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Comment by jacquesm

16 days ago

Then you could use a smaller motor which would be lighter (important for aviation) and likely cheaper.

Looking at the whole system might reveal a different answer though.

  • Highly unlikely, but since you make the claim I think you also should present that whole system evidence. From what little I know as a once upon a time bit player in aviation I suspect that that will be a very hard sell.

    For instance: I know of an invention that will spin up the wheels of a landing aircraft just before touchdown. This saves on the wear of the tires (right now it is mostly the runway that spins them up, as a result of which you see these nice rubber deposits on the touchdown areas). But it would add a few kg to the weight of the wheels so it's a complete non-starter.

    • Let's look at the marketplace for aviation piston engines. We still see the Lycoming IO360 [1] and its variants installed in aircraft today. For reference it was first produced in 1955. That's >70 year old tech which produces ~200 hp depending on the version. It's used in myriad designs because it's certified and well known. It weighs around 260 lbs. (very hand wavy calculation...) that means we are looking at roughly .76 hp/lb or 1.28 kW/kg. Compare that to 59kW/kg of the article.

      Right now, the engine is generally the most expensive as well as the heaviest component in GA aircraft. If you are developing a new airplane, you are often choosing a motor to build the craft around. You would be a fool to choose something that is not tested because (almost) nobody wants to fly a new plane with a new motor. I'm guessing that the cost of one of these axial flux motors is well below $70k. I'll guess $2k... just for ease of numbers.

      Our motor is now 46x lighter/hp and 1/35 of the cost. This means we have a lot more flexibility in our aircraft design and our budget for materials/components has gone up, or our market has gotten wider. The biggest hurdle now is to overcome the "unknown engine" which is possible when the exact motor has been mass-produced and mass-used in other sectors. By using this and not painting your design into a corner by relying on the absolute lightest motor you can get, you leave room for future designs in the same space. ie: you have set yourself up to produce the next Cessna 172.

      There are additional reasons to want a motor that is 200 hp or less which are written in FARs in the US and copied by other countries. Also, wanting a motor that is more than 200 hp is desirable for other use-cases. By having one motor that can fill both spaces you now have (waves hands) twice the reputation building power.

      Of course, there are other technical considerations such as energy storage/weight but the field is so wide that a book could be written on making comparisons. The technical landscape is also actively changing.

      [1] https://en.wikipedia.org/wiki/Lycoming_O-360