engine is not a "vacuum" engine, it is a "beta" type stirling engine.
Beta means that the power piston and the displacer are both working in
the same cylinder. This arrangement gives greater power output than the
typical two cylinder engine. The reason for this is that the
compression ratio can be higher due to less "dead" space inside the
The Duplex Vacuum Company of Chicago, Illinois made this type of engine
about 100 years ago. They were widely used in popcorn wagons and to
operate dental drills among other applications due to their silent
operation and reliability.
A unique feature of the Duplex engines is the oscillating shaft and
linkage which produces an interesting motion in operating the displacer.
The plans set consists of 8 sheets of drawings and 2 sheets of
construction and assembly notes.
Bore: .750", Stroke: .750", Flywheel
Dia.: 3.750", Height: 10-5/8" Experience
(1) Graphite rod to make piston, (2) 3/16" ID x 3/8" OD x 1/8" thick
precision ball bearings. Materials
set sold separately.
would like to thank you for all your years of coming to the PRIME
Exhibition, you were always one of the most popular builders and your
work is so beautiful." - Ram Meier, PRIME Expo (Eugene, Oregon)