Magnetic key ???WTF INSIDE running along the shaft of my 750watt rear hub motor

[atomsDoKneedHELP]

So this is about a magnetic key running along the axle of my motor

First question:
where do I go to buy one cuz I lost mine?
second question:
what is its function, How important is it to have?
third question:
is it possible to replace it with another magnet that is similar in size ?

 

[amberwolf]

hubmotors don't generally have magnetic keys on their shafts (axles), so we will need more information:

if you provide the details of your specific system (names, part numbers, links to where they were purchased (because those pages often have details you may not know but that we need), and details of the specific problem you are having, what happened before the problem started, and clear, in focus, well lit pictures of the parts in question, we might be able to provide useful responses.

also, since this is not a bicycle mechanical or structural issue or question, but instead a question about a motor, i moved it to the motor technology subsection.

 

[aroundqube]

A key running along an axle - McMaster-Carr

 

[lnanek]

I didn't know about the shaft, but it's not rare to have a magnet in the motor somewhere to measure speed/rpm.