Prop shaft nuts

Discussion in 'Props' started by ABoatGuy, Nov 27, 2013.

  1. ABoatGuy
    Joined: Aug 2004
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    ABoatGuy Member

    I'm working with a vendor who insists that on a twin installation the left turning prop should have right hand threads and the right turning prop should have left hand threads. This is on a normal SAE taper keyed shaft.

    I can't think of a good engineering reason that a properly installed fitted key, installation would loosen based on the direction of the threads. I can't find any standard that suggests this is a requirement.

    And I can think of several practical reasons why it would be an annoyance for owners (sourcing large diameter LH nuts, two spare shafts instead of one, etc.)

    Does anyone have experience with props coming loose due to LH/RH nuts?

    Thanks
     
  2. Carteret
    Joined: Jan 2004
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    Carteret Senior Member

    Double nut with cotter pins and there is no issue.
     
  3. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    I have never seen left and right threads. If they came loose as the vendor claims, they would come off in reverse. It makes no sense.
     
  4. JSL
    Joined: Nov 2012
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    JSL Senior Member

    Put on the nut (thin one) and then the lock nut (thick) plus a cotter pin and you are fine.
     
  5. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    This is just nuts. Maybe the vendor had a screw loose ?
     
  6. michael pierzga
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    michael pierzga Senior Member

    Imagine the poor engineer who pulls the props. No many are anticipating counter rotation.
     
  7. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Using different threads is the old fashioned line of thinking.
    On a tapered shaft and key, the only counter clockwise force acting on the nut is the friction of the surrounding medium. A locking ring with one or two lips bent against the nut is the normal way to secure it.
    Early automotive wheel drive shafts had different threads on each side, modern ones have a collar on the nut that is pinched or otherwise deformed to prevent turning loose.
     
  8. michael pierzga
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    michael pierzga Senior Member

    What is the name of the locking ear washer for nuts ?

    King and queen washer ?

    And why cant the second locking nut be a pelleted nut. I hate drilled shafts and drilled nuts....the thread may get burred and when a new prop is fitted the hole no longer works.

    How many times have i seated a component only to find that i have put the nut on upside down of pickup the drilled nut for component A when installing component B.

    Pain in the butt
     
  9. FAST FRED
    Joined: Oct 2002
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    FAST FRED Senior Member

    >I have never seen left and right threads.<

    On boat shafts , however it was common on bus and truck wheel nuts 50 years ago.
     
  10. CDK
    Joined: Aug 2007
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    CDK retired engineer

    I have no idea Michael, not in English, not in my native language. I've seen several variants, like a washer locked in a key way, lobes on the outside, or the thing Mercury uses, with a hexagonal seat for the nut.
     
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  11. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    I had an early 90's Leyland DAF in the UK that still had left and right threads on the wheel studs. It makes no sense since the load is axial. There will never be any torque from the wheel. Likewise, the torque on a propeller is all absorbed by the key and the friction on the taper.
     
  12. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    It's called a tab washer . . .

    [​IMG]
     
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  13. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    If so, you'd want to bolt from him as soon as possible.
     
  14. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    "pelleted nut" Is that another name for a "castle nut".

    [​IMG]
     

  15. michael pierzga
    Joined: Dec 2008
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    michael pierzga Senior Member

    Pell-it. Is somekinda trademark for self locking fasteners.

    You see them on pieces of equipment assembled by robots

    http://www.ndindustries.com/pell-it.php

    The nut or bolt has a hole bored thru and a nylon or other material pellet inserted into this hole
     
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