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Thread: More on propeller Not-Tracking

  1. #1
    grtbluyonder's Avatar
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    Default More on propeller Not-Tracking

    Background: PA22-150 lycoming 0-320 A2B, had M74DM-0-60 inspected and refurbished. Vendor magnafluxed prop bolts and returned them with washer that were substantially less in diameter than the original prop washers which they lost. Orig OD: .882 inches by about .06 thick (guess on thickness), replacements are OD: .630.

    Issue: when prop and other hardware was installed and bolts torqued, the prop would not track. Tips were out by almost 1/4 inch.

    Inspection reveled that the small washer was not compressing the bolt head into the prop as it should but barely covered the diameter of the bushings that hold the prop in place and therefore were not properly securing the prop.

    Because of this, the prop was not being held properly resulting in the tracking problem. Fortunately we did not run the engine.

    According to my Tripacer parts manual the correct washers are Univair 80122-55 washers. I ordered these and have received them but have a major concern with them. They are: 0.822" OD (OK), 0.377" ID (OK), but very thin, only 0.032" thick.

    I remember my original washers being probably twice as thick as these.

    Concern is whether or not these are correct even though the part no. is proper.

    These washers have to hold the full load of static and dynamic thrust of the prop. At 0.032 inches thick I feel they would not be strong enough. Problem is, my AME will not substitute any other washer. I want a thicker at least class 8 washer with the correct ID, OD, and at least 0.060 in thickness.

    Does anyone have any experience with the prop bolts and washers such that you can advise me if I am in danger if I use these thin washers even though they have the correct part number?

    Is there an "approved" but thicker washer that I can use and if so where can these be obtained?

    Thanks.

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    Administrator Steve Pierce's Avatar
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    Here is a thread on the same subject. http://www.shortwingpipers.org/forum...ight=80122-055 I will check the thickness from the drawing.

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    Administrator Steve Pierce's Avatar
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    From drawing 80122 on the Vagabond Drawing CD.

    80122-55 O.D. 7/8", I.D. .375/.385", Thickness .032", Material 1025 Steel.

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    With the prop bolts at such a low torque I would suspect a thicker washer to be more of a problem. You want full compression of the washer at the 25 ft-lb torque.

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    grtbluyonder's Avatar
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    Cessna standard parts for same engine 0-320 and same prop. are washers that are same ID, OD, as the 80122-55 units but they are twice as thick around 0.063 thick. Don't have any info on the Cessna spinner backing plate so a comparison doesn't mean much.

    Upshot of it seems to be, use the approved Univair parts they work and won't dig into the spinner mounting plate.

    FYI - one aircraft service org. that I contacted with the "problem" said to me "you must be an engineer" - just use the Univair washers. - how did he know my background????

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    Administrator Steve Pierce's Avatar
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    Quote Originally Posted by grtbluyonder View Post
    "you must be an engineer" - just use the Univair washers. - how did he know my background????
    Ha, I grew up with one and have several as customers and friends. Different mindset but it is mostly good.

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