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Cracked Backplates on propeller hub assembly

mike3715

Member
After investigating some play in my spinner, I discovered two of the four steel plates used to hold together my spinner hub cracked. The crack is near the large stud nuts.

Has anyone seen this issue before? Should there be washers at the base of the stud nuts?

PXL_20220605_013032889.jpg
 
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It’s hard to tell from your picture what model of RV, what prop type, or where the cracks are.
Have you had a dynamic prop balance? It looks like in your picture that the bolt heads are in the aft side of the connection to the backplate bulkhead. Standard practice would have the bolt head on the forward side with a washer, since it’s in fiberglass, but the manufacturers instructions may be different, due to interference issues, etc.
 
It's an RV-7 with a whirlwind propeller. The cracks are indeed tough to see in the photo...they basically follow the an extended line from the nut side that is roughly up/down in the photo.

And yes the prop was dynamically balanced after last install.

Thanks!
 
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Updated Photos and Info

I've attached some better photos. One highlights the crack, one shows things partially disassembled, and the other shows the prop hub info clearly. Note the MacAuley hub used by Whirlwind earlier models.

So I think the mystery is solved. Whirlwind did an overhaul in 2018 and replaced the spinner mounting plate, which is what I believe the cracked part to be. Before they did so, there were washers (you can see in earlier photo). In cracked photo, no washers. While the mounting plate is magnetic/steel, it seems pretty odd to leave off the washers. Looks like I'll be giving them a call tomorrow....
 

Attachments

  • highlighted_crack.png
    highlighted_crack.png
    1.5 MB · Views: 112
  • disassembly2_hub_info_visible.jpg
    disassembly2_hub_info_visible.jpg
    282.5 KB · Views: 91
  • disassembly6_good_comparison_to_cracked.jpg
    disassembly6_good_comparison_to_cracked.jpg
    245.1 KB · Views: 99
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