TRANSACTIONS OF THE SECTIONS. 195 



Results of Lincoln Expebiments with Continuous Bbajtes. 



The experiments to ascertain the effect of Continuous Brakes were arranged in 

 several groups, three of which involved the application of all available power for 

 stopping, sand being allowed to be used in two sets of trials out of the three. It 

 was found that the application of sand, in combination with brake-power, added 

 sensibly to the stopping-power, and on an average might be estimated as giving an 

 addition of 1-30 per cent, to the retarding force otherwise brought into play. The 

 trains were stopped by flag-signal, the driver and guards doing the utmost the 

 means afforded them allowed for bringing the train to a stop in the shortest pos- 

 sible distance. Not using sand, the retarding forces operating were found to range 

 in the respective trains from 4 1)4 to 1004 per cent, of their weights, corresponding 

 with the effects which would be produced by the trains encountering gradients of 

 1 in 20 and 1 in 10 respectively. 



Barker's Hydraulic, Clarke and Webb's Mechanical, Fay's Mechanical, and 

 Smith's Vacuum Brake produced retarding forces varying from G-47 to 5-72 per 

 cent, of the gross weight, forming a group giving an average of 6-04 per cent, of 

 retarding force, from which amount no deviation greater than 042 per cent, occurred 

 either way. 



The diagram (Plate IV.) illustrates this group of experiments. 



Three out of the four brakes last named, viz. Barker's, Clarke and Webb's and 

 Fay's, gave, when sand was used, an average of 7 - 79 per cent, of retarding force, 

 and none of them differed from that mean by more than - 15 per cent. 



These trials served to show in a very striking manner the great advantage 

 obtained by the application of a continuous brake ; for even in the least effective 

 form in which the system was presented to our notice, more than double stopping- 

 power was afforded than by the usual system of hand-brakes ; wdiilst in the most 

 effective form the stopping-power was quadrupled, enabling, in the latter case, a 

 train travelling at 60 miles an hour to be pulled up on an emergency within a 

 space of 400 yards instead of the mile required in the case of hand-brakes to 

 tender and vans. 



The highest amount of retarding force obtained in any of our trials had been 

 10t>4 per cent, of the entire weight of the train, a force which stopped a train, 

 weighing 208 tons, from 51 miles an hour in the space of 275 vards. 



In this instance the continuous breaks were applied to seventy wheels out of the 

 seventy-two wheels on which the train ran; and 94-4 per cent, of the total weight 

 was supported by those seventy braked wheels. 



This performance is above the average of the several systems ; but I am of opi- 

 nion that no system of continuous brakes should be regarded as satisfactory or 

 otherwise than provisional which should not afford a retarding power equal to at 

 least 8 to 10 per cent, of the entire weight of a train ; in other words, a power by 

 which the stoppage of fast trains can be effected in from one third to one fourth 

 the distance required under the ordinary brake appliances. 



It may be believed that the range between 5 per cent, and 10 per cent, of re- 

 tarding force, as afforded by the brakes used in our experiments, involving a cor- 

 responding range of difference in the stopping distance, will be greatly reduced 

 now that much experience in their working has been gained. 



Indeed it is satisfactory to note that already better results have been attained, 

 especially in the case of the Smith's Vacuum Brake and the Westinghouse Auto- 

 matic. 



I find in No. 801 of ' Engineering,' July 6, 1877, the record of a series of twelve 

 trials on the North-Eastern Railway of each of these two systems of brakes, said 

 to have been conducted with great care, giving as the average result of each set of 

 trials no less than 



8| per cent, of gross load in the case of Smith's Vacuum, and 



12g per cent, in the case of the Westinghouse Automatic, as the respective re- 

 tarding forces developed where the gross weight of train was 170 tons, and the 

 initial speeds ranged lrorn 44 to 64 miles per hour. 



It is obvious that the stopping distance is influenced by two primary condi- 

 tions : — 



