ON RAILWAY CONSTANTS. 



2.59 



The most important results are those relating to the train of eight car- 

 riages, because this load is the nearest approach to the average size of the 

 ordinary passenger trains usually travelling upon railways. Thirty miles per 

 hour is a fair average speed ; and the resistance encountered by such a train 

 moving at thirty miles per hour amounts, as we have already shown, to 

 nearly 1 5 lbs. per ton, or almost double the value of friction only. These 

 are results of an eminently practical tendency, indicating at what expenditure 

 of power we can expect to be able to transfer a given load, and what degree 

 of excess of power in the motive force, over and above the power required 

 to overcome the fi'iction, is necessary to the maintenance of an assigned rate 

 of speed. The friction may no doubt be made less than 8 lbs. per ton by 

 proper attention to the accurate fitting and perfect lubrication of the axles, 

 and to the squareness with which they are placed on the framing, as indeed 

 is made evident by the fact of certain carriages having run with a friction of 

 only 6 lbs. per ton ; but it is scarcely probable that a much lower amount 

 will be attained, nor indeed would the reduction be of much importance in 

 the economic working of passenger trains, which, from their high velocity, 

 must necessarily bring into play large and independent soui-ces of resistance. 



Having ascertained the resistance to trains at various speeds, and under 

 the circumstances in which they are found when employed in the regular 

 traffic of the road, the attention of the Committee was earnestly directed to 

 discovering how far any diiference in the external configuration of the train, 

 and modification of the form of the front or hind surfaces, or any altera- 

 tion in the shape of the leading vehicle, might affect the resistance it 

 experienced. 



The information obtained in the course of this part of the inquiry is of a 

 negative rather than a positive nature, proving that certain changes do not 

 aflPect the resistance, but not satisfactorily pointing to any general principle 

 whereby we can decide upon what the increase of resistance precisely 

 depends. 



The form of the front and the hind end of a train of carriages is flat, pre- 

 senting an area of 62 square feet, including a sectional transverse measure- 

 ment of the area of the axle and wheels, and springs and axle-boxes. To 

 give the train the power of more readily cutting its way through the atmo- 

 sphere, a sort of boat-shaped appendage was provided. Two boards, equal 

 in height to the body of the carriage, were united in front, at an angle, the 

 vertex being 5 ft. 6 in. before the flat front, and the base 6 ft. 6 in., cor- 

 responding with the width of the carriage. A single coach, weighing 5*37 

 tons, was dismissed from post No. 0, at the top of Sutton Plane, first with the 

 prow applied in front, and afterwards without the prow. 



The following Table is abstracted from Tables XVIII. and XIX. given 

 in the Appendix : — 



The diff'erence is only seventy yards in a distance of more than two miles ; 

 the times of performing the distance precisely the same. 



s2 



