# Copper coil wrapped tube & magnet pushed through tubing. Questions

#### RogueRose

Joined Oct 10, 2014
375
So what I am picturing is some kind of tubing, say 1" ID, and it is wrapped with 12g magnet wire in a tight coil. If a cylindrical magnet is pushed through the tube I guess a DC current will be produced.

As per my other posts on magnetic linear acceleration, caps and flywheels, (all three CAN make use of the technologies I'm researching) this question is geared on finding a way to generate quick pulses of electricity by various methods of generation. Here I am looking at compressed air or possibly even a powder charge to drive the magnet into an air shock absorber of some type or a magnetic arrester.

Sorry for so many questions here, but this is the culmination of 4 different research topics where I have gotten some mixed info.
-Does it matter the polarity of the magnet (+ or - at the front of the magnet)?
-Will the strength of the magnet effect the voltage or current produced and if so, is there a way to determine by how much?
-Will more layers/wrappings (in parallel stacked vertically) produce more output (I'm guessing current?)
-What would smaller guage wire accomplish if the same length of tubing was wrapped?
-Is there resistance against the magnet while it passes through the tube?
-If multiple tubes were run in parallel (single power source) with identical windings - terminated/connected to a single device, fired from a single source, would the pulse be synchronous? (or a way to sync them w/o caps?)

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#### Lestraveled

Joined May 19, 2014
1,946
@RogueRose
You do know that railguns is a forbidden topic here??

#### cmartinez

Joined Jan 17, 2007
7,223
I'll try to answer your question to the best of my abilities. Others in this forum might give you better (more elaborated) answers.

-Does it matter the polarity of the magnet (+ or - at the front of the magnet)?
The direction of the current (and polarity of the voltage) will be inverted, depending on the magnet's orientation
-Will the strength of the magnet effect the voltage or current produced and if so, is there a way to determine by how much?
Yes it will affect both, but to be honest, calculating that is beyond me
-Will more layers/wrappings (in parallel stacked vertically) produce more output (I'm guessing current?)
It should, since the amount of total turns also has an effect on output power
-What would smaller gauge wire accomplish if the same length of tubing was wrapped?
A more densely packed wire, so you'd get more voltage, but with less current capability.
-Is there resistance against the magnet while it passes through the tube?
Of course there is, since the magnetic field is inducing current through the coil (assuming the coil is connected to a resistive load, for instance)
-If multiple tubes were run in parallel (single power source) with identical windings - terminated/connected to a single device, fired from a single source, would the pulse be synchronous? (or a way to sync them w/o caps?)
Yes, the pulse would be synced, but with slight variations in output voltage and current due to unavoidable physical variations in the magnets and coils used, which may or may not be important in what you're trying to achieve.

#### cmartinez

Joined Jan 17, 2007
7,223

#### SLK001

Joined Nov 29, 2011
1,548
So what I am picturing is some kind of tubing, say 1" ID, and it is wrapped with 12g magnet wire in a tight coil. If a cylindrical magnet is pushed through the tube I guess a DC current will be produced.
Not DC, but AC current will be produced.

#### Lestraveled

Joined May 19, 2014
1,946
....................As per my other posts on railguns, .................
Does this post concern railguns??

#### cmartinez

Joined Jan 17, 2007
7,223
Does this post concern railguns??
man... I always fail to read the small print!

#### RogueRose

Joined Oct 10, 2014
375
@RogueRose
You do know that railguns is a forbidden topic here??
Thank you, I did not. I came across railguns as they use a linear accelerator motor which is part of what I'm researching (linear acceleration & power generation from such)

#### RogueRose

Joined Oct 10, 2014
375
Of course there is, since the magnetic field is inducing current through the coil (assuming the coil is connected to a resistive load, for instance)

Yes, the pulse would be synced, but with slight variations in output voltage and current due to unavoidable physical variations in the magnets and coils used, which may or may not be important in what you're trying to achieve.
Thanks for the reply! This really cleared up an aspect I've been having a hard time understanding. The resistance to the magnet. I've spun alternators and the seem to spin freely. I guess the resistance comes from the load put on it - duh! Don't ask how I didn't understnad that, I've always had a "missing piece" when understanding some aspects with load/resistance.
Thanks again!

#### Dr.killjoy

Joined Apr 28, 2013
1,196

#### shortbus

Joined Sep 30, 2009
8,197

#### BR-549

Joined Sep 22, 2013
4,938
With our improvement in magnetic materials and such precise feedback control nowadays, I believe much more work ought to be done with linear acceleration.

I always liked the idea of magnetic shocks.

Surely, linear acceleration doesn't have to refer to rail guns. Quick and hard doesn't imply rail gun either. Magnetic drills and hammers would have a lot less wear.

What if, instead of a oil film, we produced a magnetic film.

#### Dr.killjoy

Joined Apr 28, 2013
1,196
Why is everyone referring to a rail gun when he is using Magnetic coils instead of 2 parallel rails ?

#### Lestraveled

Joined May 19, 2014
1,946
Isn't a "rail gun" anything that fires a projectile using electrical energy as the main propellant?

#### BR-549

Joined Sep 22, 2013
4,938
I guess it's the difference between the word fire and move.

After all, we propel projectiles very hard and fast rotationally (motor) with fields.

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#### Dr.killjoy

Joined Apr 28, 2013
1,196
Isn't a "rail gun" anything that fires a projectile using electrical energy as the main propellant?
Coil guns use large coils to pull and push metal item as projectiles..
The rail gun use 2 rails that are only connected by projectile .

#### bertus

Joined Apr 5, 2008
21,045
Hello,

A coil gun will transport a piece of metal by exiting coils (giving current blasts) in a row.
I think the TS wants to move a magnet through the coils to gain power from the coils.

Bertus

#### Dr.killjoy

Joined Apr 28, 2013
1,196
Hello,

A coil gun will transport a piece of metal by exiting coils (giving current blasts) in a row.
I think the TS wants to move a magnet through the coils to gain power from the coils.

Bertus
Thanks

I am not sure the main goal cause he mention a rail or coil gun but these use power in order to fire a projectile.. The origional post talks about making power using coils .. If you looking for a single AC spike then just pass a magnet throught the windings but speed will be a great factor and further testing will be need for best performance.. If it passes to fast then you might not get anything just like being to slow.. For long AC then I would look at I think Tesla's air piston ( Sorry if I am wrong)

#### wayneh

Joined Sep 9, 2010
16,531
A cylindrical magnet passing through the bore of a short cylindrical coil will produce current in the coil. If the coil is very long relative to the magnet, I'm not so sure. I'd have to think about whether the passage of the north pole offsets or adds to the emf generated by the south pole. My gut says they will cancel and the only net effects will be where the magnet enters and leaves the coil. Surely someone has done this experiment?

One problem is the direction of the field lines. If the field is axial to the magnet, and thus axial to the coil, this means the coil won't be seeing nearly as strong a field. You want the the field lines - at the face of the magnet where they are strongest - to be perpendicular to the coil windings. It's the rate of change of a magnetic field seen by the conductor that generates the emf.

#### recklessrog

Joined May 23, 2013
985
A little off at a tangent, but I have an experimental Gyroscope that I worked on for a short while in the late 60's. It uses magnetic suspension bearings (tiny ferrite and alnico) which worked reasonably well. I think that if we had the modern very powerful rare earth magnets available back then, most of the problems with it would have been overcome. The main one being that the shaft would sometimes run into a very small amount of precession that was actually caused by gravity or G-forces.