LEGO logic gates

Basic boolean logic gates implemented in LEGO.

My friend Rachel did something similar to this, except hers were micromachined silicon, and she actually designed everything in CAD, and the design was an entire ALU. Amazing, no?

Web link of note: LEGO logic gates

Meccano Difference Engine

This guy made the Difference Engine with Meccano parts. The most interesting part to me is how he was forced to adapt the gears to store the decimal numbers Babbage’s designs require:

“Meccano does not provide us with too many examples of tenfold symmetry, so representing decimal numbers is a challenge. Fortunately we can depend on the following two observations. First, by meshing a 95t gear wheel with a 57t gear wheel we get a ratio of 5:3.  This means that 1/10th of a rotation of the larger gear corresponds to 1/6th of a rotation of the smaller one, and we have available the 6 hole bush wheel. This can provide a detent mechanism to hold the smaller gear in one of 6 positions, corresponding to holding the larger one in one of 10 positions. Second, we note that the ratchet wheel has 20 teeth.  Had not this been a multiple of 10, construction of the mechanism may well have been much more difficult.”

Web link of note: Meccano Difference Engine

MIT Differential Analyzer

I remember seeing pictures of this thing in newsreels… not on their original screenings of course.

The Differential Analyzer was MIT’s first computer, built by Vannevar Bush and his students in the early 1930s.

It looks like a table full of car transmission parts… a long glass-covered table with rods running along its length. It is entirely analog- values are stored by positions of rotating gears; there are no cams or ratchets that I remember.

The user interface is a graph- to input values the operator moves a stylus arm to different points on a graph, and the machine outputs another graph.

Web link of note: MIT Differential Analyzer