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I'm trying to find out what this common rotary detent mechanism is actually called. I see them in all sorts of cheap plastic toys, and I'd like to see if I can find them for sale, but I don't know what to search for! I modeled this one in blender for a personal project. If it's not clear in the image, the inner barrel has 4 springs that quantize the rotation of the outer ring. Is this (or something similar) something I could find in bulk, or are they always designed ad-hoc?

detent mechanism

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  • $\begingroup$ Looks like a custom job, some kind variation on a flat radial-finger-spring. Nice shape for an EDM part. You might well find it on Alibaba, but no telling what the vendor would call it. $\endgroup$
    – Pete W
    Dec 30, 2021 at 16:48
  • $\begingroup$ ehcknobs.com/pdfs/Detent%20Knob.pdf $\endgroup$
    – Phil Sweet
    Dec 30, 2021 at 20:17
  • $\begingroup$ @Phil Sweet - Yeah, that's a ball and spring style detent. Serves the same purpose, but I'm trying to reduce my part count, and make it completely from injection-molded plastic. $\endgroup$
    – Adam
    Dec 30, 2021 at 20:32
  • $\begingroup$ If you buy it, the parts count is 1 :) $\endgroup$
    – Phil Sweet
    Dec 30, 2021 at 20:45

2 Answers 2

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The way I understand it, this mechanism performs very much like the notched scroll wheel of some mice.

enter image description here

Although, probably that is not seem to be the same size or transfer the same load as the one you have in your picture.

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  • $\begingroup$ Very similar, yes. I don't need a specific load transfer; that's something I can fiddle with later if need be. It's just meant for a mechanical selector dial with discrete positions, like an old-school television dial, sans the electronics. $\endgroup$
    – Adam
    Dec 30, 2021 at 15:23
  • $\begingroup$ @Adam an unpowered stepping motor can provide the detent feel $\endgroup$
    – jsotola
    Jan 1, 2022 at 0:08
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Pretty sure that is some kind of pawl and spring disconnect. Similar to what gives a bike casette the ratcheting connection, but yours is bi-directional like a ball detent.

Closest cheap thing I could find is a rotary selector switch. It'd have extra electrical connections that you may not want or need. They tend not to have many positions though; I've used an 8 position one that had nice ball detents.

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  • $\begingroup$ It seems that pawls are specifically used with ratchets to prevent rotation in one direction. I can't seem to find a single example of a bi-directional analog, except for a ball detent, but I'm trying to minimize the number of parts I need. I can tell that you understand the functionality I described, and I appreciate the quick reply! $\endgroup$
    – Adam
    Dec 30, 2021 at 14:57
  • $\begingroup$ most common pawls are used in ratchets but term applies to any lever that stops motion- in this case motion between two rotating components. a good bit of design needs to go into these so depending on budget and quantity you may need to just approach a shaft coupler manufacturer. they do tend to have modular reconfigurable designs ready to roll though. $\endgroup$
    – Abel
    Dec 30, 2021 at 15:24
  • $\begingroup$ I think a shaft coupler manufacturer would be overkill in my case. I'm just making a small plastic counter with a numbered disk that rotates under a window. This pawl and gear will be the most complicated part, so if I can find a wholesaler, I could design the other parts around it and have them injection molded cheaply. Plenty of places offer kits of assorted gears and such, but I guess I might have to design this part myself. $\endgroup$
    – Adam
    Dec 30, 2021 at 16:03
  • $\begingroup$ if you're going to injection mold, some already make integrated ones of these in cheap plastic toys. cheap plastic gears are also injection molded. you can also start with a 3d printed prototype; even one at 2X the scale to make it easier to produce. $\endgroup$
    – Abel
    Dec 30, 2021 at 17:41
  • $\begingroup$ Yeah, my plan is to prototype with a 3d printer, then get quotes on injection molding. It just seems like such a ubiquitous component, I'm surprised there isn't anyone that has them in stock by the thousands, like the gear kits you can find at hobby shops. $\endgroup$
    – Adam
    Dec 30, 2021 at 18:13

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