Magnet Type for Heat Engine: Alnico or Rare Earth?

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Discussion Overview

The discussion revolves around the selection of permanent magnets for a newly designed heat engine, focusing on the suitability of Alnico versus rare-earth magnets, particularly in terms of their mechanical properties and resistance to high temperatures and shockwaves.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant proposes using Alnico magnets due to their robustness and high curie temperature, while seeking information on strong rare-earth magnets that may also be suitable.
  • Another participant mentions the use of carbon fiber in brushless model aircraft motors to secure magnets at high RPMs.
  • A different participant argues that carbon fiber will not prevent magnets from shattering under force and raises concerns about its flammability.
  • This participant also suggests the idea of using a stronger metal for plating neodymium magnets, considering options like steel or gold.
  • Another participant expresses confusion over how plating with gold or steel would be beneficial if carbon fiber does not help.
  • A later reply indicates a sense of defeat, suggesting that no solution may be effective in preventing magnet failure.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness of various materials and methods for securing magnets, with no consensus reached on the best approach or material choice.

Contextual Notes

Participants have not fully explored the implications of their proposed solutions, and there are unresolved questions regarding the mechanical properties and limitations of the materials discussed.

TESL@
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I'm planning to use some permanent magnets in a new kind of heat engine I designed. The properties I am seeking are:

- Resistance to shockwaves and high acceleration,
- Relatively great strength/weight ratio,
- and relatively high curie temperature.

After a quick research, I think the best fit type of magnet would be "Alnico"s which are robust and temperature resistant. However I need to know if there are any strong rare-earth magnets that do not break easily and suitable for this job,

Thank you.
 
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Some brushless model aircraft electric motors rotate at very high rpm. The rotor is wrapped with carbon fibre to help keep the magnets attached.
 
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Wrapping with carbon fiber will not decrease the force applied on the magnets so they will shatter anyway. Also, carbon fiber is flammable.

...but you gave me an idea that neodymium magnets are coated by nickel. Can I instead use a stronger metal to contain the powder?

edit: Any type of plating is possible, so I decided to coat with steel or gold. "https://www.kjmagnetics.com/neomaginfo.asp"
 
Last edited by a moderator:
If wrapping with carbon fibre doesn't help then I've no idea how plating with gold or steel helps? Guess I totally misunderstand what you are trying to do.
 
Nope, I'm wrong, nothing will help. How do we close the thread?
 

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