70 



TRANSPORTATION ON LAND BY VEHICLES:— THE VEHICLES 



A train or a horse moving a load at a fast speed, consumes more power than a train or a horse 

 moving at a slow speed. The drivers of a direct connected locomotive make one revolution for every 

 stroke of the pitman; whilst those of the geared locomotive require, at the will of the constructor, for 

 every revolution, an indefinitely large number of strokes. As a consequence its speed is slow and its 

 hauling capacity is large. Geared locomotives are too slow for long hauls. Their place is the spur 

 line rather than the main line. 



(b) Locomotives should be equipped with:- 



Syphons, to inject water at any branch. 

 Hydraulic jacks. 

 Up-to-date car replacers. 

 Spark arresters. 



Water pumps. 

 Lights fore and aft. 

 Sanders fore and aft. 

 Air and steam brakes. 



(c) "Tractive force" is the weight in pounds which a locomotive, standing on level track, with 

 speed disregarded, can lift, by tackle block and rope, out of a pit. 



It is calculated in pounds as follows: 



/i Tractive 



force 

 equals 



wherein 

 designates 



d-^ X 1 X P 



D 



XO-85 



pounds 



cl 



diameter of cylinder 

 i = length of stroke 

 p = boiler pressure in pounds 

 D = diameter of drivers 

 0'85 = constant factor 



The tractive force should be between Vi and '/,; (average '',) of the weight on the drivers, both 

 expressed in pounds; lest the locomotive is "overcylindered," causing drivers to slip too easily, or "under- 

 cylindered," preventing drivers from slipping at all. 



(d) Hauling capacity:- Hauling capacity is the weight of the heaviest train (locomotive, cars, and 

 their load) which the locomotive can start on a straight track. 



Ordinarily, the hauling capacity of a direct connected engine is: -Tractive force multiplied by 2,000 

 divided by the sum of the frictional and gravity resistance, both e.xpressed in pounds per ton, diminished 

 by the weight of the locomotive. 



Example: -Weight of locomotive, 25 tons. 



Frictional resistance, 8 lbs. per ton. 

 Gravity resistance, 30 lbs. per ton. 

 25 X 2,000 



Hauling capacity 



25 



5X38 

 The weight actually hauled should never exceed 

 Vd of the actual hauling capacity. 



(e) Makes and their characteristics: — 



1. Shay locomotive:— Ihe boiler, placed to- 

 wards the left-hand side of the framework, 

 exceeds that of the standard locomotive by 

 exceptionally large firebox, heating surface, 

 and steam space. On the right-hand side 



of the boiler, three steam cylinders are pront truck of Shay locomotive. Lima Locomotive Works, 



bolted to a bracket. All the eight wheels Lima, Ohio. 



