Generator Fan Assembly Help

[Bill Oldham]

Putting a 12V generator together and I am not sure about the fan assembly. The Porsche 356B parts book has rather poor diagrams (1-5 and 1-10) and the Stoddard is even worse, combing them in a confusing figure..
Referring to Figure 1-5 in Ersatzteil Katalog, I am guessing that the parts, assembled from the front of the engine are# 9 Fan Nut, #11 cover plate, #10 fan, #13 carrier plate, #14 fan hub, and continuing on the other end of the shaft, now referring to Figure 1-10 : #5 the pulley hub, #'s 6,7;8 the pulley halves and spacers, and #9 the pulley nut. BUT there are TWO carrier plates; where does the second carrier plate go? And is my order correct? And I have not accounted for part 12 "fan washer" on figure 1-5. 546.06.202 (part 26, no longer available from NLA). It would seem that the cover plate would function as a perfectly good washer for the fan anyway, wouldn't it?
Note that I have ignored the stuff not mounted on the shaft like the reinforcement flange and the fan housing cover.
I seem to recall some earlier postings on this subject, but searched in "vane" for a definitive instruction on fan assembly. I am sure the experts know the correct order, please help

A second question: Is a 16 blade fan OK for a1720 normal (street use)? I cannot seem to find a reference when the switch was made to the 28 blade upgrade.

Cheers
Bill

[Al Zim]

Why would you put a fan on your car that was last installed by Porsche nearly 60 years ago? Blades wiggle around and finally fail. Are the sides of the center of the hub parallel and not distorted on the corners. If so you need a new fan. The second thing to do to improve the life of the generator is the remove the cover over the holes in the fan. Zim's had been doing this for over 30 year with no ill effects. That plate was put there to reduce and whistling noise through the fan. Finally I would suggest you get a good VW service manual it will show the assembly clearer than the Porsche Shop Manual The MAXIMUM output of your generator is 22 amps then it starts to self destruct If you are using a solid state regulator from Bosch that is a 30 amp regulator. You should also calculate the wattage of the electrical components to make sure of your load. An alternator is a more positive situation since the alternator is a VW unit and will be available long after generator stuff vanishes. If you have questions give us a call 800.356.2964. al I cannot remember ever seeing a cooling fan come apart But my memory sometimes fades.

[Bruce Smith]

Hi Bill. Missed you in LA this year. I've taken several apart recently and have found various arrangements, so expect most everyone re-assembling them has used some guess work. Here's what I found works:

hub - thick washer - shims (~3) - cover plate (it doesn't touch fan in the center) - fan - thick washer - nut

Best,
Bruce

[Mike Wilson]

I would suggest a 28 blade fan, balanced and tack welded.

Mike

[Bill Oldham]

Bruce. Thanks but I had fan backwards in my head. Starting from hub going forward I meant hub, carrier plate , cover plate, fan, xx, nut. XX would be a “fan washer”, or possibly the second carrier plate? If the latter, not much room for shims because the hub length is 9mm and the carrier plates are 3.5 mm thick. With a fan thickness of 1.25 mm that leaves only a possible 0.75 mm. So if I use one 0..75mm shim between cover plate and fan, I can squeeze on the second carrier plate on the remaining 3.5mm of hub under the nut. (I like your suggestion of a shim between cover plate and fan because they really do not quite fit otherwise). Wish the Ersatzteil Katalog showed it that way. I will see how the fan clears the fan housing and use this order if clearance is ok. No comment on 16 blade fans?

[Bruce Smith]

It's a tight squeeze and tightening the nut compresses the cover plate so you may have room for more thin washers than you think. I think I'm calling the carrier plate a thick washer, and there are two.

[Vic Skirmants]

Whatever order, just be sure the fan is properly clamped. I assemble all the washers, etc., without the fan, then check to see that everything is clamped; therefore the fan will be clamped.
Personal observation: I use a 16 blade fan on the race engines. It cools better at HIGH rpm. With a small crank pulley, the fan is only turning about 7500 rpm at that engine speed. With a stock pulley, the fan is probably at that rpm at only about 3000-3500 engine speed; depending on where the belt rides in its pulley. I have never welded a 16 blade fan. Of course that is good advice for any street engine with a stock crank pulley.

[Mike Horton]

I would suggest a 28 blade fan, balanced and tack welded.

Mike

+1

[Craig Richter]

+2

Al, if you don't remember ever seeing the damage done by an exploded fan, you probably have never seen one. Catastrophic!!

[Wes Bender]

... and one shard usually finds the oil cooler. Where are you hunkered down now, Craig?

[Craig Richter]

Hi Wes, We're hang'n out down here in the mountains of Mexico on our little ranchito (MandyLand) where we see only our 6 horses, 3 dogs and a bunch of chickens, plus a few of our local helpers. Feeling pretty isolated (occasional internet), and hoping all my 356 friends have also found spots where they feel safe during these unusual days of "self isolation". Missing Speedy wheel time, but looking forward to this Summer with Lucretia in the Austrian Alps. Stay well everyone.