When to use a Castle nut and cotter pin ?

Discussion in 'Workshop Tips and Secrets / Tools' started by Pops, Feb 26, 2019.

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  1. Mar 1, 2019 #21

    Pops

    Pops

    Pops

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    Don't have to worry about it IF the prop hub drive lugs are threaded. On my VW engine prop hub that don't have drive lugs, I used all metal high temp locking nut and safety wired the head of the prop bolts. There again I use a red paint mark on the nut and bolt to check for rotation of the nut in the pre-flight. Never have had any movement. With the wood prop I check the prop bolts torque about 4 times a year.
     
  2. Mar 2, 2019 #22

    cvairwerks

    cvairwerks

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    Some of the Hartzell props use a hollow pinned castle nut that gets safety wired. The nut is pinned to keep it captive on the hub, but safety wire is used to lock them after torquing. Additionally, the nuts are taller than normal nuts and have no reduced size areas. They look more like a piece of threaded and drilled hex stock.

    Here is what they look like: http://forums.matronics.com/files/2..._The_Hartzell_Constant_Speed_Prop__3__122.jpg
     
  3. Mar 2, 2019 #23

    Toobuilder

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    The Hartzel configuration is essentially a bolt with a removable head so that it can be installed on the compact hub flange, becoming a permanent part of the propeller assembly. In service the nut/stud relationship remains fixed, and the assembly is used as a tension "bolt". The use of safety wire or cable is also not universal - some airframe manufacturers DO NOT require the safetywire or any other locking feature.
     
  4. Mar 2, 2019 #24

    Toobuilder

    Toobuilder

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    There was some discussion earlier about bolt/castle nut setups that should be torqued an appropriate value (one value for tension applications, and another for shear). The discussion stated that leaving these bolts loose makes them part of the bearing surface and does bad things to the fastener and the part - and I generally agree with this. Just for fun I'd like to point out that this "general practice" is sometimes contrary to design. My company has many examples of double shear translating joints that the bolt IS the bearing surface. A speed brake for example- machined double shear bracket which accepts a rod end on the end of a hydraulic ram. The 5/8 inch shear bolt is not only NOT snugged down to firmly capture the rod end ball in the bracket, the bolt is requred to be able to spin "by hand" after the nut and cotter pin are installed. This is one but many examples on this particular airplane design.

    The above is NOT to suggest that its OK to allow bolts to turn in a Cessna or a homebuilt, but only to illustrate that "general" maintenance practices are sometimes contrary to specific design goals.
     
    D Hillberg and Pops like this.

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