I have two gears (main is 48 teeth, driven is 20 teeth, module 0.3). The main gear is rotating in 1/3 of a turn increments, but I need to drive the second gear with only 12 teeth out of 16 of that 1/3-turn.

Changing gear sizes is not an option, I need to preserve their positions and sizes in an existing gear train. I cut a mutilated gear with 6 missing teeth per 1/3 rotation (which gives a desired 4 tooth skip) and made a spring ratchet that holds down the driven gear to preserve the timing/aid re-meshing after the skip, but it is quite noisy and increases wear and load.

How could I improve it without introducing Geneva-like timing hold (also not an option, because the gears are parts of respective compound stacks and already just 0.5mm thick)? Is gradually reduced tooth height in a mutilated gear to aid re-meshing a thing? I'd like to eliminate the hold-down ratchet. The major concern is meshing, not the timing, there could be 1 tooth skip here and there. Secondary concern is complexity of manufacturing, I'll need to modify potentially dozens/hundreds of these gears, machining down the teeth is relatively cheap.

Also, how to properly calculate the mutilated gear? Having those missing 6 teeth mentioned above to skip 4 was just trial and error.

  • $\begingroup$ start and stop the main gear as appropriate. $\endgroup$
    – Tiger Guy
    Mar 11 at 13:30
  • $\begingroup$ @TigerGuy, this option is not available. It has to make full turns but the driven gear should move intermittently, engaging with only 12 teeth out of 16 per each 1/3 of a turn of the main gear. $\endgroup$
    – atzkey
    Mar 13 at 19:20


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