ebike4healthandfitness wrote: ↑
Dec 28 2021 11:40pm
Peak efficiency....yes. But it loses in.efficiency at lower wheel speed.
With a very small wheel it won in efficiency (and power) all throughout the speed range. I was very impressed.
Very low speed efficiency doesn't matter much and is INCREDIBLY variable with what load you put on each motor vs the motor's characteristics. Don't ever compare motors on that metric. Peak efficiency and the RPM/load point it happens at is always the first clue to look at when assessing an unknown motor.
We've always known smaller wheel hubs have a power density advantage.. however, with increasing iron losses and/or increased gearing losses, there are plenty of motors which will have a bit poorer efficiency in a smaller wheel.
My eZee motor ( nicer MAC clone with a bit smaller stator ) has atrocious efficiency in my 20 inch wheel... upper 70's, low 80's.. good power? yeah.. but...
Of course the Rion RE90 has impressive specs like that. The motor spins at 1000's of RPM and is probably a 4-8 pole motor ( very low iron losses per RPM ) and probably has razor-thin laminations also, lowering the iron losses even further.
There aren't many ebike hub motors that are specifically designed for a small wheels ( which implies a lower pole count ) and have high power. The only way to get scooter-like power density is to take something akin to a 94% efficient RC motor ( astro, maytech? ), put that 4lb motor through two reductions.. what you probably see is 90% peak efficiency with a 8lbs motor + reduction assembly..
This video is now going 10 years old..
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama
My first major build:
1.6kW 8T MAC motor on a Trek 4500 MTB.
Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter:
Cannondale semi recumbent - under construction.
Maxaraya FS semi recumbent and high efficiency mid-drive - under construction.