In the October 2008 issue of Farm Collector, on pages 27 and 28 there is a picture of a "Common Sense" tractor belted to a "machine."
A machine is a contrivance that does some kind of work. This "machine" is in fact a prony brake, which is used to measure the output of an engine such as the tractor. The belt is driving a cylinder to which is clamped a simple brake. It transmits the torque through the bar to the scale under the end. The torque is then read off as pound/feet (foot-pounds) and can be converted to horsepower.
On page 4, concerning the Junkers opposed-piston engine, the diagram shows a cutaway of a 4-cylinder opposed-piston engine with two crankshafts. The accompanied diagram, though vague, seems to show one cylinder of a sleeve-valve engine with only one crankshaft. The two are entirely different engines. Although it is possible to combine them, each one is complicated enough that I doubt that would be done with any farm machinery.
Paul J. Meketa, 1645 Samedra St., Sunnyvale, CA 94087