Electromagnetic Piston using a holding magnet and permanent magnets?

geologeek

Dear all - I am new here so please be gentle

I have searched the site for a few days but alas still have a few questions on something i am hoping to make........so with your kind help - here we go!

I am looking to make a type of electromagnetic piston, basically i want to have an external section which holds a 12vdc holding electromagnet which will be placed on the outside of a tank, with an internal section that has for example a neodymium disk magnet inside a tube - so when the electromagnet is engaged it repels the permanent magnet, which will return when the electromagnet is disengaged.......

I admit there are a few details i need to think of here - as to how i can control the disk magnet to get it to return when the power is disengaged etc.......but you clever souls may also be able to help with that!

i was thinking of having the disk magnet in the central reaches of say a 4inch long tube, and constrined in this location by spacers which would prevent the magnet from straying too far - at the end of the tube on the outer edge (other side of the restraining spacer) i could have a ring magnet that repels the disk magnet so when the more powerful electromagnet is off, the ring magnet pushes the disk magnet back towards the electromagnet end..........stop me if i am way way off track!!!!

alternatively - would it be possible to alternate the direction of the DC current so the electromagnet pushes on one cycle and pulls on the other to remove the need for a repelling permanent magnet?

Of course i also need to address how the outer and inner sides will stay in alignment on either side of the tank - i am hoping this can be achieved by strong magnets to hold the housing at a distance sufficient so that the electromagnet does not have an influence.....

As you can see - magnatism other than what our earths core produces is not something i know a lot about - so forgive me that flaw please!

Any help will be greatly appreciated - and i hope you get the gist of what i hope to achieve........i doubt anyone else will want to do the same thing - but it is what i hope to achieve in the coming weeks......

So to recap - i want a disk magnet to slide back and forth by a couple of inches inside a tube with the aid of an electromagnet so that i can control its speed (and i would love it if i could control the amount of travel!!)............the inside and outside sections will ideally be held together by strong magnets at a distance sufficient to not be affected by the electromagnet when engaged.......as that would be silly if it all fell apart

Thanks so much in advance,