Simple geared counter (2-digit)?

I searched here to no avail, and have looked online but only seeings designs for sale on etsy and the like - plus they are too complicated and bulky.

I want a simple and compact 2-digit geared counter, mostly flat and with a “10’s” digit that advances by 1 when the “units” wraps around, i.e. counts from 0 to 99.

I have been working on a design similar to this, but it’s not geared to advance the “10’s”, so wonder if anyone here has come across something.
image

This is how I envision the “advance” gearing to work, but I want the digits next to each other like the pic above:
image

I reckon I can accomplish that by having the gears with digits being two stacked/glued pieces.

Oh, it would be advanced once per day on average, so it doesn’t need to be robust. It’s just for tracking use of my sodastream, and I can’t find my post-it notes! :rofl:

TIA!

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Seems to me that you could just make that exact design with the gears sized appropriately so that the number of teeth is a multiple of ten. If it were me I’d offset the middle pinion.

Something like this for the rough design:

The red circles are the numbered faces, the large blue circles are the drive gears, smaller than the printed faces to they don’t hit each other, then the small blue circle is a pinion gear. The green border is a frame, made so the wheels can be turned.

If slim is the goal, I’d look at 1/16" acrylic and use 1/16" pins to keep everything properly placed and act as axles. Should be able to do it in about 1/4" total thickness, less if you do something like a veneer for the printed surface.

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Thx. Thin is the goal, and I have clear 1/16" and black 1/25" (1mm) acrylic. Intended to make numbered rings and gears from the 1mm and use the 1/16" as the back plate, and use 1/8" acrylic for pins that go thru and are glued to the back plate. I also have a nice selection of exotic 1/32" wood that I plan to use for the face. I’m looking to make the whole thing about 2" wide, with just extension sticking out to turn the units (think ship’s wheel…)

Hey @bill.m.davis - what was the smoothest/best non-binding tooth profile you came up with?

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I will say this: acrylic on acrylic has a surprising amount of friction. You’ll probably want to lube it or add slop.

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Slop will be fine, although I also have a good selection of copper, brass and steel rods and tubes, and an assortment of hardwood dowels as well… :thinking:

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…
image

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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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