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[Michael Moore]

http://www.machinedesign.com/motion-control/axial-flux-motors-and-generators-shrink-size-weight

It mentions motorcycles and uses a BMW i3 motor in a comparison with the new design.  It sounds very promising, but these things often do.

cheers,
Michael

[T.S. Zarathustra]

Basically there has been almost no new design in electric motors since Tesla (God bless his memory) invented the AC motor about 100-150 years ago. The design of this motor is so new that a variation of it is in my 8 year old washing machine (Google "direct drive washing machine motor"). I didn't read it all, but the implied claim that "rare-earth permanent magnets" are "rare and valuable resources" is also wildly inaccurate.

[Chocula]

I am not sure I read the same article as you.  All of the images Google showed me for direct drive washing machine motors appeared to be radial flux, not the axial flux described in article.  I also read the statement from the article below to mean that designs that use more copper an bigger magnets cost more money.

Large machines also require rare-earth permanent magnets and copper for the coils. (According to to Öko-institut e.V, RF DD generators require 600- to 700-kg magnet material per megawatt.) The use of rare and valuable resources has a big impact on the cost and lifecycle analysis of RF DD machines.

This looks like an interesting design and will hopefully help reduce the weight on future motorcycles.

[T.S. Zarathustra]

I already mentioned magnets, and while Copper is not abundant, it is not rare either. Since Rare Earth Magnets and Copper are both rather inexpensive, and readily available, I still see the "rare and valuable resources" comment as inaccurate.

The reduction in weight. There is a thing called "flux magnetic saturation". That is the thing that limits size reduction of motors. Axial or radial do not affect flux magnetic saturation. The BMWI3 motor comparison is apples and oranges comparison. Lot of the extra weight in the BMWI3 motor comes from the cooling system. Most of the comparisons in the article come from comparing the radial motor to motors with gearboxes. To me the whole article reads like advertisement.

Although most of my electric motor expertise lies in the larger industrial motors. I know enough about the little siblings to state that the differences in power are mostly from the shape of the motor. Short and fat instead of long and thin. One is not necessarily better, just different power characteristics.
There are 2 large drawbacks in the radial flux motors that are not mentioned in the article. Double air gap and since they don't use stacked shims, they get larger magnetic eddy currents. 
The layout of the radial flux motor is not without merits and better and lighter motors would benefit all. The future will tell. 

[Curt]

Rare earth shortage spiked in 2011 but seems to have resolved. I didn't realize that.
https://www.technologyreview.com/s/535381/what-happened-to-the-rare-earths-crisis/

The magnetic flux lines they drew seem simplified for both motors. In reality they must contort diagonally as the motor rotates. I didn't see a comparison of how the magnetic forces translate to torque.

With the large dual rotors and double magnets it seems like there would be more rotating mass. Maybe OK for windmills, but could it affect the acceleration and handling in vehicle applications?

It seems like the length of the flux lines would be comparable between RF and AF. Their diagrams show only part of the flux lines. They seemed to imply that the lines would go from one rotor disk through the coil to the other rotor disk, but flux lines must always continue to loop back around.

I didn't understand the 50% wasted loop coils they were talking about for RF.

The claim of 96% better efficiency with "up to 97%" seems excessively precise so that they come across as junk numbers.

[igorbaldo]

Duplicate thread...

http://electricmotorcycleforum.com/boards/index.php?topic=7847.0