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The Gear Game


Everyone loves gears - they're amazing little things used all the time to do all kinds of work, but very few people really understand them in an intuitive way.  Here's a video that Nick at Maker Works gave me showing just what gears can do (there's about 6 of these videos total if you're dying for more):

Ok, so how can we make a game which incorporates all the force-transferring amazingness of gears, using relatively simple production methods and/or commercially available parts?  Wooooah buddy, hang on one second -

Prior Art - ie does this already exist?

Good question.  There are a variety of gear based games online and some gear games for kids: - online gear placement, puzzle - online gear placement, puzzle - for kids, not a board game but does involve gears - fun and easy to connect on the fridge, but not a game!

Update! - 1/13/11 - A friend showed me an old game very similar to this concept from the 60s - you can see it here on board game geek.  It's not clear what  the rules are or how the movement of the gears (or their ratio) really relate to game play, or if the gears just make the game look cooler...

Ok, so this are a couple examples from a cursory search, but I couldn't find anything that was fundamentally similar to the concept described above.  So...

Create away!

This is what I came up with.  It's a 15 x 19'' hexagonal peg board, into which 3 sizes of gears fit at (the gear ratios are 1:1, 2:1, 3:1).  Any gear has only six positions which it can touch another gear (the six edges of the hexagon around it).  The board sits off the table, and contains 3 hinged compartments which stores the gears and pegs.  The compartments are held together via tightly friction, no glue required (a neat technique of nothing the acrylic to make pieces hold together at 90 degree angles - really really useful).  The pegs are made from standard lego parts (lego cross axles, whichyou can find on the Pick and Brick website) and are pretty cheap.  The base, compartments, and gears can all be made using a 50w laser cutter in about 1 hour (this includes both rastering and vector cutting).

(top) - most recent board, seeeeeexy black version; (middle) - nice see through hinged doors to store pieces (thanks Kyle for the hinge design); (bottom) using a previous clear acrylic version of the game, examples of the gears (note the rastored edges to reduce friction)


The initial concept for gameplay was the following (this is a summary, but gets the idea across):

A gear is placed along the edge of the board on a corner, and this is designated as the scoring gear.  The goal of the game is to spin the scoring gear around as many times as possible, with each full turn earning the player a point. You can download the Android version of the game.  Selecting from a shared pile of gears (some large, some medium, some small), the first player places a gear in the exact center of the board - this is a shared gear which no one controls.  The next player then places a peg with up to 2 gears on it which must touch the center gear.  Every time a peg is placed, a flag is used to denote which player controls that gear.  The players take turns placing pegs with gears (or removing pegs they control) until a connection to the scoring gear is made.  At this point, the player who made the connection chooses which of their gears (those which have their flags on them) he/she wants to turn ONCE in order to get the scoring gear to turn and therefore score points.  It's critical to pick the right gear to turn - some gears when turned once will score 1 point, while others will score many more points, depending on how they are geared relative to the scoring gear.  Once a gear is scored, it is removed and the next player gets to choose the location of the next scoring gear along the edge of the board.

Production - Ohhhhh the troubles

Making stuff is hard, especially stuff with tight tolerances.  For this project, I used:


50W Epilog Laser Cutter (18'' x 24'' cutting surface)


Lego Cross Axles - these can be found at Lego's Pick and Brick website (started with element ID 4142865, then found that 4508553 worked better which is the picture to the left).

1/8'' Acrylic - You can get this anywhere, but I found to have particularly good prices on black and white acrylic which tend to be a bit more expensive.  The entire board and all gears are made from 1/8'' acrylic.

Gear Sizing
As always in prototyping, there were many problems.  The first interesting one was getting the gears to mesh correctly.  This took a lot of calculating (you can see my calc file below in the "Project Files" section, though it's a big mess and I should have just looked in a book before calculating my brains out, so you have been warned), until I found out that for any fixed tooth size, the ratio of the number of teeth is equal to the ratio of the diameter of the gears.  So, if I want a 1:1, 2:1, and 3:1 gear set, I used a 24 tooth, 48 tooth, and 72 tooth gears.  The gears themselves I initially created on Inkscape's gear program (see picture to the left).  This worked well, but didn't give me enough flexibility.  In particular, because the laser on the laser cutter actually cuts through about 5/1000 of an inch, you have to account for this in the gear design, otherwise the gears will not mesh perfectly.   As a result, I ended up buying a better program from Woodgears, which had more options (like adding "slop" between the gears and some other things).  This allow me to make nearly perfectly meshing gears which only interacted on the board in the 6 desired points on any given gear.


I was warned when I started this that friction was going to be a problem.  With potential gear ratios of 12:1 or higher, even a small amount of friction inhibits movement, and causes jerky motion or works causes gears to slide out of place (vertically).  Chasing down friction was a pain.  First, I created little spacers to lift the gears off the surface itself (little donuts to the right), which helped a lot.  I also made small adjustments to the hole sizes so the peg fit in the holes was snug but not high friction (again, a few thousandths of an inch makes a big difference here).  However, there was still enough friction to cause the gears to tilt and interact between the two gear layers.  After I while, I realized that the laser cutter left a small bump along any edge it cut, presumably where the acrylic melted and reformed.  This bump isn't really visible to the naked eye and is certainly small (maybe a few thousands of an inch), but definitely causes friction.  My solution was the raster (basically burn down about 1/16'' of an inch) all of the edges shave the bump off.  That's why the gears all have a circular ring around the edges (see above picture).   I later learned that this is done in industry by sending the parts through a "tumbler" which presumably knocks them about for long enough to perform the same function.


Lego parts work great.  They have surprisingly good tolerances (better than I could do on the laser cutter).  And yes, you could probably do this whole game with Lego parts, including the board!  I think it's a good idea to pitch to Lego, so if you've got an in please let me know!   I tried less expensive materials (acrylic is 3 - 5 dollars per square foot), but found that the tolerances I could achieve on acrylic were unmatched.  Polypropylene, the cheapest plastic, just melts like wax (and smells like wax) in the laser cutter, so that didn't work.  ABS plastic cut ok, but at a much slower speed than acrylic and is not significantly cheaper.  Wood may be a good option here, but I have not yet tried it.

I also create a storage location integrated into the game board for the gears themselves.  See below:


Scoring means counting how many times a gear turns... sounds easy, but it's actually kind of hard if you're goal is to make as much as possible on the laser cutter.  My first attempt was to count turns the way an old record works - us a pin which tracks in a long path towards the center (see picture).  Well, with these small pieces that really didn't work (see the slinky which I created when the path was too dense and it vector cut instead of raster cut!).  The next idea was to use a Geneva Mechanism (see wiki entry) to convert one full rotate of the scoring gear into a partial rotation of an additional counting gear.  This works fine, but not you need an additional gear which gets in the way on the board.

Ultimately, I create some simple pointer flags, which serve the dual purpose of indicating who controls the peg (by color), and pointing in a certain direction.  The players have to visually count the turns, but at least with the pointer they can be more accurate (I admit, not a perfect solution but it's workable at least in a prototype).

Production Cost and Labor

See "Gear Game Economic Analysis" in the Project Files section below for details of in-house production (using the epilog laser cutter) and outsourced production (using services provided by the many game manufacturers of the world).  Overall, for in-house production on the laser cutter I figure about 18 dollars per unit of materials cost with about 1 hours of total labor time (includes production, packing, and shipping) and 1 hours of laser cutting.

Remaining Hurdles

Creating a Narrative

I was really excited about this game when I started and had some specific concepts about gameplay that I thought were very clever.  However, as I actually played the game, I found that I personally didn't enjoy it that much.  It was clever and interesting, and really made you think, but wasn't that fun.  In particular, it completely lacks a narrative or a story.

Project Files

I use Inkscape for all my vector graphics and The Gimp for non-vector stuff (I know, it's not very professional, but it's open source, free, and works great for me) and Openoffice for all officey stuff (if you can't open them, you can convert them to Microsoft formats easily on so quit complaining, besides Openoffice is free and you should have it anyway <end rant>).

Below files can be found on my public google docs Here.

"Gear Game Final.svg" - Main file for making the board and gears.  This file is .svg.  I have found that at least for the 50W epilog laser cutter, you cannot effectively print from Inkscape itself.  Follow the rules written on the svg itself for laser settings.  Then, select the items you wish to cut, then go to file-->document properties.  Choose the "resize page to content" option with .02'' borders on all sides and click on the "resize.." button.  Once the page is resized, you can go to file-->save a copy and save the file as a  pdf (DPI = 600, and click the "export area is page" box).  Print to your laser cutter from this PDF file.  Note that in the .svg there are several different prints options (don't try to print the whole thing!).

"Gear Game economic analysis.ods" - My quick numbers of cost of production, production quantities for in-house (ie making them one at a time on the laser cutter at Maker Works), or outsourcing in batch.

"Gear Game gear calculator.ods" - Crazy gear calculations which I really didn't need to do.  Just go read about gears on wiki first, or get this great book called "Mechanisms and Mechanical Devices Sourcebook" by Neil Sclater and Nicholas P. Chironis.  It also has lots of good information about gears and many other things.

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