Yoyo with automatic return mechanism

This yoyo features an automatic return mechanism. When you throw the yoyo hard enough it will go into a “sleeper”, centrifugal forces push the clutch mechanism apart and release the axle. The axle can then spin freely. When the yoyo slows down, the clutch will engage again and to yoyo returns to your hand.

Hardware needed:

• 2 x 8mm steel balls
• 2 x 19mmx7mm springs (I had to stretch mine a bit, maybe longer or stronger springs would be more ideal)
• any type of silicone (I recommend flowable silicone, but I used red silicone gasket)
• 1 x 30mm m4 hex bolt and m4 nut
• o-ring that fits the axle

Print recommendations:

• As many walls as needed so it is completely solid without any type of infill
• Tree supports for the middle part of the clutch side
• Support for the recessed parts of the non-clutch side
• Supports as needed for the clutch arms

Assembly:

• fill the recessed ring of the non-clutch side with silicone. This is used for the Yoyo string to grab onto when you want to return the yoyo manually
• insert the steel balls into the clutch arms
• pop the clutch arms into place. You can optionally secure them with a washer and a self tapping screw in the provided holes, but they stay in place without a screw
• insert the Springs
• insert the m4 hex screw into the clutch half
• slide the axle sleeve over the m4 bolt
• put the o-ring onto the axle (the deeper grove is for the string, so use the other one)
• slide the axle over the sleeve and check if it spins freely
• insert the m4 nut into the other half and screw the halves together. Don't over tighten, otherwise you'll break the sleeve. You can use loctite on the m4 nut to keep everything together nicely
• attach a yoyo string, I recommend to wrap it two times around the axle as shown in the images

Check if the clutch arms can move freely, otherwise sand them a bit. You can also sand the sleeve and the axle and apply a little bit of oil if you'd like. 

Have fun! Here is a simple tutorial on how to throw the yoyo: 

(There are also files for a yoyo without the clutch mechanism, they should work, but I have not tested them yet)

EDIT: Added V2 for one half, where the silicone groove is closer to the center to provide better response.