No, I mean the teeth, I got the pivot axles working really well on one project I did, but the teeth would want to grab each other in a bad way. I didn’t want to be on the hook for lube, so slop it was.
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Love it. Simple but functional.
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For the gear for counting like this, I would probably try a Geneva wheel (instead of a traditional gear).
Example found in this thread:
Have the “ones” digits on the first wheel and the “tens” digits on the other.
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Brilliant! Thanks, I knew you’d be the one to ask!
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I wanted to make one too. I found out the first step was to make a geneva gear.
There are few designs for 3d printing. Auto Counter with rollover by FidelioScorpio - Thingiverse
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I REALLY want to make one of these. But I already have (at least) two other projects I am trying to finish first…
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I found round teeth to work best for acrylic.
I would use a single tooth on the singles wheel and ten teeth on the tens wheel. That way when you make one full rotation of the singles wheel the tens wheel moves one place.
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I have the design pretty much done using a geneva mechanism, but I spotted some minor irregularities with a couple of components, and should have included the digits early on vs. trying to align everything when the rest is done. I’m going to re-draw it with those corrections, then cut one. It’s so small, I’m not concerned about making test parts first. The only except will be the face plate, that will be from one of my exotic hardwoods - nothing passes thru the face plate - the gear pins will recess slightly into an engraved depression, so I can make the face from anything (likely a scrap of acrylic or draftboard) and tape the front to the rear just to validate the mechanics.
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FWIW I switched my design of a pendulum clock I am working on from wood and MDF, to acrylic on account of the warping of the gears. I have not had any trouble with the acrylic gears as long as the cut speed and power leave the face of the cut polished and not streaked. For such a small proyect you could even polish the acrylic gear faces with a quick pass with the flame of a lighter.
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Makes sense for a clock which runs continually and requires very low friction, but this will be powered by hand, turn ~1 revolution every 10 days for the first digit, and 1/10th that for the “tens”…
I’m trying to work in a simple way to make the first digit “ratchet”, so it lightly clicks into place. I have three ideas, one will require no additional thickness…
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11 magnets would work but thickness is an issue. Hmm, curious to see what you are thinking.
Very crude outline of what I thing will work. The teeth will be on the numbered dial, and very shallow…
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This was my experience also. Acrylic gears worked so much better than MDF or plywood. Though plywood was better than MDF.
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Oher than the face plate, this will be all acrylic - although for the axles I am going to use aluminum tubing. I had selected a hardwood dowel (I think walnut) but then spotted the tube and it’s almost identical diameter (3.5mm.) I have needle files, including a tapered round, to soften the inside of the gears if needed, and possibly the mating gear profiles if I think it’s needed.
Again, this will be powered by a small nudge of a finger typically once daily, so I don’t think friction will be an issue.
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Any thoughts on the ‘spring’ for the ratchet design I posted?
I have some 1/64" plywood and was thinking of cutting a 1mm strip from that, turned sideways. The range of motion required should only be a mm or two. The arm would then be straight, and I’d glue a half-circle to glue to the end to engage the gear. The 1/64" ply is unfinished, so any number of adhesives would work - probably just use regular wood glue or CA.
Also going to use rings of vinyl as spacers to give me a tiny bit of wiggle room. I have many to choose from but I have some that is as thin as a sheet of paper.
I had better luck with a gravity-fed ratchet, but I don’t think that fits your need here.
I needed strength and was mounted vertically. I think the method you talked about should work. I have done that style before also and it should meet your need.
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Although I suspect your design(s) used thicker material, what did you use for a spring? I would have liked to use a steel spring and ball-bearing, but not much to choose from that’s 1mm in diameter… 
I just cut a small test sample from the same 1mm acrylic and although it flexes just fine, I doubt it would hold up like the 1/64mm ply…
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I was using medium clear acrylic or thick green-glass acrylic. Your materials are thinner, but your design shouldn’t require as much resistance as mine did either. I did have this balanced, using it on each side of the gear, not just in one place.
Are you looking for a nice stop indicator, or are you wanting it to prevent it from going backwards?
The spring was just an arced acrylic arm.
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Yes… it will need to be reversible.
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