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Straightening Bent Fan Blades For V6

Discussion in 'Early CJ5 and CJ6 Tech' started by jwmckenzie, Mar 9, 2017.

  1. Mar 9, 2017
    jwmckenzie

    jwmckenzie Sponsor

    Boston, MA
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    I have an original fan, 5 blade for my 225 V6, but a couple of the blades are bent.

    Thoughts on straighten the blades?
    [​IMG]
     
    Last edited by a moderator: Mar 10, 2017
  2. Mar 9, 2017
    Dandy

    Dandy Member 2020 Sponsor

    Estherville IA
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    I've got 2 that need some help, I'am not sure how to go about it....Mine aren't as bad as yours, but they need work...

    Watching this.....On straightening them....
     
    Last edited: Mar 9, 2017
  3. Mar 9, 2017
    Walt Couch

    Walt Couch sidehill Cordele, Ga. 2020 Sponsor 2019 Sponsor

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    You do know that one blade that is off set is normal don't you? I have read the design was to cut down on fan noise. That is the same one I have on my TUX and it's original.
     
  4. Mar 9, 2017
    oldtime

    oldtime oldtime

    St. Charles,...
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    Just thinking here .... but so long as you don't add or cut metal away the balance should remain the same.
    Right !
    So in theory you should be able to true up the blade tips without effecting the overall balance.
     
  5. Mar 9, 2017
    jwmckenzie

    jwmckenzie Sponsor

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    Yep, the tips on a couple of the blades are bent, like the motor was dropped, gently, on the fan blade. Kinda like an airplane prop after a belly landing, only not that bad
     
  6. Mar 9, 2017
    jwmckenzie

    jwmckenzie Sponsor

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    In theory, I guess so. May give it a try and stand back when I fire it up. Probably would just increase the noise if it isn't perfect.
     
  7. Mar 9, 2017
    oldtime

    oldtime oldtime

    St. Charles,...
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    Should be easy to true the runout with the fan mounted on a bearing and using a dial indicator.
     
    jwmckenzie likes this.
  8. Mar 9, 2017
    jpflat2a

    jpflat2a what's that noise?

    Riverside CA
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    Check closely around the rivets where the blades are attached.
    If the blades crack it will in and around those rivet mounting holes.
     
  9. Mar 10, 2017
    jwmckenzie

    jwmckenzie Sponsor

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    So, got out the body bang'in tools and started in on the fan blades.

    Before:
    [​IMG]

    After:
    [​IMG]

    needs a bit more fine tuning, but the metal seemed to know how it wanted to go back.

    Looked at the rivets, no cracking. Will get it blasted and mounted some how to measure the fins against one that was not damaged.

    Maybe Focker can move this thread to the Restoration forum, as I think this has turned into a resto instead of a WTB.
     
    Last edited: Mar 10, 2017
  10. Mar 10, 2017
    oldtime

    oldtime oldtime

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    Wow that was bent pretty bad but looks much better now.
    If its just the blade tips that got bent it will likely come out good.
     
  11. Mar 10, 2017
    jwmckenzie

    jwmckenzie Sponsor

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    Here is the set-up.

    [​IMG]

    Screwed a water pump to the bench, and mounted the fan. Lots of measurement error here, but repeated measurements and using averages, the +/- is 0.07". Any thoughts on what might be acceptable?

    Before I am done, will measure 3 places on each blade, bottom, center and top. To improve this process I will dot three locations on the blades so I can get back to measuring the same locations on each blade multiple times.

    This wooden bench approach is pretty wonky
     
    Last edited: Mar 10, 2017
  12. Mar 10, 2017
    oldtime

    oldtime oldtime

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    Don't really know what specs are standard conerning fan runout... but I think .010 should be acceptable.
    Balance is far more important than runout.

    Not super accurate but do you have a lawn mower blade balancer ?

    I think the worst you can do is prematurely ruin a pump bearing.
     
  13. Mar 10, 2017
    Focker

    Focker That's what I do, I know things and I fix stuff. Staff Member 2019 Sponsor

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    Moved to Tech.
     
  14. Mar 10, 2017
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member

    Tantallon, Nova...
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    You need to be careful with those things, years ago someone posted a pic of their hood after a fan blade broke off- it was quite impressive.

    I think it was this thread but the pic has disappeared :(


    also-

    H.
     
  15. Mar 10, 2017
    jwmckenzie

    jwmckenzie Sponsor

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    Agree. If I get this thing statically balanced (headed off to the lawnmower shop shortly to see if they have a mower blade balance), I will put it on the jeep and see how it spins. If I get vibration, I will go back to the 4 blade fan that was on there before. If no vibration, will inspect for cracks after a few hours, then 10's of hours, then every year when I get it out for the summer, until I have bigger worries.

    More to come.
     
  16. Mar 10, 2017
    jwmckenzie

    jwmckenzie Sponsor

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    Reading on the web thing, vibration in a fan is also caused by the shape of the blade, so I wanted to make sure the profile of the blades are the same. Since the tip is 1 1/2 inch from the thick metal holding the shape of the blade, If I can get that consistent, then it's easy to feel or see if the contour from the heavy metal to the tip is consistent.

    I simply traced the profile of each tip and compared it to the others. #1 Blade was not bent, so it's the reference. You can see the before tracing, #2 and #4 needed some work. The after pic is after straitening each blade.




    [​IMG]
     
  17. Mar 10, 2017
    jwmckenzie

    jwmckenzie Sponsor

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    I am done for a while on this one, its as good as it gonna get. Will get it painted and mounted after the engine goes back in.

    Got the blades to +/- 0.012", The lawn mower balance worked out pretty well, and all blades were within 1/8 inch from the flat surface.

    As a point of reference, I measured my 4 blade fan. The blades came out +/- 0.15". This fan is made by riveting two pieces together with a fan blade on each end, making adjacent blades the thickness of the material different. The difference not associated with the way it is made.

    It balanced within 1" from the flat surface.
     
  18. Mar 11, 2017
    oldtime

    oldtime oldtime

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    Excellent effort.
    Good luck and let us know how it turns out.
     
  19. Mar 12, 2017
    Walt Couch

    Walt Couch sidehill Cordele, Ga. 2020 Sponsor 2019 Sponsor

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    It's probably better now than factory original. Good job.
     
    timgr likes this.
  20. Mar 12, 2017
    jeep2003

    jeep2003 Well-Known Member

    Vestal NY
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    This reminds me of some of the threads over on the Porsche forum. Its a Jeep for god sakes they were probrobly 3/4 inch out from the factory lol nice effort but chasing dauntless vibrations is a lost cause :)
     

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