Visible Works: A Mechanical Cabinet

Visible Works: A Mechanical Cabinet

Ancient Mechanics, Contemporary Controls and a touch of whimsical elegance.

This odyssey starts with Extravagant Inventions: The Princely Furniture of the Roentgens, an 

Exhibit at the Metropolitan Museum of Art (Oct 30, 2012- January 27, 2013).  The Exhibit featured the work of Abraham and David Roentgen, 18^th century furniture makers who sold their work to the likes of Marie Antoinette, Catherine the Great and other royal houses of Europe.  Their work is visually stunning.  But it was the “automata” that they incorporated into their work that seduced me.  There are drawers, secret compartments, easels, and game boards that fly open with the push of a button or the twist of a nob.  A good illustration is their Berlin Cabinet.  

I spent too much time studying their work, in particular, the mechanisms they used.  The Roentgens

made it hard on me.  They hid their mechanisms.  I decided to make a piece in which the mechanics would be quite visible; indeed, the mechanism would be the featured element of the piece.  The work of the Roentgens was elegant, elaborate and complex.  Lacking their talent and resources, I decided to go for elegant but simple.  The motive power for the Roentgens was springs and weights I decided on a small electric motor controlled by a microprocessor.

I had little background for what I wanted to do so there was a lot of learning and many new kinds of technical and design decisions.  There are a number of ways to convert circular motor power to the linear action needed to control a drawer. I decided on involute gears and a rack.  This led to an extended detour to learn about the geometry of gears (involute gears have complex shaped teeth) and how best to fabricate them in wood.  (The easiest and most reliable method for cutting these intricate gears, that I found, is on the table saw!) 

I also began playing with and learning how to program and use a small (2 3/4” X 2 1/8”) microprocessor, an Arduino.  The microprocessor mediates between the user’s signal to open or close the drawer at a particular speed and the direction and speed of the motor.  A ship’s old fashioned Engine Order Telegraph (chadburn) serves as the inspiration for the user control and a small potentiometer is hidden therein. The Arduino also controls LEDs and responds to switches indicating when the drawer is fully extended or closed by turning off the motor.  Everything is powered by a 9 volt battery. 

A variety of esthetic design decisions loomed throughout.  I decided on a single drawer on curved legs (bent laminations).   Mechanical visibility was paramount so the gears reside on the top of the cabinet as does the controller and the motor housing.  Power from the motor is transmitted to the gears by a visible leather belt; the belt tension is adjusted via a visible wooden screw.  The sides of the cabinet are open and all but the back of the drawer is visible as the drawer opens and closes; the adjustable rack is fully visible on one drawer side.  To further enhance visibility I used contrasting woods:  The cabinet and legs are dark (walnut) and the mechanical components are light (olive ash burl veneer).  The piece that emerged has a kind of “Hugo Cabret” sensibility.

The need to hide some components raised additional design questions.  As much as I wanted to draw attention to the mechanical aspects of the piece I also wanted to hide the electronic substrate.  The electric motor and the potentiometer (to control speed and direction) are hidden in small cabinets.  To make these components accessible the cabinets are held down with rare earth magnets.  The Arduino, a circuit Board and the battery are hidden in a small box fixed to the underside of the top.  (The back of the drawer is placed sufficiently back from the end to of the drawer to allow the drawer sides to hide the box when the drawer is closed.)  The wires are hidden in channels cut into the underside of the top.  There are 4 hand tightened screws holding the top to the cabinet.  Thus everything under the top is accessible by removing the screws. 

This piece is a far cry from the work of the Roentgens.  It is not nearly as grand in scale, as sophisticated in workmanship and design or as opulent.  Perhaps, however, it has some visual grace.  And, if you like to know how things work, you may even find a bit of charm in this whimsical display.

(Click HERE to see a video showing the piece coming together and doing its thing!)

Wood:  Walnut, curly maple, olive ash burl veneer

Other materials:  Leather belt; electronic components including, Arduino computer, potentiometer, electric motor, switches, LEDs; metal fittings such as sleeve bearings, axles, hubs.

Finish: Wipe on Poli over shellac.

Dimensions: (Depth x Width x Height): 171/2” x 141/2” x 40”