Machine Kinematics
solved, then drawn
Theme

The thread: The crank is the argument

A mechanism is not a state, it is a relation between an input and an output. The figures are draggable because turning the crank is the explanation rather than a decoration on it.
ABO₂O₄crank (input)couplerrocker (output)crank rocker · residual 0.0e+0positioned by solving, not by drawing Linkages

Four bars and four pins

The smallest interesting machine there is. Four lengths decide everything about it — which link can turn all the way round, how hard it pushes, where it stops and whether it can be assembled at all — and every one of those is a number that falls out of a solve rather than a judgement about a drawing.

 Astroke = 2.000 = 2 × crankpositioned by solving, not by drawing Linkages

The slider-crank

Replace one pin of a four-bar with a slide and you get the mechanism in every reciprocating engine ever built. Its stroke is exactly twice the crank throw and does not depend on the connecting rod at all. Everything else about the motion depends on the rod, including the part that is always described as a sine wave and is not.

All themes