THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



63 



TABLE VIII. 

 CONSUMPTION OF COKE ON THE GREAT WESTERN RAILWAY. 



2d. That with a load of .50 tons, which may be considered to be the 

 extreme load of a first-class train, a mean rate, at fnll speed, of S.") miles per 

 hour, in both directions, has been accomplished upon the line at present 

 opened, viz., 22J miles, the e.xtreme gradient being 4 feet per mile ; 

 and that this has been performed with engines of an average evaporating 

 power of 1G5.6 cubic feet of water per honr, and with driving wheels 7 feet 

 diameter; and cylinders, IG inches diameter. 



3rd. That with engines of a less evaporating power, or equal to 1 15 cubic 

 feet of w.ater per hour, the aver.age speed with a load of 50 tons has been 32 

 miles an hour ; the engines having eight feet driving wheels, and twelve 

 inch cylinders. 



4th. That the extreme r.ate of speed accomplished on the London and 

 Birmingham Railway, has been 40.9 miles an hour, with the Harvey Combe 

 engine, and with a load of 34^- tons, but only for a short distance. 



5th. That with a load of 50 tons, a mean rate of 32 miles an hour, at full 

 speed, has been accomplished, on a stage of about the same length as upon 

 the Great Western, or 24^ miles; the extreme gradient being 16 feet per 

 mile, and with engines, the mean evaporating power of which is equal to 

 94.85 cubic feet of water per hour, and with 5 feet driving wheels, and 

 cylinders 12 inches diameter. 



6th. That on both railways, the consumption of coke, or power required 

 to accomplish the above stated performances, has been as nearly as possible, 

 in the ratio of evaporating powers of jthe respective engines. 



7tb. That a high rate of velocity can only be attained by a very great 

 sacrifice of power, the following table, shewing the relative performances of 

 two of the most powerful engines on the Great Western, with respect to 

 speed and load, and also the consumption of coke per ton per mile : — 



We come now to the determination of the first section of the report, viz. ; 

 —the question of the attainment of a higher rate of speed, on the Great 

 Western Railway than on other railways, whether the increased width of 

 gauge, is or is not, either necessary, or best adapted for the accomplishment 

 of tUis speed,and to what extent. 



We find, from the results previously enumerated, that a higher rate of 

 speed has been attained on the Great Western Railway, than on other rail- 

 ways. This has been accomplished by the increased power of the engines 

 employed on that railway, above that of those on other railways ; before, 

 however, we can determine whether the increased gauge, is or is not, neces- 

 sary, or best adapted for the accomplishment of this object, and to wliat ex- 

 tent, we Huist enquire whether engines of the power by which such perform- 

 ance waselfected on the Great Western Railway, or such a power of engine as 

 would accomplish that rate of speed, can be applied on railways of the ordi- 

 nary width. 



The estimated powers of evaporation, of the largest of the engines on the 

 Great Western Railway, is 288.28, as per table ; and this engine per- 

 forms a mean rate of speed with 50 tons, of 35 miles an hour. The evapo- 

 rating power of the Harvey Combe engine is, by the same table, 16.;). 87, and 

 this engine performs a mean rate of speed of 32 miles an hour. Tlie largest 

 engines manufactured by Messrs. R. Stephenson and Co. , and in use upon 

 the Newcastle and Carlisle Railway, have, however, an evaporating power of 

 253.21; and an engine, built by the same manufacturers, for the Leicester 

 and Swannington Railway, has an evaporating power of 263.8. The 

 .■Eolus engine on ihe Great Western Railway, which is the ne.xt powerful 

 engine on that line, has an evaporating power of 228.09, and this 

 engine eflfects a mean rate of speed of 32 miles an hour, with 50 tons. 

 ?»o. J7.— FBBBUAay, 1839. Vol. II. 



We see, therefore, that there are engines in use upon Railways of the ordi- 

 nary width, more powerful, in the proportion of 263 : 228, than an engin^ 

 upon the Gre.at Western Railway, which effects a rate of speed, within thref^ 

 miles an hour, of the most powerful engine on that railway. We have had 

 no opportunity of subjecting these more powerful engines, on ordinary rail- 

 ways, to experiment, which would have been very desirable on the present 

 occasion; but we find such engines with an evaporating power of 165.21) 

 efl^ecting the same rate of speed on those railways, as the engine of 228.09 on 

 the Great Western ; and therefore the presumption is, that engines on rail- 

 ways of the lesser width of gauge, of the evaporating power of 253.21, or 

 263. 8, would effect an increased velocity, ([uite equal, if not greater, than 

 that of the largest engine on the Great Western Railway. 



This conclusion results from the engines on the ordinary railways, yielding- 

 a greater comparative useful efl'ect than the engines on the Great Western 

 Railway; partly owing to the much greater disproportion between the weight 

 and power of the engines, and the useful load on the latter than on the former ; 

 and partly owing to the increased resistance of the road, and also of the car- 

 riages themselves. Those parts only of the increased resistance, however, 

 which relate to the additional strength and weight of the engines, and car- 

 riages, and which is produced by the enlarged wind scare of the carriages, are 

 attributable to the wide gauge. We shall afterwards see, how much of the 

 increased power, on the Great Western Railway, exhibited by the preceding 

 experiments, as being necessary to drag the same quantity of goods, at the 

 same rate of speed, beyond that on railways of the ordinai-y width, is to be 

 placed against the width of gauge ; the inference which appears to me to result 

 from these experiments is, that with engines of the same power, a greater result, 

 and consequently a greater rate of speed, nmy be realised on the ordinary 

 width, than upon the increased width of gauge of railway. If the object be 

 to accomplish the greatest possible speed, a wide gauge is unquestionably 

 better adapted for the construction of Ihe largest possible engines, than the 

 narrow gauge ; considerable doubts may, however, be entertained if a gauge 

 of seven feet is the best for this purpose, and whether a less width of gauge, 

 taking into consideration every circumstance affecting the question, would 

 notalTord every requisite facility for the erection of engines, capable of attain- 

 ing a ma.\imum rate of speed. 



The question, therefore, whether an increased width of g.iuge is or is not 

 neeessaiy, depends almost entirely upon the determination of what rate of 

 speed it is advisable to attempt, or it is resolved upon to establish. If a mean 

 rate of 32 miles an hour at full speed be suflScient for the purpose, or such 

 increased rate as engines of the largest dimensions now in use on other rail- 

 ways can accomplish, then it will not be necessary, so far as the motive 

 power is concerned, to increase the width of gauge. But if a greater rate of 

 speed is required, the question assumes a diffeient shape ; and it must then be 

 ascertained if an engine can be erected upon the lesser width of gauge to 

 perform that rate of speed. 



As this appeared to be a very important part of the inquiry, I asked Mr. 

 Brunei the question as to the rate of speed proposed for both passengers and 

 goods. His answer was; —" The rate of speed proposed I conceive also to 

 be quite uncertain, my own opinion being, that it will always be ILxed at the 

 highest which we can maintain with regularity. With moderate loads we 

 might fi,x it at 35 miles an hour, and shortly, when the road is in complete 

 repair, and kept cleaner, when the short trains are established, so as to render 

 one stopping unnecessary, and our engineers more experienced in the ma- 

 nagement of the engines, at higher speeds, I think we may attain 38 to 40 

 miles." 



If the object be the attainment of the rate of speed assigned by Mr. Brunei, 

 the present engines, it will be seen by these experiments, cannot accomplish 

 that performance, including all the vicissitudes of weather and other casualties; 

 and, therefore, if a mean rate of speed of 40 miles an hour, including stops, 

 is to be attempted, more powerful engines will be required. 



These experiments, however, show the immense sacrifice of power inci- 

 dental to an extreme high rate of speed, or the accomplishment of a rate of 

 38 or 40 miles an hour, above that of 32 or 35 miles. If economy of con- 

 veyance is to be taken into consideration, it becomes a serious question 

 whether such a system should be acted upon as that of providing for an inde- 

 finite rate of speed, or that a maximum rate should not be determined upon, 

 and that such standard should be composed of that speed which will best suit 

 the public conveyance generally, and at the same time comprehend every pos- 

 sible economy and regularity. It is, however, not necessary to enter further 

 upon this at present, as the determination will be influenced to a certain ex- 

 tent by other facts elicited in the course of this incjuiry, .tnd wliich, in my 

 opinion, leads to the conclusion that the limit of practical speed, combined 

 with the requisite economy, is that which can be attained by engines capable 

 of being erected on a lesser width of gauge than seven feet. 



The preceding experiments having been made for the purpose of ascertain, 

 ing the comparative power required to work the trains upon the Great 

 Western road, contrasted witli the power required to work trains on railways 

 of the ordinary width and construction, — and were quite necessary, in a 

 practical point of view, to show the comparative aggregate amount of 

 eft'ective power given to the load by the engines at present employed on that 

 line, and the effective power produced by the engines on other railways. But 

 these experiments, however extensive and valuable, do not determine the 

 whole question, for although they show the amount of power required to 

 work the respective railways, yet that power is employed to overcome the 

 aggregate resistance of the engines, the friction of the carriages, and the re- 

 sistance of the road ; it became, therefore, extremely desirable that we should 

 separate the results, to arrive at practical conclusions, by which to make a 



