Marble Machines as Mechanical Computing Machines

We have been investigating mechanical computing machines during Inventors Club this fall. So natural we wanted to build our own.

Our Explorers group in the morning were working in teams to make a marble machine that would guide a marble from the top corner to the bottom corner of the board. The marble machine got more interesting when the students added circuits into their machines. When the marbles arrived  at the end of their journey they completed a circuit, announcing to the world that their journey was complete.


Afternoon Inventors were also working on the Computing Machines. Their goal was a little more intricate. They were challenged to develop a machine that would count the number of marbles put into the system or do something after 5 marbles were added to the machine.

Adventures in Mechanical Computing - Part 2

The more I read about mechanical computers the more fascinated I become. I wanted to share some of the stories and resources I shared with the Inventors Club students from the Fall session.

To understand what a mechanical computer is we have to think about what a computer is. I think of a computer as a machine that deals with information. You give a computer some input, the computer works with  that information and gives you some information back. If we think about computers in this broad sense we can argue that computers have been around for 1000's of years.

One of the oldest examples is the Antikythera. This machine was a complicated system of gears that would model the motion of the planets and moon. It even predicted eclipses. It is speculated to be the work of Archimedes. It is an amazing feat of engineering. There is a great  NOVA episode exploring this early computer and the story of how a group of scientist reversed engineered this complicated device. It is fascinating!

Charles Babbage often gets credit for designing the first modern day digital analogue computer. Babbage started first on a difference engine in 1822. This machine would calculate polynomial functions by subtraction. Before he completed his device he began to imagine a more sophisticated machine that could perform many more operations. This machine came to be known as the Analytical Engine.

Here are some fun examples of more recently constructed mechanical computing machines.

Binary Adder - This machine is not particularly old, but I still think it is pretty interesting.

The machine uses marbles to add binary numbers together. Each rocker can represent a 0 or 1. Here is a good video describing how it works. 

Another fun mechanical computer is Evil Mad Scientist's giant DigiComp II.  This machines uses marbles, or eight balls in Evil Mad Scientist's case, to do addition, subtraction, or many other computations. 

Our final example of a mechanical computer is a ball clock. In this machine each marble represents a unit of time. Once a minute a new ball would be added to the top of the ramp. Can you tell what time it is according to this clock?

Were you thinking 8:38? Give your self a back on the back. 

Adventures in Mechanical Computing

During the Fall session of Inventors Club we are exploring mechanical computing.

Most of the first mechanical computers were really mechanical counters so that is where we are starting. During the first two weeks of our Inventors Club, we are making a machine that can count marbles. We were inspired by our friends in the Tinkering Studio at the Exploratorium who have been doing some very creative work with marble machines. We took that same basic setup and applied a layer of historical context to create mechanical computers (more on that soon).

The challenge was to input data (a marble) into the upper left corner of the machine and collect the marbles in the lower right corner of the machine. For our older students we gave them the added challenge of "doing something interesting" once three marbles were entered into the machine. Many of our younger students also incorporated circuits into their machines as well.

Each team was given a set of materials(molding, dowels, PVC) to create the track for the marbles.

 The older students had to build the pegboard structure from scratch before they could do anything else. We just gave them the materials and a blueprint.

It was good practice building from a sketch and also served as tool training.

Henry got creative and found other materials from the workshop to incorporate into the machine. At the end of the run the marble activates a motor, spinning a propeller.

Another team collected their marbles into a bucket. Once three marbles dropped into the bucket the bucket would sink and the other bucket would rise.



We were experimenting with a binary digital counter circuit.
We were quite pleased with how well it worked! It gave us some new ideas that we hope to play with soon.