Building a "Reverse" solenoid ..?

Question

I am wrapping the magnet wire around a plastic core.

Then I am slipping the core into a steel tube.

It seems to me the flux should push against the steel tube and push wire wrapped core.

When I send current thruough wire nothing happens. Tested with typical solenoid design and the windings should be adequate.

Thanks

Answer 1

I assume that by "reverse solenoid" you mean that you want to achieve the mechanical effect of pushing rather than pulling with the solenoid "armature" that is the part that moves.

The solenoid operates by creating a magnetic Field within it's hollow core. Theoretically , no magnetic field exists outside the core. The armature is attracted into the magnetic field and thus produces movement. If the armature is held stationary within the core, this does not reverse the magnetic effect and try to repel the coil from the core, as the armature is still attracted to the magnetic field within the core.

The solution to the mechanical question of obtaining "push" as opposed to "pull" is to arrange the armature to be held outside the core of the solenoid against a spring. A non magnetic pin (eg brass or stainless steel) is attached to the armature to pass through the core and emerges through a slide hole or bearing.

When current is applied to the solenoid coil, the armature will move into the magnetic field within the core, against the spring, and the pin will emerge through the slide hole, the mechanical effect of which will be a "push".

For more detailed therory for solenoids see:

http://en.wikipedia.org/wiki/Solenoid

Answer 2

In a solenoid, the entire magnetic flux is contained inside and so it should have essentially no effect on the steel tube. If the wire were wrapped AROUND the tube, the tube would act as the core and would become magnetized.

Answer 3

Assuming the steel tube is held stationary, the core will move onto the steel tube, if the starting position is not completely on the steel. Also if the steel is a permanaent magnet, and you apply DC to the coil it will move. Otherwise there is no reason for the coil to move from one location to another along the tube.