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Electromagnetic Propulsion

  1. Jan 17, 2014 #1
    I am interested to know if a copper coil wrapped around a iron pipe could be used to propel another iron pipe capped at both ends through the larger pipe with the copper coil around it?

    I am thinking that the larger iron pipe would need to be slotted from end to end and insulated from the copper wire insulated coil. inside the outer pipe, the smaller pipe with end caps would need to be insulated from the larger pipe with a non conductor such as cardboard, air or both. Consider dc, pulse and ac

    There are alternate positions for magnetic coils but I want to look at this option first.....jim
  2. jcsd
  3. Jan 17, 2014 #2
    Yes. I'm assuming that the coil is wrapped around the outside of the larger, stationary pipe and is insulated from it.
    The smaller pipe fits within the big pipe snugly but not tightly and is lubricated so that it can move freely through it - even with substantial side forces. The coil would then be energized to draw the small pipe in and then turned off as the smaller pipe moved through the center. You would then need to depend of momentum to keep the smaller pipe moving the rest of the way through.
  4. Jan 17, 2014 #3


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    Why use an iron pipe for the outer pipe? Even with some slots, you have a ferrous material in the way of the magnetic field, which will partially shield the inner ferrous pipe from the coil's magnetic field. Slots mainly help with eddy currents, which wouldn't appear to come into play given your problem statement.
  5. Jan 17, 2014 #4


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    Staff: Mentor

    And BTW, why is the title of your thread "Electromagnetic Propulsion"?
  6. Jan 18, 2014 #5


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    sounds like he wants to make a coil gun

  7. Jan 18, 2014 #6
    the idea actually works and is know for a very long time.
    many old cassette recorders use this type of moving metal plug surrounded by a coil to move some physical mechanisms that either stopped or satrted the play.
    also other devices like some electromagnet valves of older type use this.

    as berkeman said you need a dielectric material for the outer pipe on whcih the coil sits and then a metal inside the pipe and when you will apply voltage to the coil the metal will move, how it will move depends on what kind of power you apply , either AC or DC or a single pulse of DC.etc
  8. Jan 20, 2014 #7
    Well a coil gun is partly right except that the projectile needs to be hollow to carry passengers and the metal gun barrel tube needs to be several hundred miles long and be evacuated so that we wouldn't be pushing a column of air through the barrel. The barrel would form a closed loop several hundred miles long.

    I understand that wrapping an iron rod with a coil increases the magnetic field 1000 fold. I was trying to come up with a concept that would enhance the coils effect. Another thread here suggested that the outside pipe would need to be cut length ways to prevent the pipe from acting like a shield. That should render the pipe as simply an iron core and enhance the coil fields. Maybe not...I will probably need to go to recycling and get some stuff and experiment to get this figured out. I am thinking now that when a coil is turned on that the poles would be at either end of the tube which wouldn't help. In fact the pipe would have to be in sections equal in length to each coil which looks too complicated.

    I have been looking at the proposal of Elon Musk from Tesla Motors at www.spacex.com/sites/spacex/files/hyperloop_alpha-20130812.pdf

    The hyperloop concept suggests an evacuated tube with the pods sitting on sled type rails that float on an air cushion provided by compressed air from inside the pod. I think that would add air to the vacuum and defeat the purpose of the vacuum.

    The hyperloop works by having the magnetic fields generated inside the outer pipe. It however requires a rail system to be built inside the tube.

    I was hoping for the pods to float freely through the tube levitated and propelled by magnetic fields. The propulsion and levitation might happen by placing U shaped iron core electromagnets along the outside of the pipe with the iron at the poles entering the pipe through insulated holes in the pipe. In this case the pipe need not be iron but needs to be strong enough to hold 48 passengers in a pod at 600mph.

    I am also thinking the pipe would be better buried instead of elevated. except where the ground is too hard. This way an old rail right of way could be used without expensive pilars or impact from other vehicles or stuff moving about on the surface like NIMBYs
  9. Jan 21, 2014 #8
    well Im not sure for such sizes and wights and kinetic energies involved but small metals of a very precisely made shape and coils around them can be made to levitate or in other words to float in the tube or any other place they are in with less than mm cleaances between the floating object and the coil etc.
  10. Jan 21, 2014 #9
    These devices are pretty common and are typically called solenoid actuators or just solenoids for short. The metal slug in a solenoid has a spring on it and the coil can pull the slug in or let it spring back out. They are used to control throttles, valves, and stuff like that.

    Have you looked into maglev trains?

    About evacuating the tube, it's actually pretty hard to maintain a large vacuum, or so I've been told. Like your train, wind resistance is a problem for large electric generators too. The solution that some people use is to seal the rotor in a chamber and fill it with hydrogen. The lighter atoms of hydrogen yield less resistance as the rotor spins.
  11. Jan 22, 2014 #10
    yes I looked at maglev, but couldn't figure out which north and south poles were with which coils as only poles were noted in diagrams.

    Do any actuators have a metal tube inside the coil?
  12. Jan 22, 2014 #11
    Well I am thinking one way valves along the tube set at one atmosphere. So if the train begins pushing air above one atmosphere, then the valves would maintain the pressure at the front and back of the train at one atmosphere. That is because the tube is a closed vacuum loop. At 600mph any small leaks might create some air to push which would be telieved through the valves.

    Side loops would allow pods to exit the main tube to let passengers on and off through air locks
  13. Apr 13, 2014 #12


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    No rails, at least not for wheels. The Hyperloop concept supports the passenger capsule on a compressed air cushion
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