Gains from N40 magnets on Grin V2/V3 motor are impressive compared to N35 magnets on Grin V1 motor

[ebike4healthandfitness]

Here is the gain with Cold Phaserunner:


The stronger magnet increases torque per amp and increases efficiency at all speeds except at the very top end.


Here is the gain with Kv set identically for both motors:


Here is the gain with 60 amp controller and Kv set identical for both motors:




Here is the gain with 100 amp controller and Kv set identical for both motors.

 

[ebike4healthandfitness]

My guess is that the motor would do even better with stronger magnets.

The only downside of more powerful magnets appears to be lower speed for a given voltage due to higher back EMF.

 

[neptronix]

Justin wrote some info about this a while ago.

You get a small reduction of efficiency and increase of cogging while cruising, but you get better efficiency on hill climbs/acceleration.. the efficiency difference roughly evens out and it makes this small DD more suitable for 26"-29" wheels it's typically installed on.

I think it is a pretty good choice!

 

[ebike4healthandfitness]

Justin wrote some info about this a while ago.

You get a small reduction of efficiency and increase of cogging while cruising, but you get better efficiency on hill climbs/acceleration.. the efficiency difference roughly evens out and it makes this small DD more suitable for 26"-29" wheels it's typically installed on.

I think it is a pretty good choice!

Experimenting with the calculator I noticed (for an upright mtn bike) the small reduction in efficiency during cruising only happens when using the slowest wind with the lowest amp controller and 20" wheels. In all other cases the V2/V3 are more efficient during cruising.

 

[ebike4healthandfitness]

Going beyond increasing magnet strength, how about increasing pole count.

One thing increasing pole would do is allow for a taller stator without increasing the outer diameter of the drive. This because a higher number of magnets allows the stator diameter to grow while keeping the air gap (between permanent magnets and stator) the same.

Taller stator would in turn allow a greater amount of copper mass.

The greater amount of copper mass then allows for greater strength magnets to be used.

With that noted, I've read one downside to increasing pole count is larger eddy currents. This means that thinner laminations would be needed.

 

[neptronix]

The RH212 is that motor, and it's a bummer it doesn't have superthin lams.

 

[ebike4healthandfitness]

The RH212 is that motor, and it's a bummer it doesn't have superthin lams.

Comparison of two .35mm lamination motors (Nine Continent RH212 with 28mm stator and Nine Continent 3007 with 30mm stator):

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SIDE NOTE: I did not set Kv to be identical on both motors. What you see is the true Kv for those two particular windings.



That is a pretty big difference in performance. This especially as the RH212 has a 2mm narrower stator.

Also notice how the RH212 doesn't lose in efficiency even at the top end.

I wonder what the magnet strength of each motor is?