Nanorex, Inc. - NanoEngineer-1 Gallery: MarkIII(k) Planetary Gear

NanoEngineer-1 Gallery: MarkIII(k) Planetary Gear

Name: MarkIII(k)
Designer: K. Eric Drexler
Date: 2004
Number of components: 12
Number of atoms: 3,853
Width: 4.2 nm
Height: 4.2 nm
Depth: 4.2 nm
Gear Ratio: 45:16
Speed Ratio: 2.8125:1
Output Torque: > 1x10^–18 m-N
Angular Speed > 10 GHz
Power > 1 nW
Power Density > 10 GW/cm²
Efficiency > 99.8%

This is the MarkIII(k), a planetary gear created by K. Eric Drexler. A planetary gear couples an input shaft via a sun gear to an output shaft through a set of planet gears (attached to the output shaft by a planet carrier). The planet gears roll between the sun gear and a ring gear on the inner surface of a casing. The animation below was produced from a NanoEngineer-1 molecular dynamics simulation. A section of the casing atoms have been hidden to expose the internal gearing assembly.

Planetary gears are attractive targets for molecular modeling because (with careful choice of planet numbers and sun- and ring-gear symmetries) the overall symmetry of the system virtually guarantees low energy barriers along the desired motion coordinate. They also pack considerable complexity into a small structure.

Planetary gears are common mechanical systems used for speed reduction (= torque multiplication). Macroscale versions are found in automobile transmissions, electric screwdrivers, and Mars landers.

The MarkIII(k) gear updates an early 1990s design by Drexler and Merkle, modified to reduce interactions between the sun gear and the bases of the planet gears. The original version was designed with very small moving parts in order to fit the computational constraints of the time. The planet gears are near the lower limits of diameter for functional gear components, and because of this, the "gear teeth" in this system are better thought of as smooth, low-amplitude corrugations in the gear surfaces.

The single covalent (sigma) bonds linking each of the nine planet gears to the carrier gear are easily seen in this POV-Ray image.

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