Exactly, you decrease Kv by increasing the number of turns, you have to reduce the wire diameter to be able to have more turns, so by halving the Kv the resistance goes up by 4, the torque doubles for the same current, and the losses multiplies by 4
But if you feed half the current, you will have the same torque with the same losses
For a given motor design and amount of copper, the motor torque capabilities are independent of Kv, what matters is Km, that represent how much torque a motor can produce for a given unity of power loss, unfortunately nobody publish this number since it would be clear what motors are good and which ones are junk, so the whole misunderstanding of Kv got spread out
But the bigger problem is @Howiep is the VESC poor tracking at low speeds, same problem I’m facing in my similar setup, the situation you want the most torque, that is on really steep hills, is the one VESC fails to deliver
skull motors uses 105mm wheels no? Maybe stay around 65-70Kv is a better bet. PLease post updates. It’s super interesting. How did you come up with the 20awg?
Wow I posted, went to bed, and woke up to a whole conversation!
Fair enough, but I am still looking to increase motor size over the 6354 (which weights about 600g). Also looking for a higher quality motor that can more efficiently turn those amps into motion.
I’m looking for this setup to provide about 50% of the power, so any motor that works well as an esk8 dual setup should work well enough I think.
That’s a shame - I hadn’t heard that before. Anyone got any tips on settings to make it run more efficiently at these low speeds? Also - details of your build?
I’m now supporting the other end of my motor with a pillow block bearing for ease of mounting. I’m confident I could rig something like this up for a different motor. But shouldn’t need to for a hub/DD motor.
@hummieee Did you ever make any smaller motors like what I’m looking for?
Not at the moment, but I’m gathering some equipment to start making some tests on motors and actually rating them, to put to the side all the marketing that comes with them, I want to figure out how much they can actually handle in a bunch of situations, everything done in the bench so its consistent
In the future I want to build a inertia dynamometer, this would make possible to plot a efficiency curve and quantify how bad is the torque at low speeds, if sensors or encoders help, and a bunch of other cool stuff
One thing that may help according to @mishrasubhransu is to set it up using sensors and set a sensorless ERPM higher than the default value, the motor I’m using doesn’t have sensors so I can’t test that
maybe that motor has a bearing already on both sides of the rotor. I think it might. the often missing bearing support is on the shaft end. I don’t think the bearing you added is going to support the rotor.
I might have some motor that could work but best you get the outrunner from hobbyking or somewhere with bearings on both sides.
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
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
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?
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
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.
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
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