]849.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



181 



leading lines of railway since the introduction into general use of 

 a class of engines considerably more powerful, and by consequence 

 larger and heavier, than those in use four or five years ago, has 

 been sucli as to attract the notice of the public, and to call forth 

 the anxious attention of those on whom more immediately devolve 

 the duties of engineering and management. That there has been 

 deterioration, more especially in the rails themselves, and that it 

 has been lately manifesting itself far more rapidly than had been 

 calculated upon, is evident from the additional strength now given 

 by most engineers to the rails and other parts of the permanent 

 way, in order that repairs may be less continuous, and renewals 

 less frequent. 



If the question be regarded in a general view as connected with 

 economy, whether of first cost or annual maintenance, it will be 

 manifest that these two points have an essential bearing on each 

 other. A system of road may be expensive in its first construc- 

 tion, yet cost so little in maintenance, and last so long a time, as 

 to be in the end far cheaper than a road less expensively formed, 

 but requiring greater annual outlay, and more speedy replacement. 

 Circumstances being equal, the annual cost of maintenance dis- 

 tributed over a period of years, and including both labour and ma- 

 terials, should form a very distinguishing test to apply in ascer- 

 taining the merits or defects of the different constructions of per- 

 manent way now in use; for it may fairly be argued that the road 

 which costs least to repair will also last the longest, a state of effi- 

 ciency and security being presumed. 



Acting on tliis view, the writer has endeavoured to collect such 

 facts in regard to mode of construction, and cost of maintenance, 

 on different lines, as might suffice when collated, to determine tlie 

 most advantageous, and ultimately economical, mode of construc- 

 tion, as well as to obtain some practical information as to the 

 points wherein existing systems appeared weali or defective ; and 

 had intended simply to offer these facts, so far as they might be 

 useful, for the consideration of the members of this Institution. 

 But in pursuing this investigation, and attempting the proposed 

 comparison, it became apparent that the cost of maintenance was 

 controlled by elements not only not common to the different sys- 

 tems under consideration, but varying even on contiguous porti(ms 

 of the same line; these elements being, the nature of tlie sub- 

 stratum, or material of formation; the character of the ballast; 

 and the extent and kind of the traffic; — circumstances which, 

 whilst they render it difficult to arrive at any accurate average of 

 the cost of maintenance on any particular line, make it imj)ossible 

 to deduce satisfactory results from a comparison of those ave- 

 rages. 



It therefore becomes necessary to take up the question more at 

 large, and to ascertain the conditions of stability and efficiency 

 which are required in all permanent way, and tlie manner in which 

 the various systems at present in use meet those conditions. 



The principal of these conditions may be arranged as under : — 



1. Sufficient platform or bearing surface on the ballast to prevent the 

 whole road from being crushed down into the ballast. 



2. Sufficient bearing surface of the various parts one on another to pre- 

 vent their crushing into each other. 



3. Sufficient cross-ties to secure uniformity of gauge between the two 

 rails composing one line of rails. 



4. Sufficient side stiffness in each rail. 



5. Sufficient strength, quality, and shape of materials, to prevent their 

 crushing in themselves. 



6. Such general precautions as shall tend to the protection and preserva- 

 tion of the more perishable portions from atmospheric and other influ- 

 ences ; on this last point, however, it will not be within our limits at present 

 to enter. 



These conditions satisfied, the questions of economy and sim- 

 plicity of construction, remain for consideration. 



The bearing surface of the permanent road on the ballast has 

 been variously provided. Amongst the more prominent of tlie 

 modes now in use we may notice roads laid upon, 



1. Stone blocks. 



2. Cross sleepers (of usual make). 



3. Cross sleepers (of usual make) brought nearer together at the joints, 

 with a larger sleeper under the joints. 



4. Cross sleepers of triangular section. 



All of the foregoing usually sustain and secure the rail by the interven- 

 tion of chairs. 



5. The longitudinal hearer used on the broad gauge lines. 



6. The same as laid on the narrow gauge at London Bridge. 



7. A combination of the cross sleeper with the longitudinal bearer now in 

 use on the Midland Great Western Railway of Ireland, and formerly laid 

 down on the Croydon line. 



In these three plans, a flat-bottomed or a bridge rail is bedded on and 

 secured directly to the longitudinal bearer. 



8. And lastly, the system introduced on the South Coast lines, and on the 

 Great Southern and Western of Ireland, in which a bridge rail is imme- 

 diately fastened to cross sleepers. The cross sleepers in the case of the 

 Southern and Western of Ireland vary considerably in size, and are placed 

 at proportional distances, tl.i; great body of the support being under the 

 joint. 



Briefly to compare the amount of bearing surfaces respectively 

 presented to the ballast under tlie several systems mentioned above, 

 it will be found that, assuming a length of rail at 18 feet, 



1. With stone blocks there are l'33ft. super per foot run of rail. 



2. With cross sleepers (of usual make) equally distributed, l'12ft. super 

 per foot run of rail. 



3. With the same brought nearer together at the joint, r36 ft. super per 

 foot run of rail at the joint, and for ift. l-J-in. each side of joint ; and 1'04 

 ft. super per foot run of rail, over the 9 ft. 9 in. remaining to make an 18 ft. 

 length. 



4. With sleepers of triangular section rather more surface is presented to 

 the ballast. 



5. With that used on the broad gauge lines, 125 ft. super per foot run of 

 rail. 



6. With the longitudinal bearer used at London Bridge, 1-17 ft. super per 

 foot run of rail. 



7. With the combination of the longitudinal and cross sleepers used on the 

 Midland Great Western of Ireland, 1"43 ft. super per foot run of rail ; and 

 in cases where more sleepers are introduced on boggy or peaty ground on the 

 above line, or in the road on the Croydon line, 1'75 ft. super per foot run of 

 rail. 



8. With the construction adopted on the Great Southern and Western 

 Railway of Ireland, a general average of 1-50 ft. super per foot run of rail; 

 the proportions varying from 250 ft. super per foot run of rail at joint, to 

 0'93 ft. super per foot run of rail in centre of rail. 



The next point for attention is the amount of bearing surface of 

 the several portions of the permanent way one on the other, neces- 

 sary to prevent their crushing into each other. 



On instituting a similar comparison to the previous one, it will 

 be found tliat, assuming as before an 18 feet length of rail, 



1 and 2. — With stone blocks and cross sleepers placed at equal distances 

 apart, which may be regarded as the older forms of construction, wheri 

 rather light chairs were used, there are 20 super inches per foot run of rail 

 at the joint, and 17 super inches per foot on the remaining length. 



3 and 4. — With cross sleepers br'ought nearer together at joint, of usual 

 make, or of triangular section, with large chairs, 23^?^ super inches per foot 

 run of rail at joint, and 4 ft. 1 J in. on each side of joint ; and 16J super 

 inches per foot run of rail for the 9 ft. 9 in. remaining to make up 18 ft. 



5, 6, and 7. — With the longitudinal bearer used on the broad gauge lines 

 and at London Bridge, and with the construction used on the Midland Great 

 ■Western Railway of Ireland, and on the Croydon line, 60 super inches per 

 foot run of rail, 



8. — With the cross sleepers to which a bridge rail is immediately attached 

 on the Great Southern and Westei'n of Ireland, a general average of 16 in. 

 super per foot run of rail, in proportions varying from 27 in- super per foot 

 run of rad at joint, to 10} in. super per foot run of rail in centre of length. 



It must be remarked that in these last four instances, whether 

 with bridge rails or flat-bottomed rails, packing plates are placed 

 under the joints, and in the road at London Bridge at intervals 

 along the rail, to prevent it from burying itself in the timber, more 

 particularly at the joints; and that on the broad gauge lines a 

 packing of hard wood is introduced between the rail and the 

 bearer, which presents to the longitudinal timber a surface of 108 

 superficial inches, or 0-75 superficial feet per foot run of rail, 

 through which the fastenings for securing the rail pass. 



The modes adopted for tlie preservation of the gauge next claim 

 our attention. ^Vith stone blocks there is no provision for this 

 beyond the stability of each individual block. With cross sleepers 

 this essential object is very completely secured. AVith longitudi- 

 nal bearers this point is secured by cross timbers with strap bolts; 

 these bolts securing the longitudinal timbers hard up against the 

 ends of the cross pieces. In the case of the Midland Great 

 Western Railway of Ireland and the old Croydon line, as has 

 been before mentioned, cross sleepers are used with the longitu- 

 dinals. 



The next point for consideration is the side stiffness in each in- 

 dividual line. With stone blocks and cross sleepers, whatever be 

 the kind of rail used, the side stiffness depends entirely on the 

 strength of the rail itself to resist lateral strain between the points 

 of support. The rails used with longitudinal bearers are in them- 

 selves very stiff laterally, whether of the bridge or flat-bottomed 

 section, and their immediate connection with the longitudinal 

 bearers gives a further amount of side stiffness to this construction. 



From the foregoing remarks we collect, that stone blocks as a 

 means of support on the ballast, although presenting a large 

 amount of bearing surface on the ballast, and being in themselves 



