Speedometer Magnet

A

ALJ

Member
My Speedometer magnet is dead. How do I recharge it? The speedometer is the oval shaped SW speedometer. It is disassembled. I may have caused the problem by getting the magnet to close to some tools made of ferrous material.

Do you think placing a strong horseshoe magnet across the poles of the speedometer magnet would recharge it?

I expect someone to suggest sending it to Papa Nick. That may be an alternative, but I would like to do this myself if possible. That is what I enjoy about this hobby.

Any suggestions will be appreciated.
 
You can charge it up using a strong magnet, be sure to keep the same polarity or it will go dead in short order. I use an electro magnet charger made by Stewart Warner, it has 3 settings, usually use medium. Some times it will overcharge, sometimes I have to use high, just trial and error.
 
Mark in MT said:
You can charge it up using a strong magnet, be sure to keep the same polarity or it will go dead in short order. I use an electro magnet charger made by Stewart Warner, it has 3 settings, usually use medium. Some times it will overcharge, sometimes I have to use high, just trial and error.
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Thanks for the reply. When you say keep the same polarity, does that mean north pole to north pole and south to south? I thought it would be opposite that.
 
Correction: Thanks Mark for refreshing my memory!!

The magnet is a horseshoe shape and the sliding window affects the magnetic field in the air gap between the N and S pole of the magnet which allows calibration.


The truncated triangular shaped piece in the attached photos provides the air gap between the N and S poles of the magnet.
otos.
 

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The magnet itself is a horseshoe magnet with the ends pushed together to make a circle. The very early ovals had no wedge shaped piece in them, the hole was open between the ends, and had a temperature compensating brass part on top of the magnet.
 
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