Tetherball Spinner

I got a tetherball for my dog for play. It works great and he loves it! The problem I encountered was that when he'd get the tetherball rope wrapped around the pole (which is obviously the goal when you're actually PLAYING tetherball), he had the ball captive and could actually bite/puncture the ball.

Rather than continually replace the tetherball, I designed a “pole topper” that spins freely around. So, the tetherball can swing around the pole freely in the same direction indefinitely. So far, it works very well to wear out my dog and preserve the tetherball.

The hardware required is a bit of a mixed bag determined by what I had easy access to. I've uploaded the model files in addition to STLs so that you can adapt to your particular tetherball pole and/or hardware.

What You Need

As designed, the model is intended to work with the GoSports Tetherball Game Set, available on Amazon. In addition to the tetherball set itself, I used:

• (3) 5/16-18 x 1.5" -OR- M8-1.25 x 40mm stainless steel bolts
• (1) 5/16-18 -OR- M8-1.25 eye bolt - I use a 5/16" x 5" - longer generally works better as it gives more leverage to spin the top!
• (6) 608 bearings - preferably sealed for outdoors
• (4) #10-24 x ¾" stainless steel flat-head machine screws
• (1) 5/16-18 x 2.5" -OR- 8mm-1.25 x 50mm stainless steel carriage bolt
• (1) 5/16" -OR- 8mm-1.25 stainless steel nylon lock nut
• (3) 5/16" -OR- 8mm stainless steel washers

I found that printing at 101% scale gave good clearance with the hardware. Your results may vary.

Printing

I printed at 0.2mm layer height. I enabled supports touching the build plate only for the spinner and pole topper to help with the bearing cavities. For the “pole topper” part, print with extra walls for the surface on which the spinner bearings roll. If printing in the orientation of the provided file, that's extra bottom walls. I printed with 16 bottom walls (3.2mm of walls before starting infill).

I scaled to 101% before printing which seems to provide good clearance for hardware with my printer. In particular, the pole topper clearance was just about perfect at this scale … I had to press the bearings in with a vise but they were easy to press in.

I printed mine using PLA because I wasn't sure how well it would work. But since this is intended for outdoor use, PETG or something else is probably a better choice than PLA.

Assembly

Print one of each: spinner, pole topper, and bottom bracket.

Insert a 608 bearing into each of the four cavities in the spinner and secure by threading a bolt through each (at least one of these is an eye bolt).

Insert 608 bearings into the top and bottom of the pole topper.

Insert the 5/16" carriage bolt through the top of the spinner, then through 2-3 stainless washers (to take up the space between the spinner and pole topper), then through the pole topper top/bottom bearings, then secure with a washer and lock nut.

Untie the tetherball from the rope attachment ring on the top pole. You will attach the rope to the spinner instead once assembled.

Slide the bottom bracket over the pole from the bottom until it rests against the bottom of the rope attachment ring.

Set the assembled spinner/topper on top of the rope attachment ring and line the holes up with those on the bottom bracket.

Secure the bottom bracket to the pole topper using the four machine screws.

Tie the tetherball rope to one of the eye bolts and adjust the rope length such that your dog can't actually get their mouth on it easily. It seems to work best when the dog has to jump up (front paws off the ground) to get to the ball.