In article , OM
om@our_blessed_lady_mary_of_the_holy_NASA_researc h_facility.org
wrote:

http://www.meccano.us/differential_a..._da/index.html

...Now, if only I could find that one done with Lego robotics parts
that popped up a few years back.

He also has a Difference Engine, if you prefer digital.
http://www.meccano.us/difference_engines/rde_1/

--
David M. Palmer (formerly @clark.net, @ematic.com)