String Puller

The objective of this device is to act as a binary mechanical display capable of playing an animation.

The front side is a spandex sheet while the back side is set of 64 cams and followers with strings which pull the spandex surface, producing dimples.

Shown here are some of the outputs from the mechanical display.

Two sequences have been designed:

1) A tree which grows then falls down

2) Exploding squares

The back side showing a chain drive.

An image showing a close-up of the cams and followers.

Careful design enables a tight profile and ease of construction. Almost every piece of the device was fabricated from the same sheet of 3mm acrylic.

Square patterns

Falling Tree sequency.

A Matlab GUI was written to allow the user to design a sequence. It generates all 64 cam curves and outputs them in .dxf format ready to be cut by a lasercutter. An example of an output is provided below.

A A four part piecewise function defines all the cams. The functions are:

0 to 0 (constant radius)

0 to 1 (increasing radius)

1 to 0 (decreasing radius)

1 to 1 (constant radius)

A multiplexer capable of 5x5 = 25 binary outputs using only 5+5 = 10 active components.

Another version of the above; though, greatly simplified.

Ideas stem from another. This is the concept for a mechanical multiplexer which could one day enable thousands of strings to be actuated with only hundreds of active components. In this example 15 spools could be wound with just 3+5=8 active components.

The long term goal is a high resolution (10,000 strings) programmable mechanical display capable of displaying complex 3d geometries rather than just dimples.