Chris's 3D Printed, Fully Mechanical Computer

This is is a simple, 3D-printable (caveat: It requires some springs, bearings, rubber bands, and nuts/bolts), fully-mechanical computer. It has 3, single-digit base-10 counters for memory, and processes a chain of 10-position punch cards. With the included program, it will compute the first few digits of the fibonacci sequence.

Step 1: Instructions

This is more of a 3D-printable, mechanical computing construction kit, as replicating mine exactly might be difficult, as well as unnecessary.

1. I laser-cut a copy of 'pegboard.dxf' to give me a useful 12"x12" work area with holes cut every 0.5" to mount everything. Mounting things is left as an exercise for the reader (feel free to craft your own solution).

2. We need a way to process instructions! Print out one of these: http://www.thingiverse.com/thing:101077 and assemble it. This will let you drive 10 independent signals based on the cards you give it. Be sure to print out the 'conditional catch' and frame, rather than the 'unconditional' one.

3. Print out 2 copies of the jacquard_base_and_axle_holder, along with 10 copies of the jacquard_base_pulley. It is designed to use a 5/32" brass rod as the axle (same one used in the punch card reader 'griff', and available at hobby stores). Mount the punch card reader to the pegboard.

4. Print out 3 copies of this: http://www.thingiverse.com/thing:101068 - this will serve as the memory for the machine.

5. Secure all three counters to the pegboard so that they are parallel to one another, and have one hole of spacing between them. The zero_detect levers need to all be able to rotate the same shaft.

6. Print out 2 copies of the zd_shaft_frame (these support the zero_detect shaft on both ends, and allow it to rotate freely).

7. Print out two copies of the zd_drive_shaft, a copy of the zd_drive_shaft_end, and a copy of the zd_pulley_shaft_end.

8. Print out 2 copies of the zd_shaft_lever and zd_extended_lever.

9. Assemble the zero_detect drive shaft such that a lever is bolted to the shaft for each counter, and the lever extends above the zero detect arm of each counter. The levers should be in the same orientation such that when any counter is reading zero, the shaft gets rotated. The pulley_end of the zero detect shaft should be near the 'conditional catch frame' of the punch card reader.

10. Tie a string around the end of the conditional_catch lever arm. Through the creative use of pulleys, connect it to the pulley end of the zero detect shaft in such a way that when a zero_detect_arm rotates the shaft, the conditional catch lever gets lifted into position to rotate the card cylinder.

11. Print out like 2 dozen copies of the 'plastic pulley' (or use real pulleys if you can afford them and/or want your machine to work reliably). Print out at least 3 copies of the vertical_pulley_holder (to place beneath the zero-detect arms of the counters).

12. Route the strings from each hook to the ratchet pulling arms of all three counters, as well as the the very end of each zero detect arm on the counters. The layout I used (if you want to be instruction compatible with my Turbo Entabulator) is thus:
D=Decrement, I=Increment, Z=Zero_detect. R1=leftmost counter, R2=Rightmost counter

Left-to-right: {R1D, R3I, R1I, R3Z, R1Z,NOP,R2D, R3D, R2Z, R2I}

Due to the size of the plastic pulleys I was using, and the layout of the registers, I had alternating strings coming from opposite sides of the card reader. The strings should go around the pulleys at the base of the card reader, before being attached to each hook with the M2 set-screws. Each hook should effectively pull straight-up on the string in order to maximize the 'throw'. I found that it works best to tie the string to the ratchet pulling arm, and then make it fairly taught on the setscrew when the hook is in its lowest position.

I used embroidery floss to connect everything, which is generally a terrible idea, but I had it lying around. Something with a little bit of 'give' is nice, as the tolerances on the machine aren't great. Fiddling with the string tension is a big part of troubleshooting this thing.

1. Print out the four instruction cards and lace them together in order (I did this when they were 'in-place' on the cylinder, so that the spacing would be right). If you are facing the card reader with the crank-side closest to you, the embossed instruction numbers should be in the upper-left corner of each card.

An openscad model of the punch card would probably be great to use with the thingiverse 'app creator' thing, but I haven't had time for that yet. Thick cardstock should work fairly well (I think the cards I printed are 0.1" thick), I would think.

1. Turn the crank while humming the 'Powerhouse' song by Raymond Scott and marveling at your very own a 3D-printed, entirely mechanical computer!