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Vintage Magnetic Speedometers restoration

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spider rust
Posts: 135
Joined: Mon Apr 07, 2014 2:45 am

Vintage Magnetic Speedometers restoration

Post by spider rust »

Some time ago I bought a WW2 Veigel Tachometer from Germany for my 1938 BMW R12, with a near new dial plate for the side car version speedometer. The issue with these is the loss of magnetism from the magnet rotor.
I took it to a professional speedometer restoration, and they tested the magnet which had little left in it.
They said we cannot remove the magnet from its drive shaft due to not having a puller and the risk of fracture to its die cast housing. So I bought a good MAW but again it had the same problem as the Veigel, so eventually I found a business who said they could remove the magnet and re magnetise it. I paid over $300 and got back a restored instrument.
The post war case spoilt it for me so eventually I found a NOS? Veigel in Germany and purchased it.
When I stripped it down to clean and do some restoration, its not as difficult as you might think, during this work I noticed the magnet rotor had moved up on its drive shaft and was fowling the post that the cup pinion sits in.
And when the speedometer cable was screwed in, it would push these parts together, so once again I was faced with the issue of re magnetising the magnet and then pushing back the magnet down its spindle to eliminate the end shake.
Unintentionally I grabbed the end of the drive shaft and to my surprise could rotate the magnet on it a tiny amount.,
I then understood the magnet is simply a press fit on.
So using a small brass drift and a small tack hammer gave the drive shaft a couple light taps which moved it down through the magnet with little effort releasing it from the drive shaft. It felt like a tapered shaft, I need to measure it with a vernier to determine that. Anyway the myth of removing the magnet from these instruments is a simple easy task if done carefully
there is little risk of damaging the die cast case. I'll follow with a diagram or photos.

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