Can magnets on a cylindrical object be used for projectiles?

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Discussion Overview

The discussion revolves around the feasibility of using magnets on cylindrical objects to launch projectiles. Participants explore the mechanics of magnet-driven rotation and the potential for generating torque to propel a projectile through a channel formed by the cylinders. The conversation includes comparisons to existing devices and considerations of materials and forces involved.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant proposes using two wooden cylinders with magnets to create torque for launching a projectile, drawing parallels to magnetized fans.
  • Another participant questions the design, suggesting it resembles a rail gun and asks for clarification on the mechanics involved.
  • Concerns are raised about the projectile being attracted back by the magnets as it exits the channel, potentially reducing its velocity.
  • Some participants suggest that electric motors would be more efficient than magnets for spinning the cylinders.
  • There is a discussion about the limitations of permanent magnets as a continuous power source, with references to conservative forces and energy storage.
  • One participant mentions the possibility of aligning magnetic poles diagonally on a cube, leading to further exploration of magnet shapes.
  • Another participant asserts that the proposed system is not a perpetual motion machine, clarifying their understanding of magnet behavior over time.

Areas of Agreement / Disagreement

Participants express differing views on the practicality and efficiency of using magnets versus electric motors, as well as the mechanics of projectile propulsion. The discussion remains unresolved regarding the effectiveness of the proposed design and the implications of magnetic forces.

Contextual Notes

Participants highlight limitations related to the assumptions about magnet behavior and the mechanics of the proposed system. There are unresolved questions about the necessary materials and forces required for effective operation.

Who May Find This Useful

Individuals interested in experimental physics, magnetism, mechanical design, and projectile motion may find the discussion relevant.

Alanay
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What I mean is if I have 2 cylinder objects made out of a light wood for example with 6 or so magnets on either face spread evenly and another magnet behind it causing it to spin could it generate a good amount of torque to shoot a small projectile between the two cylinders. To give you a better image you may have seen people putting magnets on their fans and holding another magnet close to it causing the fan to rotate. I'm talking about something similar but with a lot more pull (10 kg and maybe more for the 2 outer magnets).

EDIT: If you still can't picture it imagine the left cylinder moving counter clockwise and the right cylinder moving clockwise so whatever is in between can be shot out.
 
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Alanay said:
What I mean is if I have 2 cylinder objects made out of a light wood for example with 6 or so magnets on either face spread evenly and another magnet behind it causing it to spin could it generate a good amount of torque to shoot a small projectile between the two cylinders. To give you a better image you may have seen people putting magnets on their fans and holding another magnet close to it causing the fan to rotate. I'm talking about something similar but with a lot more pull (10 kg and maybe more for the 2 outer magnets).

EDIT: If you still can't picture it imagine the left cylinder moving counter clockwise and the right cylinder moving clockwise so whatever is in between can be shot out.
Can you Upload a sketch?
 
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berkeman said:
Can you Upload a sketch?
Here
ArlBX4a.png

http://blob:http://imgur.com/ea934414-893d-47f6-ac60-46e228ed142c
 
Last edited by a moderator:
so you want to make a weapon ?
 
davenn said:
so you want to make a weapon ?
It kind of looks more like a toy to me, but I'm still not getting it...
 
berkeman said:
It kind of looks more like a toy to me, but I'm still not getting it...

OK I will let you keep an eye on it
just going to PM you re such things
 
Alex Shi said:
http://blob:http://imgur.com/ea934414-893d-47f6-ac60-46e228ed142c
Is this not just a normal rail gun design?
Welcome to the PF.

LOL, show me the rail...?
 
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berkeman said:
Welcome to the PF.

LOL, show me the rail...?
What do you mean? You can understand the concept from that image alone surely
 
Alanay said:
What do you mean? You can understand the concept from that image alone surely
No, sorry. I'm not understanding what you are trying to do.

And please don't call me Shirley.
 
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  • #10
berkeman said:
No, sorry. I'm not understanding what you are trying to do.

And please don't call me Shirley.
Well, like I said imagine 2 cylinders on either side of a smooth path that are being rotated using magnets, left one going counter clockwise and the right clockwise. If you put a projectile the same width as path wouldn't the 2 cylinders shoot it out. I already know the answer my real question is what would the cylinders and path have to be made from and what kind of force would the magnets need or at least what kind of speed the cylinders need to be going.
 
  • #11
Alanay said:
2 cylinders on either side of a smooth path that are being rotated using magnets,
Rotated how using magnets? Some kind of motor arrangement? Where is the varying current flowing to generate the rotational forces?
Alanay said:
If you put a projectile the same width as path wouldn't the 2 cylinders shoot it out. I already know the answer my real question is what would the cylinders and path have to be made from and what kind of force would the magnets need or at least what kind of speed the cylinders need to be going.
No. If there are magnets on the rotating cylinders and you place a ferrous ball near them at the bottom, the ball will be attracted to the magnets and accelerate upward. But as it starts to exit the path at the top, it will be pulled back by the magnets, which will slow its velocity. You may get a net velocity out of the top, but it will be less than if you switched off the magnets as the ball reached its maximum velocity before exiting the channel...
 
  • #12
berkeman said:
Rotated how using magnets? Some kind of motor arrangement? Where is the varying current flowing to generate the rotational forces?

No. If there are magnets on the rotating cylinders and you place a ferrous ball near them at the bottom, the ball will be attracted to the magnets and accelerate upward. But as it starts to exit the path at the top, it will be pulled back by the magnets, which will slow its velocity. You may get a net velocity out of the top, but it will be less than if you switched off the magnets as the ball reached its maximum velocity before exiting the channel...
The projectile would not be magnetic. The magnets are simply used to make the cylinders spin.
 
  • #13
Alanay said:
The projectile would not be magnetic. The magnets are simply used to make the cylinders spin.
Oh, like a tennis ball launcher machine? Why not just use electric motors to spin the cylinders? They would be much more efficient.

https://i.ytimg.com/vi/oZjx7F1doGs/hqdefault.jpg
hqdefault.jpg
 
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  • #14
  • #15
Alanay said:
To give you a better image you may have seen people putting magnets on their fans and holding another magnet close to it causing the fan to rotate.

If you mean videos like this one..

..then you need to know it's fake.
 
  • #16
CWatters said:
If you mean videos like this one..

..then you need to know it's fake.

I'm not talking about that, more like this:
jrs-wheel.png
 
  • #17
I might as well post this question in this thread: Can you have the north and south pole aligned diagonally on a cube. So instead of 1 face being north and 1 south, you'd have 1 corner north and 1 south?
 
  • #18
That doesn't work either.

Permanent magnets alone cannot be used as a continuous power source. Read up on conservative forces https://en.wikipedia.org/wiki/Conservative_force . In short the force between two magnets is conservative. This means that if one magnet moves relative to the other, around any shape path such as a circle, and ends up back where it started, then the net work done or produced is zero. The fan in that video or your disk above returns to the starting position (or an equivalent) at least once per revolution, therefore it is not possible for it to do any work (it can't power a lightbulb).

However magnets can be used to store energy like a spring (eg Two magnets with their North poles together). In that case the system stores energy provided by something else (eg your hand) but it can't provide power continuously/indefinitely.
 
  • #19
PS This and other perpetual motion machines are banned topics according to forum rules so this thread is likely to be closed.
 
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  • #20
Alanay said:
I might as well post this question in this thread: Can you have the north and south pole aligned diagonally on a cube. So instead of 1 face being north and 1 south, you'd have 1 corner north and 1 south?

Sure. You can make magnets virtually any shape you like.
 
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  • #21
CWatters said:
PS This and other perpetual motion machines are banned topics according to forum rules so this thread is likely to be closed.
This is not perpetual obviously I know that, I don't think the thread will be closed. I'm not asking how to make a perpetual machine. Magnets demagnetise over time I know that. Take a look at this.
 
  • #22
Thread closed for Moderation...
 

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