Why did the pulley come off my generator?

[SoCalCoupe]

Didn't see this coming. I was on a holiday ride today, heard a commotion under the hood and then the unmistakable clang of a part hitting the pavement.

My generator pulley came off. Didn't have the right tools with me so I had to be towed home.

I rebrushed the generator about 6 months ago and if I remember correctly, got the pulley on correctly and snugged back down. Wouldn't swear to it, but it would have been fairly obvious if I hadn't. I do remember thinking that it seemed odd to have no keyway, lock, or retainer nut but thinking it through, the direction of rotation would continuously tend to tighten the pulley.


Is there supposed to be a retaining nut? Car didn't have one when I bought it a few months ago. The 32-41 shop manual doesn't specify but the 42-48 shop manual does show one. The C&G Ford parts catalog doesn't have one. It would have to be pretty thin. Know where I could get one?



It's a stock 1941 Ford with a flathead, stock generator and stock 6V pos ground electrical system.

The only thing I can think of is something causing the generator to 'motor' but my ammeter indications have seemed normal. Some charging after startup then settling down to nearly neutral but just a hair charging after a few miles.

I feel like a dummy and want to prevent this from happening again.

Any thoughts?

[koates]

If your generator pulley has an internal thread and screws onto the armature shaft then there is a groove around the very end of the armature shaft where a circular circlip clips on there to prevent the pulley from unscrewing. Did you fit that circlip on there ? If you left it off then the pulley would be able to unscrew completely off the armature shaft. Regards, Kevin.

[SoCalCoupe]

Originally Posted by koates

If your generator pulley has an internal thread and screws onto the armature shaft then there is a groove around the very end of the armature shaft where a circular circlip clips on there to prevent the pulley from unscrewing. Did you fit that circlip on there ? If you left it off then the pulley would be able to unscrew completely off the armature shaft. Regards, Kevin.

Kevin, thanks for the reply! That must be it. There is a groove around the very end of the armature shaft that would hold a circlip. I'm absolutely positive there wasn't a circlip there when I took it apart. Had to Google it, now I know what it is. Should be relatively easy to source.

Hard to say, but before I bought it, I think this car hadn't been driven more than a few miles since it was restored maybe 10 years ago. Now that I'm putting some miles on it, the gremlins are surfacing.

There is also what looks like a keyway groove parallel to the shaft but no key and no key groove in the pulley so I couldn't couldn't tell how it was supposed to work. Perhaps mismatched parts meant it wasn't functional.

[Terry,OH]

Sounds like you have an aftermarket universal armature since the key is for the earlier pulleys that are retained by a nut. I have not seen one with the keyway and the threaded on pulley with a clip groove. Below is the clip you need.

[Newc]

Backing off the speed [gas] can cause the generator to over speed. I've been warned. Newc

[petehoovie]

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Originally Posted by Terry,OH

Sounds like you have an aftermarket universal armature since the key is for the earlier pulleys that are retained by a nut. I have not seen one with the keyway and the threaded on pulley with a clip groove. Below is the clip you need.

[aussie merc]

you may need to loctite on the nut on low strength should do just some extra insurance

[koates]

Originally Posted by aussie merc

you may need to loctite on the nut on low strength should do just some extra insurance

There is no nut on this type of pulley and shaft. The pulley is threaded and screws onto the armature shaft with the circlip on the end of the shaft in the grooved shaft. The fan belt drives the generator pulley clockwise which tightens the pulley on the shaft thread. Regards, Kevin.