The following is a copy of the minutes of a meeting of the Railway Engineering Division of the Institute of Civil Engineers. The meeting was to discuss a paper written regarding the development of Lawley Street Goods Depot following its destruction by fire in 1937. A copy of the original paper is available for purchase from the Institute of Civil Engineers.
Birmingham, Lawley Street: Modernization of Goods Depot
ICE Engineering Division Papers, Volume 6, Issue 4, 01 January 1948
The Authors introduced the Paper with the aid of a series of lantern slides and a film. They stated that in the design of a large section of the equipment they had been faced with an entirely new set of circumstances with no previous experience to guide them. The time schedule of operations was very tight, and it was essential that the installation should work from the first without modification or alteration. But by the correct application of basic principles, coupled with the closest attention to detail, both in design and construction, at every stage, the desired result had been achieved.
Mr JF Bickerton observed that the present Western Region goods depot at Hockley, Birmingham, constructed during 1939 and 1940, dealt with an average daily traffic of about 1,400 tons and was fully comparable in size with the Lawley Street depot. By contrast, however, it was of the older-fashioned manual type, with about 3¼ acres of platform deck, all at wagon level, covered by 5 acres of roof.
The lay-out of the Lawley Street depot had obviously received much thought, and a high order of ingenuity had been displayed. The machinery was impressive, and Hockley had nothing whatever to compare with it. Mr Bickerton, however, felt that a no simplification had been produced in the essential movements of consignments, which remained more or less the same as in a manual shed ; but the introduction of machinery wherever possible systematized the working.
A manual shed such as Hockley relied upon intelligent operation, and was very adaptable and, indeed, sensitive in that respect. On the other hand, the mechanical system seemed to be much less adaptable to changing conditions and was liable to be upset by mechanical breakdown at any one of a large number of points. Some movements which were amongst the simplest in the Hockley shed were very complicated at Lawley Street. That applied especially to transhipments, which had to make a roundabout trip from one wagon to the other, including a journey outside the shed in open drays; incidentally, that involved a change of transport from the battery-operated vehicle to the horse-drawn vehicle.
The only advantage which he could see in the whole mechanized process was a possible reduction in the figures for man-hours per ton handled. There was no reason to doubt that had been achieved at Lawley Street, but at what cost? The true comparison could be only on commercial value, and in that respect the Paper left its readers in the dark. The cost-per-ton statistics maintained by the Commercial department usually included only the pay-bill charges for the actual handling staff, and could be considerably reduced by the use of mechanical equipment, the cost of maintenance of the equipment itself being conveniently disregarded. It would appear that the capital cost, depreciation, and maintenance charges on the Lawley Street scheme would be very high, and he would like to know whether any information was available as to the extent to which that had added a hidden cost. When that was taken into account, did the mechanization still produce a lower cost per ton?
Reverting to the actual lay-out, it would be observed that mechanization was applied wholly to the unloading of wagons; when no unloading was in progress, the machinery was at a standstill. The forwarding side of the shed was all manual, and, being of the perambulatory type, was open to criticism, since it did not encourage and, in fact, scarcely permitted good loading of the wagons for dispatch. Drays from, the town and from the tranship section of the "Received" shed arrived at the forwarding wagons indiscriminately, and the wagons had therefore to be loaded indiscriminately, or the consignments had to be held back on the drays. Some discrimination was essential, and he imagined that that could be achieved only by the provision of a large number of drays and adequate space for storing them.
The wagon traverser at the end of the shed was a very costly machine, and it would be interesting to know whether it was put in from choice or whether its use was dictated by the limitations of the site. Since it was provided, would not it have been better to put it under cover, so as to make it less susceptible to winter conditions?
Mr RL McIlmoyle observed that, as was done by most engineers, a very detailed inquest had been conducted after the end of each job to find out all the things which were capable of improvement; and in every case, no matter how much thought had been devoted to the job beforehand, many such things had been found; in the next job improvements had been incorporated, but still further defects had been discovered, so that design was in a constant state of flux, moving from what was supposed to be the best on one occasion to something better next time.
It was inevitable that a certain degree of standardization should be considered in the future, but's far as design was concerned it was necessary to be very careful. Standardization could be very useful, but no two jobs were the same and, in addition to the fact that improvements were always possible, it was necessary to take into account the difficulties of the site. If standardization was desirable, it should be a performance standard rather than a rigid standard as regards design. It was possible to standardize loads and permissible stresses, and perhaps the kind of life expected from the materials; but after that the designer should have a free hand.
A combined warehouse and goods shed was a very common arrangement on parts of the London Midland Region and on other railways, but the Lawley Street depot was an example of a departure, and he thought a correct departure, from that principle.
When the old shed was burnt down, a transhipping shed at Derby had been almost completed. There was no question of a warehouse there, wide circulating areas and a wide space for cartage between decks were provided, and there was no restriction by columns. The central span was 180 feet, and the columns were at 70-foot centres. Apart from the freedom of movement afforded during the normal working of the shed, if any rearrangement became necessary it could be carried out without having to wreck half the building, as had been necessary with many of the older sheds which had been modernized.
It was obvious that if the new Lawley Street depot was to be successful it should be of much the same type, and that had at once raised the problem of the warehouse overhead. If comparable spaces were to be provided, it would be necessary to construct very heavy and deep girders to carry the amount of overhead accommodation required, which would probably mean having three floors. Apart from that, there was the fact that a goods-handling shed and a warehouse involved entirely different operations. In the shed it was necessary to have freedom to move the traffic about, but a warehouse required complicated movements of a different kind. An estimate was made of what it would cost to put a warehouse over a structure of the kind in question, with the spaces which the Goods Terminal Superintendent considered essential, and it was shown to be much cheaper, purely in physical cost, to put the warehouse on another site and have the advantages of freedom of movement in the goods shed, together with the advantages of having the warehouse as a self-contained structure where arrangements could be made for the incoming and outgoing traffic to be handled economically and satisfactorily. That was decided on, and the slides exhibited by the Authors had shown the result in so far as the goods shed was concerned.
The warehouse had not yet been constructed. The bottom storey would be utilized largely for handling incoming and outgoing traffic. The traffic would enter by rail and be stored in the warehouse on one of the floors, and later would go out largely to road vehicles at one end of the structure. Movement between rail-level and the floors would be by lift. The structure itself would not require very considerable spans, and the estimate proposed at the time showed that it would be a very reasonable structure from the point of view of cost. Unfortunately, owing to present day conditions, its erection had not yet been possible, but he considered that it would be as efficient in operation as he believed the goods shed to be.
Mr Harold Savage observed that the most impressive feature of the depot was the apparent lack of effort, even during peak periods. That afforded a striking comparison with the scene of intense activity in the ordinary goods shed, with men barrowing in all directions and goods piled on the decks.
Doubtless lack of space had prevented the Authors from telling the story of the growth of the mechanization of goods sheds, of which Lawley Street was the final flower. It would have been useful if the Authors could have given some description of the "teething" troubles and of the way in which those troubles had been overcome.
He would be interested to know their views with regard to the size of shed which justified a mechanization scheme such as that at Lawley Street. Mr. Bickerton had mentioned the obvious advantage which the Authors had enjoyed in starting with a clear site, whereas many problems in the improvement of goods sheds today arose in dealing with sheds of comparatively recent origin, which one would hesitate to contemplate destroying entirely in order to start afresh.
With regard to wagon discharging, the Authors had given 2 feet 6 inches as the minimum recommended width of deck on each side of the conveyor. The Western Region was particularly interested in that problem, because what was referred to as the zonal working scheme for goods handling had been introduced, which concentrated traffic on a restricted number of goods sheds. That had led to consideration of the way in which those sheds could be developed to facilitate the handling of an increased quantity of traffic. Most were what might be termed medium size sheds. For the guidance of all concerned, a type layout plan had been prepared.
The essential feature on the inwards or "Received" side was the conveyor belt with the platform on each side ; but with the size of shed which was contemplated only one conveyor belt would be necessary, and therefore it was not necessary to consider the much more elaborate and ingenious apparatus used at Lawley Street for dealing with the flats after they came off either conveyor and taking them to either side of any deck. On the outward side, the lay-out which was contemplated comprised the perambulation which had been illustrated in the film shown by the Authors.
Attempts had been made to get information from all possible sources. An obvious source was the Proceedings of the American Railway Engineers Association, but they had not provided anything that could be applied directly. The American type of shed generally seemed to be a two-storey shed, with the tracks and platform at the lower storey and the road at the upper storey, lifts being used from the platform to road-level. That did not seem likely to form a satisfactory arrangement. Another unusual feature was that one platform served quite a number of adjoining roads. The Americans were enabled to do that by setting their roads so that the wagon doors came opposite each other; they cleared the wagons on the road immediately adjoining the platform, and then laid down decking to the wagons on the next road and trucked through those on the inner road, and so on road by road. He would be interested to know whether the Authors had studied that procedure and whether they held any views about it and as to why the Americans had adopted that idea rather than the one-level lay-out, which appeared to be a better proposition.
Mr J McHardy Young considered that the lay-out of the shed was admirable, but he wished to make one criticism. On page 14 of the report reference was made to the capstans, and the Authors had stated : "A capstan of this type has a somewhat similar characteristic to the normal hydraulic capstan, many examples of which are still in operation at older depots." That seemed rather anachronistic, in view of the complicated mechanism in the rest of the shed. He suggested that it might be possible to have a shallow pit in the 4-foot way with a small Jubilee track carrying some light electrical towing device. That would save room and also man-power.
With regard to the roof spans, the Authors had not described that part of the work very fully, and the slides exhibited by them did not show the construction of the shed; but he had been fortunate enough to have a set of the drawings, and he considered that the span of the roof was not suitable for the type of truss adopted. That question might perhaps be more suitable for discussion by the Structural and Building Engineering Division, but he understood that the erection had involved the use of a large quantity of temporary work, and he would like to have some particulars of the erection costs.
In that connection, for a somewhat similar shed on the Southern Region, comprising a combined tranship shed and warehouse, with the warehouse portion at one end, the roof was of lattice girders and north light trusses, which were put up with one breakdown crane and no temporary work.
Mr McIlmoyle had referred to the question of a warehouse and goods shed being provided together. In the case to which Mr Young had referred, the handling in the warehouse was by means of goods lifts and chutes, whilst the handling in the tranship shed was effected by continuous monorail crane, running right round the loading docks, which transferred the goods from the wagons into the road vehicles.
Mr WC Clenshaw questioned the statement, on page 17, that the air raid shelter was formed in mass concrete, with walls 12 inches thick. The roof actually carried the roadway traffic to the yard, and both walls and roof were reinforced for that traffic and for the earth pressure.
Further, he believed. that the statement that the deck of the non-ferrous metal shed was designed for a load of 3 cwt per square foot, applied only to the more lightly loaded areas near the deck edge, and that elsewhere, where stacking might occur, a load of 1 ton per square foot was taken.
It had been mentioned, that the work on the foundations involved spanning over some old culverted watercourses. The foundation over a three-barrel culvert carried three stanchions which came almost immediately in the centre of the culverts, and to avoid interfering with them - they were the property of the Birmingham Corporation - a relatively shallow continuous foundation beam was constructed above them, but bearing on the existing walls, the outer walls being strengthened as necessary. It was cast on a layer of sand, which was afterwards raked out to avoid damage to the arches of the culvert.
The extent of the goods shed proper, and the large spans, .made it a notable example of steel roof design. Structures of such magnitude certainly required careful consideration in regard to their form. An alternative scheme in reinforced concrete was considered, particularly in view of the desirability of saving steel at the time. In the scheme prepared for Lawley Street, to obtain a comparison with steelwork, there were two spans of bowstring arches, each of just over 100 feet span, and a rigid frame with one of 86 feet, span to form the crane bay. In order to accommodate the reaction of the 100-foot span arch, one leg of the frame of the crane bay was bifurcated and the end of the arch housed inside. Concrete rocker bearings were proposed for the ends of the arches to take up temperature movements. The estimated saving in steel was about 30 per cent, but the spans were smaller and shuttering might have proved difficult. Pre- cast slabs could, however, have been used for the roof.
Another design in reinforced concrete, of pre-stressed, hip-plate construction, had spans of about 90 feet. It was possible also, with ordinary reinforced concrete construction with a hip-plate design, to provide similar spans. In the case of a goods shed built at Johannesburg, of greater area than the Lawley Street shed, the spans were 90 feet and, with ordinary, reinforced concrete hip-plate construction, the slab being 34 inches thick, a successful structure was built about 1941. That form of construction should be quite suitable for spans of the order of 100 feet, though by pre-stressing bigger spans could be achieved, with a great saving in steel.
Mr W Handy observed that, having been concerned with the choice of drive for the flat traverser, he could say that much consideration was given to whether it should have hydraulic variable speed gear, a straight slip-ring motor, or a Ward-Leonard drive. Owing to the importance, which the Authors had emphasized, of everything working properly without a hitch, it was decided to adopt the variable-speed-gear, which had worked very well indeed and had given no trouble.
Estimating was done in sections, and the electrical estimator tended to do everything possible to keep down the costs of his estimate, forgetting that if electricity supplies to plant were interrupted a large amount of capital stood idle. It was necessary to look at a job from the point of view of the whole scheme, and if the electricity-supply arrangements cost a little more - very little more in proportion to the cost of the whole scheme - to make them thoroughly reliable and enable them to be serviced without inconveniencing the operating department, that extra cost should be incurred, as was done in the case of the Lawley Street depot.
Another point which was sometimes overlooked in the early stages was the provision of a servicing workshop. It was no use coming along afterwards and asking for a corner for a workshop. Under "sorting" on page 8, reference was made to "drays." In the Paper generally, the word "drays" was used to mean the internal drays. If the word "cart" could be used for external drays that would make for easy reading. The same point arose on page 12 and 13. The "variable speed pump" mentioned on page 10 was really a constant speed pump and should be described as a variable speed gear pump.
Mr FG Umpleby observed that the initial thought and expenditure devoted to making provision for constant availability of the mechanical appliances had paid handsomely; no major breakdowns had occurred and maintenance costs had been very low. It might be asked whether that was in part due to the loading falling rather below the estimated maximum, but from the experience gained it would appear that the machinery would easily cope with heavier usage.
The traversers, being of unique design, probably gave the greatest cause for satisfaction. They could almost be described as selective conveyors. The incorporation of hydraulic operation had led to smoothness of working and great precision of control, and the quietness of movement was notable. When looking at the film, which was a silent one, it had struck him that not much more noise emanated from the actual operation, when men were moving goods about.
It would be observed from Plate 3 that the two traversers ran on parallel tracks, and therefore, as both worked towards the centre, they were right and left handed. The spare traverser, which was housed at one end of the track, might be required on either road, and could be turned as necessary while hung by the Goliath crane. The lifting tackle for that movement could be attached quickly and required no adjustment. (A sectional drawing [Plate 2] was provided with the minutes but not Plate 2 as referenced here - Editor).
Mention should be made also of the jumper connection which was available to provide electric power for driving the traverser into the standby position after the end of the long-travel conductors had been reached. Those conductors were of rigid construction, which had simplified the means of support. Hitherto the collectors had been made of bronze, but consideration was being given to fitting flat carbon inserts. Maintenance instructions for the traverser and, in fact, for all the mechanical and electrical equipment in the depot, were scheduled in detail, and that had been found very helpful.
Full use did not seem to be made of the creeper feeds where the flats were unloaded. The latter were carried on roller-bearing axleboxes and could be pushed easily by hand, but that meant a man having to leave the deck and step down to the lower level to do it. It was questionable whether those creepers would be included in a reproduction of the Lawley Street scheme. In any case, some modification of the mechanism for engaging the flats with the creeper feed had been found necessary.
The importance of the wagon traverser in the scheme of operation had led to special provision against failure. In that connection, a control panel having a contactor capacity considerably greater than that normally incorporated for similar duty was provided and had proved completely trouble-free.
Mr E Falconer observed that the 1,400 tons of miscellaneous traffic referred to in the Paper represented more than 40,000 packages per day, which had to be sorted from wagon to town dray or vice versa, whilst proper loads had to be built up for the sake of economy in cartage working or line working. That involved a tremendous amount of handling and sorting, so that the porterage work involved a very high proportion of the cost of dealing with the miscellaneous goods traffic; in fact, in many cases the cost at the terminals - because the goods had to be handled at both the forwarding and the receiving points - was more than the revenue received.
Some years ago, therefore, a small committee had been appointed to discover what could be done to reduce costs, and that committee had tackled the matter in a way which was probably new in dealing with such work, namely, on engineering lines, approaching the problem from the point of view of time study and job analysis. Some remarkable things had been found, but in the time available he could mention only one or two. It was obvious that the larger the station the greater would be the barrow runs; at the same time, unfortunately, there was a tendency towards a smaller barrow load. To deal with a ton of miscellaneous traffic at a large goods shed, it was quite likely that the average walking distance of the barrow men would be something like 2 miles, of which 1 mile would be empty running, simply bringing the barrow back to get another load.
At the Lawley Street depot the idea was to do as much as possible mechanically, and to move the traffic about and sort it in such a way that it could be dealt with in large loads. The question whether it achieved the object aimed at, of reducing costs and at the same time improving the working, could be answered by an emphatic affirmative. The handling work and porterage work was done with about half the staff that would be involved in dealing with the traffic in a shed of the old type of a size for dealing with 1,400 tons of traffic a day. That meant that, in comparison with the old type of shed, the saving in annual working costs would pay for the construction of the shed in from 8 to 10 years. In addition, a big working advantage was gained in that the forwarded traffic was finished with at 7:30 pm, whereas in the old type shed work went on until about 11:30 pm. Great advantage to the working of the traffic on the line resulted from having it ready for dispatch four hours earlier, and in getting it into the stations at the other end correspondingly earlier.
The traverser and capstans were deliberately introduced in order to reduce the calls on the locomotive power, and they had been very successful. Considerable difficulty had been experienced with the men, who objected to mechanization on principle, but that had been overcome, and the men were now intensely proud of their station. Last autumn he had taken a party of Frenchmen round. He himself had retired two years earlier and the men had not recognized him. One man had said to him, "What do you think of our station, sir?" He had replied that it was not bad, on which the man had said: "It's a fine station; it's the finest station in the world. It runs like clockwork." He had been very proud to hear that, and it could well be imagined that the engineers responsible were very pleased to know that the staff now looked upon it in that way.
The French National Railways, faced with the need for rebuilding a large number of their big goods stations, had visited England to see what had been done. As a result, all the plans already made had been scrapped, and the present plans for the new goods stations on the French National Railways were based on London Midland ideas.
The Lawley Street shed was built during the war, which in itself was remarkable, because he believed that schemes of such magnitude had to be submitted ultimately to a Committee of the War Cabinet. In the end, the War Cabinet had sent a representative to Lawley Street, and Mr Falconer and Mr Ingall had spent a good deal of time in trying unsuccessfully to convince him of the need for the depot. Finally, Mr. Falconer had said to him: "You people are the most illogical that I have ever met. Because we cannot work the traffic in this place, and have not the station to do so efficiently, we shall probably have a thousand wagons standing outside waiting to be unloaded: "He had turned to the Agent for confirmation, and the latter had said that there would be 1,700. Mr Falconer had continued: "The War Cabinet send planes over Germany night after night, losing mens lives and expensive aircraft, in order to bomb places like the marshalling yards at Hamm and to put perhaps a hundred wagons out of action which any engineer can put right in twenty-four hours; but because you will not allow us to build this place there will be 1,700 wagons standing outside continuously, day by day. Those wagons cannot be stored in the air ; they must be stored on running lines, and this line from the West of England is very important. All your shipping is coming to the Western ports, and the goods come on this line, which is one of the most congested and important lines in connection with the war effort. Because of your attitude, we shall have 1,700 wagons standing about in our marshalling sidings and blocking the main line. "The representative of the War Cabinet saw the force of that statement, and that was the reason why it was possible to build the Lawley Street depot during the war. That in itself illustrated the importance of having efficient terminal working.
Mr MF Barbey observed that , as the building was about 640 feet in length and 340 feet wide, it would have been strange if so large a site had been found to be clear of obstructions, and in fact, two large brick structures did exist upon it above ground, and quite a number of complications existed below ground.
Details of the old watercourses at Lawley Street had been given by Mr Barbey in 1943. The investigations were made during the summer of 1940, and Fig. 3 showed the main culverts involved. The shed was in the angle between the Birmingham to Stafford line (the old Grand Junction Railway) and the line of the old London to Birmingham Railway from Euston. Before those two railways were built, there was a road called Watery Lane (marked B in Fig. 3), and in 1806, Lawley Street was carried down across the area marked A¹, A² and A³. At that time, the river Rea followed the course A³GJ, with a branch (marked C) into a mill stream which, since 1758, if not earlier, had always been considerably larger than the river Rea itself. That branch portion of the original river or mill stream existed as an open stream until about 1839, when it was culverted; but at the time the new Goods Shed came to be built, and the site was being investigated, it was not known that such a culvert existed.
That was because in 1869 a diversion was made, as shown by line D¹, D²; that culvert was in turn reconstructed in 1891, and again in 1933 as the triple-barreled culvert which had already been mentioned, and having three spans of about 12 feet each. The original culvert C had long been dead, but prior to the building of the shed it was investigated and found to be still there, though blocked up.
A further complication arose because, about 1869, the course of the river Rea marked G was completely abandoned, and replaced by that marked F. Again, prior to 1839 the river was given an alternative course, marked H, which was discovered from the fact that land sold to the Midland Railway Company, for the development of the site, had its boundary along that line. The diversion to line E, part of the present course F E D¹D², of the existing triple culvert, took place about 1850.
The Authors, in reply, stated that, in general, all tranship traffic had necessarily to be discharged from the incoming wagon and taken by barrow, either to an outgoing wagon or, as was very frequently the case, to be deposited on the deck adjacent to the position where the outwards wagon would ultimately be set. Under the Lawley Street system the internal dray was virtually a "mobile deck" for transferring the goods from the discharging point to the loading-up point; there was no question of placing goods to berth intermediately. The Authors would not classify the movement of the internal drays to the out-going wagons via the weighbridge (to obtain accurate weight of the traffic dealt with) as less straightforward than the very common practice, on sheds with multiple decks, of irregular barrow movements via trucking bridges. The change over from electric tractive unit to horse was facilitated by quick coupling devices, and the respective means of traction had been chosen as best suited to the operation to be performed, namely, in the first case, point-to-point movement in bulk and, in the second case, involving intermediate stops with the driver riding on the body of the internal dray and thus conveniently placed to give assistance in loading the goods.
The whole of the wages staff in the Lawley Street shed were debited to handling, including the electric tractor drivers, the internal station carters, and the "flat" traverser and crane drivers. The capital cost of the machinery was less than 20 per cent of the whole. Mr Bickerton had conceded that there should be an advantage in the figures for man hours per ton handled. That, patently, was the objective, bearing in mind the cost of labour, and he could take it definitely that the improvement effected in man hours per ton as a result of mechanization more than covered the interest, depreciation, and maintenance cost of the equipment. The Authors believed that, whilst Hockley was largely a manual shed, the deck was designed to carry mechanical appliances, such as mobile cranes.
Mechanization was invaluable in wagon discharging, which was the purpose for which it was introduced. During that part of the day when it was not required, the machinery was not in use; that was inherent in the deliberate separation of the shed into received and forwarded sections. That provided adequate opportunity for proper maintenance for which, incidentally, a special CME. workshop had been provided. Very little interruption had been experienced from mechanical breakdowns. Operators of "two-way" goods sheds would be well acquainted with the difficulties involved in changing over from received to forwarded working, especially when received traffic was unusually heavy or arrived out of course.
The Authors could not appreciate Mr Bickerton's criticism that the forwarded wagons "had to be loaded indiscriminately." On large deck type sheds, traffic for any particular outwards wagon would be arriving first from a variety of inwards "tranship" wagons, and later in consignments from miscellaneous town and zonal collection units. The choice had to be made between berthing the whole of the traffic and then loading to wagon, or, loading to wagon currently to the maximum extent. Extra handling, and delay incurred in placing the traffic on to the deck and later in picking it up again for loading, should be restricted to the absolute minimum because of the cost and the necessity for early dispatch of trains. The Lawley Street system provided a "mobile deck," as previously pointed out and, should it be desired to hold back the loading of an exceptional consignment, that could be accomplished without additional handling; but, in practice, the majority of the drays were completely discharged in one cycle of operations, and the empty drays became available for further use. Mobile power cranes operating on the cartways provided easy means for dealing with articles difficult to handle manually.
The annual charges on the wagon traverser at the end of the shed represented something less than the wages of one capstanman. What was more important, the saving in engine power, which was a very costly item, produced a marked economy by the use of the traverser. The appliance was deliberately installed to afford a means of shunting to be independent of, and provide relief for, shunt engine power.
It was designed especially for operation in the open, and no undue difficulty had been met with under winter conditions. There was therefore no point in incurring additional expense by placing the traverser under cover.
In reply to Mr Savage, as the result of the detailed consideration given at every stage, the teething troubles encountered on bringing the plant into operation were small and were dealt with during the time when the operating staff were under training. It was hardly correct to state that the work was carried out on a clear site, as certain existing buildings were necessary to keep the depot working. The distance of the conveyor from the edge of the deck was established in the experimental layout and it was found that 2 feet 6 inches allowed for wagon doors being dropped on to the deck, with ample clearance between the wagon door and the conveyor. With regard to the American type of depot, it was not possible to comment usefully on any particular lay out, without full details of actual traffic and site conditions; but the retention of vehicles as trucking platforms would not appear to be the last word in efficiency; moreover, the vast difference between the American "box car" and the British closed van or open wagon should also be borne in mind. Time and effort had been spent in the early investigations which led up to the mechanized depot, and it was obvious that only for the larger depots would such a scheme as that carried out at Lawley Street be practicable; but in smaller depots mechanization could also be carried out effectively.
In reply to Mr McHardy Young, the erection of the trusses presented no difficulty and required little temporary work, although a stiffening beam was lashed to the trusses to provide stiffness when raising them from the horizontal position in which they were assembled and riveted. The design was very economical in steel, requiring only 9 lb. per square foot covered, including bracing and purlins; but, as the steelwork was carried out by contract, actual erection costs were not available. The capstanmen usually preferred the hydraulic to the electric capstan, as the former was more flexible, could be stalled, and would exert a steady pull under those conditions. The capstan referred to by the Authors met the operational requirements by virtue of the special motor fitted to those machines. Consideration had been given from time to time to the movement of wagons other than by capstan. At Derby, St. Mary's depot, wagons were moved by an underdeck "mule" remotely controlled. However, such devices as those suggested by Mr Young were suitable only when frequent moves had to be made. At the Lawley Street depot the wagon movements were infrequent and for that duty there could be no doubt that the capstan was the better proposition.
In reply to Mr Handy, an alternative to the hydraulic drive was considered but, in view of the fact that it was necessary to make the job work right from the start without any question, there could be no doubt that the electrohydraulic drive offered the simplest solution. A satisfactory machine could be made with all electric drive, at all events so far as the long-travel motion was concerned; the cross-traverse motion lent itself particularly to hydraulic operation, but it would be possible to construct a machine having direct electric drive on the cross-traverse, and also on the elevating motion, which would work quite satisfactorily. There would probably be some slight loss of time, and a highly skilled driver would be required to obtain the desired precision in operation. It was very important, in any mechanized layout, that alternative supplies of power should be available in the event of failure. The question of spare parts was also of considerable importance, so that in the event of any failure due to accident or wear and tear, replacements could be made easily. For many of the appliances at Lawley Street a duplicate machine was waiting in case of accident. Three flat traversers were available to do the duty of two, and one of them was always standing ready in case of failure, although it had not yet been used in any serious case of breakdown. The traversers were rostered to be brought into service in turn, and the one taken out was then overhauled. By that means an attempt was made to prevent any possible hold-up in the operation of the traversers. A spare battery tractor was also always available. The outside traverser was a very important item in the equipment. Although it was not duplicated, the designers had attempted to ensure freedom from mechanical breakdown by designing everything with a certain element of over safety factor. For example, in the electrical equipment the contactor gear was 50 per cent larger in capacity than would normally be required for a commercial machine. The Authors believed that it would be generally accepted that with all such machines it paid to put in something a little better than would be put in by the average commercial firm. It did not pay to cut down to the bare bones on vital details.
In reply to Mr Umpleby, the Authors had tried to cover the maintenance side by adequate spares, backed up by a complete manual of instructions, and that had been of very great help in carrying out the maintenance of the plant. It was probable that, in any future scheme of comparable size, creepers would not be put in, because, for operating reasons primarily, they were not used to the extent that had been anticipated when they were first installed. 0wing to limitations of space the Authors had not gone into detail about the jumper cable at the end of the traverser bay, but they acknowledged its presence.
They were indebted to Mr Falconer for his able contribution to the discussion, and wished to thank him for his assistance in enabling them to present the facts.
Mr Barbeys description of the river Rea and of old watercourses encountered during the construction of the depot, illustrated in detail the hidden difficulties (mentioned by the Authors on page 16, ante) on what had been referred to in the discussion as "starting with a clear site."