A simple gear set and pegboard I created for a maker day event at the library. I would have preferred to just use something that was already out there, but as is typical for me, I began to want certain features / tweaks, so I just made my own. This was all modeled in TinkerCAD, gears with the gear generator shape.

I wanted:

• something simple, small, light for kids

• a grid / board that supported a large combination of gear connections

• a way to drive gears without turning by hand

• an indicator for direction when turning

Ended up with:

• 5mm spaced grid board

• Works with 10T, 12T, 18T, 20T, 21T, 24T, 30T, 31T, 40T gears (some with tiny spacing error)

• Direction indicator as small hole in gears

• Handle / driver

• PDF activity for kids (8+)

I initially didn't want to use pegs and fully open pegboard holes because I wanted the gears to be standard with hole in the center and no attached peg. So I initially started with a true board of pegs for gears to slip onto, but then realized I would be very limited with gear placement without some deep hubs on the gears to clear the peg heights. So then I moved onto a design with gears that slotted onto removeable pegs with separate c-clips to keep them on (like @osamutake models). The pegs screwed into slots on the board and then c-clips locked the gears onto them. This worked, but then I realized it wasn't so simple for kids, and the print resolution would have to be very fine to ensure threads were clean and c-clips were strong enough for kids to not break them. Kids screwing pegs in and out of the board and snapping c-clips into place, especially if the prints weren't perfectly clean, was going to be a problem.. So finally I reluctantly accepted a pluggable gears design into a holed pegboard as posted (similar to design by @Ioannis Tsar).

The grid spacing evolved from 10mm to 5mm to support more gears. Also evolved from a hexagonal shape initially to conserve space and keep diagonal distances equilateral, but then the 5mm hypotenuses worked well even with small spacing errors, so I kept the grid shape for simplicity.

Only 10T, 12T, 20T, and 30T gear models are included, but if you use the gear shape generator in TinkerCAD (which is very easy to use), you can easily make more gears (18T, 21T, 24T, 31T) that will work with most other gears in the same pegboard. Gears are 4mm thick with a module of 1 and "pitch angle" of 20. The gear peg is 3.25 x 3.25 x 5.5. I tapered it a bit so it is thickest at base and slightly thinner at top so it fits more neatly into the pegboard. The plus mark indention is two 2mm x 4mm x 2mm perpendicular rectangles meshed together.

The handle was redesigned several times. I've uploaded my 3rd attempt, which technically works, but still not driving the gears as well as hoped. Could definitely benefit from redesign. The problem might be the only 2mm insert into the gears.

I had to print about 100 pieces of everything (sans 40T gears), so needed fast prints. Profile defaults to Random seam so seam is less of a hurdle. A grid pegboard at 0% sparse infill, 0.24mm layer print worked fine for me for my event. Gears were printed with 10% infill. A few posts snapped if kids were rough, so consider higher infill for longer lasting model. Sanding posts definitely helps but is time consuming. I would only recommend if you wanted to keep the kit around for a long time. If it's a one-off event, the gears work fine once snapped in and turned a bit.

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