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. =C. BENZ. SELF PROPELLING VEHICLE. No. 385,087. Patented June 26, 1888.= [Illustration: 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.]