Radial engines do have one 'master' rod per throw. The other rods on
that bank of cylinders are connected to journals (lower end bearings)
on the master rod.


This might help understand the basics of how all that stuff goes
around:
http://www.aviation-history.com/engines/radial.htm


along with this animation:
http://www.wsaa.net/radial.htm


More explanations and animations:
http://travel.howstuffworks.com/radial-engine1.htm
(see also links at the end of the series of articles)


These are some of the people who sell plans and apparently at least
partial kits:
http://www.cincinnati.com/ageless/


This place seems to have some models, though the link to the aircraft
stuff is broken:
http://www.railwayshop.com/radial_engines.shtml


Some close-ups of innards:
http://www.robart.com/R780/r780con.html


Miscellaneous labors of love with link to a discussion forum:
http://www.engine-museum.com/



Cheers,
--Joe