Figure 7.—Drawing showing principle of the Atkinson engine; this feature
is what the Duryeas were trying to achieve with their free-piston engine, by
substituting the free piston for the unusual linkage of the Atkinson.
(Smithsonian photo H3263-A.)
Figure 8.—Drawing of 1885 Benz engine, showing
similarity in general appearance to Duryea engine. From
Karl Benz und sein Lebenswerk, Stuttgart, 1953.
(Daimler-Benz Company publication.)
The Ames plant customarily had a summer shutdown during August; thus, during August of 1891 Charles and Frank had access to a nearly empty plant in which they could carry on experiments and make up working drawings of the proposed vehicle. It cannot now be conclusively stated whether any parts were made for the car during August or the remainder of the year. It is more likely that the brothers attempted to complete a set of drawings. Frank Harrington, chief draftsman at Ames, may have helped out at this time; from Charles' statement of April 14, 1937, it is learned that he did prepare drawings during 1892.
Figure 9.—Illustration from U.S. patent 385087,
issued to Carl Benz, showing the horizontal plane
of the flywheel, a feature utilized by the Duryeas in their machine.