Except that looks like an inrunner and likely has fewer poles and will have less iron losses at 10k rpm than what we use.
The most efficient way to run any motor is a split between iron and copper losses. Spin the motor on ur table at full speed and whatever iron losses occur are what they will always be at that speed (unless motor gets magnetic saturation).
I think vedder showed 8k rpm was a top speed of our 12x14 motors before iron losses generally overcome copper when riding. But if ur an acceleration freak it’s probably worth going faster as your copper losses go higher.
I looked at the paper, and that graph is simply used as an example of a graph that they would like to produce. It’s not an actual test of anything provided in the paper. That graph could be mapping literally any motor and have no relation to our esk8 sized outrunners.
2 Likes
I didn’t read anywhere it said what motor or how many magnets. It looks like an inrunner and surely had fewer than our common 12x14
this shows increasing efficiency with motor rpm at constant torque & above a certain threshold, decreasing efficiency with increasing torque…
https://www.researchgate.net/figure/Rimfire-55-Motor-Measured-Efficiency_fig3_326263042
1 Like
http://vedder.se/2014/10/chosing-the-right-bldc-motor-and-battery-setup-for-an-electric-skateboard/
It would be nice to see the details and would depend on how hard you ride or what specific motor and one with .15mm laminations will be much more efficient at high speed than with cheap common .35 mm lams
The real revealer is just spinning the motor on the desk at top speed and comparing that current draw to copper losses in use
So if your motor spins 8-10k rpm at the cruising mph, you have tuned for ideal efficiency.
with a 14 pole outrunner that has common .35 or maybe .25mm lams 8-10k rpm will likely be less efficient according to vedder. if u found a motor with .15mm lams that speed would likely be more efficient. But depends on the load and how u ride. Have to get data to really see
The motor in vedder’s description is most efficient at 8.5k rpm (below that speed the core losses are insignificant compared to copper losses under load), but going 18mph while the motor turns 8.5k rpm will be more efficient in terms of wh/mi than going 35mph while the motor turns 8.5k rpm because of the wind/rolling resistance.
Lol my max rpm on my street board last ride was like 6700 and I have 190kv motors
How high KV you people trying to run
So if all you cared about was efficiency & keeping the motors cool, you would increase your gear ratio (sacrificing top speed) such that your motor was turning 8.5k rpm at your avg cruising speed. You could do 8.5k rpm with 190kv & 12s.
@Yeahthatperson experience lines up with Lacroix’s claims.
I’m not going to be convinced one way or the other until I test it in the real world, or see someone else do a legit test.
1 Like
Not gonna happen given I max out at like 95% duty if I really try
Also, I don’t really think it will ever get to 8.5k
I maxed out at about 81% duty on that ride, out of 96% effective
I’m not convinced all this RPM hobbgobb makes any difference. I think we are realistically talking about a range difference of a few hundred feet
190kv at 12s would exceed 8.5k rpm on a full battery
1 Like
Hm fair but you don’t want to always be riding at max duty cycle, then your top speed is garbage in this hypothetical scenario
Gearing to max out at your average speed makes a very boring board
Edit: checked on a different ride, hit 94% duty cycle at 34% battery, ended up being 7490 rpm at 35mph
3 Likes
Higher gearing has more drag, less gearing free rolls better. This comes into play when you are cruising. If you want max power then more gearing and faster spinning motor makes sense. That efficiency doesn’t necessarily correlates to efficiency at slower pace. Some hub motors are super efficient with no gearing at slow steady pace, once you get on the power hub motors are not the most efficient anymore.
2 Likes
I’m half tempted to just go out and run some tests myself - I just received 3 different motor sprockets that’ll take me from 6.2 to 5.2. However I’m lazy, and retensioning is a pain with the tire in the way and loctite to dry so it might take a while before I actually switch it out.
How bad would it be if I run one wheel with different pulleys, and unplug the phase leads from the motor I’m not testing and run 1WD during the tests 
3 Likes
No one said getting the most efficiency would be exciting…
1 Like
Sounds good. with the one motor being subjected to double the load as two it’s especially going to be more efficient with a bigger gear ratio.
But what would be the test and the test will decide what gearing is most efficient? The bigger the load the more so the motor will be efficient going faster
1km @ 20mph with two different ratios… I’ll predict the higher gear ratio with the faster spinning motor is more efficient.
