Talk:Sarrus linkage

Talk
Various things confuse me. 81.131.19.118 (talk) 08:57, 10 September 2010 (UTC)
 * What's a "reference guideway"? Is that like the groove that holds a piston in place?
 * Why would it be desirable to avoid having one of these?
 * "Two perpendicular hinged rectangular plates positioned parallel over each other" - isn't perpendicular a direct contradiction of parallel? I guess they're perpendicular to the other (unmentioned) plates, or to the linear motion, but I don't like having to guess.
 * Why do all the six plates in the animation have large round holes in? Perhaps the idea is to make the illustration clearer, but I thought at first that perhaps things are supposed to fit in the holes, so in fact the holes make the illustration less clear by being distracting.
 * What's so three-dimensional about a space crank, or planar about the Peaucellier–Lipkin linkage? (Manually redirecting "space crank" to crankshaft doesn't help, since that article doesn't discuss 3D vs. planar.) The P-L linkage must be somewhat 3D, so the bars can move over one another. An ordinary steam-engine crank mechanism could be made similarly flat. What's the difference?

The P-L linkage is considered 2-D because its entire operation can be described with only X-Y coordinates. The Sarrus linkage requires at least one pair of hinge plates to occupy a Z coordinate.

What makes the Sarrus linkage less known is that it is not rigid in practical use. Instead of depending on in-plane loads between the pivots it requires torsion resistance from flat plates. Flat plats are relatively not stiff in torsion, leaving this a curiosity with limited practical application. Even if the hinges are interference fit, the flexure of the hinge plates will allow excess rotations and translations between the stages. Three d dave (talk) 16:16, 25 April 2015 (UTC)