Sunday, October 05, 2008


Notes on the Sarrus linkage

During the 18th and much of the 19th centuries accurate guide rails for machinery were simply not available. For that reason, the machines of the First Industrial Revolution tended to rely on linkages rather than guide rails. James Watt of the Watt steam engine fame, designed one of the first practical linkages for providing straight line guidance for his engines. Watt's linkage was followed by a succession of other, different approaches. In my opinion, the Peaucellier linkage is easily the most elegant.

It has seemed to me that a self-replicating 3D printer might well utilise linkages, which are easier to construct, rather than accurate guide rails

The problem with most of the linkages is, however, that they are 2D. By the time you either reinforce them to provide guidance in three dimensions they become either complex or bulky. For that reason, I've long been enchanted by the Sarrus linkage.

I've found watching it move is positively hypnotic. Since commissioning Tommelise 2.0 and carrying it over to production work I've had some time to consider what sorts of concepts belong in a third generation Tommelise. Of course, the Sarrus linkage came up almost immediately.

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If you can get it to work, a Sarrus linkage based RepRap would be great - chiefly because, in theory, the linkage itself could be reprapped, whereas you could never hope to do that with the metal bars currently in use.
Yeah, that was my idea. Problem isn't the linkage per se but the hinges.
It seems like the hinges could be reprapped with the classic teardrop through holes (of course there's been some cheating on the overhang rules I notice :3) and then use (greased) reprapped pins...

Of course all that depends on the scale...
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