Wheel Diameter or Magnet Number ?

[Tucuman]

In order to adjust the speed shown on the SW900 display so that it coincides with the GPS value, either the Wheel Diameter or the Magnet Number settings can be used. Are these two ways of doing totally equivalent? Is there any reason to precisely set the actual number of the hub motor poles ?

 

[E-HP]

In order to adjust the speed shown on the SW900 display so that it coincides with the GPS value, either the Wheel Diameter or the Magnet Number settings can be used. Are these two ways of doing totally equivalent? Is there any reason to precisely set the actual number of the hub motor poles ?

They aren't two ways of doing it, they are the two parts of doing it. You need the magnet poles for the the display to know how many revolutions the wheel is making. You need the diameter to determine how much distance is covered with each revolution. Between the two, you can determine the bike speed.

 

[AHicks]

In order to adjust the speed shown on the SW900 display so that it coincides with the GPS value, either the Wheel Diameter or the Magnet Number settings can be used. Are these two ways of doing totally equivalent? Is there any reason to precisely set the actual number of the hub motor poles ?

They aren't two ways of doing it, they are the two parts of doing it. You need the magnet poles for the the display to know how many revolutions the wheel is making. You need the diameter to determine how much distance is covered with each revolution. Between the two, you can determine the bike speed.

I'll add to that - but don't be real surprised if it's doesn't line up with a GPS. Most generally accept the results as "good enough".

 

[Tucuman]

Thank you E-HP and AHicks for your replies!
I understand that the number of poles provides the information of the motor revolutions while the wheel diameter allows to calculate the distance covered with each revolution. However, I wonder if these two values are always used together for the velocity calculation or if the number of poles is ever used alone for any other purpose. In my case, I do not know the number of poles and I wonder if setting the wrong number may have some negative consequences.

 

[AHicks]

Thank you E-HP and AHicks for your replies!
I understand that the number of poles provides the information of the motor revolutions while the wheel diameter allows to calculate the distance covered with each revolution. However, I wonder if these two values are always used together for the velocity calculation or if the number of poles is ever used alone for any other purpose. In my case, I do not know the number of poles and I wonder if setting the wrong number may have some negative consequences.

Assuming worst case, you set it up incorrectly. It's not hard to check with your speed with a GPS and fine tune the number as required.

It's NOT going to burn your system down or anything like that....

 

[Tucuman]

OK AHicks, in this case I will set the wheel diameter to 26.4 (measured value) and the magnet number to 58, which gives the best velocity agreement with GPS.