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| NanoEngineer-1 Gallery: Universal Joint |
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This model of a universal joint is based on a 1992 design by K. Eric Drexler and Ralph Merkle while working together at Xerox PARC. This first animation loop (above) was created from a NanoEngineer-1 molecular dynamics run. It is the first nanomechanical simulation done on the universal joint. The simulation shows the results of the universal joint in which the shafts are bent at 20° relative to each other.  This animation shows the results from another simulation run in which the shafts of the universal joint are bent at 40°. This animation has been slowed down to make it easier to view and understand the hinge dynamics .  Two rotary motors, shown in the image above, are connected to a set of atoms in each shaft and have the following parameters:
 This image shows the universal joint displayed in lines mode. This provides a clearer look at the two rotary motors and how they are connected to the atoms in the shaft. In these images, the shafts connected to the hinge of the universal joint are bent at 20°. I used the following parameters for the molecular dynamics simulation shown in the two animated GIFs above:
The simulation took almost exactly 24 hours to complete on my Dell laptop.  This pair of images show the newer design (left) next to the original design (right) by Drexler and Merkle. The new version contains roughly %55 of the atoms of the original, which makes a big difference when running molecular dynamics simulations on your laptop like I do. This was the primary motivation behind trimming down the original model. Dr. Merkle provides this background about the original universal joint: The design was part of an effort to design molecular machines that have no sliding parts. Like the buckling logic, it has only bending and flexing, eliminating any concerns about sliding motion causing some mysterious problems (recall that people were more skeptical of molecular machines back then). It was originally designed on PolyGraf from BioDesign (later to become MSI).A universal joint is a joint in a rigid rod that allows the rod to 'bend' in any direction. It consists of a pair of ordinary hinges located close together, but oriented at 90° relative to each other. Universal joints are common wherever a driveshaft needs to turn a corner; a driveshaft with a universal joint can freely rotate through the universal joint, and no gears are required to couple the two ends. The most obvious example of this application of a universal joint is in the driveshafts of automobiles, a technology known as the Hotchkiss drive. - Mark |
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