Magnet Type for Heat Engine: Alnico or Rare Earth?

In summary, the conversation discusses the use of permanent magnets in a new heat engine design and the desired properties for the magnets, including resistance to shockwaves and high acceleration, a high strength/weight ratio, and a high curie temperature. The individual is considering using robust and temperature resistant "Alnico" magnets, but is also looking for strong rare-earth magnets that are less prone to breaking. There is also a brief discussion about using carbon fiber to wrap the magnets, but it is determined that this will not be effective. The individual then considers plating the magnets with steel or gold, but ultimately concludes that nothing will help and asks how to close the thread.
  • #1
TESL@
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8
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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  • #2
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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  • #3
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"
 
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  • #4
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.
 
  • #5
Nope, I'm wrong, nothing will help. How do we close the thread?
 

1. Which magnet type is better for a heat engine, Alnico or Rare Earth?

The answer to this question depends on the specific application of the heat engine. Alnico magnets have been traditionally used in heat engines because of their high magnetic strength and temperature stability. However, Rare Earth magnets, such as Neodymium and Samarium Cobalt, have become increasingly popular due to their even higher magnetic strength and resistance to demagnetization at high temperatures. It is best to consult with a materials expert to determine which magnet type is most suitable for your specific heat engine design.

2. What is the difference between Alnico and Rare Earth magnets?

The main difference between Alnico and Rare Earth magnets is their composition. Alnico magnets are made from aluminum, nickel, and cobalt, while Rare Earth magnets are made from alloys of Neodymium, Iron, and Boron or Samarium, Cobalt, and Iron. This difference in composition results in different magnetic properties, with Rare Earth magnets being significantly stronger. Additionally, Alnico magnets are more resistant to corrosion, while Rare Earth magnets can be more vulnerable to oxidation.

3. Are there any disadvantages to using Rare Earth magnets in a heat engine?

While Rare Earth magnets have many advantages, there are a few potential disadvantages to consider. One is their high cost compared to Alnico magnets. They also have a lower Curie temperature, which is the temperature at which a magnet loses its magnetic properties. This means that Rare Earth magnets may not be suitable for use in extremely high-temperature heat engines. Additionally, Rare Earth magnets can be brittle and may require special handling and care during assembly and use.

4. How do I determine the appropriate magnet size for my heat engine?

The size of the magnet needed for a heat engine will depend on several factors, such as the size and design of the engine, the required magnetic strength, and the temperature at which the engine will operate. It is important to consult with a materials expert or refer to magnet size and strength calculators to determine the ideal magnet size for your specific heat engine.

5. Can I use a combination of Alnico and Rare Earth magnets in my heat engine?

Yes, it is possible to use a combination of Alnico and Rare Earth magnets in a heat engine. This can be especially beneficial if you want to take advantage of the high temperature stability of Alnico magnets while also incorporating the stronger magnetic properties of Rare Earth magnets. However, it is important to carefully consider the design and placement of the magnets to ensure they work together effectively and do not negatively impact the performance of the heat engine.

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