Back in Chicopee again, Charles began planning his first horseless
carriage. Frank later stated that they leaned heavily on the Benz
patents in their work;[8] but while the later engine and transmission
show evidence of this, only the Benz manner of placing the engine and
the flywheel seem to have been employed in the original Duryea plan.
Charles reversed the engine so that the flywheel was to the front,
rather than to the rear as in the Benz patent, but made use of Benz'
vertical crankshaft so that the flywheel rotated in a horizontal plane.
Previously most engines had used vertical flywheels; Benz, believing
that this practice would cause difficulty in steering a propelled
carriage, explained his reason for changing this feature in his U.S.
patent 385087, issued June 26, 1888:
In motors hitherto used the fly-wheels have been attached to a
horizontal shaft or axle, and have thus been made to revolve in a
vertical plane, since the horizontal shaft is best adapted to the
transmission of power. If, however, in this case we should use a
heavy rotating mass, corresponding to the power employed and
revolving rapidly in a vertical plane, the power to manage the
vehicle or boat would become very much lessened, as the flywheel
continues to revolve in its plane. I therefore so design the
apparatus that its crank shaft x has a vertical position and its
fly-wheel y revolves in a horizontal plane.... By this means the
vehicle is not only easily controlled, but also the greatest safety
is attained against capsizing.
To the Duryea plan, Benz may also have contributed the idea for
positioning the countershaft, though its location is sufficiently
obvious that Charles may have had no need for copying Benz. Charles
wisely differed from Benz in placing the flywheel forward, thus
eliminating the need for the long driving belt of the Benz carriage. Yet
he did reject the bevel gears used by Benz, which might well have been
retained, as Frank was later to prove by designing a workable
transmission that incorporated such bevel gears. The initial plan, as
conceived by Charles, also included the details of the axles, steering
gear, countershaft with its friction-drum, the 2-piece angle-iron frame
upon which the countershaft bearings were mounted, and the free piston
engine with its ignition tube, since hot-tube ignition was to be
employed. No provision was made, however, for a burner to heat the tube;
nor had a carburetor been designed, though it had been decided not to
use a surface tank carburetor. The plans called for no muffler or
starting arrangement.[9] Many engines of the period were started simply
by turning the flywheel with the hands, and Charles felt this method was
sufficient for his carriage.
[Illustration: 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.)]
[Illustration: 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.
[Illustration: C. BENZ.