I’ve been modeling some new motors and came up with some weird results, basically it seems that 6396/6389 motors are really inefficient, as in they that a lot of power just to spin the motor itself
For those who can, I would ask do do a simple test, run your motor at max speed, without a belt or not in a gearbox and let me know what ERPM and motor current it does under this no load condition, as well which motor you are testing and it’s Kv
6374 and above is what I need
My tests are still in progress, but so far it seems that compared to 6355, a 6389/6396 takes as much as 10 times the power to be spun at any given rpm, when in theory it should be close to two times more give the stator is around 2 times as long
Thanks a lot and hope to figure this out because it’s taking the sleep out of me lol
Thanks man, to be honest if you can’t do without, do it with the gearbox, just let me know, the values are so much higher than they should that even with some additional drag for gears and wheel bearings it will still be possible to find what is happening
Really the question here is if all bigger motors are the same and find out why this is happening
We are talking about a possible 10~20% range increase being possible just by swapping motors
im just wondering would the can design have any impact on this? e.g. open can / closed can
also since the can also spin the shaft, i imagine 8mm and 10mm shaft would also have a difference?
That’s a 6374 so around 750g outrunner vs. 56114 around 1100g inrunner.
Less poles and centered rotating mass definitely make some difference regarding free roll.
I‘m curious to do a range test to see how big is the difference between those two setups.
Thanks for the data, this is better than I’m getting a similar speed, you are getting around half the losses
At higher rpm the vents could have an impact, but more testing in needed. Same for the shaft, bigger shaft = higher bearing ball speed that could have an impact, but if we have that much power being lost on bearings something is really wrong
Looking forward to it, but makes sense, less poles = less core losses, and also having less magnet mass also reduces the losses
They come with a trade off of less torque density usually
Thanks man, this is exactly the kind of data I’m looking for, and yours is almost a perfect match to what I got
My next test is taking out the big bearing, it shouldn’t have this effect, but lets see what happens
This is the data I have so far, cross check with a multimeter to rule out a wrong esc measurement, there is an error but nowhere near enough to explain the high no load current draw
Just some revelations, seems like the problem is actually the VESC 6 current measurement, way off from what actually is, and that caused me to overestimate the efficiency
This is the same TB 6355 on the 100D and the VESC and both compared with the actual power with a multimeter
Do you think the data (amps) of unweighted spinning motors is about the same difference as if weighted?
I mean e.g. if you have 2 motors in different sizes but with same kv and same vesc settings . Let’s say with same board, same gearing and so on. If the 6355 pulls 2A (unweighted) and the 6384 4A at max. speed, what does that mean in real world riding? Would e.g. the smaller motor need 30A and the bigger 60A motor amps under same circumstances and load?
I have some motors which I could test but don’t have a bench setup and lack of time right now. Hopefully I can do it soon.
I think it would be also interesting for you to get real kv data from people, not what the manufacture claims. Personally I never managed to get the kv number from Vesc-Tool, I tried it several times. Or I do something wrong. How is the correct way please?
I made the experience the bigger the motor the smaller the range on the same board. And on the MTB the motors often pull (almost) the max motor amps from standstill e.g. on dirt. If I set them to 80 motor amps each, they pull it. I was surprised when I saw that I always need 130-160A motor amps from standstill slightly uphill in the woods (no matter if 6374 or 6384). Also once my BMS shut off at 120A battery amps even though the vescs are limited to 100A batt amps, guess it was a voltage spike.
