...Grasshopper Clockwork
...Inertia Clockwork
.........Gear Cutting
.........Sample Gears
.........Rotary Table
.........Parts Disassembled
.........Escapement Revealed
...Simplicity Clockwork
...Gear Machine Clockwork
...Concentricity Clockwork
...Egg Drawing Machine
...Brown Eggs
...Green Eggs
...Fun With Trigonometry
...The Milling Machine
...Inside the Controller Case
...Rear of Controller Case
...The Interface Board
-ProTrac Support


Designed and built by Ed Legler, 2008.

The Concentricity clockwork was inspired by the work of David C. Roy.

To see David Roy's work:

Concentricity is powered by a two Negator constant force springs and runs for about an hour with a full winding of 22 1/2 turns.  The springs were purchased from Stock Drive Products.  Look for Spring Motors.

The springs provide torque to the wooden gears and ultimately apply torque to the center gear.  A pawl mounted to the inner surface of the center gear locks the center gear and the two spring driven larger gears to the inner flywheel so that it can rotate as a complete assembly.  A pawl mounted to the outer surface of the center gear allows the inner flywheel assembly to rotate clockwise relative to the outer flywheel.  During running mode the inner flywheel assembly rotates clockwise while the outer flywheel rotates counter clockwise.  When they run out of momentum due to imbalance they will eventually both start rotating/rocking backwards.  This backwards motion allows the pawl on the outer surface of the center gear to catch a pin on the inner surface of the outer flywheel.  When it does it causes a momentary recoil of the center gear relative to the inner flywheel allowing the inner pawl to fall from its pin on the outer surface of the inner flywheel.  The springs will then impart torque to both the inner and outer flywheels until the pawl on the inner surface of the center gear once again catches the pin on the outer surface of the inner flywheel.  Both the inner flywheel assembly and the outer flywheel will once again be in running mode.  Running mode generally lasts for about a minute.  The gearing from the large gears to the center gear allow about a third of a rotation of each spring.

The video at right shows the first working prototype of the Concentricity.