# Youtube rail gun videos physics

1. Jan 5, 2014

### Crazymechanic

So I once saw a intersting video made by some guys for a school project , now I finalle decided to have a share with you and ask some question. Such videos are also put up by the free energy guys but let's not focus on that for now shall we.

So basically as you can see it's two lines of magnets in a what appears to be a 45 degrees angle and same poles from both sides facing inwards towards the track.The middle magnet is being put in and is constantly pushed forward because the same poles repel.
Also you can see that they use a metal in the middle on which the sliding magnet moves because without it the middle sliding magnet stops at the end where the last side magnets are located , but with the middle metal extended and going further than the side magnets the sliding magnet is able to escape from being stuck at the end due to the ineartia it gained while being accelerated towards the end, also the metal on which the magnet slides probably extends the magnetic field little further outside the main lines were the side amgnets are located.

So this got me wondering, well if you would make a circle of such magnets and put a track below the middle sliding magnet the magnet would eventually stop after passing a while or not move at all since the magnetic field lines would close end to end , but what would happen if we would put such magnet strips one after another but with a little distance between each one and the metal on which te sliding magnet slides also had to be isolated from the next one , I wonder would the sliding magnet keep sliding into each next one , because if it can exit one of these rails then from the ineartia it has it could enter the next one and so on, basically a linear motor of sorts.
Well watch the video and tell me what you think?

Last edited by a moderator: Jan 5, 2014
2. Jan 5, 2014

### turbo

I don't have the authority to shut this down, but generally rail-gun threads are not allowed on PF.

3. Jan 5, 2014

### OmCheeto

NO! Not until I explain why it won't work. This may take me a few minutes.

4. Jan 5, 2014

### Crazymechanic

wait wait , why shut it down?
In no place or paragraph did I said that there is a overunity free energy blah blah blah thing involved here , I'm not that dumb I do understand how nature works , atleast down to such basic levels.

instead I wanted to understand for how long of a distance could such a magnet travel before being stopped by either the magnetic forces themselves or whne the ineartia stops.
So maybe I should ask how far could this magnet get if we would put some continuing magnet lines ahead of this first one in a linear fashion but with a little distance so that the sliding magnet doesnt get caught in the field of the last magnets.
there is no free energy here just magnet magnet repulsion of the same poles , nevertheless I wanted some opinion on tis, thank you.

5. Jan 5, 2014

### OmCheeto

Someone posted a similar question awhile back, and while I was building the device on my back porch, the thread was locked. You really get a "feel" for what is going on when you built these, and why they won't ever work.

If you take out your pen and paper and draw the setup they have, with and without the metal strip, drawing in the magnetic flux lines, you'll see exactly why it behaves the way it does.

With the metal strip, they basically created a long magnet. The permanent magnets have very little effect on the projectile, as the forces on the north and south ends are neutral, except for the metal strip in the middle.

If you were to circularize(?) the system, or whatever you are trying to do, there would be no north or south pole to act upon the projectile, so it would just sit there.

ps. This device is also patented, but I'm too lazy to google it again.

6. Jan 5, 2014

### Crazymechanic

yes as I said before if you would make a circle it won't work because of what you just said , I'm speaking about linear mode here , well I think I get how the thing goes myself , so you have say S poles facing from all sides all the way down as far as the side magnets go , then you have a middle magnet which has S on one end of it and N on the other , now putting the N first and the S last in makes the magnet kinda sucked in at first because the N being in front tries to reach the S at the sides , now as the middle magnet is sucked in the back of it has S polw which is now pushing against the S from the sides , so while it gained ineartia it had enough kinetic energy to escape the end of the magnet line and since te N is now away from the S there is only the S from the back pushing the magnet out of the line against the S from the sides,

so basically why this works is because while the magnet is in the middle it accelerates for a while , that is as long as it tries to reach equilibrium with the side magnets , and while it does so it gains kinetic energy which in this case is enough to throw it out of the magnet line without getting stuck at the end.
is that correct?
So if this is correct I wondered what would happen in one would put a identical magnet strip like the one that accelerated the first one right after the first one but not connect it directly metakl to metal so that the field lines could not extend and make the magnet stuck , in other words make it such that the exiting magnet with t's kinetic energy it gained can be thrown into the next one , that's all I'm wondering , i hope you and other get the idea.

And don't tell me that permanent magnets can't do work as I already know that. :)

7. Jan 5, 2014

### OmCheeto

I would modify the experiment. Rather than lining up gobs of "propulsive" magnets like the boys did, use only 2 magnets, with the magnetic flux lines directed to varying lengths of metal strip. My guess is that the results would be the same. I'm also predicting that there is a point at which lengthening the metal strip yields diminishing results.

8. Jan 5, 2014

### Crazymechanic

definitely, the longer metal strip is only needed to guide the sliding magnets head out of the field which would otherwise capture it and make it stuck I guess , as w can see in the video as long as the head is out and the back being the same pole as the sides repels it even further the magnet can have it's kinetic energy enough to overcome the attracion and with a little bit of repulsion at the end escape the field and move out with whatever kinetic energy it has left from te initial acceleration state inside the magnet line.

Still I wonder what would happen if I put another magnet line asfter the first one but not in direct metal to metal contact to not close the field lines and make the magnet stuck, if it would enter a magnet line with the kinetic energy it had left from the previous acceleration, escape could it get the same propulsion fowards once again ? In theory it should why not , but hows in practice , actually this experiment is so simple I and possible anyonewith two hands could replicate it I just don't want to get so much magnets to understand a simple thing. :)

9. Jan 5, 2014

### OmCheeto

This is looking more and more like a

I took a short break, to visualize what on earth you are talking about.

Observe the video. The projectile is originally repelled by the "projectile system".

ps. metal to metal contact is not required to close field lines.
pps. PF google: Omcheeto tuna fish cans are those magnets? Never mind. I love PF.

Last edited by a moderator: May 6, 2017
10. Jan 5, 2014

### Crazymechanic

after one magnet rail like this the magnet comes out accelerated with some kinetic energy , after entering another one and then another and probably som more depending on the situation it will stop or get stuck in one of the later ones and nothing further will happen , ?

ps. I agree about the metal to metal not needed for closing field lines thing for sure.
i've should have said a distance far enough apart for the next ones to not be affected by the previous ones.

11. Jan 5, 2014