512 



LOCOMOTIVE, COMPRESSED-AIR. 



same size as the upper ones, with which there 

 is a frictional contact. There being no resist- 

 ance, when motion is communicated to the 

 upper wheels, the same motion is transmitted 

 to the lower ones by friction. The contact 

 between the main driving-wheels, which are 

 actuated by the machinery, and those which 

 draw the train by the force communicated to 

 them, is not at the outer periphery of the latter, 

 which runs on the rails, but at a second tread, 

 which is much smaller in diameter. By this 

 device, although the circumference of the two 

 wheels is about the same, the wheel which rolls 

 over the rails revolves more rapidly than the 

 upper one, which turns synchronously with 

 the strokes of the piston. 



To prevent slipping, an air-pump is employed, 

 which is operated from the cab, and which acts 

 on a system of levers, by means of which the 

 frictional contact between the upper and lower 

 drivers is diminished or increased, as occasion 

 may require, without disturbing the bearing of 

 the lower wheels on the rails. The engine is 

 also provided with an equalizing truck, so as 

 always to preserve the bearing on the rail. The 

 parts are so arranged that the center of gravity 

 of the locomotive will not be so elevated as to 

 render it liable to leave the track in turning 

 curves. 



An increase of the speed of locomotives as 

 ordinarily constructed can be attained only by 

 an enlargement of the driving-wheels, or by 

 an increase in the number of the strokes of 

 the pistons. To enlarge the drivers beyond a 

 certain limit is found objectionable, since by 

 so doing the center of gravity of the locomo- 

 tive is so elevated as to cause a swaying or 

 gauge motion, and the locomotive is liable to 

 leave the track, especially on curves ; and it is 

 found impracticable to materially increase the 

 number of reciprocations of the piston, except 

 at the expense of fuel and the straining of the 

 boiler to carry steam at such a pressure as to 

 overcome the expansion of steam in the cylin- 

 ders. 



By means of this ingenious and boldly novel 

 manner of applying the power through auxil- 

 iary drivers, a large increase of speed is ob- 

 tained from a given size of driving-wheel, with- 

 out increasing the number of piston-strokes or 

 the amount of fuel consumed. Or, at a con- 

 stant rate of speed, a heavier load can be hauled 

 with the same consumption of coal, owing to 

 the completer development of the effective 

 force of the steam. The Fontaine locomotive 

 has a theoretical advantage over engines of the 

 ordinary type of 80 per cent in speed or trac- 

 tion, and a practical gain of 30 per cent over 

 engines of the same size is claimed to have 

 been demonstrated. An engine of the new 

 type has drawn a train over the Pennsylvania 

 Railroad between New York and Philadelphia 

 at the rate of 90 miles an hour. The second 

 engine built on this model, made at the Grant 

 Locomotive Works, in Paterson, New Jersey, 

 has a total length of wheel-base of 21 feet 5 



inches, being constructed for a track of 4 feet 

 8J inches gauge. Its total weight, loaded, is 

 62,000 pounds ; weight on the driving-wheels, 

 82,000. The driving-wheels are 70 inches in 

 diameter, the friction-tread 56 inches in di- 

 ameter, and the upper driving-wheel 72 inches 

 in diameter. The stroke of the cylinder is 24 

 inches, diameter of cylinder 16 inches. The 

 tank has 2,000 gallons capacity. There are 

 140 tubes, 2 inches in diameter and 11 feet 

 long. The grate is 62i inches by 33 ; the 

 total heating surface, 906 square feet. 



LOCOMOTIVE, COMPRESSED-AIR. Sev- 

 eral quite workable compressed-air motors 

 have been tried and put into practical employ- 

 ment upon street- railroads with partial satis- 

 faction in France, Belgium, Great Britain, and 

 the United States. None of the devices for the 

 use of compressed air thus far invented has 

 stood, however, the practical and commercial 

 tests of utility and economy, although every 

 effort was made in the cases of some of these 

 to make them succeed. Notably, the Mekar- 

 ski air-engine, which was tried in Paris, re- 

 ceived abundant financial support, and was 

 only abandoned after a thorough trial. Scott 

 Moncrieff, of Glasgow, built an engine from 

 which good results were obtained as far as 

 its mechanical workings were concerned, but 

 which never advanced beyond the experiment- 

 al stage. The idea was not likely to be aban- 

 doned, however, after many failures, on ac- 

 count of the peculiar adaptation of compressed 

 air to mechanical motors for street-railroads. 

 Steam is too destructive and uncontrollable an 

 agent to be used directly on street- railroads, 

 aside from the serious inconveniences of smoke 

 and noise, which no devices yet invented have 

 been able to obviate to a sufficient extent. 



The employment of compressed air as a ve- 

 hicle for storing up mechanical energy to be 

 used at a future time or at a distance is at- 

 tended by two serious difficulties. The first 

 is the technical difficulty of the construction 

 of reservoirs and joints so hermetically tight 

 as to prevent leakage, and the fatal loss of 

 power which it entails if the motive power is 

 to be stored up for any length of time or 

 transmitted any distance. The second diffi- 

 culty is due to a universal property of gaseous 

 matter, explicable by the kinetic theory. The 

 application of pressure to any aeriform fluid 

 is attended by a rise in temperature and a pro- 

 portionately greater resistance to be overcome 

 in obtaining a given degree of compression. 

 If the compression is performed very slowly 

 and gradually, no increase in the sensible heat 

 of the gas occurs, and consequently no loss of 

 power ; but it is impracticable to conduct the 

 operation with such extreme slowness that 

 the molecules of the gas are not excited to 

 greater kinetic activity, which is the cause to 

 which the excess in the increase of pressure due 

 to rapid compression, the increase which is 

 attended by a rise in temperature, is attributed. 

 The compression which takes place at such a rate 



