S.C. Suction Stroke' 

 C.W. Compre 

 W.K.Wor/Cln</ Stroke 



FS. Extiaust Stroke 



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.) 



carriage, explained his reason for changing this 

 feature in his U.S. patent 385087, issued June 26, 

 1888: 



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.) 



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 contrib- 

 uted 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. Vet he did re- 

 ject the bevel gears used by Benz, which might well 

 have been retained, as Frank was later to prove by 

 Pesigning 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 counter- 

 shaft 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. 



The Ames plant customarily had a summer shut- 

 down 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. 



Duryea, op. cit. (footnote 5). p. 6. 



Paper 34: the 1893 duryea automobile 



