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Putting the prop together

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  • Putting the prop together

    So a while back I posted how I had problems removing the old prop. Well the IA and me finally got it out. Then I got a sensenich propeller.
    Now another IA has aligned the prop (the 1 and 2 marks) per tdc on cylinder 1 as is required for correct balance and the back plate is in with the bolts protruding.
    All that is left is put in the front plate, the washers, the nuts and proper torque plus cotter pins.
    BUT there are 10 washers. So we were both scratching our heads.
    The guy who has removed the prop is unreachable and absolutely positively 0 pictures of a prop assembly sequence onlne... thanks to the rent seeking associated with such esoteric knowledge I guess.
    So I have to GUESS. The DB-12 manual is also mute on the subject.
    And my guess is that a set of washers goes on first, then the front plate, then the second set of washers.
    But if I try to do that the bolts don't protrude much.
    Anyone has a clue here?

  • #2
    Doesn't the spinner strap attach with TWO washers per bolt? One on each side of the strap.

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    • #3
      Not all of the props are the same thickness. Assemble the prop on the hub with the correct bolts and washers and install on the crankshaft as an assembly. Coat the taper with Cor-Ban or Mastinox when you assemble the hub to it. Make sure you can hand prop the engine.

      EO

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      • #4
        My guess is if it has a spinner that the bolts for the bracket got one washer, and the four remaining bolts had two. That would be a total of 10. Also remember that if you are switching from a wood to a metal prop the bolt length will be different, and the metal props do not use the crush plate.

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        • #5
          Don't forget to re-torque wood props at least twice a year, during the season changes spring>summer and autumn>winter because of changes to humidity in the wood.

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          • #6
            Originally posted by Robert Lees View Post
            Don't forget to re-torque wood props at least twice a year, during the season changes spring>summer and autumn>winter because of changes to humidity in the wood.
            And after the first few hours of operation with a new installation.

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            • #7
              Indeed! Thanks for the prompt.

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              • #8
                Great info. Well I measured the old prop vs. the new one and got 3.6 in vs. 3.75 inches (in decimal). This explains why the bold's hole isn't reachable by the castle nut's incisions.
                Do you guys recommend slightly thinner washers?
                Oh and my new prop is out of wood.
                Is there positively ANYWHERE a video of the whole process? I mean the lack of data is astounding. And of course recent high school aged newly minted A&Ps have never ever been remotely taught in their mechanic schools how to put on a wooden prop.
                Last edited by taylormarc; 10-08-2021, 14:44.

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                • #9
                  Thin washers are fine. The big thing is to not over torque the propeller and damage the hub. The torque required is considerably less that for a 3/8" bolt in other applications. And don't sell out those just out of high school kids just yet, my 18 year old son can change a wood prop.

                  Oh, since you have a tapered shaft and prop hub, don't forget the bushings in the bolt holes on the propeller.

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                  • #10
                    Here is the thread when I went "WOOD". See post #23 on page 2.




                    Mike Wood
                    Montgomery, TX
                    '46 BC12D
                    N44085 #9885

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