The coupler's motion at 60°
Every point drawn as a stub is a point of the coupler's own plane, and the stub is that point's velocity — solved, not sketched. They all point different ways and they are all consistent with one statement: at this instant the whole plane is turning about a single point, the pole, marked with a cross. It is off this frame at 1.4 coupler lengths from the crank pin, which happens whenever the coupler is close to translating. The arrow through it is the pole's own velocity, which is a quantity about the motion rather than about any point of it, and half of everything in this field follows from its direction and its size. positioned by solving, not by drawing.
The motion, not the mechanismdraggable: crank anglewide
Where it is used
- The mechanism drops out The motion, not the mechanism
- What a coupler point draws The paths points trace
- Every point has a centre The motion, not the mechanism
- The straight-line problem The paths points trace
- Three positions, and a circumcentre The problem backwards
- The circle of points going straight The motion, not the mechanism
- What the fourth position costs The problem backwards
- The other pole The motion, not the mechanism
- Three linkages, one curve The problem backwards
- Where the coupler is turning The paths points trace
- A construction with no arithmetic in it The motion, not the mechanism
- Where the curvature stands still The motion, not the mechanism
- Free to turn and unable to Contacts that only push
- The straightest point there is The motion, not the mechanism
- Where the precision points go The problem backwards
- Four positions brought together The motion, not the mechanism
- Six things a centre is not Drawn wrongly
- The linkage that is only nearly right The problem backwards
- Where a curve has a corner The motion, not the mechanism
- Exact because two circles roll The motion, not the mechanism
- The circle a point stays on longest The motion, not the mechanism
- A curvature is a size with a minus sign The motion, not the mechanism
- How long a pivot stands in for a linkage The motion, not the mechanism
- The linkage, put back from two curves The motion, not the mechanism
- The two numbers are the curves' own The motion, not the mechanism
- The frame seen from the coupler The motion, not the mechanism
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