generator pulley (fan mount)

V

V8Barn

Senior Member
I want to put a fan on a 1940 generator. It has a threaded pulley. Does anyone have a pulley that take a fan? Who makes an aftermarket pulley that is threaded and has the fan mount? Thanks! Rich
 
Rich,
The typical '39 standard 2 brush generator pulley that accommodates a
fan is held on with a nut...it does not have internal threads, at least any
that I've ever seen. I can rework certain fan mount pulleys to go on your '40
generator if no one has a quicker idea.
Charlie ny
cas5845@yahoo.com
 
I learned the hard way that there are fan-mount generator pulleys that ARE threaded on, and using a puller on one does not yield very good results. I then
also found out how difficult it is to find one that is not broken... Evidently, these were used on 39 stds which still had the fan mounted on the generator
instead of on the front of the crankshaft. Maybe Charlie is correct that they
were not originally threaded and that later on, the threaded type were issued
for service replacement??? I recall that "someone" is making new threaded
pulleys that can be used to convert the later generators that came with a
stamped "screw on" pulley with no fan mount. I am a Mac's dealer and may
have seen them on one of their monthly dealer bulletins? Try searching their
retail website and you might find what you need. I think the threads are 5/8"-
20???
 
The 39 pick up has a threaded pulley with the 4 threaded boss's for a fan. Walt the pulley you mentioned doesn't have the fan blades and the generator would get hot. I used one on my 39 pick up but this was one of the alternators I put in the generator shell. The alternator has two fans in it so I didn't need the fan on the pulley. The air on the generator is drawn in from the rear and exits out the front. G.M.
 
There are 4 different armatures for the 81A-10000 series generators and I think they are all set up for 3-brush operation (no regulator). (further investigation shows 2 for 3-brush and 2 for 2-brush) The drawings in the green book show woodruff keys but they are just drawings. The later 99A and O1A 2-brush generators have several armature changes in the change over to the 21A series. There could have been aftermarket generators as well since there were still so many old Fords on the road after the war. I imagine a lot of stuff was mixed and matched during overhauls of this stuff back in the day.

Mac's has 81A type pulleys and O1A type pulleys but there is no mention of threaded shaft. The 39 standard would have been the last of the passenger generator mounted fans with 3-brush operation. 85 hp and 60 hp had similar set ups but the 60s may have enterchanged somewhat over the years. I think even they went to a crankshaft mounted fan in 1940. I wonder how many of the older 3-brush types were changed to 2-brush set ups over the years?

Kerby
 
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I, too, am trying to come up with a way to have a fan-mount generator, using a later, threaded-armature-type generator. I measured the threads, and found that the '20 tpi' gage fits, but in reality, the thread is actually metric, 17 x 1.25 mm (at least on the 46-48 examples that I have). I suspect this is likely because Henry made the generator shaft to fit the '203-type' bearing that is used, then created the 1.25 pitch for it. I've tried to find a 17 x 1.25 tap, to use for modification of a 'fan-mount-type' pulley, and have had no luck. Lots of 17 x 1.5 taps, but no 17 x 1.25.
I called the Mac's tech folks, and had a guy measure the replacement pulley that seems to be closest to 39 STANDARD,
 
38 & 39 Standard were a 2 brush generator with a threaded fan mount pulley.
The fan mount pulley with the keyway is for the earlier 3 brush generators.
The 38 & 39 standard fan mount pulley will work on the 56 & later 12 volt armatures.
I just completed one for my 36 pickup. Bill
 
Rich,
Yep it's a 17mmx 1.25 thread and as Bob says these taps are
not a typical on the shelf item. That 1.25 pitch is REAL close to 20
tpi and might work. Certain fan mount pulleys have small enough bores
that can be opened up and then tapped to size....except the tap seems to
be not readily available. However the thread could be CHASED on a lathe.
I have a few of these fan mount pulleys and just for the challenge
I'm going to bore 2 of them and chase the threads on my lathe in the
morning. A spacer will need to be made as well but that should be no big
deal.
Charlie ny
cas5845@yahoo.com
 
I bought a tap and die last summer when I made the 6 volt alternators for my own use. I just walked over to my pile of papers and remembered seeing the literature from where I got them a few week ago. I must have ran it through the sheader when I was reduceing the pile, I'll check and see if I can find the address. G.M.
 
I,ve got a die in front of me that has .665 x 20 NS stamped on it, Below that it says Armature die. On the other side it says Made in USA, No brand name.
It screws onto a NOS two brush armature perfectly. Some day I'll learn how to post pictures. Bill
 
According to the Green Book, the thread size on the armatures of the 38-39 2-brush generators is 21/32" x 20. This is for the pulley retention nut. A weird size for sure. However, this may not be relevant to the thread -on pulleys.
 
The picture of the 81A-10000-D 2-brush shows a woodruff key and a nut but it has the larger threads. The 81A-10000-E 2-brush is not shown in a diagram but it may have had a similar armature to the 21A series since the were threaded. Replacement pulleys could have been the last ones made for spares. The 21A series generators used 8BA armatures for replacements

The 21/32 X 20 thread size is definitely not common. It would have to come from a specialty supplier or one off manufacturer.

Kerby
 
The 21/32 tap can be ordered but if I recall it cost about $150.00. The GM Delco alternator has threads that are within a few thousanths of the Ford pulley and the G.M. nuts fit right on the Ford shaft. I had trouble finding it but I found a supplier that sell tools and an alternator test unit to alternator repair shops and got the metric tap and die from him. I looked back in my old emails and favorites and could not find anything. The tap and die are up in Pa. with the packing slip. If someone needs one bad and can't find it I can get my son to go down to the shop and find the packing slip. G.M.
 
i have two gen. with a pully for fan mount held on with a nut & the housing has 3 leads. field gen ground. i have had them since hector was a pup & have no idea what there off of. let me ask a dum question could you use a 35 36 front mount & armsure. & a 40-48 housings with the fields? older than dirt & still learning
 
Richard, The 36 generator housing is about a 1/4inch smaller in diameter than the later two brush housings. Starting about 38 the two brush housings are the same diameter as the 12 volts. I used a 38 front plate and pulley on a early 60s 12 volt
generator for my 36. Bill
 
The early 3 brush generators have a smaller diameter shaft with a keyway and no threads in the pulley and are held on by a nut. G.M.
 
G.M, the GM alt thread size may be why I have found the threaded pulley does not fit just right on a GM alt, it is slightly loose. Have had to use the key type pulleys on them.
 
Here are two of the seven 6 volt alternators I made useing the Ford threaded pulley's and GM lock nuts. Everything was tight even after 2,000 mile on my 39. I used 2 lock nuts for extra safty. G.M.
 

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