pipe on the bottom. A small coil of in. pipe, in series with the larger coil, surrounds the oil outlet, in order that these tanks may handle the heavy oil of Kern county. The outlet valve which discharges into a 1% in. pipe, is controlled by a vertical lift rod at tached to a bell crank, the latter being connected to another bell crank on the outside of the front head. It is customary to connect the outside bell crank with some point in the cab by means of a string, so that in case of a break-in-two between engine and tender. the jerk on the string, in conjunction with the spiral spring above the valve, will operate to close the latter. The vertical rod just beside the valve rod, and extend ing through the top of the tank, is a measuring stick. The water compartment has the usual equipment of splash plates and outlet valves, the latter being sur rounded by copper strainers, and discharging into 3 in. pipes leading beneath the floor to the front of the tender.
Some of these improvements and figures shown are taken from data secured in Mexico. Oil has been adopted as a fuel there within the last few years. The arrangements shown are the results of careful investi gations by the engineers, after a thorough study of the most successful oil burning locomotives in the United States and Europe. They are very similar to the ones used today by the leading railways in the United States now using fuel oil. The average cost of chang ing locomotives to oil in Mexico is about $500 gold.
To show typical operating conditions on railroads at present burning oil, the author has gathered the data presented in the remainder of this section. Fig. 65 shows an interesting chart prepared by a rail way company giving the cost per mile for locomotive repairs, and the consumption of oil during the same period.
The front end design of locomotive has an im portant bearing on their economical operation, as the forward chamber is in reality a vacuum pump, which draws the gases and air from the fire-box and tubes and discharges them through the stack. The vacuum created depends upon the size and shape of the nozzle used. The tests recorded below indicate the great difference in efficiency which is secured with different nozzles.
Evaporation Nozzle. Draft per hour Round 10.2 inches 43,702 lbs.
Rectangular 14.6 inches 49,284 lbs.
Elliptical 19.6 inches 58,882 lbs.
The size and length of the tubes also affects the amount of fuel consumed when coal is burned, the longer the tube, the less the fuel used per square foot of grate surface. But since the combustion of oil is completed so much more quickly than that of coal, when a coal-burning locomotive is converted to an oil burner the area of the fire-box must be increased, and the tubes shortened, to attain the highest effi ciency. With this arrangement the temperature of the smoke box gases will be lower than that of the steam, showing that the tubes are absorbing all the heat units available. But in locomotives having long tubes and small fire-boxes, the combustion does not entirely take place in the fire-box, some unburned car bon through the tubes in the form of smoke, and as a result of the low temperature at the rear end of the tubes, this is precipitated in the form of soot. This makes necessary frequent sanding of the flues to remove the soot, and also lowers considerably the evaporation of water per lb. of oil fired.
The accompanying report gives an interesting com parison between passenger locomotives and freighters of the consolidation and mallet types.