CHAPTER XX 
MOTIVE POWER AND ROLLING STOCK 
A. LOCOMOTIVES 
There are two 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 
150 tons. Saddle-tank locomotives of from 20 to 35 tons' weight 
are sometimes 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, is used on some main line logging roads 
that have sharp curves. It has two sets of engines mounted 
under the boilers, each connected to independent groups of 
driving wheels. The rear engine is fixed rigidly to the boiler 
like 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 cylinders on the front truck 
through an articulated pipe. The forward pony truck is pivoted 
and may swing from side to side, independently of the trucks 
bearing the engines. The cylinders are single or compound 
expansion, and the exhaust steam of the rear engine is used in 
the cylinders of the forward engine, thus effecting a saving in fuel. 
The advantages of this type of engine are that the wheel base 
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