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I have built purely mechanical pinball machines before which used score compartments the balls would fall into to keep track of points. I am now trying to find a way to count points without losing the balls, i. e. a mechanical counter that is triggered by the ball.

I should add that I am using simple tools (wood, bandsaw) and want to avoid ready-made parts as much as possible. Also, this is a mini-pinball machine (69 cm x 34 cm), so everything has to be rather small.

I was thinking of building a ratcheted wheel which would be under rotational force (I'm thinking weights as springs don't provide a constant force) and held by a spring-loaded arm. The ball passing that arm should temporarily release the ratchet to advance the wheel by exactly one notch. I have pictures attached of my prototype. My problem is that I need exactly the right balance of forces in order for it to work, which is super fiddly and I probably won't get it to work reliably. Does someone have an idea for a reliable "one-notch-advance"? Will I essentially need to build a clock escapement? Prototype overview Prototype detail

jmagica
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    an escapement appears to be a suitable answer to the low force requirement. – fred_dot_u Oct 15 '21 at 09:13
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    I agree with escapement. Have a look at https://www.youtube.com/watch?v=6Yk3d5S8QTE for some inspiration perhaps – Jonathan R Swift Oct 15 '21 at 14:21
  • Also have a look here https://youtu.be/rjWfIiaOFR4?t=36 . It's made from wood, so it should provide a good template. Detailed plans are at https://woodgears.ca/counter/ – NMech Oct 15 '21 at 14:42
  • Thanks, I'm aware of Mathias' mechanical counter, but it's way too intricate, I'm looking for a very basic assembly. – jmagica Oct 15 '21 at 17:20

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I agree with going for an escapement mech. However, your comment about not wanting to use a spring seems odd, seeing as springs are what power clocks & wristwatches, not to mention a lot of resettable counting wheels like this in electromechanical commercial pinball machines.

So, maybe if installing an escapement doesn't help, consider an "amplifier" analog. That is, the ball rolls against a lever with minimal resistance, which then triggers a secondary mech via level-length or gearing power gain.

Carl Witthoft
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  • Yes, clocks are powered by springs, and the problem needing a constant force caused the invention of the balance spring and that's one of the solutions I thought I might use (buy a used egg timer), I am just trying to use as few ready-made parts as possible.

    Could you elaborate on your amplifier example? How would some gearing create a a counting mechanism? I have actually played around with a pulley-operated "gearing" but I always have the problem that the force coming from the ball varies quite a bit.

     – jmagica Oct 15 '21 at 17:03
  • @jmagica my idea, not at all thought through, was to use either your existing design or an escapement, but to allow the ball to trigger a low-force lever which then, via see-saw effect or some other mechanical method, can activate your counter wheel even if that has higher resistance. – Carl Witthoft Oct 15 '21 at 17:13
  • I'll accept this answer as some more look into the escapement mechanism made me realize that a few tweaks to the shape of my ratchet ("rounded saws tooth") and the "arm" made it work. I took a short video: https://youtu.be/pnwZRcIH9Lg Thanks everyone! – jmagica Oct 15 '21 at 18:34