Редактирование: Molecular Machinery (раздел)

===Universal Joint===

{{Molmac
| Image = UniversalJointAnimation1.gif
| Author = Mark Sims, based on a 1992 design by [http://e-drexler.com/p/idx04/00/0404drexlerBioCV.html K. Eric Drexler] and [http://www.merkle.com/ Ralph Merkle]
| Date = May 25, 2006
| ComponentNumber = 3 (which form a single covalent structure)
| AtomNumber = 6,622
| Width = 4.0 nm
| Height = 4.0 nm
| Depth = 6.4 nm
| FileName = UniversalJoint
| Extension = mmp
}}

This molecular model of a [http://en.wikipedia.org/wiki/Universal_joint universal joint] is based on a 1992 design by K. Eric Drexler and Ralph Merkle while working together at Xerox PARC. The animation loop (above) was created from a NanoEngineer-1 (NanoDynamics-1) MD simulation run. The animation shows the results of the universal joint in which the shafts are bent at 40° relative to each other.

Two rotary motors, shown in the image above, are connected to a set of atoms in each shaft and have the following parameters:

* Torque: 1 nN-nm
* Initial Speed: 0 GHz
* Final Speed: 50 GHz

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 to create the molecular dynamics simulation shown in the two animated GIFs above (which took ~24 hours to complete on my Dell laptop):

* Frames: 2000
* Steps per frame: 10.0 femtoseconds
* Temperature: 300

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:

<blockquote>''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).</blockquote>
''

<blockquote>''You can check out pictures of two variants at http://www.zyvex.com/nanotech/visuals.html which has both a pure hydrocarbon design, and a design with N and O terminations of the surface (in addition to H termination).''</blockquote>

''- Dr. [[Ralph Merkle]]''

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.