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A question chaps... There seems to be some speculation (?) about whether there is a different number of windings, and if thicker copper has been used. 

Are these assumptions (based on the fact that the is more room), or so we know for a fact that there are more windings with thicker copper? 

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On 6/8/2017 at 10:33 PM, Marty Backe said:

I have never met or read about an EUC rider who only used their wheel for commuting.

Commuting is a great use for EUCs. However, soon it will not be your only use, or even your primary use. Fun will become your main reason for riding!

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"ability to take more current"...

This is where the resistance of the windings comes into play.  Kv refers to open circuit or no load rpm per volt.  As a load is put on the motor, winding current will increase.  Kt can be derived from Kv and winding resistance.

The increased current causes a drop to the actual voltage the windings see.  So, a lower RPM.

Small motors with low KV are wound with smaller diameter (higher gauge) wire.  So, when load increases, the effective voltage decreases faster than with a motor with the same KV and bigger wire.

But, if the voltage drop due to winding resistance is limiting the RPM, then overheating will likely be the limiting issue--not torque.

 

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3 minutes ago, DaveThomasPilot said:

"ability to take more current"...

This is where the resistance of the windings comes into play.  Kv refers to open circuit or no load rpm per volt.  As a load is put on the motor, winding current will increase.  Kt can be derived from Kv and winding resistance.

The increased current causes a drop to the actual voltage the windings see.  So, a lower RPM.

Small motors with low KV are wound with smaller diameter (higher gauge) wire.  So, when load increases, the effective voltage decreases faster than with a motor with the same KV and bigger wire.

But, if the voltage drop due to winding resistance is limiting the RPM, then overheating will likely be the limiting issue--not torque.

 

Saying it a different way--

The physical size of the motor is irrelevant, but:

There's more room for copper windings.  More windings provide higher torque (and lower RPM) per volt.

Larger windings (fatter, larger diameter, lower gauge wire) means RPM doesn't decrease as fast as load is added.  The winding resistance only indirectly affects speed and torque.  If voltage drop in the windings is large, overheating will quickly occur!

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27 minutes ago, The Fat Unicyclist said:

A question chaps... There seems to be some speculation (?) about whether there is a different number of windings, and if thicker copper has been used. 

With the armature of any motor you have a physical airspace, ideally you want to as much as possible, to totally fill that with copper as the more copper you have got the more current and lower resistance you will have. You can do that two ways (or any intermediate way between those two.)

  1. you can have a large number of turns of a single, or small number of, thin strands of wire = low Kv, low maximum current, high torque constant. Will support a high(er) voltage.
  2. you can have a very small number of turns of very thick wire, in practice it is usually lots of thin parallel wires as that will better fill the airspace with as much copper as possible = high Kv, high maximum current, low torque constant, suits a lower voltage.

Additionally whether the coils of the armatures are connected together in star or delta configuration also impacts the Kv value.

So, whilst a larger motor will, inherently be prone to having a lower Kv, since a small motor and large motor can be wound with exactly the same Kv (but the larger one would require less turns of thicker wire.) then the torque of a larger motor will be significantly higher due to its higher current capability 

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29 minutes ago, Keith said:

With the armature of any motor you have a physical airspace, ideally you want to as much as possible, to totally fill that with copper as the more copper you have got the more current and lower resistance you will have. You can do that two ways (or any intermediate way between those two.)

  1. you can have a large number of turns of a single, or small number of, thin strands of wire = low Kv, low maximum current, high torque constant. Will support a high(er) voltage.
  2. you can have a very small number of turns of very thick wire, in practice it is usually lots of thin parallel wires as that will better fill the airspace with as much copper as possible = high Kv, high maximum current, low torque constant, suits a lower voltage.

Additionally whether the coils of the armatures are connected together in star or delta configuration also impacts the Kv value.

So, whilst a larger motor will, inherently be prone to having a lower Kv, since a small motor and large motor can be wound with exactly the same Kv (but the larger one would require less turns of thicker wire.) then the torque of a larger motor will be significantly higher due to its higher current capability 

So, I think we're saying the same thing.   Larger wheels have more room for more/bigger copper wire.  I'm just pointing out that just being physically bigger doesn't mean more torque.  Just the opposite, all things being equal (which they probably aren't).

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17 minutes ago, DaveThomasPilot said:

Does anyone know if the motors are custom designed for EUC use?   Or, are they purchsed from OEM suppliers for which specifications can be found?

 

At least Daao Electric (AKA Xinaoma / DAAO) has done motors specifically for EUCs ("self-balancing wheelbarrows"), they have some listed in their catalog (some even with IPS -logos in their sides), but I know that for example Firewheel motor is theirs, but not listed:

http://www.daaomotor.com/html/Self-balancing_Wheelbarrow_Motor/

Unfortunately, they don't seem to list much specs for the motors in their pages.

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12 minutes ago, DaveThomasPilot said:

Thanks!

There aren't any detailed specs there (that I could find).

I wonder If the method for specifying motor power is consistent, and what that method is?

No idea how the "nominal value" is calculated / measured, but ecodrift.ru has done dynamometer-tests on many wheels to measure the power outputs

RW-GT16.gif

 

There's probably more in their pages, but it is in Russian (use Google Translate or whatever)

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16 minutes ago, esaj said:

No idea how the "nominal value" is calculated / measured, but ecodrift.ru has done dynamometer-tests on many wheels to measure the power outputs

RW-GT16.gif

 

There's probably more in their pages, but it is in Russian (use Google Translate or whatever)

Interesting chart....

Typical "specmanship" would mean specifying the peak power, regardless of what rpm (KMh = kilometers per hour?).   It would be nice to know what load current they used and how that current would relate to something like an X pound human on level ground, going up a y% slope,etc. 

Hopefully, the load is something  representative of real use.

 

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