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Registered Member #3215
Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780
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
Registered Member #11591
Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556
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?
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.
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600
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.
Registered Member #3215
Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780
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 ...
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?
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.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
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)
Registered Member #2906
Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727
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.
Registered Member #3215
Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780
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
Registered Member #11591
Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556
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
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.
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600
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.
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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Circular railgun?
