business. Sinclair erroneously states that Whetstone's valve gear 

 used "a small return crank" (an outside-mounted eccentric crank), 

 when actually a single eccentric for each cylinder, mounted as in the 

 usual Stephenson motion on the forward driving axle inside the frame, 

 drove the valve in combination with the crosshead. ^^^^ Many years 

 later, at the suggestion of Coleman Sellers, Whetstone prepared a 

 precise mechanical description of this valve gear which appeared 

 in the Journal of the Franklin Institute. ^^'^ (The following account is 

 based on this article and pertinent extracts are reprinted as Ap- 

 pendix 3.) 



Whetstone developed his form of the radial valve gear while 

 working with the Sellers on the grade-climbing locomotives for the 

 Panama Railroad in 1851 and 1852. Because the highly complex 

 grade-climbing machinery entirely occupied the space between the 

 locomotive frames, preventing the usual placement of four eccentrics 

 on the front driving axle, a conventional hook or link motion was 

 impossible. Therefore W^hetstone devised a valve gear which re- 

 quired only two eccentrics on the forward driving axle; all other 

 parts were mounted outside the frame. 



This motion was used on the two large Sellers grade-climbing 

 engines (see p. 84J built for the Coal Run Improvement Railroad 

 and on many other locomotives built by Niles & Company. To 

 my knowledge, however, it was not employed by any other builders. 

 In April 1854 W^hetstone also devised a practical system for the 

 layout of Stephenson link motions so that the admission and cutoff 

 were absolutely uniform in every position of the link, whether for- 

 ward or in reverse. ^^^^ This was accomplished by preparing a series 

 of full-size layout drawings and reapportioning each part of the 

 mechanism until it would cut off square at all points. This graphic 

 layout was further checked by the construction of full-size, adjust- 

 able working models. This method was followed for each class or 

 new design of engine built and, when completed, the layout and 

 model could be followed for any other engines built on the same 

 plans. With this method tedious and makeshift adjustments or 

 alterations on engines being fitted up in the shop could be avoided. 



^^^ Development of tlie Locomotive Engine, pp. 362, 457-458. 



155 (February 1882), vol. 113, pp. 106-117. 



156 Coleman Sellers' journal, April 13, 1854, Peale-Sellers papers. 



102 



