THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



59 



detailed descriiition of Mr. Brunei's plan of constructing the Great Western 

 Railway, furtlierthan what is absolutely necessary to explain the principles of 

 construction, and in wlual respects it differs from that of other railroads. 



The plan adopted by Mr. Brunei is tliat of a continuous bearing of timber 

 with piles upon which the iron rails that constitute the track of the wheels 

 are placed. 



The construction may be thus shortly described : Longitudinal timbers of a 

 scanning- of from five to seven inches in depth, and twelve to fourteen inches 

 in breadth, and about thirty feet long are placed along the whole line. Then 

 these timbers ate boiled to cross sleepers or transoms at intervals of every 

 fifteen feet ; double transoms each six inches broad and nine inches deep 

 being placed at the joinings of each of the longitudinal timbers, and single 

 transoms of the same scantling being placed midway between the joinings. 

 These transoms stretch across, and are boiled tb all the four lines of rails. 

 Within the two lines of rails of each track, piles of beech are driven from 

 the upper surface of the railway into the solid ground, so as to retain a firm 

 hold thereof, and the transoms are bolted to the heads of these piles. — Viile 

 JMirri/ition and Cuiisinicliuii of the llaibeuy, in Jimrnal No. 7, page 1(5G, 

 Vol. /. 



This plan is pointed out very clearly by Mr. Brunei, in his report to you on 

 the 22d of .January, 1838, and presented to the shareholders at the half yearly 

 meeling on the 27lh of February, 1838. — Vide Journal Xo. 1 , page ICG, 

 Vol. I. 



At the subsequent meeting (Oct. lOlh, 1838) of the Great Western Railway 

 proprietors, Mr. Brunei thus gives his reason for the adoption of this plan of 

 constructing the road : — 



" The mode of laying the rails is the next point which I shall consider. It 

 may appear strange that I should again in this case disclaim having attempted 

 anything perfectly new, yet regard to truth compels me to do so. I have 

 recommended in the case of the Great Western the principle of a continuous 

 bearing of limber under the rail, instead of isolated supports, an old system 

 recently revived, and as &uih I described it in ray report of January, 1838 ; 

 the result of many hundred miles laid in this manner in America, and of some 

 detaclu'd portions of railways in England, were quite sufficient to prove that 

 the system was attended wiih many advantage?, but since we first adopted it 

 these proofs have been multiplied; there need now be no apprehension. There 

 .are railways in full work upon which theexperiment has been tried sufficiently 

 to prove beyond doubt, to these willing to be convinced, that a permanent way 

 in continuous bearings of wood may be constructed, in which the motion will 

 be much smoother, the noise less, and consequently — for ihey are effects pro- 

 duced by the same cause — the wear and tear of the machinery much less ; 

 such a plan is certainly best adapted for high speeds, and this is the system 

 recommended by me and adopted on our road. There are, no doubt, differ- 

 ent modes of construction, and that which I have adopted as an improvement 

 upon olliers, may, on the contrary, be attended with disadvantages. For the 

 system 1 will strenuously contend, but I should be sorry to enter with any 

 such determined feeling into a discussion of Ihe merits of the particular mode 

 of construction. I would refer to my last report {vide Journal No. \'2.page22!i, 

 vol. 1) for the reasons which influenced me, and the objects I had in view in 

 introducing the piling ; that part which had been made under my own eye 

 answered fully all my expectations." 



These appear to have been the reasons for the introduction of this system 

 of railway construction, and the objections raised against it have been — The 

 increased cost of construction beyond that of other modes, — the additional 

 expense of keeping it in repair ; — -and that it does not accomplish tlie objects 

 proposed by Mr. Brunei, in recommendiug it to your notice, — that the motion 

 of the carriages is much greater than upon ordinary railways of the best con- 

 struction, — and that there is a considerable increase of resistance to the 

 carriages. 



Tlie professed .advantages to be derived from the increased width of gauge, 

 and the construction of the road by continuous bearings and piles, are so ex- 

 tensive and numerous, while on the other hand, the objections alleged against 

 them are equally so, that it appeared to me, as stated previously, with the 

 exception of awaiting the result of the test of time, there was only one mode 

 of determining these complicated questions with any degree of satisfaction, 

 viz., to endeavour to investigate as many of the points as possible, by experi- 

 ments instituted for the e.xpress purpose, and to ascertain if by this mode 

 such a number of facts could be obtained as would, with the aid of the expe- 

 rience already obtained of the woiking of the system, enable me to arrive at 

 conclusions which would, to unprejudiced persons, determine the important 

 questions submitted to me. 



On a review of all the proposed advantages and above-enumerated objec- 

 tions, the most important points to be determined by experiment appeared to 

 me to be comprehended within the following heads of inquiry ; — 



1 . The question of the .attainment of a higher rate of speed than on other 



railways ; whether the increased width of gauge is, or is not, either 

 necessary or best adapted for the accomplishment of this object, and to 

 what e.xtent. 



2. The mechanical advantage or diminution of friction, by being enabled to 



increase the diameter of the wlieels, without raising the bodies of the 

 carriages ; and in what respect, and to wh.at extent, the friction or resist- 

 ance of the carriages is affftted by, or bears upon the peculiar construc- 

 tion of the road. 



3. The comparative advantage or firmne.=s of base, or road track, of the Great 



Western Railway, with continuous timberbearings, eilherwilh orwithout 

 piles, and if it does or does not produce a greater steadiness and smooth- 

 ness of motion to the carriages, and to what extent. 

 These were the questions which appeared to me could not be delennined 



in any other way than by experiment, but which appeared to be capable of 

 solution by that method, and which likewise appeared to constitute the 

 foundation of the entire system ; for if the plan was not either necessary for 

 the realization, or did not effect a greater rate of speed than ordinary railways ; 

 if no diminution of friction v/as accomplished, and if no increased steadiness 

 of motion to the carriages was produced, at least, a very considerable portion 

 of the inducements for a departure from the ordinary plan would be destroyed : 

 but if, on the contrary, the whole or some partof these desiderata were accom- 

 plished, then it remained to be determined whether the advantages did or did 

 not counterbalance the disadvantages or objections to the system. 



Allainnient of Speed The first question to determine was, therefore, that 



of the .attainment of speed. The most conclusive manner of effecting this 

 appeared to be, to subject .all the different descriptions of engines upon the 

 line to experiment; to ascertain at what rate of speed they could travel, the 

 loads they were capable of dragging at diUerent rates of speed, and the com- 

 parative power required to accomplish these different performances. Having 

 thus obtained the power of the Great Western Railway engines upon that rail, 

 way, by instituting a similar set of experiments on other railways; we then 

 had the comparative result of the engines as to speed, and performance upon 

 the railways of the ordinary width and plan of construction, and upon the 

 Great Western Railway. 



A set of experiments for the purpose of ascertaining the performances of 

 the several engines on the Great Western Railway was therefore commenced, 

 and were conducted as follows : — 



A certain number of first and second class carriages were selected and 

 weighed ; they were then loaded with such a weight as would equal that of 

 their full complement of passengers, with their luggage. A certain number of 

 trucks were also selected, weighed, and loaded with the weight which they 

 were calculated to carry. 



The engine selected for the experiment was weighed, and also the tender,— 

 the quantity of coke in the fire-grate of the engine was carefully observed at 

 the commencement of Ihe experiment, and .also tlie quantity of water in the 

 tender. The engine was then attached to the carriages fixed upon for the ex- 

 periment, put in motion, and proceeded to the end of the stage without stop- 

 ping. The coke having been previously weighed into bags, the quantity put 

 into the firegrate during the journey was recorded, and at the end of the trip 

 the fire-grate was filled >ip, as nearly as could be estimated, to the same 

 height above the fire-grate as it w,as at the commencement of the trip, and 

 the quantity thus consumed correctly ascertained. Tlie qu.anlity of water at 

 the beginning of the trip being known, the boiler was kept to the same 

 height during the journey, the quantity of water left in the tender at the end 

 of the journey was gauged, and thus the quantity evaporated in the trip w,as 

 obtained. 



The mode of conducting the experiments was this : — Comiuencing at P.id- 

 dington, the engine dragged the train from the depot to the first half-mile 

 post, when it was stopped ; the steam was then applied to the cylinders, and 

 the time noted ; for the first mile the time was recorded at every 1 10 y.ards, 

 for the purpo.se of ascertaining the progress of obtaining the average speed, 

 and afterwards at every quarter mile. The train then proceeded until it 

 arrived at the twenty-first mile post, when the steam was shut off from the 

 cylinders, and the train allowed to come to rest of itself. The quantify of 

 coke consumed, and water evaporated, during each journey was ascertained 

 as previously explained ; and the rate of speed being taken at every quarter 

 mile, the rate of velocity was also obtained, not only during that part of tlie 

 journey at which a maximum rate of speed was kept up, but also the lime 

 occupied in getting up the speed, and also of bringing the train to a state of 

 rest. The same process was observed in the return trip from M.aidenhead to 

 Paddington ; Ihe engine and train was brought up to Ihe twenty-second mile 

 post and slopped, the steam thrown upon the pistons, and the time, coke, and 

 water, ascertained in the same manner as in the former case. 



Table 1. is the result of the experiments of the power of the Locomotive 

 Engines on the Great Western Railway, arranged in a tabular form, &c. ; 



By classifying these experiments, under the respective lo^ds by which the 

 powers of the engines wero tested; we hare the comparative results, ai regards 

 the performances of the different engines with performances of the different 

 engines with specific loads, and the consumption of fuel, or power required to 

 drag these loads at certain rates of speed. 



On attentively considering the result of these experiments, as exhibited in 

 the following tables, we find that the extreme mean maximum rate of speed 

 accomplished by these engines, has been 41.1.^) miles an hour, with the North 

 Star Engine, hut the load which was taken at that rate of speed was only 15 

 tons. It may here bo observed, that the rate of speed shown in these tables, is 

 the mean rate from the time the engine obtained its full speed, until the steam 

 was shut oft'at the end of the experiment ; and comprehended a distance gene- 

 rally of 19 miles, as may be seen on inspecting the tables in note E, Appendix. 

 A greater extreme rate was accomplished for a short distance, during some of 

 the experiments, as much as 45 miles an hour. The above expression of the 

 maximum mean rate of speed, is therefore the average rate of travelling from 

 one end of the stage to the other, after the engine had got into full speed, and 

 until the speed was .igain checked at the end of the stage. 



A rate of 40^ miles an hour has, it will be seen, been accomplished by another 

 engine, the Apollo, but with a load of only nine tons ; when the load was in- 

 creased, both with this engine and with the North Star, the speed was corre- 

 spondly reduced. The result of these experiments show that to effect a mean 

 rate of about 40 miles an hour, exclusive of the lime of getting up the speed 

 and stopping at the termination, between the two ends of a stage, about twenty 

 miles in length, the load cannot be more than from I o to 20 tons, with engines 

 of the power of the North Star. 



