NUG (New Guy) Fan Belt Question

Lembomw

Lembomw

Senior Member
NUG again, fan belt problem this time.
Since the only thing that was being used to hold the generator so that the fan belt had some tension on it was a triangular piece of 2 x 4 wedged between the engine block and the generator, I decided to get the generator tension brace and a new belt from Bratton’s. The belt that is on there is in bad shape. Anyway, the brace went in easily and held the generator so that the tension on the old belt was perfect. I then put on the new belt and in order to put tension on the belt, the generator was so far over it is almost touching the radiator pipe….and the generator is now about ¾ of an inch beyond the reach of the tension brace. I measured the structure of both belts and they were basically the same except for the outside circumference. The old belt has an outside circumference of 43 inches and the new one is 44 inches. I called Bratton and talked to Jeff. He is a real helpful and patient person. He waited until I went to the garage with my cell phone so I could give him the measurement for the diameter of the pulleys on the generator and crank. Both were the correct size. Jeff said that he would send me another belt just in case the first one sent was somehow not correct. Got the replacement belt the next day (unbelievable) and it was the same as the first one sent – 44 inches. I went to a couple of auto parts stores but they did not have a V belt that was thick enough to fill up the grooves in the pulleys.
Does anyone have an idea as to why a new stock belt (2 of them) would cause the generator to be so far over in order to tension the fan belt? Also, anyone happen to know what the outside circumference of their fan belt is? I don’t know what to do now to get a new belt that will work.
Thanks again for your input, Mark
 
They are supposed to be 43" with everything stock. Looks like they sent you the wrong one twice. I also needed a new belt last week and walked into NAPA and asked for a belt for a '29 Ford and I had it that afternoon.
The tension bar is aftermarket as the stock configuration does not have the bar, you just tighten up the mounting bolt. The generator does not require a very tight belt like an alternator does.
 
I've used Brattons fan belts for years. I've never measured them. They just work. Is your generator pully the correct diameter? Or do you have an alternator with a smaller pully?
 
I should also let you know, that belt is awfully tight when new. I had to take the pulley off of the generator, put the belt in the pulley and reattach the pulley to the generator. Then when it stretches a little it will be just right.
 
FanBelt.jpg


I'm thinking a 43" belt might measure 44" around the outside of the belt. As Greg said, the belt doesn't need to be very tight. Some might think my belt is too loose, but it only needs to be tight enough so the fan and generator don't slip. For sure you don't need the tension gizmo, unless you're running an alternator.
 
I used a NAPA 25-22434 belt. It won't win you any points in competition but it works with a tube type gen or a Powerhouse, either one.
 

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Tom Wesenberg said:
FanBelt.jpg


I'm thinking a 43" belt might measure 44" around the outside of the belt. As Greg said, the belt doesn't need to be very tight. Some might think my belt is too loose, but it only needs to be tight enough so the fan and generator don't slip. For sure you don't need the tension gizmo, unless you're running an alternator.
Click to expand...

Thanks, Tom. A picture's woth a thousand words.

Ford's words on the matter evolved between 1928 and 1931, so I think that original owners may have been surprised at how "loose" "A" fan belts were.

On page 204 of the Service Bulletins: "The belt is adjusted to the proper tension when the car leaves the factory and this adjustment should not be changed unless the belt slips. The adjustment is easily made by loosening the generator adjusting arm stud nut, and moving the generator forward. Do not tighten the belt more than is actually necessary to keep it from slipping."

By the late '31 editions of the Instruction Book, underlining was added to emphasize "this adjustment should not be changed unless the belt slips." and "forward" was changed to "toward you."

I suspect that the underlining may have been added because over-tightened belts were causing premature generator bearing failure. I've also always assumed that the "slipping" reference relates to the belt being tight enough for the engine to drive the water pump and the generator without slipping/squealing.

I've seen belts so tight that you could pull the belt by hand and turn the crankshaft. I think that's way too tight... not good for either water pump or generator.

The single generator bolt is all you need to maintain the tension on a properly adjusted belt.
 
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is anyone using a NAPA belt with a alternator with the small pully and if so do you have a part # you would like to share, thanks
 
Thank you for all the information. When I talked to Jeff at Brattons, while he was on my cell phone I went to the garage and measured the diameter of the generator pulley and the crank pulley. He said that they were both what they should be. My greatest concern is that when I put on the 44 inch belt the generator was only about 1/8 of an inch away from the bottom radiator hose/pipe. Once the belt stretched a little it would be touching the pipe. I looked on another parts supplier website ( I do not remember it was Mac or another one) but they list both a 43 and a 44 inch belt. I will go to NAPA today with the part numbers provided and see what they have. Thanks again, Mark
 
My belt has been on for about 5 years and hasn't stretched any. Do you have the correct water pipe for the year of your car? Also I think some repro radiators don't have the correct angle on the bottom outlet. Any pictures?
 
Thst generator and alternator tension brace "assembly" might need a dollop of modification. The slot might be too short for your setup. Drill a new hole about 1/2" closer to the gen/alt end of the bracket. Then, use your recip saw to chunk out the piece between the hole and the slot. File away the burrs and give it a shot of paint. Voila! Now you can adjust the fan belt tension and keep your alternator from falling onto the radiator return pipe.
I had to do this recently to get a fanbelt to fit and it worked great. Very little fuss and no muss.
I can tell you from a fellow traveler's experience that it is very hard to modify the slot when all you have for a vise is a road sign post and the only tool you have to lengthen the slot is a file. We did have the file and lots of elbow grease, so I shouldn't complain. And four Model A's had extra parts caches with three replacement belts! (Traveling with my friends, I don't have to worry too much about emergency parts!!)
Bottom line ... wihile you are still in your garage and close to your tool chest, make sure that the backup fan belt in your breakdown kit fits. Don't wait to find out it won't work when you are on the side of a country road ... in the rain! BTDT!
 
Model A Man said:
is anyone using a NAPA belt with a alternator with the small pully and if so do you have a part # you would like to share, thanks
Click to expand...
I'm using the Ford Script belt that I got from Sacramento Vintiage. That's what I used when it had a generator, and it's the same belt I'm using with a small pulley alternator as well.
 
I use NAPA belt # B-41. It's an industrial belt but it's the right size and these engines don't run a lot of RPMs anyway. I've never had any problems with the B-41. The problem I have with the regular NAPA belt is that the belts with the notched inside make a "scritching" noise at idle that drives me crazy.
 
Model A Man;
I use a NAPA 25-20426 with an alternator and small pulley. It works well for me and gives me plenty of lower-hose clearance.
 
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