514 MEMOIR OF DANIEL TREADWELL. 



IV. Curves. — One of the questions of considerable importance in the economy of railroads which has 

 jet remaineil undetermined, is presented iu the resistance produced In" passing the loads over the curves 

 in the road, made in horizontal planes, as compared with moving in straight lines upon the same planes. 

 The Worcester road contains no level curve of sufficient length to yield any experiments for solving this 

 question. I often made direct observations, however, upon the dynamometer, as the trains passed tiie 

 short level curves, and I was seldom able to perceive anj' sensible increase of the draft over that required 

 for the same train upon the straight parts of the road. 



A single experiment was tried on a part of the road three miles in length, and made up of a series of 

 curves. To find the resistance produced l)y the curve alone we maj- take tlie resistance due to the com- 

 mon friction on the level and straight railway as shown hy these experiments, and the resistance due to 

 elevating the load as shown by calculation, and the sum, whatever it may be, which is required to 

 make them equal to the actual and observed resistance may be taken as the resistance due to the curves. 

 The results from this experiment failed to show any essential resistance from the curves hy the method 

 followed, and jxt it is evident that the cars pass more freely upon the straight than upon the curved 

 parts of a raihva}\ ... I tiiink that we may conclude that tiie resistance from a curve of 2,000 ft. radius 

 is not greater than ^e'^^th part uf the load, or an elevation of two feet in a mile. With curves of a smaller 

 radius the resistance is increased probably in a much more rapid proportion than that of the reduction of 

 the radius. 



A more important objection to curves than that of their increasing the resistance, however, is found 

 in this : that as thej- generally pass round hills or through deep cuts, it is impossible for the engineer 

 when upon them to see whether the road is clear and passable for many rods before him. Hence he 

 must either run verj- slowly, or be in constant danger of accident This danger is so great that it is 

 always advisable to obtain for all railways straight lines, if possible, even if at the disadvantage of hav- 

 ing them of such ascents as shall yield resistances manj- times gi-eater than would be given by the curves 

 for which thej' have been substituted.* 



V. JSxperiments to detemime the Eesistance of Cars mounted upon Gudgeons of different Sizes, xcJien 



running upon Railroads. 



Saturday, October 29th, run with the engine Meteor twice to Newton Corner, drawing each time two 

 cars, as follows : — 



Experiment Xo. 1. 1 car carrsinsj apparatus and two persons; gudgeons 1| inches in diameter, weight, 4,670 lb. 



1 car loaded with iron ; gudgeons 3 inches in diameter, weight 11.1.50 



15,820 lb. 

 Expei'iinent Xo. 2. 1 car can-ying apparatus as in experiment Xo. 1 (the same car and load was used 



for the apparatus in all the experiments), weight 4,670 1b. 



1 car loaded with stone and iron; gudgeons 1|^ inches iu diameter, weight . . . 9,210 



13,880 lb. 



The wheels of all the cars used are three feet in diameter. The weights named are those of the cars 

 and their loads. 



» The eflect of curves contains many factors, — the relative height of the inner and outer rails, the form of the tread of the 

 wheels, the length of the train independent of the load, and the velocity. It is still a subject of discussion with civil engineers. 

 The practical objection to curves as regards safety is fully acknowledged, even when the road is worked with the aid of the 

 telegraph. Mr. N. N. Forney, in his book on Locomotives, says (1886): "It may be stated that the most recent experiments 

 have shown that the resistance of good American cars does not exceed 6 lb. per ton of 2,000 lb. at verj- slow speed on a straight 

 and level track. With reference to the influence of speed on the resistance, it must be admitted that our knowledge is very in- 

 exact, and probably the law or laws which govern it is not well understood. Our knowledge of the resistince due to curves is 

 also in a very unsatisfactory condition, but the most reliable information we have indicates that the resistance is equal to about 

 half a pound per ton of 2,000 lb. per degree of curvature." Mr. Treadwell's experiments with a speed of 15 miles an hour, a 

 curve of 2,000 feet radius (3°) treated by the methods now adopted, would give a resistance of 8.5 lb. to the ton of 2,240 lb., 

 .-iubstautially the same as that obtained from recent experiments. — W. 



