CHAPTER XX 



MOTIVE POWER AND ROLLING STOCK 



A. LOCOMOTIVES 



There are two general types of locomotives; namely, rod 

 and geared. 



Rod Locomotives. — These have the power transmitted from 

 the cylinders to the drivers by means of a connecting rod. They 

 have a longer wheel-base than geared locomotives, consequently 

 they cannot take as sharp curves, but are the best type for a 

 smooth, well-maintained road of easy grade, and because of their 

 speed are especially serviceable for main-line engines when the 

 haul exceeds 7 or 8 miles. 



Those used for logging purposes range in weight from 20 to 

 115 tons. Saddle-tank locomotives of from 20 to 35 tons' weight 

 are often used on spur tracks, and are more efficient for their 

 size than types with a tender because there is less dead weight 

 for the engine to carry. For main-line work locomotives of 40 

 tons or more are in general use. 



A special form of rod locomotive, known as the Mallet Arti- 

 culated Locomotive, has recently come into use on logging roads 

 that have sharp curves. The essential features are two sets of 

 engines mounted under the boilers, each connected to independent 

 groups of drivers. The rear engine is fixed rigidly to the boiler 

 in the same manner as for the regular pattern of rod locomotive. 

 The forward engine and driving wheels are so attached to the 

 boiler that the truck may have a lateral motion when taking 

 curves. This truck is connected to the rear engine by means 

 of a radial draw-bar and steam is transmitted to the cyhnders 

 on the front truck through an articulated pipe. The forward 

 pony truck is pivoted and may swing from side to side, inde- 

 pendent of the trucks bearing the engines. The cylinders are 



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