluminum foil for contacting. the movement alone will produce plasma/arcs that will consume your foil in no time, dont you think?
Even with just placing a ball on 2 parallel wires will make the thing practically questionable. It will kind of float on its plasma and since the ball is not restrained down with pressure the contact will be horible. I dont know if you ever watched a trams wheels on the rails.. even with that pressure you sometimes see it arcing.
But yeah: interesting idea. you are practically limited by radial forces only and you could have a quite long acceleration distance in a good form factor. the increase of speed will actually put some pressure on the rails... hmmh.
First electromagnetic accelerator with an inherently spinning projectile
hahaRe: Circular railgun?
Shrad, Wed Jan 21 2015, 10:17AM
totally imaginary concept but very related... if you have a torus in which the interior had two conductive zones acting like rails, and a bead of mercury which would act as the shell, would it accelerate and evaporate and form a rotating plasma in the torus?
I guess the conductive rails would have to be superconductive and contain nothing but the mercury
accelerating a projectile would be easily achieved in a circular accelerator, but for a railgun it would be really difficult to design a mechanical path disconnection which would be applicable at such speeds
Shrad, Wed Jan 21 2015, 10:17AM
totally imaginary concept but very related... if you have a torus in which the interior had two conductive zones acting like rails, and a bead of mercury which would act as the shell, would it accelerate and evaporate and form a rotating plasma in the torus?
I guess the conductive rails would have to be superconductive and contain nothing but the mercury
accelerating a projectile would be easily achieved in a circular accelerator, but for a railgun it would be really difficult to design a mechanical path disconnection which would be applicable at such speeds
Re: Circular railgun?
dexter, Wed Jan 21 2015, 03:38PM
first alot of force will be wasted in the radial direction
2nd the above looses depends highly on the radius - the smaller the radius the bigger the looses - to such extent that at a certain radius the projectile would stop inside the loop or even burst through the rails
also the projectile will move in a straight line after leaving the gurved rails - so no curve the bullet still remains in the fiction world :)
if you have the materials build it regardless of how counterintuitive it sounds
dexter, Wed Jan 21 2015, 03:38PM
first alot of force will be wasted in the radial direction
2nd the above looses depends highly on the radius - the smaller the radius the bigger the looses - to such extent that at a certain radius the projectile would stop inside the loop or even burst through the rails
also the projectile will move in a straight line after leaving the gurved rails - so no curve the bullet still remains in the fiction world :)
if you have the materials build it regardless of how counterintuitive it sounds
Re: Circular railgun?
BigBad, Wed Jan 21 2015, 05:46PM
You're still going to need to wind up the voltage though, the top speed of a railgun is limited by the back emf of the rotor; it's actually a form of universal motor.
BigBad, Wed Jan 21 2015, 05:46PM
DerAlbi wrote ...
A railgun is a device that is particulary known for its wear and tear of its rails. I do not think that you could use aluminum foil for contacting. the movement alone will produce plasma/arcs that will consume your foil in no time, dont you think?
The thing is the current is a lot lower, with a normal railgun you need super high current to get decent speed before the end of the rail, with this you can go around lots of times at lower acceleration.A railgun is a device that is particulary known for its wear and tear of its rails. I do not think that you could use aluminum foil for contacting. the movement alone will produce plasma/arcs that will consume your foil in no time, dont you think?
You're still going to need to wind up the voltage though, the top speed of a railgun is limited by the back emf of the rotor; it's actually a form of universal motor.
Sulaiman wrote ...
the principle sounds workable
but in a glass jar ?!
how about something like
model railway track glued to the inside of a pvc pipe?
PVC is really too soft, you'll get lots of rolling friction; you need something really hard like steel or glass.the principle sounds workable
but in a glass jar ?!
how about something like
model railway track glued to the inside of a pvc pipe?
wrote ...
first alot of force will be wasted in the radial direction
No, the radial isn't (directly) lossy. The friction force is lossy; which is proportional with the rolling friction (and the radial force.) For steel on steel or steel on glass, that's going to be pretty high.first alot of force will be wasted in the radial direction
wrote ...
2nd the above looses depends highly on the radius - the smaller the radius the bigger the looses - to such extent that at a certain radius the projectile would stop inside the loop or even burst through the rails
Yes you probably wouldn't want two rails with a gap between them; although if the ball bearing weighs a gram and the g-force is a 1000, then that's only a kilogram force; 10 N.2nd the above looses depends highly on the radius - the smaller the radius the bigger the looses - to such extent that at a certain radius the projectile would stop inside the loop or even burst through the rails
wrote ...
also the projectile will move in a straight line after leaving the gurved rails - so no curve the bullet still remains in the fiction world :)
I think that's rather the point if we can work out how to do the release mechanism! ;)also the projectile will move in a straight line after leaving the gurved rails - so no curve the bullet still remains in the fiction world :)
Re: Circular railgun?
Shrad, Wed Jan 21 2015, 07:07PM
lower current times the number of passes required to achieve the wanted speed... as soon as friction damage from much more passes does not exceed one high power shot damage yes, but I don't think that would be the case
Shrad, Wed Jan 21 2015, 07:07PM
lower current times the number of passes required to achieve the wanted speed... as soon as friction damage from much more passes does not exceed one high power shot damage yes, but I don't think that would be the case
Re: Circular railgun?
BigBad, Wed Jan 21 2015, 11:01PM
It's just a slip ring; they can have pretty decent life.
BigBad, Wed Jan 21 2015, 11:01PM
It's just a slip ring; they can have pretty decent life.
Re: Circular railgun?
Shrad, Thu Jan 22 2015, 08:55AM
I think that due to current flow, movement and conduction losses at the interface would induce more stress and ablation with multiple passes at a low voltage/power than one pass at high voltage/power
You can always use a kind of conductive lubricant like graphite, on rails in a material which produces a conductive oxidation layer
I could well be wrong as I have no practical experience in railguns ;)
Shrad, Thu Jan 22 2015, 08:55AM
I think that due to current flow, movement and conduction losses at the interface would induce more stress and ablation with multiple passes at a low voltage/power than one pass at high voltage/power
You can always use a kind of conductive lubricant like graphite, on rails in a material which produces a conductive oxidation layer
I could well be wrong as I have no practical experience in railguns ;)
Re: Circular railgun?
BigBad, Thu Jan 22 2015, 05:48PM
There's going to be pro and cons but a lot of it is i^2 R heating of the slip ring, and i is low.
BigBad, Thu Jan 22 2015, 05:48PM
There's going to be pro and cons but a lot of it is i^2 R heating of the slip ring, and i is low.
Re: Circular railgun?
hen918, Thu Jan 22 2015, 06:14PM
As DerAlbi says a railgun with aluminium (on its) rails would be a one shot device. Tungsten is a good material for high temperatures / wear but you would still get deposits off of the steel projectile.
Shrad, If you use conductive powder / lubricant you risk shorting the rails out and it arcing over.
EDIT: oh, and the Lorenz forces are going to try and force the rails apart, so if they aren't completely rigid energy is going to be wasted that way.
EDIT2: The projectile will have to be moving when it hits the rails. Theoretically it is possible to do it stationary, however it is very difficult to do it that way practically.
hen918, Thu Jan 22 2015, 06:14PM
As DerAlbi says a railgun with aluminium (on its) rails would be a one shot device. Tungsten is a good material for high temperatures / wear but you would still get deposits off of the steel projectile.
Shrad, If you use conductive powder / lubricant you risk shorting the rails out and it arcing over.
EDIT: oh, and the Lorenz forces are going to try and force the rails apart, so if they aren't completely rigid energy is going to be wasted that way.
EDIT2: The projectile will have to be moving when it hits the rails. Theoretically it is possible to do it stationary, however it is very difficult to do it that way practically.
Re: Circular railgun?
Ash Small, Thu Jan 22 2015, 06:25PM
Two steel rings (or other suitable metal) held close to each other and a mechanism for moving the rings apart for projectile release.
Only drawback is timing the release, so you can control direction, but if the mechanism is surrounded by a spiral of one turn (if that makes sense), you have directional control as well.
Ash Small, Thu Jan 22 2015, 06:25PM
Two steel rings (or other suitable metal) held close to each other and a mechanism for moving the rings apart for projectile release.
Only drawback is timing the release, so you can control direction, but if the mechanism is surrounded by a spiral of one turn (if that makes sense), you have directional control as well.
Re: Circular railgun?
BigBad, Fri Jan 23 2015, 12:02AM
The tricky bit with a spiral like that is that if it releases at the wrong moment the ballbearing will go slamming into the start of the spiral.
BigBad, Fri Jan 23 2015, 12:02AM
The tricky bit with a spiral like that is that if it releases at the wrong moment the ballbearing will go slamming into the start of the spiral.
Re: Circular railgun?
Ash Small, Fri Jan 23 2015, 02:06PM
I realise this. Some form of 'timing mechanism' is required. The 'separation mechanism' needs to be triggered at a point that aviods this. The exact detail of the timing mechanism will depend upon the properties of the rest of the system.
Ash Small, Fri Jan 23 2015, 02:06PM
BigBad wrote ...
The tricky bit with a spiral like that is that if it releases at the wrong moment the ballbearing will go slamming into the start of the spiral.
The tricky bit with a spiral like that is that if it releases at the wrong moment the ballbearing will go slamming into the start of the spiral.
I realise this. Some form of 'timing mechanism' is required. The 'separation mechanism' needs to be triggered at a point that aviods this. The exact detail of the timing mechanism will depend upon the properties of the rest of the system.
Re: Circular railgun?
klugesmith, Fri Jan 23 2015, 04:56PM
If the track is a finite helix instead of a circle, there's a place for injecting the projectile and a place for letting it fly away. As with any very long railgun, you need to worry about voltage drop in the rails.
Correct me if I'm wrong, but the electromagnetic propulsion depends on the rails carrying current _behind_ the projectile and no current ahead of the projectile. A circular rail (for benchtop "spinner" experiments) needs at least one electrical gap next to a power connection. That will define the direction of rotation.
That's in contrast with the classic "ball bearing motor" trick. I can attest that those run in whichever direction you choose to start them. Fun thing to do with a low-voltage rewound MOT, when you get tired of abusing nails and small wires.
klugesmith, Fri Jan 23 2015, 04:56PM
Ash Small wrote ...
Only drawback is timing the release, so you can control direction, but if the mechanism is surrounded by a spiral of one turn (if that makes sense), you have directional control as well.
Only drawback is timing the release, so you can control direction, but if the mechanism is surrounded by a spiral of one turn (if that makes sense), you have directional control as well.
If the track is a finite helix instead of a circle, there's a place for injecting the projectile and a place for letting it fly away. As with any very long railgun, you need to worry about voltage drop in the rails.
Correct me if I'm wrong, but the electromagnetic propulsion depends on the rails carrying current _behind_ the projectile and no current ahead of the projectile. A circular rail (for benchtop "spinner" experiments) needs at least one electrical gap next to a power connection. That will define the direction of rotation.
That's in contrast with the classic "ball bearing motor" trick. I can attest that those run in whichever direction you choose to start them. Fun thing to do with a low-voltage rewound MOT, when you get tired of abusing nails and small wires.
Re: Circular railgun?
Shrad, Fri Jan 23 2015, 05:02PM
voltage drop in the rails could be addressed with multiple parallel connections to several parts of the path, no?
for the release mechanism, a sensor at an interval x+k of the release point and another one at an interval x of the first sensor, a simple timing circuit repeating the timing between sensor 1 and sensor 2 triggered by sensor 2, and a modifier k for setting delay in mechanical device used for releasing the projectile
Shrad, Fri Jan 23 2015, 05:02PM
voltage drop in the rails could be addressed with multiple parallel connections to several parts of the path, no?
for the release mechanism, a sensor at an interval x+k of the release point and another one at an interval x of the first sensor, a simple timing circuit repeating the timing between sensor 1 and sensor 2 triggered by sensor 2, and a modifier k for setting delay in mechanical device used for releasing the projectile
Re: Circular railgun?
klugesmith, Fri Jan 23 2015, 05:16PM
Shrad, I think you're missing the point of my second paragraph (in prev. post), or I am wrong.
Let's start with a conductive bridge (or sliding wire, in the EM textbooks) carrying current between two rails, and a current source connected to one end of the rails. There's an EM force tending to push the bridge away from the current source, increasing the rectangular loop's area and inductance.
Suppose the rails are powered from both ends. What defines the partition of bridge current between the two sources? Relative resistance of the rail sections? If the currents match then there's no propulsive force. I think it makes no difference if the bridge is moving to begin with.
klugesmith, Fri Jan 23 2015, 05:16PM
Shrad, I think you're missing the point of my second paragraph (in prev. post), or I am wrong.
Let's start with a conductive bridge (or sliding wire, in the EM textbooks) carrying current between two rails, and a current source connected to one end of the rails. There's an EM force tending to push the bridge away from the current source, increasing the rectangular loop's area and inductance.
Suppose the rails are powered from both ends. What defines the partition of bridge current between the two sources? Relative resistance of the rail sections? If the currents match then there's no propulsive force. I think it makes no difference if the bridge is moving to begin with.
Re: Circular railgun?
Ash Small, Fri Jan 23 2015, 06:13PM
Place a gap in the rings, so the projectile repeatedly starts at the beginning.
If only one side of the rings 'opens up', this gives us a lot more directional control, but some timing mechanism would still probably be required. If the projectile breaks a light beam it tells where it is, and the time taken to circle, which gives us it's speed.
EDIT: Pneumatic rams may be useful here.
Ash Small, Fri Jan 23 2015, 06:13PM
Place a gap in the rings, so the projectile repeatedly starts at the beginning.
If only one side of the rings 'opens up', this gives us a lot more directional control, but some timing mechanism would still probably be required. If the projectile breaks a light beam it tells where it is, and the time taken to circle, which gives us it's speed.
EDIT: Pneumatic rams may be useful here.
Re: Circular railgun?
BigBad, Fri Jan 23 2015, 06:47PM
But it's less of an issue, because the current and resistance losses are smaller anyway.
BigBad, Fri Jan 23 2015, 06:47PM
Shrad wrote ...
voltage drop in the rails could be addressed with multiple parallel connections to several parts of the path, no?
Yes, but you'd need multiple breaks in the rails as well, as others have noted.voltage drop in the rails could be addressed with multiple parallel connections to several parts of the path, no?
But it's less of an issue, because the current and resistance losses are smaller anyway.
Re: Circular railgun?
Shrad, Fri Jan 23 2015, 09:00PM
that would be a nice experiment... a steel ball, two copper tubes and arewound MOT ^^
Shrad, Fri Jan 23 2015, 09:00PM
that would be a nice experiment... a steel ball, two copper tubes and arewound MOT ^^
Re: Circular railgun?
BigBad, Fri Jan 23 2015, 10:34PM
Not entirely sure we need high voltage.
The theoretical top speed of a railgun is apparently (
v = V/(BL)
where V is the voltage, B is the magnetic field (probably very low it's not even a full turn) and L is the width of the rails.
I plugged some numbers in, and got absurdly high speeds, which will never, ever be reached of course.
Even a NMh battery might be too much; probably not; but mains voltage could be scary, even with a current limiting resistor in there, like a kettle or something; you've got a few horsepower trying to push a teeny-tiny ballbearing along.
BigBad, Fri Jan 23 2015, 10:34PM
Not entirely sure we need high voltage.
The theoretical top speed of a railgun is apparently (
v = V/(BL)
where V is the voltage, B is the magnetic field (probably very low it's not even a full turn) and L is the width of the rails.
I plugged some numbers in, and got absurdly high speeds, which will never, ever be reached of course.
Even a NMh battery might be too much; probably not; but mains voltage could be scary, even with a current limiting resistor in there, like a kettle or something; you've got a few horsepower trying to push a teeny-tiny ballbearing along.
Re: Circular railgun?
DerAlbi, Sat Jan 24 2015, 04:16PM
>> (probably very low it's not even a full turn)
there are no half turns.
I would suggest you start experiementing
DerAlbi, Sat Jan 24 2015, 04:16PM
>> (probably very low it's not even a full turn)
there are no half turns.
I would suggest you start experiementing
Re: Circular railgun?
Andy, Sat Jan 24 2015, 07:42PM
The final speed is set by E/B or the change of rail distance, you can increase the voltage buy dischargeing higher and higher voltage onto the rails or you can have more and mor resistance or you could change tje distance between electrodes, or maybe have a copper coating that gets vaporized then it becomes Al, or have the voltage quicly turned off with the shell change from 2H to 0.05ohm short.
Pics
Andy, Sat Jan 24 2015, 07:42PM
The final speed is set by E/B or the change of rail distance, you can increase the voltage buy dischargeing higher and higher voltage onto the rails or you can have more and mor resistance or you could change tje distance between electrodes, or maybe have a copper coating that gets vaporized then it becomes Al, or have the voltage quicly turned off with the shell change from 2H to 0.05ohm short.
Pics
Re: Circular railgun?
BigBad, Sun Jan 25 2015, 01:22AM
The flux from that is entirely non consequential.
BigBad, Sun Jan 25 2015, 01:22AM
DerAlbi wrote ...
>> (probably very low it's not even a full turn)
there are no half turns.
There kinda of is. I'm completely unconcerned about the part of the turn that isn't through the projectile, and is situated well away from the projectile >> (probably very low it's not even a full turn)
there are no half turns.
The flux from that is entirely non consequential.Re: Circular railgun?
DerAlbi, Sun Jan 25 2015, 04:26PM
Now you talk about mutual- and stray inductance.
Thats not much arugment for fractional turns. If the current-loop is not completeley closed, its by definition not a loop and no current could ever flow. I dont want to go off-topic here. i just want to reduce "unphysical" concepts for understanding. Just google "fractional turn transformer" and learn how hard it is actually to get fractional turncounts. And maybe do some research about mutual and stray inductance in e-motors. It helps a lot to avoid such misconceptions.
DerAlbi, Sun Jan 25 2015, 04:26PM
Now you talk about mutual- and stray inductance.
Thats not much arugment for fractional turns. If the current-loop is not completeley closed, its by definition not a loop and no current could ever flow. I dont want to go off-topic here. i just want to reduce "unphysical" concepts for understanding. Just google "fractional turn transformer" and learn how hard it is actually to get fractional turncounts. And maybe do some research about mutual and stray inductance in e-motors. It helps a lot to avoid such misconceptions.
Re: Circular railgun?
Shrad, Sun Jan 25 2015, 06:50PM
has someone ever thought of segmented rails and projectile being switches in a switching converter where inductors/capacitors would be discharged mechanically?
would it be possible to achieve a kind of magnetic pulse compression so that the circuit accelerates exponentially, like with a kind of EMP generator where the projectile release rupture current would be used as a ETG "launch stage" discharge ?
just two ideas that come into my mind this late sunday after some beers and cakes ;)
Shrad, Sun Jan 25 2015, 06:50PM
has someone ever thought of segmented rails and projectile being switches in a switching converter where inductors/capacitors would be discharged mechanically?
would it be possible to achieve a kind of magnetic pulse compression so that the circuit accelerates exponentially, like with a kind of EMP generator where the projectile release rupture current would be used as a ETG "launch stage" discharge ?
just two ideas that come into my mind this late sunday after some beers and cakes ;)
Re: Circular railgun?
hen918, Sun Jan 25 2015, 10:16PM
The problem is that the projectile has to outrun the explosion. Which, as it accelerates pretty slowly, it won't.
hen918, Sun Jan 25 2015, 10:16PM
Shrad wrote ...
has someone ever thought of segmented rails and projectile being switches in a switching converter where inductors/capacitors would be discharged mechanically?
would it be possible to achieve a kind of magnetic pulse compression so that the circuit accelerates exponentially, like with a kind of EMP generator where the projectile release rupture current would be used as a ETG "launch stage" discharge ?
just two ideas that come into my mind this late sunday after some beers and cakes ;)
has someone ever thought of segmented rails and projectile being switches in a switching converter where inductors/capacitors would be discharged mechanically?
would it be possible to achieve a kind of magnetic pulse compression so that the circuit accelerates exponentially, like with a kind of EMP generator where the projectile release rupture current would be used as a ETG "launch stage" discharge ?
just two ideas that come into my mind this late sunday after some beers and cakes ;)
The problem is that the projectile has to outrun the explosion. Which, as it accelerates pretty slowly, it won't.
Re: Circular railgun?
BigBad, Tue Jan 27 2015, 01:54AM
BigBad, Tue Jan 27 2015, 01:54AM
DerAlbi wrote ...
Now you talk about mutual- and stray inductance.
Thats not much arugment for fractional turns. If the current-loop is not completeley closed, its by definition not a loop and no current could ever flow. I dont want to go off-topic here. i just want to reduce "unphysical" concepts for understanding. Just google "fractional turn transformer" and learn how hard it is actually to get fractional turncounts. And maybe do some research about mutual and stray inductance in e-motors. It helps a lot to avoid such misconceptions.
Sorry, but this isn't a transformer either, and Faraday's law (in the n dPhi/dt sense) does NOT apply to it!!!Now you talk about mutual- and stray inductance.
Thats not much arugment for fractional turns. If the current-loop is not completeley closed, its by definition not a loop and no current could ever flow. I dont want to go off-topic here. i just want to reduce "unphysical" concepts for understanding. Just google "fractional turn transformer" and learn how hard it is actually to get fractional turncounts. And maybe do some research about mutual and stray inductance in e-motors. It helps a lot to avoid such misconceptions.
Re: Circular railgun?
Shrad, Tue Jan 27 2015, 08:27AM
I remember that battery and magnets thing inside a spiral copper wire moving along, and it mated in my mind with a story of pyrotechnic aided EMP generator where a fusing charge was, well, fusing an inductor to reduce its value as the magnetic field increased by shorting turns successively to generate a final EMP via the shorted end discharge
if we use a double set of conductors parallel to each other in a tubular barrel which would have spiraling carvings like a gun cannon, with way narrower turn spacing to achieve inductor effect, would it be possible to accelerate a conductive projectile using such magnetic pulse compression techniques?
I guess two parallel conductors would cancel each field out due to current direction being opposite... what about a single conductor surrounded by teflon or something, and a metallic casing which would act as iron to enhance the magnetic field as well as provide current return for the projectile?
this would, I think, provide projectile rotation as well as acceleration, and could even benefit of a ETG type initial launch
any thoughts about that?
Shrad, Tue Jan 27 2015, 08:27AM
I remember that battery and magnets thing inside a spiral copper wire moving along, and it mated in my mind with a story of pyrotechnic aided EMP generator where a fusing charge was, well, fusing an inductor to reduce its value as the magnetic field increased by shorting turns successively to generate a final EMP via the shorted end discharge
if we use a double set of conductors parallel to each other in a tubular barrel which would have spiraling carvings like a gun cannon, with way narrower turn spacing to achieve inductor effect, would it be possible to accelerate a conductive projectile using such magnetic pulse compression techniques?
I guess two parallel conductors would cancel each field out due to current direction being opposite... what about a single conductor surrounded by teflon or something, and a metallic casing which would act as iron to enhance the magnetic field as well as provide current return for the projectile?
this would, I think, provide projectile rotation as well as acceleration, and could even benefit of a ETG type initial launch
any thoughts about that?
Re: Circular railgun?
BigBad, Tue Jan 27 2015, 10:02AM
That's just a spiral railgun. I'd thought about it, but I don't immediately see any major advantage. I'm not knocking it, it makes the railgun longer, but unless you turn the spin into motion somehow, what does it help?
BigBad, Tue Jan 27 2015, 10:02AM
That's just a spiral railgun. I'd thought about it, but I don't immediately see any major advantage. I'm not knocking it, it makes the railgun longer, but unless you turn the spin into motion somehow, what does it help?
Re: Circular railgun?
Shrad, Tue Jan 27 2015, 08:15PM
in my idea, the rail wouldn't be a rail as in a railgun, but rather a solenoid with the intput end connected to the barrel body, and a discharge between the rail free end and the body, and the projectile closing the circuit (that's more of an hybrid between a railgun and a coilgun)
the projectile would be pushed by the magnetic field produced by the current traversing the solenoid, and with the displacement would short turn after turn and the magnetic field would displace itself rapidly as the solenoid would reduce in size
the projectile would then always be in the first half of the solenoid hence no sucking back and no need of segmenting and timing
there could be an issue about the back EMF produced when the projectile is released, but I can't figure if it would push or suck the projectile, as the EMF would be of inverse direction than the previous magnetic field but the projectile would then be, if I'm not wrong, in the second half of the shorted last one turn and instead of being sucked would then be repelled
that would require a massive supply though and I don't know which sizing would be adequate for sustaining a discharge that long
this is food for thought though, I have no experience in that field and am solely interested in the exercise of imagination, but I think it was worth discussing as this is somewhat related to a circular railgun and a spiral circuit like mentioned previously
Shrad, Tue Jan 27 2015, 08:15PM
in my idea, the rail wouldn't be a rail as in a railgun, but rather a solenoid with the intput end connected to the barrel body, and a discharge between the rail free end and the body, and the projectile closing the circuit (that's more of an hybrid between a railgun and a coilgun)
the projectile would be pushed by the magnetic field produced by the current traversing the solenoid, and with the displacement would short turn after turn and the magnetic field would displace itself rapidly as the solenoid would reduce in size
the projectile would then always be in the first half of the solenoid hence no sucking back and no need of segmenting and timing
there could be an issue about the back EMF produced when the projectile is released, but I can't figure if it would push or suck the projectile, as the EMF would be of inverse direction than the previous magnetic field but the projectile would then be, if I'm not wrong, in the second half of the shorted last one turn and instead of being sucked would then be repelled
that would require a massive supply though and I don't know which sizing would be adequate for sustaining a discharge that long
this is food for thought though, I have no experience in that field and am solely interested in the exercise of imagination, but I think it was worth discussing as this is somewhat related to a circular railgun and a spiral circuit like mentioned previously
Re: Circular railgun?
hen918, Tue Jan 27 2015, 08:37PM
Just in case you don't know: an explosively pumped magnetic flux generator uses high explosive (which is illegal in most countries/states) to force the windings of a loosely wound coil, which already carries a relatively small current, and therefore magnetic field from another source like a battery, closer together. BANG: physically compressed magnetic flux with a massively high dI/dt. the output wires can either be shorted to produce a massive EMP, or they could be connected to another low impedance output, like another coil.
it could be connected to a rail gun, however the pulse time would be so short the projectile would probably just vaporise; a Lorentz type projectile launcher would be much more efficient, as the coupling between the Lorentz ring and the coil decreases proportionally to the square of the distance between them. Therefore you want the most energy to be imparted the closer they are together.
hen918, Tue Jan 27 2015, 08:37PM
Shrad wrote ...
I remember that battery and magnets thing inside a spiral copper wire moving along, and it mated in my mind with a story of pyrotechnic aided EMP generator where a fusing charge was, well, fusing an inductor to reduce its value as the magnetic field increased by shorting turns successively to generate a final EMP via the shorted end discharge
if we use a double set of conductors parallel to each other in a tubular barrel which would have spiraling carvings like a gun cannon, with way narrower turn spacing to achieve inductor effect, would it be possible to accelerate a conductive projectile using such magnetic pulse compression techniques?
I guess two parallel conductors would cancel each field out due to current direction being opposite... what about a single conductor surrounded by teflon or something, and a metallic casing which would act as iron to enhance the magnetic field as well as provide current return for the projectile?
this would, I think, provide projectile rotation as well as acceleration, and could even benefit of a ETG type initial launch
any thoughts about that?
I remember that battery and magnets thing inside a spiral copper wire moving along, and it mated in my mind with a story of pyrotechnic aided EMP generator where a fusing charge was, well, fusing an inductor to reduce its value as the magnetic field increased by shorting turns successively to generate a final EMP via the shorted end discharge
if we use a double set of conductors parallel to each other in a tubular barrel which would have spiraling carvings like a gun cannon, with way narrower turn spacing to achieve inductor effect, would it be possible to accelerate a conductive projectile using such magnetic pulse compression techniques?
I guess two parallel conductors would cancel each field out due to current direction being opposite... what about a single conductor surrounded by teflon or something, and a metallic casing which would act as iron to enhance the magnetic field as well as provide current return for the projectile?
this would, I think, provide projectile rotation as well as acceleration, and could even benefit of a ETG type initial launch
any thoughts about that?
Just in case you don't know: an explosively pumped magnetic flux generator uses high explosive (which is illegal in most countries/states) to force the windings of a loosely wound coil, which already carries a relatively small current, and therefore magnetic field from another source like a battery, closer together. BANG: physically compressed magnetic flux with a massively high dI/dt. the output wires can either be shorted to produce a massive EMP, or they could be connected to another low impedance output, like another coil.
it could be connected to a rail gun, however the pulse time would be so short the projectile would probably just vaporise; a Lorentz type projectile launcher would be much more efficient, as the coupling between the Lorentz ring and the coil decreases proportionally to the square of the distance between them. Therefore you want the most energy to be imparted the closer they are together.
Re: Circular railgun?
BigBad, Wed Jan 28 2015, 01:32AM
A slightly different idea is when you spin the spiral with the ball bearing, and then release the ball bearing at the right moment.
The spiral then acts a bit like a Trebuchet; the ball bearing takes the energy from the spiral and turns it into straight-line motion, and as far as possible, stops the spiral from spinning.
Not sure that a railgun idea is what you want then though, an ordinary universal motor might be better.
BigBad, Wed Jan 28 2015, 01:32AM
A slightly different idea is when you spin the spiral with the ball bearing, and then release the ball bearing at the right moment.
The spiral then acts a bit like a Trebuchet; the ball bearing takes the energy from the spiral and turns it into straight-line motion, and as far as possible, stops the spiral from spinning.
Not sure that a railgun idea is what you want then though, an ordinary universal motor might be better.
Re: Circular railgun?
Shrad, Wed Jan 28 2015, 11:12AM
in that case I replace the explosive with the actual conductive projectile, and use the inductor to be shorted as a rail for the return path... I guess it could be seen as two rails with one being the barrel and the other one the solenoid...
the EMF generated would push the projectile forward till the end of the solenoid, if you see where I go
Shrad, Wed Jan 28 2015, 11:12AM
in that case I replace the explosive with the actual conductive projectile, and use the inductor to be shorted as a rail for the return path... I guess it could be seen as two rails with one being the barrel and the other one the solenoid...
the EMF generated would push the projectile forward till the end of the solenoid, if you see where I go
hen918 wrote ...
Just in case you don't know: an explosively pumped magnetic flux generator uses high explosive (which is illegal in most countries/states) to force the windings of a loosely wound coil, which already carries a relatively small current, and therefore magnetic field from another source like a battery, closer together. BANG: physically compressed magnetic flux with a massively high dI/dt. the output wires can either be shorted to produce a massive EMP, or they could be connected to another low impedance output, like another coil.
it could be connected to a rail gun, however the pulse time would be so short the projectile would probably just vaporise; a Lorentz type projectile launcher would be much more efficient, as the coupling between the Lorentz ring and the coil decreases proportionally to the square of the distance between them. Therefore you want the most energy to be imparted the closer they are together.
Shrad wrote ...
I remember that battery and magnets thing inside a spiral copper wire moving along, and it mated in my mind with a story of pyrotechnic aided EMP generator where a fusing charge was, well, fusing an inductor to reduce its value as the magnetic field increased by shorting turns successively to generate a final EMP via the shorted end discharge
if we use a double set of conductors parallel to each other in a tubular barrel which would have spiraling carvings like a gun cannon, with way narrower turn spacing to achieve inductor effect, would it be possible to accelerate a conductive projectile using such magnetic pulse compression techniques?
I guess two parallel conductors would cancel each field out due to current direction being opposite... what about a single conductor surrounded by teflon or something, and a metallic casing which would act as iron to enhance the magnetic field as well as provide current return for the projectile?
this would, I think, provide projectile rotation as well as acceleration, and could even benefit of a ETG type initial launch
any thoughts about that?
I remember that battery and magnets thing inside a spiral copper wire moving along, and it mated in my mind with a story of pyrotechnic aided EMP generator where a fusing charge was, well, fusing an inductor to reduce its value as the magnetic field increased by shorting turns successively to generate a final EMP via the shorted end discharge
if we use a double set of conductors parallel to each other in a tubular barrel which would have spiraling carvings like a gun cannon, with way narrower turn spacing to achieve inductor effect, would it be possible to accelerate a conductive projectile using such magnetic pulse compression techniques?
I guess two parallel conductors would cancel each field out due to current direction being opposite... what about a single conductor surrounded by teflon or something, and a metallic casing which would act as iron to enhance the magnetic field as well as provide current return for the projectile?
this would, I think, provide projectile rotation as well as acceleration, and could even benefit of a ETG type initial launch
any thoughts about that?
Just in case you don't know: an explosively pumped magnetic flux generator uses high explosive (which is illegal in most countries/states) to force the windings of a loosely wound coil, which already carries a relatively small current, and therefore magnetic field from another source like a battery, closer together. BANG: physically compressed magnetic flux with a massively high dI/dt. the output wires can either be shorted to produce a massive EMP, or they could be connected to another low impedance output, like another coil.
it could be connected to a rail gun, however the pulse time would be so short the projectile would probably just vaporise; a Lorentz type projectile launcher would be much more efficient, as the coupling between the Lorentz ring and the coil decreases proportionally to the square of the distance between them. Therefore you want the most energy to be imparted the closer they are together.
Re: Circular railgun?
Sulaiman, Wed Jan 28 2015, 01:02PM
one variation of this circular accelerator may be that if not too large, (e.g. use 1/4" ball bearing)
then there is the achievable possibility of adding a permanent magnet field
(something equivalent to the magnetic structure of a loudspeaker)
so that lower rail current with many revolutions of the projectile would be feasible.
(More like a linear/homopolar motor than a rail gun)
(no need for a gap in the rails)
Sulaiman, Wed Jan 28 2015, 01:02PM
one variation of this circular accelerator may be that if not too large, (e.g. use 1/4" ball bearing)
then there is the achievable possibility of adding a permanent magnet field
(something equivalent to the magnetic structure of a loudspeaker)
so that lower rail current with many revolutions of the projectile would be feasible.
(More like a linear/homopolar motor than a rail gun)
(no need for a gap in the rails)
Re: Circular railgun?
DerAlbi, Fri Jan 30 2015, 12:36AM
But ok, i will leave the discussion^^ this deep s**t does not seem to be of interest anyway.
DerAlbi, Fri Jan 30 2015, 12:36AM
Sorry, but this isn't a transformer either, and Faraday's law (in the n dPhi/dt sense) does NOT apply to it!!!In every energy conversion from electric to kinetic energy (electric motor) there is a coupling factor. It are allways magnetic fields interacting (attracting or repelling). And where there is a coupling factor there is stray and mutual inductance. It does not need to be a transformer, just because you associate it to a transformer.
But ok, i will leave the discussion^^ this deep s**t does not seem to be of interest anyway.
Re: Circular railgun?
Shrad, Fri Jan 30 2015, 08:50AM
this simple image would illustrate my idea more easily
it represents the barrel in a longitudinal cut with barrel end at right side and projectile enter at left side
dashes represent turns of conducting material placed in spiraled grooves inside the non conductive surrounding
greyed turns represent a connection to the outer conductive barrel, orange turns represent a spiraled conductive rail which serves dual purpose of a conductive rail as well as an solenoid inductor
power is applied between the barrel and the orange conductive spiral at barrel right end, and projectile introduced at left side closes the circuit when introduced
the magnetic flux created by the current flow in the solenoid would attract the projectile to the right, which in turn will shorten the inductor... in my twisted mind the projectile would then be accelerated, be always in the first half of the solenoid, etc... and for what I know the back-emf when opening the last spire of the inductor would occur when the projectile is over the next half of the solenoid and thus it would be pushed away
Shrad, Fri Jan 30 2015, 08:50AM
this simple image would illustrate my idea more easily
it represents the barrel in a longitudinal cut with barrel end at right side and projectile enter at left side
dashes represent turns of conducting material placed in spiraled grooves inside the non conductive surrounding
greyed turns represent a connection to the outer conductive barrel, orange turns represent a spiraled conductive rail which serves dual purpose of a conductive rail as well as an solenoid inductor
power is applied between the barrel and the orange conductive spiral at barrel right end, and projectile introduced at left side closes the circuit when introduced
the magnetic flux created by the current flow in the solenoid would attract the projectile to the right, which in turn will shorten the inductor... in my twisted mind the projectile would then be accelerated, be always in the first half of the solenoid, etc... and for what I know the back-emf when opening the last spire of the inductor would occur when the projectile is over the next half of the solenoid and thus it would be pushed away
Re: Circular railgun?
hen918, Fri Jan 30 2015, 04:16PM
If the projectile is magnetic: the emf (front or back) would always attract the projectile, as a magnetic object is attracted to either pole.
If the projectile was non-magnetic: the emf (back or front) would always repel the projectile, as the current induced is the same as the current in the coil.
hen918, Fri Jan 30 2015, 04:16PM
Shrad wrote ...
this simple image would illustrate my idea more easily
it represents the barrel in a longitudinal cut with barrel end at right side and projectile enter at left side
dashes represent turns of conducting material placed in spiraled grooves inside the non conductive surrounding
greyed turns represent a connection to the outer conductive barrel, orange turns represent a spiraled conductive rail which serves dual purpose of a conductive rail as well as an solenoid inductor
power is applied between the barrel and the orange conductive spiral at barrel right end, and projectile introduced at left side closes the circuit when introduced
the magnetic flux created by the current flow in the solenoid would attract the projectile to the right, which in turn will shorten the inductor... in my twisted mind the projectile would then be accelerated, be always in the first half of the solenoid, etc... and for what I know the back-emf when opening the last spire of the inductor would occur when the projectile is over the next half of the solenoid and thus it would be pushed away
this simple image would illustrate my idea more easily
it represents the barrel in a longitudinal cut with barrel end at right side and projectile enter at left side
dashes represent turns of conducting material placed in spiraled grooves inside the non conductive surrounding
greyed turns represent a connection to the outer conductive barrel, orange turns represent a spiraled conductive rail which serves dual purpose of a conductive rail as well as an solenoid inductor
power is applied between the barrel and the orange conductive spiral at barrel right end, and projectile introduced at left side closes the circuit when introduced
the magnetic flux created by the current flow in the solenoid would attract the projectile to the right, which in turn will shorten the inductor... in my twisted mind the projectile would then be accelerated, be always in the first half of the solenoid, etc... and for what I know the back-emf when opening the last spire of the inductor would occur when the projectile is over the next half of the solenoid and thus it would be pushed away
If the projectile is magnetic: the emf (front or back) would always attract the projectile, as a magnetic object is attracted to either pole.
If the projectile was non-magnetic: the emf (back or front) would always repel the projectile, as the current induced is the same as the current in the coil.
Re: Circular railgun?
BigBad, Fri Jan 30 2015, 05:17PM
Incidentally, you can make them any size you want; you line the inside of the loop with a row of permanent magnets; forming a magnetic hoop and run the ballbearing along the outside.
BigBad, Fri Jan 30 2015, 05:17PM
Sulaiman wrote ...
one variation of this circular accelerator may be that if not too large, (e.g. use 1/4" ball bearing)
then there is the achievable possibility of adding a permanent magnet field
(something equivalent to the magnetic structure of a loudspeaker)
so that lower rail current with many revolutions of the projectile would be feasible.
(More like a linear/homopolar motor than a rail gun)
(no need for a gap in the rails)
Yeah, that's a homopolar motor.one variation of this circular accelerator may be that if not too large, (e.g. use 1/4" ball bearing)
then there is the achievable possibility of adding a permanent magnet field
(something equivalent to the magnetic structure of a loudspeaker)
so that lower rail current with many revolutions of the projectile would be feasible.
(More like a linear/homopolar motor than a rail gun)
(no need for a gap in the rails)
Incidentally, you can make them any size you want; you line the inside of the loop with a row of permanent magnets; forming a magnetic hoop and run the ballbearing along the outside.
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