Even before the invention of the Janney coupling a semi-automatic coupling device had been used extensively on passenger cars. But this device which in effect was that of two crooked fingers hooked together, allowed the ends of the coaches to swing and roll in a manner most disagreeable to many passengers. The Janney couplings corrected this, since these couplings in their improved form hold the ends of the cars as in a vice.
A COMPARISON—THE OLD AND THE NEW
Stephenson's locomotive and its tender, when loaded to full capacity with fuel and water, weighed seven and three-quarter tons. The locomotive itself was a trifle over seven feet long. In 1909 the Southern Pacific Railway purchased a Mallet Compound locomotive which, with its tender, weighs three hundred tons, or approximately forty times the weight of the little Rocket. This great locomotive is over sixty-seven feet long, or some nine times the length of the Rocket, and will haul more than twelve hundred tons back of the tender.
THE DEVELOPMENT OF THE LOCOMOTIVE.
The lower figure represents a longitudinal section of a modern French locomotive, for comparison with the sections of the famous engines of 1829. The weight of the "Rocket," with its four-wheel tender which carried 264 gallons of water and 450 pounds of coke was 4-1/4 tons. The French locomotive with its tender in working order, carrying 3300 gallons of water and five tons of coal, weighs 99 tons, and the length of the engine and tender is 56.3 feet.
The cylinders of the Rocket were eight inches in diameter, with a seventeen inch stroke; the high-pressure cylinders of this Mallet locomotive are twenty-six inches in diameter, and the low-pressure cylinders are forty inches. But curiously enough the driving wheels of the two engines show little discrepancy, those of the Rocket being fifty-six inches in diameter, as against fifty-seven for those of the larger engine. The total heating surface of the Rocket was one hundred and thirty-eight square feet, that of the new locomotive 6,393 square feet. To heat this great surface oil is used for fuel, so that the task for the fireman is lighter than on many locomotives less than one-half the size.
On this locomotive there are two sets of cylinders driving two sets of driving wheels on each side, making a total of sixteen drivers in all. From the size of these drivers it is evident that the engine is designed for strength rather than speed, although of course relatively high speed can be attained if desired. On the section of road over which it operates there is a maximum grade of one hundred and sixteen feet per mile, and it was for negotiating such grades with full loads that the locomotive was designed.