CATALOGUE OF THE MECHANICAL ENGINEERING COLLECTION. 83 



wheels were made of cast-iron with hollow spokes and rim, which at 

 that time was a remarkable novelty. The section of the spokes was 

 of the old form, and the rim was of very much the same shape as 

 that in use at the present time. Another important improvement 

 adopted in the construction of this locomotive was counterbalancing 

 the weight of cranks, connecting rods, and piston. This counter- 

 balancing was effected by casting the rim of the wheel opposite the 

 crank in solid metal, while the other part of the wheel was made 

 hollow. The importance of counterbalancing was not recognized 

 until several years after it had been introduced by Rogers, Ketcham. 

 and Company, and when attention Avas drawn to it many doubted 

 the necessity of balancing anything more than the crank. 



Cat. No. 180,245 U.S.N.M. 



FIG. 38. ROGERS, KETCHAM & CO. " SANDUSKV '' LOCOMOTIVE, 1837. 



Model of Locomotive Invented by Asa Whitney, TJ. S. Patent No. 1653, 

 June 27, 1840. Transferred from the United States Patent Office. 



To secure greater traction, this locomotive was designed to operate 

 all wheels as drivers. The boiler, cylinders, etc., are secured to a 

 framework supported on two four-wheel trucks. The forward truck 

 is free to revolve about a center pin through the intervention of coni- 

 cal friction rollers traveling through circular arcs, and the rear truck 

 likewise is equipped with rollers that it may conform to the curva- 

 tures and undulations of the track. 



The power of the engine is transmitted to the wheels through two 

 bell cranks and other connecting rods and cranks above and on each 

 side of the boiler to a main central sliaft beneath the boiler on which 



