This is a very purpose-specific item... Here's a quick video for a little more info on what this is.
Hoover carpet cleaner (PowerScrub SpinScrub 50), and probably many other models -- the spinning carpet-scrubber part of it stopped spinning.
I found a stripped gear in the turbine assembly was the cause of failure. I modeled a replacement and it fits perfectly; as good as new. It's a super easy repair, about a dozen phillips screws, nothing more.
The gear this item replaces has these characters embossed on it (for search results):
POM< DC2 38558004
Oh, and grease it up nice and good. While you're in there make sure the bearing isn't seized up (jam a screwdriver and give it some good strong turns to break it free)
Printing:
Doesn't need any rim, support, whatever, standard default settings. Obviously print large flat side down. If anything give it an extra perimeter or two for strength.
Use pretty much any material other than PLA (I used PETG and feel good about that decision. Nylon would be an excellent choice).
Grease it up (make sure your grease doesn't eat plastic)
The washer goes on first. Washer is separate for printability reasons, no performance change.
.2mm layer height is probably best