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Technical Flathead fan noise

Discussion in 'Traditional Hot Rods' started by twostickmutt, Feb 16, 2019.

  1. twostickmutt
    Joined: Oct 18, 2015
    Posts: 65

    twostickmutt
    Member

    I just put an alternator on the 39 standard. . The radiator fan is mounted to the alternator pulley. Everything works great except for the noise from the fan now. It sounds like a prop job on take off. I realize the fan is spinning faster due to the smaller pulley but the noise is awful. If you take the fan off it is quiet like normal even at half throttle. Could there be some kind of turbulence or something between the radiator fan and alternator fan fins ? It's too noisy to drive. It's a 4 blade 16 inch original fan. I want to leave the alternator on and I'm looking for suggestions. Thanks for looking.
     
    Last edited: Feb 16, 2019
  2. flatford39
    Joined: Dec 3, 2006
    Posts: 2,091

    flatford39
    Member

    What difference would it make if the fan was mounted to a generator or an alternator??? You already tested it withe fan off and it was quiet.

    How close or far away is the fan from the radiator. Should around an inch.
    Maybe you need a larger pulley on the Alternator to slow down the fan.
     
  3. dwollam
    Joined: Oct 22, 2012
    Posts: 652

    dwollam
    Member

    You said it yourself, the pulley is smaller hence the fan is spinning much faster.

    Dave
     
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  4. twostickmutt
    Joined: Oct 18, 2015
    Posts: 65

    twostickmutt
    Member

    Mounted on the generator it was quiet. Fan is about an inch from the radiator just like when it was on the generator.. The only difference is the smaller alternator pulley thus giving the fan a lot more speed. I'm having a hard time believing that the extra fan speed with the smaller pulley would make so much noise but anything is possible.
     
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  5. rusty valley
    Joined: Oct 25, 2014
    Posts: 547

    rusty valley
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    if its a fan mounted on a delco, it will get quiet after the fan goes thru the hood. the ford generator had better bearings for the fan load
     
  6. Mr48chev
    Joined: Dec 28, 2007
    Posts: 24,191

    Mr48chev
    ALLIANCE MEMBER

    You just might want to go back and study the Alternator parts drive end and commutator end bearing charts For both Ford and Delco in the years that would be applicable
    https://www.rockauto.com/en/catalog...alternator+/+generator+drive+end+bearing,2484

    https://www.rockauto.com/en/catalog...alternator+/+generator+drive+end+bearing,2484

    203 bearing on the front of both Ford and Delco standard size alternators and the needler bearing on the back of both is close enough.
    You can believe all the BS you want but they have the same bearings.
     
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  7. Desmodromic
    Joined: Sep 25, 2010
    Posts: 193

    Desmodromic
    Member

    Buy a pair of glass-packs. If still a problem, pull the internals out.
     
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  8. goldmountain
    Joined: Jun 12, 2016
    Posts: 649

    goldmountain

    How about removing the alternator fan? With the engine fan mounted there, the alternator should run cool anyhow.

    Sent from my SM-T350 using The H.A.M.B. mobile app
     
  9. BJR
    Joined: Mar 11, 2005
    Posts: 5,077

    BJR
    Member

    I think the alternator front bearing is not set up for a load pulling it forward. When the fan spins fast it is pulling air from front to back, causing the alternator pulley to pull forward against the bearing. I think you need a stock fan with pulley in the center, and the alternator mounted on the side.
     
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  10. miker98038
    Joined: Jan 24, 2011
    Posts: 364

    miker98038
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    I don’t have a clue about the bearings, but do some math on the pulley sizes and rpm at the fan. Having had a clutch fan fail and lock up at 2500 rpm, it’s hard to believe the noise they make. Smaller fan, less pitch, IDN?
     
  11. Aaron D.
    Joined: Oct 27, 2015
    Posts: 437

    Aaron D.
    Member

    One simple thing to check is the tracking of the blades. If one blade got bent (out of track) during the change, the fan could make more noise.
     
  12. twostickmutt
    Joined: Oct 18, 2015
    Posts: 65

    twostickmutt
    Member

    I should have thought of that.
     
  13. Mac VP
    Joined: May 13, 2014
    Posts: 264

    Mac VP
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    All of the early Ford generators, up through 1938, AND 1939 Standard Fords, had the cooling fan mounted to the generator pulley. Every one of them used a Timken tapered roller bearing on the fan end of the armature.....not a ball bearing. And you can’t just swap in the tapered bearing for the ball bearing.

    This is the problem everyone faces when trying build a hot rod. Up through 1937 the Ford generators were the 3 brush 6 volt type, which used the simple cut-out (mounted on top of the generator) to control the charging. Certain 1938 and Standard 1939 cars with the factory radio were equipped with the 2 brush generators, made for use with the firewall mounted voltage regulator. Because those types were on vehicles with generator mounted fans, they still got the tapered roller bearing......good hot rod candidates, but very hard to find these days.

    Seems that the only real choices in today’s builds is to stay traditional 6 volt with the 3 brush stock generator.......or mount an electric fan and use a modern 12 volt alternator......or convert a typical 1940-48 flathead 6 volt (2 brush type) generator to 12 volt and use an electric fan.

    Hiding the fan in front of the radiator eliminates the “ugly non-traditional” look, wherever it’s possible. It’s not such an easy thing to do with a Model A grill. Your choice of early or late flathead V8 engine always limits what you can do as well.
     
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  14. 42merc
    Joined: Dec 19, 2010
    Posts: 544

    42merc
    Member

    Van pelt. What about the '39 standard & trucks with a two brush generator & a fan mount pulley. Are there different bearings ?
     
  15. partssaloon
    Joined: Jan 28, 2009
    Posts: 313

    partssaloon
    Member

    Try using a pulley off of a tractor alt. to slow the fan speed down
     
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  16. Mac VP
    Joined: May 13, 2014
    Posts: 264

    Mac VP
    Member

    Guess I didn’t make it clear ...... those 39 Standards (and the pickups) with the 2 brush generators, still had to have the Timken tapered roller bearing at the front of the generator because they still had the generator pulley mounted fan.

     
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  17. twostickmutt
    Joined: Oct 18, 2015
    Posts: 65

    twostickmutt
    Member

    Thanks everyone for your replies. I may go with an electric fan set up and do away with the stock howler.
     
  18. ROADSTER1927
    Joined: Feb 14, 2009
    Posts: 2,423

    ROADSTER1927
    Member

    Get a less efficient fan and a different pulley.
     
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  19. jimvette59
    Joined: Apr 28, 2008
    Posts: 675

    jimvette59
    Member

    Good decision using a electric fan for reliability .
     
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  20. How much slower would the alternator spin with the pulley from the generator (or a pulley of the same size)? Too slow, or fast enough to keep up?
     
  21. twostickmutt
    Joined: Oct 18, 2015
    Posts: 65

    twostickmutt
    Member

    I believe it would be too slow to charge at an idle that was the reason for the small pulley. it charges now real good at idle with the headlights on. i'm going with the electric but thanks for the reply.
     
  22. Petejoe
    Joined: Nov 27, 2002
    Posts: 9,684

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

    Another option would be to go to a early to late 50’s 12 volt generator.
    Simply cut the mounting tabs off the housing and the length and diameter is the same as the originals.
    IMG_2488.JPG
     
  23. town sedan
    Joined: Aug 18, 2011
    Posts: 900

    town sedan
    ALLIANCE MEMBER


    I think the problem with using the later generator is the same as using an alternator. Not having the tapered roller bearing at the front of the case.

    My question is when things let go what's more likely to be damaged the radiator, or the hood?
    -Dave
     
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  24. twostickmutt
    Joined: Oct 18, 2015
    Posts: 65

    twostickmutt
    Member

    I think it will be safer all the way around with electric. I had a fan blade break on me one time and it wasn't pretty. Another reason too is that fan is 80 years old and has made a lot of revolutions .
     
  25. twostickmutt
    Joined: Oct 18, 2015
    Posts: 65

    twostickmutt
    Member

    I'm hoping a 16 inch puller fan will do the trick. The stock fan is 16 inch so here's hoping plus I can put it a little bit lower on the radiator instead of up at the top.
     
  26. continentaljohn
    Joined: Jul 24, 2002
    Posts: 4,038

    continentaljohn
    Member

    My question if the bearing is a issue whats the power generator using in there set up. The 39 ford came with the fan mounted generator and many of them still running around stockers.
    I have to ask why not go with a powergen type setup? And have seen them in stock applications.
    I understand your going with a electric fan but would love to figure out whats going on and solve the problem and may help others in the future...
     
  27. town sedan
    Joined: Aug 18, 2011
    Posts: 900

    town sedan
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    I believe the Powergen suffers with the same lack of the tapered roller beraring up front. I've no personal experience with the unit, but I've heard this from a few sources.
    -Dave
     
  28. twostickmutt
    Joined: Oct 18, 2015
    Posts: 65

    twostickmutt
    Member

    My biggest complaint was the noise from the fan with that smaller alternator pulley. I don't think you would get the charging rate at idle or low or mid throttle with the standard pulley, I'm not sure. At idle the fan noise is very loud and at 2 to 3 thousand rpm's I could only imagine. I looked into a power gen and if I remember right they have a smaller pulley too.
     
  29. jimvette59
    Joined: Apr 28, 2008
    Posts: 675

    jimvette59
    Member

    Give it a go.
    Hey twostick maybe a fan with a fluid action that will only spin X amount of RPMs can be used . ???
     
  30. twostickmutt
    Joined: Oct 18, 2015
    Posts: 65

    twostickmutt
    Member

    I think i'm just going with the electric for now and if that doesn't work out i'll try something else then I don't have to worry about the front bearing and the noise.
     

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