it seems to support the shaft as it comes out. the rotor needs support.
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Yes sorry I’m so dumb, thanks.
hobbyking sk3 has a bearing but it’s supported with the plastic fan. Some of the newer bigger torqueboards and maytechs have a real support bearing.
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Yep, 105mm flat ground here so not as much torque needed, I just wanna go fast
Minichopper4me posted this link to his rewind experience with these hubs, first he did 10 winds 3 strands 21awg and ended up 113kv then he rewind them again with 15 turns 2 strands and said it topped out at 25mph, so I’m going between the two looking for 30-31mph max so I can comfortably cruise around 25
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Edit - I just realized my photo was taken from a poor angle. The bearing supports the can end. 
But that’s beside the point I think because surely, any esk8 hub/DD motor should be more than capable of dealing with these forces - it’s made to deal with the wheel loading while mounted on only one side.
I’m just looking for the best one I can get at around a 900g weight.
If u take the motor apart it likely has no bearing supporting the bell on the left in this pic. U could push hard with ur hand there even and possibly bend rotor into stator. Or maybe that motor does have a support bearing I don’t know
Looks like plenty of support to me -
But I’m looking to upgrade from this motor to see if I can get the concept working within my size/weight constraints.
I was planning to go over to Aliexpress/eBay and buy something that looks workable, but was hoping to find something that gives me the best chance of making a motor this size work.
@hummieee I’ve read dozens of posts from you talking about optimizing a given motor size - shielding/copper density/magnet quality, etc. what’s the weight/diameter of the smaller “steelhubs” motors you sell?
Are there any other similar options that are well made?
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Did you actually had problems with the motor mechanical side going bad?
Kepler at endless sphere runs friction drive setups like our for years on regular motors and I’ve never read of him having any sort of problems
If your motor are breaking there is too much pressure on it the it it’s setup, it should have just enough contact force to avoid slip at the power you chose to run, any more and you are just wasting energy and stressing the motor
I don’t sell anything these days though and moved away from smaller motors.
So that motor is supported on both sides @Pedrodemio says u don’t need support on both sides anyway surprisingly.
Seems Kepler does fine with the regular out runner but does recommend using a motor w support on both sides as youve got anyway
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Nope the motor works just fine, it just can’t handle the lower speed climbing I need it to do. I’ve got the pressure dialed in pretty well as you describe.
Yes his setup works very well, but he lives in Melbourne - much flatter and cooler than here in Brisbane. His setup is also geared towards road riding. Mine works well under those conditions too, but ultimately I’m trying to build a mountain bike.
If his (and others) can work with a little high kv aero motor I feel I should be able to get the improvement I want with a modest motor size/efficiency increase instead of 2.5x the weight/size in a raptor or TB motor.
I like the idea and could make something like this with a bunch of other esk8 parts and may try if I fail with the current way. But I’m still keen to try for direct drive only for the same reasons people here persevere with hub motors on their boards.
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Agree about Kepler
I will suggest one thing, increase the motor temperature limit, some setups induces lots of noise on its measurement, and even then 80°C is still pretty safe
What currents are you using?
I’ll try a higher temp, cutoff currently starts at 70 and ends at 80C so not much headroom.
I’m now running about 40amp max for motor/battery. Tried going down to 30 without much benefit.
Thinking I might try one of these Maytech motors. Should be within my specs with the urethane removed. https://www.electric-skateboard.builders/t/maytech-hub-motor-vesc-and-truck-review/31413
Also want to consider one if the elofty DD motors.
@Pedrodemio I like your setup, and hopefully the VESC shortcomings aren’t too terminal or can be overcome.
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I will bring my IR thermometer on my next ride, bit by hand feel it’s way over 80°C, but I’m running just 25 amps on the motor, I know the magnets on mine should be good up to 120°C, but the glue that hold them down will probably break earlier.
One thing that worries me in the tire itself, I don’t know how rubber will behave in these temperatures, even more if you stop with a hot motor cooking just one place
Having a motor with more poles helps since the ERPM goes up and get out of the low efficiency zone quicker
My setup is fine I think, I’ve been sketching ways to use two motors with a dedicated reduction, but the goal would be to avoid pedaling at all
But as it is is does the job, I want to pedal
Thought I’d briefly revive this thread,
Thanks for your help so far.
So I’m thinking about just going with a larger SK8 or Trampa 6364 motor, which has about a 40% bigger stator and corresponding Km increase than the 6354 I’m using now.
I’ll stick with 120-140kv so I can keep my 7s battery.
But I’m still surprised by the lack of hub improvements over time, I remember reading posts like this this from back in 2016 - https://www.electric-skateboard.builders/t/the-nicest-hub-motors-for-sale-cheaper-than-anywhere/1002/765?
Those hummie steel motors had small 4725 stators (same as my current motor) and by most accounts running a double was okay with hills. Does anyone make a modern equivalent?
As mentioned earlier in the thread - surely it’s down to better winding density, type, and shielding.
Edit - it looks like Mellow hubs are picking up this concept with their stator that allows efficient winding. Too bad it looks impossible to buy a motor only.
@Pedrodemio @Gamer43 I’m also interested in the VESC low speed tracking issues. Can anyone point me to somewhere I find out more about its contribution to heat losses?
The two motors I’m considering have a pretty good Km for their size, but are 14 pole. Is there any way quantify the benefit of going with a 20 or 24 pole motor for 750~1500RPM running?
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Those 4725 motors would get hot if pushed. No getting around small motors getting hot
More poles isn’t going to help the km except maybe the tiniest bit and it’s more for reduced cogging
The additional heat losses result purely from the higher current required to produce the desired torque.
As an example, let’s say the VESC is only 75% efficient at generating torque at low speed, and 100% efficient at high speed. This means it requires 33% more current to get the same amount of torque at the lower speed than is required at the higher speed. Using numbers, let’s say you want 1Nm of torque at high speed, and the VESC needs to send 10A into the motor to get that torque. That means at low speed, it will take 13.3A of current to get that same 1Nm of torque at low speed.
Since power dissipation is proportional to the square of current, this means you’ll generate about 80% more heat at lower speeds to get the same torque output.
These are just numbers to illustrate an example, I am not sure how much the performance varies on low Kv hub motors.
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Hopefully I will manage to build an inertial dynamometer in the near future ™ to shed some light on all that, plus efficiency maps for motors
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I had the intent of doing that to but school got in the way and unfortunately it is kinda far down on the to do list.
I would love to see some of that to get some comparable numbers between different esc’s and motors and maybe even batteries.
Oh and move to Sweden, here you won’t have any issues with motors overheating.
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Not sure if this still is a problem, but I would do it from a mechanical engineering side: Oil cooling or airflow.
To get more (low speed) torque you need a bigger airgap diameter (there are other ways, but the diameter goes in quadratic, all other improvements linear at best). Bigger airgap means bigger stator, bigger stator means bigger rotor, means bigger motor and more weight. Maybe even same power/weight but only at “high” rpm where you wont need it anyway.
So TLDR: get more airflow through the motor, e.g. by a small fan on one side, or if your motor is sealed anyway, fill it halfway up with oil.
The same thing is done for normal ebikes to get more power out of the small motors.
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Thanks Giga,
I’m slowly coming around to that same conclusion too, but still with as big a motor as I can stand to limit the wasted energy into heat.
On your point of airflow - I’ve had some success with a Trampa 6364 118kv motor. I know it’s based on the Turnigy SK8 design (and likely made at the same factory) but with the bigger stator, low kv and and internal fan (and vent holes) I’m getting close to my target hill climbing endurance compared to the SK8 6354 I used use.
Just need to fiddle with the VESC settings some more and add an extra helper fan to the end of the motor and it might be pretty workable.
Still want to try one of those Mellow motors though.
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I added a fan to my Trampa motor to increase the airflow but it didn’t lower the temps significantly (or lower them during fast coasting like I’d hoped). I think I need to better understand the stall/pressure/airflow characteristics of fan blades. I know this has been tried and tested with success on out runners before but can’t remember where.
@Giga did you see any success with your oil cooling experiments?