Anyone replaced alternator slip rings? Help with tape and soldering please.

[R-mm]

This is a Bosch 469 115amp Alternator from a 90's Porsche.

1. Does anyone know if that is likely high temperature tape holding the wiring to the rotor shaft? (see white band). I believe I need to cut it off in order to access the rotor wiring? Search tells me Kapton tape is a good high temp option.

2. Can anyone walk me through how the old ring gets de-soldered and if it is likely potted / epoxied onto the shaft?

 

[Cheep]

I have never replaced any, looks like you have copper left on there, machine it and use it.

 

[Grant Gunderson]

That looks like it’s epoxy potted on to the shaft to me. As @Cheep stated above looks to be copper left. Can You clean it up and then adjust the contact? Or maybe machine a copper bushing to use over it to get back to the original OD?

 

[R-mm]

I have a new slip ring arriving today. I did machine the old one down, there is very very little thickness left it would not be worth re-using.

 

[zimman]

This is a Bosch 469 115amp Alternator from a 90's Porsche.

1. Does anyone know if that is likely high temperature tape holding the wiring to the rotor shaft? (see white band). I believe I need to cut it off in order to access the rotor wiring? Search tells me Kapton tape is a good high temp option.

2. Can anyone walk me through how the old ring gets de-soldered and if it is likely potted / epoxied onto the shaft?

I'm shocked you found parts. Shocked.
Zim

 

[R-mm]

Also found the rectifier board, tolerance ring and suppression capacitor. None of them Bosch originals. To be determined over time how well each performs.

 

[MiteyF]

I'd guess it's varnish dipped, just like you'd see on most electric motors.

This was an old, kinda wacky Century Electric I re-did on my lunch breaks for a personal project.

 

[GMSF]

The slip ring leads are held on by winding tie string that is soaked in varnish to harden it. Clip off with flush cutters, re tie with a porous flat string and harden it with cyanoacrylate glue or Dolph’s ac-41 spray varnish if you want to be technical.

It will be challenging to desolder and replace only one of the rings. I would suggest replacing them both as a set. Heat them and they should press off. Hard to see in these pictures but you may be able to pull the connection down and attempt to reuse it, you can also splice them in an easier area below the rings.

Its important that the rings be insulated from the armature shaft. If you have access to a lathe i would turn a phenolic bushing, press the new rings on to it in the correct spacing and press that onto the shaft. Ordinary JB Weld works well as a nonconductive epoxy if needed. You could secure the rings to the shaft using this alone but it would be hard to maintain concentricity, and i would suggest machining the assembly to at most .005” of runout relative to its bearing journals.

Best of luck in your project