Reid's 6.885 page
Linkages
A braced contraparallelogram
Read about it, or
see it.
Classification of drawable sets
A proof that the sets that can be
drawn by planar linkages are exactly the compact semi-algebraic sets
(plus the entire plane). Also includes a construction for a linkage
which draws the union of two drawable sets.
Optimal linkages
"Proofs" that multiplying an angle by
n requires Θ(log n) bars and the general Kempe
construction requires Θ(n2) bars.
Kempe's theorem paper
Draft of an outline for a paper
describing the "original" proof of Kempe's theorem, as well as some
extensions.
Infinitesimal carpenter's rule theorem
Demonstrations of a algorithm
for finding an infinitesimal motion of a flat linkage.
Explanation of the algorithm.