Dr Nim is a plastic, gravity powered computer from the 1960s that plays the game, Nim, against a human player. Recently Michael Gardi made a 3D scale model of Dr Nim, which you can download and print on a 3D printer.
The Amazing Dr. Nim is a toy invented by John Thomas Godfrey and manufactured by Education Science Research (E.S.R., Inc.) in the mid-1960s. It consists of a marble-powered plastic computer capable of playing the game of Nim. The machine selects its moves through the action of the marbles falling through the levers of the machine.
The "game board" is a based on the mechanical Digi-Comp II digital computer (also a Godfrey creation). It has memory switches that hold bits of data. The unit is programmed by lobed levers that affect and are affected by marbles that are released from the top of the game. Three of the levers set the start position. The fourth lever is the 'equalizer' option; if set, the player can win if they play perfectly. The last lever is used to indicate who's turn it is, the human or Dr. Nim's.
Game play is described in the manual that was bundled with the game and can be found here:
There are many good online references for the game. The following video is especially informative and entertaining:
And this article speaks to the relevance of a game like Dr. Nim in today's digital world:
The Dr. Nim offered here is a 2/3rd scale model of the original (.673 to be precise). This keeps the size of the game down to about 210 mm x 205 mm which will hopefully make Dr. Nim accessible to more 3D printers out there (including mine ;-). I have tried to keep the game as true to the original as possible within the constraints of the differing technologies (FDM vs injection molding) and the information available to me. One other concession was to 3D print the folding stand rather than attempting to employ the wire stand of the original.
I did not in fact own an original Dr. Nim when I created this model. The model you see here was developed from pictures obtained online, and from pictures and information graciously provided by Dr. Nim owners. Thank you so much Jaap Scherphuis and Charles E. Leiserson!
Recently I did acquire a vintage Dr. Nim. Upon inspection the only thing I changed was the angle that the game is played at (about 30 degrees) as determined by the Hinge Stoppers.