Transactions of the American Society of Civil Engineers, Vol. LXX, Dec. 1910 | Page 3

10 miles in length than on longer grades, and that, even when unexpectedly stopped, it is capable of starting again as soon as the steam pressure is sufficiently built up. Conversely, it should be practicable to use a higher rate of ascent on shorter grades on any given line without decreasing the load which can be hauled over it. In other words, what is known as the "ruling grade" is a function, strictly speaking, of the length as well as the rate of grade.
In any discussions of the practicability of using a higher rate on the short grades, which the writer has seen, the most valid objection has appeared to be the danger of stalling and consequent delay. As far as momentum is relied on, this objection is valid. Within the limits of the load which can be handled by the steam, it has small value, as it is only a question of waiting a few minutes until the pressure can be built up to the point at which the load can be handled. As this need only be an occasional occurrence, it is not to be balanced against any material saving in cost of construction.
The writer does not know of any experiments which will throw much light on the value of heat storage as separated from momentum, though the following discussion may prove suggestive:
A train moving at a rate of 60 ft. per sec., and reaching the foot of a grade, will have acquired a "velocity head" of 56.7 ft., equivalent to stored energy of 56.7 �� 2,000 = 113,400 ft-lb. per ton. On a 0.002 grade (as in Item 15 of Table 1) the resistance would be, gravity 4 lb. + train 4.7 lb. = 8.7 lb., against which the energy above given would carry the train through 113,400 �� 8.7 = 13,034 ft., say, 2.5 miles, leaving 5 miles to be provided for by the steam production. Examining the items in the table having grades in excess of 10 miles, it will be noted that 16% is about all the weight on drivers which can be utilized by the current supply of steam. In Item 15 the energy derived from all sources is equivalent to 24.3%; hence the stored heat may be considered as responsible for an equivalent of 24.3% - 16% = 8.3% for a distance of 5 miles.
TABLE 1.
=========================================================================== Item No. |Length of grade, in miles. | |Rate of grade. | | |Maximum curvature. | | | |Compensation. | | | | |Gross weight of load, in tons. | | | | | |Weight of tender, in tons. | | | | | | |Weight of locomotive, in tons. | | | | | | | |Weight on drivers, in tons. | | | | | | | | |Percentage of weight on | | | | | | | | |drivers utilized in draft. | | | | | | | | | |Class. | | | | | | | | | | | | | | | | | | | | --+-----+------+------+----+-----+--+-----+-----+-----+-------------------- 1| 0.06|0.066 | | | 115| | 37.5| 29 |0.358| 8-28-1/3 C 2| 0.33|0.0203|25��20'| | 242|25| 35 | 23 |0.285| 8-28 C 3| 1.0 |0.06 |16�� |0.05| 192|22| 57.5| 50 |0.310|10-36 E 4| 1.3 |0.0127| | | 600|16| 40 | 32.5|0.300|Mogul. 5| 1.4 |0.0128| 3��12'| | 750|15| 51 | 44 |0.270|10-34 E 6| 2.0 |0.01 | | |1,000|15| 51 | 44 |0.291|10-34 E 7| 2.2 |0.013 | 3�� | | 725|15| 51 | 44 |0.245|10-34 E 8| 2.5 |0.0144| 6�� | | 400|27| 42 | 32 |0.237|10-32 E 9| 2.5 |0.004 | | |2,700|70| 96.7| 85.8|0.207| H 6 - A 10| 3.5 |0.033 |14�� | | 100|25| 35 | 35 |0.160| 11| 3.6 |0.035 |10�� |0.05| 236|22| 57.5| 50 |0.245|10-36 E 12| 4.0 |0.0085| 4�� | |1,020|30| 51 | 44 |0.256|10-34 E 13| 6.0 |0.0145| | | 308|25| 38 | 28 |0.207|10-28 D 14| 6.0 |0.020 |10�� |0.05| 460|32| 57.5| 50 |0.242|10-34 E 15| 7.5 |0.002 | | C |6,152|86|134.5|109.5|0.243|Mallet. 16| 9.75|0.018 | | | 200|18| 29 | 29 |0.170| 17|10.0 |0.006 | | C |6,173|86|299 |265 |0.203|Mallet. 18|12.0 |0.018 |10�� | | 280|30| 51 | 44 |0.160|10-34 E 19|12.0 |0.022 | | | 850|74|175 |156 |0.166|D-D 16 20|13.0 |0.022 | | | 800|74|177 |158 |0.153|D-D 1 21|13.0 |0.022 |14�� | | 415|50| 91 | 83 |0.154|Consol. 22|16.0 |0.0044| | | 950|30| 51 | 44 |0.164|10-34 E 23|20.0 |0.022 | | | 500|62| 97.5| 90 |0.170|F 8, Consol. 24|20.0 |0.022 | | | 800|74|177 |158 |0.159|L-1, Mallet. ===========================================================================
============================================================================ |Maker. |Railroad. |Reporting Officer. |Year. --+--------+----------------------------+-----------------------------+----- 1|Baldwin.|Morgan's Louisiana & Texas |Newell Tilton, Asst. Supt. |1880 2| " |Long Island |S. Spencer, Gen. Supt. |1878 3| " |Atchison, Topeka & Santa Fe |J. D. Burr, Asst. Engr. |1879 4| " |Chillan &