Hi everyone from ES, I'm just wondering, what makes a 80mm stator from an electric skateboard/scooter hub motor (similar to RC outrunner's stator most of the case) run much more wattage (For example, 1000 watt) compare to a small but typical 80mm stator from a bike hub motor (200 watt), given it has the same diameter, length and pole etc. IMHO, I think maybe the quality of windings, lamination and magnets makes a difference? Any other factors? I'm comparing EXACT lamination sizes of 24N28P given 50mm ID, 80mm OD, 30mm length, and of course 65kg TOTAL LOAD all being constant. (KV&KT debatable) (greenish stator from scooter, while bike's silver stator). The real question is, what sets them apart? Why not just use a super big scooter/skateboard hub motor and put in into a bike? It would most probably produce identical torque right?
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Bike vs Skateboard hub motor (What sets them apart?)
- Thread starter chinyp
- Start date
There was a year when endless-sphere had a lot of experiments with 80mm RC outrunners. There were articles on how to add hall-sensors or even optical sensors, so that these motors can be run with a common ebike controller. RC controllers (ESC's) are surprisingly small for what they can do, but also expensive.
Adding voltage ripple suppression capacitors to the power inputs fixed one common problem, but...many of these motors are intended to run at high RPMs without much load (a propellor spinning in the air). Therefore (and I'm just repeating what I "think" I remember) there is a big issue with inductance. Some of the RC motor of greatest interest were shorter, with a bigger diameter (120mm 150mm diameter?). and they had the greatest inductance.
The smaller the diameter, the faster they spun, and they required a LOT of reduction to drive a 26-inch wheel. Most came with a high kV so they could spin fast when using low volts (12S 44V was common).
Thus posted a tutorial on rewinding the 80-85 and 80-100 RC motors, plus re-terminating them to a wye configuration (as opposed to the faster delta). To this day, RC motor manufacturers still don't make a motor configured for ebikes. five years ago, there weren't as many motor choices, but now?...there is "just enough" choice that...I don't know of anyone adapting an RC motor to an ebike.
Deecanios Astro build from 2008
https://www.electricbike.com/deecanios-astro-mid-drive/
Roys eCortina
https://www.electricbike.com/roys-ecortina/
Adding voltage ripple suppression capacitors to the power inputs fixed one common problem, but...many of these motors are intended to run at high RPMs without much load (a propellor spinning in the air). Therefore (and I'm just repeating what I "think" I remember) there is a big issue with inductance. Some of the RC motor of greatest interest were shorter, with a bigger diameter (120mm 150mm diameter?). and they had the greatest inductance.
The smaller the diameter, the faster they spun, and they required a LOT of reduction to drive a 26-inch wheel. Most came with a high kV so they could spin fast when using low volts (12S 44V was common).
Thus posted a tutorial on rewinding the 80-85 and 80-100 RC motors, plus re-terminating them to a wye configuration (as opposed to the faster delta). To this day, RC motor manufacturers still don't make a motor configured for ebikes. five years ago, there weren't as many motor choices, but now?...there is "just enough" choice that...I don't know of anyone adapting an RC motor to an ebike.
Deecanios Astro build from 2008
https://www.electricbike.com/deecanios-astro-mid-drive/
Roys eCortina
https://www.electricbike.com/roys-ecortina/
thepronghorn
1 kW
First off, spinningmagnets - while your links are often useful, your responses sound like you are robot with prewritten statements that hit on certain keywords. Perhaps you could address the question here or at least acknowledge that you aren't specifically addressing the question.
To the OP, if you compare identical motors placed at the hub of a longboard wheel vs. a 26" bike wheel, the longboard hub motor will be capable of much more power since it is spinning much faster than the bike hub motor. If you consider a 100mm longboard wheel (about 4") then the longboard motor will spin 26/4=6.5x faster than the bike motor for the same speed which means it should be able to make several times more power.
Motor power is the product of speed and torque. Motor torque is mostly determined by motor size, since we have identical motors here they have the same torque producing capability. The motor in the smaller wheel spins a lot faster than the motor in the bigger wheel, so it makes much more power.
To the OP, if you compare identical motors placed at the hub of a longboard wheel vs. a 26" bike wheel, the longboard hub motor will be capable of much more power since it is spinning much faster than the bike hub motor. If you consider a 100mm longboard wheel (about 4") then the longboard motor will spin 26/4=6.5x faster than the bike motor for the same speed which means it should be able to make several times more power.
Motor power is the product of speed and torque. Motor torque is mostly determined by motor size, since we have identical motors here they have the same torque producing capability. The motor in the smaller wheel spins a lot faster than the motor in the bigger wheel, so it makes much more power.
Basically I am trying to compare a 100mm hub motor from longboard with a 100mm hub motor from scooter and/or bike. They are both 100mm hub motors with different power output and kv. I found a 4 inch and 5 inch 200-300watt hub motor for scooter and bike at uumotor.com that made me curious of the differences. Why is it an apple makes 2000watts and the other apple only makes 200watt? My first thought was, quality of stator, windings and magnets? What if both the motors have same kv too? Lets just try and compare if it has the same ID, OD, length, load and 24n28p. The difference that I noticed are only the quality, kv and kt. You guys? Btw, thanks for the feedbacks guys.
nutnspecial
10 MW
It's actually the very nature of the electric motor in 'doing work' afaik. Motor parts/build quality are a consideration, but the main issue is hubs are limited by design, and the bigger wheel you drive (which means taller gearing for a hub motor), the more of a disadvantage they are at for our intentions here.
Generally, the smaller the wheel, the better the hub can perform.
Now, if we're cross-testing board motors on bikes and visa versa, and there is a large discrepancy even when kV is accounted for, we have some other stuff to talk about. Maybe that's even what you were getting at, but I didn't see any data leaning in that direction.
, so this one got me going :lol: 
But I suppose it just must be some sort of odd compliment, because all SM's many contributions I've seen have always been beyond reproach. Thanks for the laugh though lol.
Generally, the smaller the wheel, the better the hub can perform.
Now, if we're cross-testing board motors on bikes and visa versa, and there is a large discrepancy even when kV is accounted for, we have some other stuff to talk about. Maybe that's even what you were getting at, but I didn't see any data leaning in that direction.
Hehehehehe! I'm a conspiracy "theorist"
, so this one got me going :lol: But I suppose it just must be some sort of odd compliment, because all SM's many contributions I've seen have always been beyond reproach. Thanks for the laugh though lol.
As has been said above, if you run a specific class of motor at a a higher speed, you can achieve a higher power output.chinyp said:
You need to think of the wheel as an active element in the transmission. With a 5 or 6 inch wheel, the radius of the wheel is not much greater than the air gap radius of the motor, so, there's a relatively small mechanical disadvantage. With a 26 inch wheel the wheel radius could be 6 times the airgap radius of the motor and so could have a 6:1 mechanical disadvantage which means the torque requirement could be 5 times greater than that on the scooter wheel. The only exception to this is with friction drive where the wheel is effectively an idler between the drive roller and the road surface and therefore the relation between the air gap radius and the drive roller radius are the only things to be considered.
That's quite surprising.spinningmagnets said:
Have you looked at the Tangent middrive system?
Or the assorted friction drives, like Kepler's eboost?
Or the Add-E and it's clones?
Or bobc's BB-drive build?
There are a few others I can't recall the name of that've been seen now and then in the for-sale section and the motor tech section--some are BB drives, some other types of middrive, some friction; I just don't recall any details of them.
First of all, what's wrong with being a robot? (LOL)
Amberwolf, you are right...I had forgotten about those.
Amberwolf, you are right...I had forgotten about those.
AFAIK if you want to know where differences mainly are, you should know that it is only due to motor diameter (ebikes have wider diameter motor and thicker) and copper inside, then you add build quality (assembly, type of magnets, windings, etc).
Bigger motor does not need as much power as smaller motor to give out same torque. Ever tried to move a 20Kg weight on a metal pipe first by rotating the pipe, then by rotating the weight itself? It rotates easily when you move the weight by the edge but is harder when you use the pipe in the center. Sorry ladies but size counts.
Ok, about why it acts this way in nature? Answer is tangential force (for once I know of something technically enough to speak a little :lol: ). Larger motor means the force applied by motor is born further away from the center, resulting in more tangential force being deflected from the center. The further away your forces move from the center, the more torque you get out of it. Once we get better motor technology with tangential forces far away no matter the size, you'll see more homogenous motors.
Bigger motor does not need as much power as smaller motor to give out same torque. Ever tried to move a 20Kg weight on a metal pipe first by rotating the pipe, then by rotating the weight itself? It rotates easily when you move the weight by the edge but is harder when you use the pipe in the center. Sorry ladies but size counts.
Ok, about why it acts this way in nature? Answer is tangential force (for once I know of something technically enough to speak a little :lol: ). Larger motor means the force applied by motor is born further away from the center, resulting in more tangential force being deflected from the center. The further away your forces move from the center, the more torque you get out of it. Once we get better motor technology with tangential forces far away no matter the size, you'll see more homogenous motors.
Chalo
100 TW
There's still RPM per volt, and inrunner vs. outrunner to consider.
The fact is that nobody uses the same physical size motor with the same windings to directly drive wheels of such disparate sizes. So your question might be interesting to you, but it's irrelevant to real world applications.
The fact is that nobody uses the same physical size motor with the same windings to directly drive wheels of such disparate sizes. So your question might be interesting to you, but it's irrelevant to real world applications.
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