Handbook of Railroad Construction; For the use of American engineers. / Containing the necessary rules, tables, and formulæ for the location, construction, equipment, and management of railroads, as built in the United States.

by George L. Vose

376. Table 11. Showing the mean cylinder steam pressure for any percentage of admission, the initial pressure being from 50 to 150 lbs. per inch.

Initial pressure in pounds.	MEAN CYLINDER PRESSURE, ADMISSION BEING IN HUNDREDTHS OF THE STROKE.
	10	15	20	25	30	35	40	45	50	55	60	65	70	75
50	7	12	16	20	23	26	28	31	33	36	38	40	42	44
60	9	14	19	24	28	31	34	37	40	43	46	49	51	53
70	10	17	22	28	33	36	40	43	47	50	54	57	59	62
80	12	19	26	32	38	42	41	49	54	58	62	65	68	71
90	13	22	29	36	42	47	51	54	60	65	69	73	76	80
100	15	24	32	40	47	52	57	62	67	72	77	81	85	89
110	16	26	35	44	52	57	63	68	74	79	85	89	93	98
120	18	29	38	48	56	62	68	74	80	86	91	97	102	107
130	19	31	42	52	61	68	74	81	87	94	99	105	110	116
145	21	34	45	56	65	73	80	87	94	101	107	113	119	125
160	22	36	48	60	70	78	85	93	100	108	114	121	127	134

PART II.
CARS.

WHEELS AND AXLES.

377. Of the mechanical details of car building it is not necessary here to speak; but of those matters which fit a car for special duty, and depend upon particular characteristics of any road, such as the gauge, something must be said.

The trend of the wheel tire, as remarked in Chapter XIII., is not turned cylindrical, but conical. A perfectly straight road would of course require no cone upon the wheels; the object of the latter being to vary the wheel diameter when upon curves. The general practice is to give a certain standard cone to all wheels, for all gauges. This is quite wrong, as will be seen by the following formula, which is from “Pambour on the Locomotive Engine.”

Fig. 156.

Let m m′, fig. 156, represent the outer rail, and n n′ the inner one. The circumferences upon the same axles must evidently vary as the length of these curves, which are included between the same radii.

Let D, be the diameter of the first wheel, and d, that of the second; and we shall have,