TheSamba.com :: View topic - 38a generator

Fri Mar 08, 2019 6:23 am

So I'm nearly finished fitting a 38 amp generator onto my 71 bus. I've got the right backing plate, fan hub, generator, and cast iron pulley. Last night when I tried to swap out the 30a pulley for the 38a pulley, the cast iron pulley rubs on the back face of the generator. The two long machine screws that hold the generator sandwich together are rubbing on the back of my cast iron pulley.

This 38a generator is a rebuilt Bosch unit from Wolfsburg West. Am I missing a spacer or something? If it's an original 38 amp generator body and a pulley from between 68 and 71, they should be fitting if I have all the parts. So I must be missing some kind of spacer or bearing that goes in between the fixed housing end piece and my pulley that's flying around.

If someone could help me out by taking a photo or telling me a part number or something along those lines, it would be much appreciated.

Fri Mar 08, 2019 7:18 am

How about a picture of these offending screws?, I don't recall anything sticking out of mine, it's still dark right now but I'll have a look later.

Fri Mar 08, 2019 8:19 am

I seem to recall that there is a small spacer that goes on a 38 amp between the pulley and bearing. I looked on the fiche and it might be pictorial number 25A on fiche 92 but I can't tell if that is it or not. VW calls it a washer but it looks like a small top hat in the fiche.

Fri Mar 08, 2019 10:47 am

I just rebuilt mine. There are spacers that go on both ends.

Here, you can see the spacer as the last item on the shaft before the pulley

Here you can see the gap between the pulley and body

Fri Mar 08, 2019 11:16 am

All the generators/alternators used in these old VW's have spacer rings pressed onto the
shaft, which stick out from the gen/alt body enough so the pulley (and fan hub on the other end)
can seat on it and not rub. For some reason, "rebuilders" frequently forget to put this thing back on, or
use parts where a different-thickness spacer is required, but not used. There are numerous
posts here on thesamba about folks installing a rebuilt unit, and having the pulley rub.

In the case of generators, the standard rings are 20.4 mm OD, 15 mm ID (the shaft diam.), and 6 mm thick.
I've got a dozen or so of those things from salvaged parts, I'll send one if you PM your info. Better check the
other end, too, as that one might be missing as well.

Fri Mar 08, 2019 11:17 am

@busdaddy @Jack_O_Trades - I'll get some photos. Maybe you guys can help me figure out what's wrong. I do have a spacer in there but it only sticks out just a bit. Not enough to keep the pulley off of the housing. Ok, more to come soon. I'll take lunch in a few and go take the generator pulley off so I can take a few photos. Thanks guys!

Fri Mar 08, 2019 11:38 am

Took some more photos without the pulley.

If needed I can pull the end piece off to offer more detail on the stack of components

Fri Mar 08, 2019 11:46 am

Okay thanks for the additional photos. It looks like your spacer sticks out further than mine does.

I slid the pulley on and turned it a few times so you can see where the screw heads rub the back of the pulley

Fri Mar 08, 2019 11:50 am

Your screw heads are also too proud. They are supposed to be recessed in counter-bored holes. Ditch the washers

As far as the spacer goes you are probably missing the grease shields which also act as spacers/shims. Would order some shims/races from McMaster. Do not use washers as the two faces of a washer are not necessarily parallel.

Fri Mar 08, 2019 11:55 am

If I take those screws out to remove the washers, are the guts of the generator going to fall around or cause me not to be able to get them back in for some reason? Or do I have to/should I take the generator out to do this work?

I'm familiar with McMaster. Do these shims/races slip behind the collar/spacer? I can slide that collar off of the shaft and there is a narrow corridor around the shaft. Do you have a photo of the shims/races that you are taking about?

Fri Mar 08, 2019 12:11 pm

There are a couple of approaches you can take.

First off, you will not be able to remove the screws until you disassemble the fan side because they are used to mount the generator to the backing plate and have nuts on them.

Once you have liberated the generator you can remove the screws one at a time to remove the washers. When you reinstall the screws, you need to be careful how the coil wiring is routed internally. I prefer to have the coil wires outside of the screws between the screws and the can so that there is minimal risk for chaffing with the armature.

As far as the correct spacing. My spacer is 3mm proud of the end cap. I don't know if this is correct as I just rebuilt this generator and have not checked it for belt alignment on my engine. At the minimum, you don't want the pulley rubbing on anything.

Here are the shims

https://www.mcmaster.com/92927a179

They have an OD of 20mm, the bore on the cap is 21mm so they would fit above or below your spacer.

The easy way is to stack them inside the bore. The correct way is to probably pull apart your generator and look at what you have to see what you are missing. Either way will probably work.

The reason I think your grease shields may be missing is because the original bearings were not shielded, hence the grease shields. The newer bearings used for rebuilds are shielded so the original shields may have been tossed.

That being said. It looks like your spacer is short by 2-2.5 mm. The missing shields would only make up for about .5mm.

So, maybe you have the wrong spacer. My spacer is 6mm thick.

Fri Mar 08, 2019 12:43 pm

@Jack_O_Trades, thanks for the info and the link. I'll come back with some more photos later today or tomorrow. I just had this engine out last weekend to put the generator in and I guess it's coming out again. Can't win for losing. I should've waited until i had the pulley before switching them out. #$@&%*!

Fri Mar 08, 2019 1:00 pm

If you can reach around and get the nut off the fan and get the 2 lower bolts or screws out of the backing plate down between the manifold and shroud you can remove the generator with the engine installed, if any of those are a problem the engine has to come out.

Fri Mar 08, 2019 1:54 pm

When I hit similar problems with an alternator I had rebuilt, I bought a set of 0.020" shim washers on eBay and stacked them until the pulley stopped rubbing.

Fri Mar 08, 2019 6:51 pm

hylomatt wrote: @Jack_O_Trades, thanks for the info and the link. I'll come back with some more photos later today or tomorrow. I just had this engine out last weekend to put the generator in and I guess it's coming out again. Can't win for losing. I should've waited until i had the pulley before switching them out. #$@&%*!

There will be no swearing around here:

https://itinerant-air-cooled.com/viewtopic.php?f=76&t=13387#p226031

Tue Mar 12, 2019 6:27 am

Berg sells a shim. GB 438

Tue Mar 12, 2019 6:37 am

Pulley shim kit...
Make sure both your upper and lower pulleys are in alignment when you are done.

https://www.cbperformance.com/product-p/1915.htm