Repairing a tach generator

[Durango2k]

...yes.

First of all, my Generator worked, but it sometimes felt stuck / sticky inside.

So I opened it. Pry of the rear alloy cover. Look inside, and find a centre star-shaped rotor, rubbing on a loose (what the heck...) stator. Okay, how can I fix the stator properly ? I have to pry out this metal insert ring...desaster struck.

Below the ring, if lever around here, you'll break the wire coil. Darn.

So, I had to remove the stator (solder of the two contact wites), then use a cutter blade to separate it, and the caaaaareefully pull it apart without more damage inside to the wires.

Finally, used a multimeter to find the breaks caused by my screwdriver. Un-roll the wire, and solder - repair it. It is lacquer-protected wire, so you have to put the end of the wire into the liquid solder (tin) for a few seconds to burn of the lacquer. Then tin it, and close the break point.

After that, isolate the breaks and fix it all a bit up using epoxy like JBWeld. Before doing so, check the coil for continuity again to be sure - and only use a few blobs, don't cover it in epoxy.

Then, put the coil back in the alloy case, fit the rotor, and balance the stator in the outer case with some paper tabs, so that the rotor runs trouble-free. Use some epoxy to fix it there.

Assemble the rest... Job done.

Carsten

[PeterCrespin]

Probably there was nothing wrong before you started tinkering, since all permanent magnet alternators have 'tight spots' when rotating them, because flux density varies as the magnet poles pass by the stator coils. Have you never felt a bicycle dynamo?

Hopefully there will still be nothing wrong with it after you have finished putting it back together and it will feel as good as it did before you took it apart...

Try gripping the drive in a variable-speed drill chuck and measure the AC output.

[Durango2k]

Hi Pete,

My city bike is a Peugeot - don't ask how often I had to open its dynamo.

Oh and I repaired my Hillman Imp's dynamo a few years ago.

If you want me to do so I can send pictures from the polish / scratch marks where the rotor touched the stator. I had a lengthy debate with myself wether I should open it or not- but thinking what may happen if it fully blocks under load at, say, 3500, made me open it to check.

I will get it back to work. I can feel voltage with my tongue when rotating it already, loosely put back together.

I just wondered how the stator was fixed in the case first time - because it was ratteling loose when I opened it ?

Carsten

[adam]

I had a broken wire in a spare I had and a loose bush, managed to lazer weld wire and used bearing fit for the bush.

Adam

[Durango2k]

I think I'll drill a small hole and use a pin or an M2 screw.

Carsten

[Bernie2015]

Hi Durango2 Im trying to pry off the alloy cover as you mentioned any tips?