Journal of the Institution of Locomotive
Volume 39 (1949)
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Journal No. 207
Dymond, A.W.J. (Paper No. 482)
Forty years of automatic train control the Great Western system. 3-32. Disc.: 33-51.
Fourth Ordinary General Meeting of thc Session 1948-49 hcld at the Institution ot Mechanical Engineers, London, on Wednesday, 15 December 1948 at 5.30 p.m, Mr K.J. Cook, occupying the chair/
Includes an extensive contribution by P. Lomas (pp 34-40 on the Hudd system).
Patrick, D. (Paper No. 483)
Some notes on American locomotive practice 1948. 54-86. Disc.: 86-111.
Sixth ordinary general meeting held at the Institution of Mechanical Engineers, London, on Wednesday 16 February 1949 at 5.30 p.m., Colonel Harold Rudgard, President, occupying the chair.
Firstly commented upon the American loading gauge: 16ft in height and 11ft in width and rail loads of 28 tons per axle being almost universal, and 32 tons on some line. Train loads of 5000 tons were common place. Began with the unorthodox types of steam locomotive: the T1 4-4-4-4 Duplex type constructed at Altoona Works of the Pennsylvania Railroad, the 6-4-4-6 S1 and 4-4-6-4 Q2 Duplex type were also noted, although it was noted that further Duplex locomotives were unlikely to be constructed due to the excessive length of the coupled wheel base. The 6-8-6 direct-drive non-condensing locomotive built by Baldwin for the Pennsylvania Railroad weighing 260 tons without tender was also mentioned and illustrated. The Baldwin 4-8-0+4-8-4 Baldwin non-condensing steam turbine electric for the Chesapeake & Ohio RR with a grate area of 112ft2 and the potential to develop 6000 hp: it had the advantage of the turbine could operate at a speed independent from that of the locomotive. Attention then turned towards conventional steam locomotives: the Niagara class 4-8-4 employed by the New York Central RR: these two-cylinder locomotives had produced 6600 ihp on test at 85 mile/h. The streamlined 4-6-4 for the Milwaukee RR were commended ffor their pleasing appearance which did not sacrifice accessiblility.
On freight locomotives the four-wheeled trailing truck had become essential to accommodate a firebox of adequate dimensions. Non-articulated types included 2-8-4, 4-8-4 and 2-10-4: Fig. 6 shows a Lima-Hamilton 2-10-4 for the. Chesapeake & Ohio RR. The Mallet articulated locomotives were mainly non-compound. Fig. 7 shows a Lima-Hamilton 2-6-6-6 operated by the Chesapeake & Ohio RR. Fig. 8 illustrated an American Locomotive Company 4-8-8-4 for the Union Pacific RR with 23½ x 32 in cylinders and a grate area of 150.3ft2
Cast steel bed frames with cyinders cast in were almost universal. Fig. 9 shows those fitted to a Niagara class. The Author noted that the manufacture was confined to one specialist plant and that there was little probability of cast steel beds being widely adopted outside North America. The bogie frames were also made from cast steel (Fig. 10 shows a delta truck)..
The boiler design of the Duplex T1 class was examined more closely, although many features were almost universal. Nicholson thermic syphons were used in multiple to provide adequate circulation, to increase boiler output and provide safety. The Security Circulator is illustrated in Fig. 12.. Table grates had tended to replace rocking grates. Crown axleboxes, roller bearings, box-pok wheels were almost universal. Walschaerts gear was popular, although some locomotives employed Baker valve gear and Franklin poppet valves were sometimes used. For the historian of the steam locomotive Patrick provided a good overall perspective. He was probably less successful in assessing the impact of the diesel electric locomotive where the main design features noted were the ability to work in multiple and the cast steel bogies. Electric traction was restricted to the GG1 Pennsylvania RR 4-6-6-4 which could produce 4620 hp at the rail and the flexible transmission was commended. Brief mention was made of gas turbines.
It is realised that the colossal reserves of easily-mined bituminous coal in the USA are not being utilised to the best advantage, and an ambitious project has been sponsored by the Bituminous Coal Research Association in this connection. The intention is to design and build a locomotive incorporating a self-contained power plant consisting of a gas turbine designed to burn coal as fuel, the coal being suitably processed on the locomotive itself. Research and development on the project are being vigorously pursued by the principal locomotive builders, turbine and accessory manufacturers, and university research organisations. Patrick cited J. S. Tritton in his Presidential Address to this Institution in 1947 Further information is contained in Papers read before the American Society of Mechanical Engineers and the Association of American Railroads in 1947 by Mr. John I. Yellott and Mr. Charles F. Kottcamp. The question is: Can the gas-turbo-electric locomotive, in view of its complication, be built and utilised in such a manner that in comparison with other forms of traction it will possess an overall economic advantage, bearing in mind the facilities available for servicing the locomotive, the availability and price of fuel, and the incidence of both depreciation and of obsolescence in relation to the capital expenditure involved. In the Author's opinion the answer will not be available for some years.
As British locomotive engineers, confronted with widely varying problems to meet the requirements of home and overseas railways, we naturally turn from a review of American practice to a consideration of future developments in our own sphere, where conditions are vastly different from those obtaining in the USA. It is the Author's opinion that the modern steam locomotive will for many years to come remain the most suitable form of motive power for service on a vast proportion of the world's railways. This applies particularly to relatively undeveloped territories where traffic consists mainly.of basic materials, hauled over long distances, and where of necessity the locomotives must be operated and maintained under adverse conditions as regards man-power and equipment. The inherent simplicity of the steam locomotive and the remarkable elasticity it possesses to meet widely varying demands for power output, together with the relatively low initial cost, are still sufficient to more than offset the problematical advantages of other forms of motive power under such conditions of operation.
The Author acknowledged his indebtedness to the American Locomotive Company, Baldwin's Ltd. Lima-Hamilton Corporation, General Motors (Electro-Motive Division), the Chiefs of Motive Power (New York Central System and Pennsylvania Railroad respectively), General Steel Castings Corporation, and the publishers of the Railway Mechanical Engineer," for photographs .
Discussion: H. Rudgard (86) opened
the discussion noting that during WW2 when iron ore had to be moved from
Kettering to Scotland two class 8 2-8-0 freight locomotives coupled together
hauled a gross load of 2850 tons.
Cox (87-8) noted that orders placed in 1948 in the USA for locomotives covered 69 steam, 2,524 diesel-electric and 2 electric. This complete swing-over to the diesel-electric locomotive in the USA. was a tremendous fact, and it seemed to persist in spite of three factors which one would expect to slow it down, if not at present, at any rate as things developed.
The first concerned the mileages which the locomotives were able to accumulate. Much had been said of the duties which called for annual mileages of 200,000 and above, and quite rightly a great deal of prominence had been given to the capacity of the competing steam locomotive to go a good way towards meeting those mileages, but the plain fact was that there were in the USA tens of thousands of locomotives which did not attain greater mileages than from 20,000 to 50,000 a yearsomething of the order that was obtained in Britain countryso that one would imagine that there were limitations from the time-table and rostering point of view to the continued acceptance of locomotives whose high first cost was more especially suited to high mileage.
Cox claimed that although "there was a high degreee of standardization" of American diesel locomotives "railroads were now accumulating a series of locomotives from three or four independent makers which differed in every possible detail". The third point was that this great development had gone forward without any real knowledge of what the repair costs were. He had never spoken to any traveller returned from the USA who had been able to find out specifically what the repair cost situation was, and the American Railroad Association in its published literature had had to confess its inability to meet this point. In the USA, much more than elsewhere, the steam locomotive was reaching the limitations of its ability to do the job. To illustrate that, he would refer to two points.
The first was the relationship between boiler efficiency and rate of combustion. With the train loads referred to rates of combustion were necessarily very high on American engines and boiler efficiency probably did not average more than 60-65 per cent. This had the effect of stultifying to some extent all the advances which had been made in improved cylinders and valve events,' so that, as Ralph Johnson points out in his book, the overall thermal efficiency of the modern American locomotive is no greater than 6 or 7 per cent. This is a good deal lower than can be obtained elsewhere where operating conditions allow of boiler efficiencies of 70-75 per cent being obtained.
The second point was the limitation of the gas area through the tubes in regard to the total output of the locomotive. The area at that point in relation to the grate was the best single index that there was of the maximum capacity which a boiler could turn out. He had looked over the ratios of something like 60 modern American locomotives, and the average percentage of free area through the tubes in relation to the grate was 10.2 per cent., and 52 out of the 60 had percentages of less than 11 .5. That was a limitation which was imposed, in spite of the very generous loading gauge, by the mere fact of trying to get the boiler between the loading gauge and the wheels; whereas in this 'country, and he suggested in many others, it was possible 'even with the wide. firebox to obtain 15 per cent. and upwards, which allowed a more unrestricted steam production at maximum capacity ..
E.C. Poultney (88-9) said the Author had presented an informative picture of motive power practice on the railways of the United States at the present time. There appear to be certain design features that can be said to be mainly responsible for the very high horsepower capacity of modern American locomotives, and these are summarised as follows:
(1) The Superheater.
(2) Mechanical Stokers.
(3) Feed Water Heaters.
(4) The 4-Wheeled Trailing Truck.
(5) The Cast Steel Locomotive Bed Framing.
(6) Improved Motion Parts including the Woodard or Tandem Main and Side Rod Assembly.
(7) Large Valves and Long Travel Valve Gear.
Items (1) to (4) influence boiler capacity, and items (5) to (7) the features which enable the steam supply to be utilised in the production of tractive effort and horsepower. From the point of view of boiler capacity, it can be said that the introduction of the 4-wheel trailing truck in 1925 by the Lima locomotive works, marked the beginning of large advances in boiler capacity. In 1927 this feature was first applied to Pacific and Mountian type locomotives by the American Locomotive Company. The New York Central Hudson 4-6-4 and Northern Pacific 4-8-4 were respectively the first examples. Mr. Poultney illustrated the great development of the horse-power capacity of high speed locomotives in the USA during the last 20 years. He then referred to the latest steam motive power on the New York Central. These engines can develop a maximum of 6,600 h.p. at 85 miles an hour; and said if we assume that at this rate of working the cylinders require 17 lb. of steam per i.h.p. power, that would mean an evaporation of 112,000 lb. of water per hour, corresponding to 23 lb. per sq. ft. of heating surface. It also meant that 56,000 lb. of steam must be passed through each cylinder per hour and 9,300 lb. must be passed through each cylinder per minute equal to 21,000 ft3. of steam per minute. While these figures were not put forward as being absolutely correct, they were probably close enough to give a fair idea of the large quantity of steam which has to be handled by the valves distributing the steam in the cylinders, and draws attention in a very forcible manner to the importance of large portways and passages.
R.C. Bond (89-90) said that he agreed with the Author concerning the probable future of the steam locomotive taking the world as a whole, but Mr. Cox had rightly drawn attention to the trend of events in America and had quoted figures indicating the numbers of new locomotives of various types at present on order. Those figures were very impressive, and they gave a true and reliable picture of the position as it would be in the immediate future; nevertheless, he thought that Mr. Cox would agree with him that even today by far the greater proportion of the total tonnage moved in America was hauled by steam locomotives.
In America, as in other countries, there had been the usual answer to the challenge of new types of motive power in the form of special and more complicated types of steam locomotive. Fig. 3 of the Paper showed the C. & O. steam turbo-electric locomotive, and in time there would also be the pulverised coal gas turbine locomotive. It was not possible accurately to forecast what the future of that locomotive might be, but it was a little difficult to avoid the conclusion that steam turbo-electric locomotives might run the risk of incorporating within themselves all the disadvantages of every known form of motive power.
He thought that the important lesson to be learnt from the Work which the New York Central Railroad had been doing was the extent to which the ordinary simple, conventional steam locomotive could be developed to meet the challenge of the newer forms of motive power. While it was perfectly true that the bulk of American steam locomotives ran little more mileage per annum than locomotives in this country, the Niagara 4-8-4 locomotives, and the 4-6-4 locomotives which preceded them, were running very large mileages per annum, he believed up to 300,000, and that was largely the result of close attention to details of design and maintenance.
Steam locomotives were worked very much harder, in relation to their size, in America than in this country, and it was for that reason that steel fireboxes, welded tubes, water treatment and roller bearings were now entirely. normal features in modern American locomotive practice.
For how much longer the present proportion of diesel to steam locomotive construction would continue in America he did not know. When he was in the USA eighteen months ago there was no sign of any reversal of the trend, but he could not help feeling that it would come in time and that sooner or later the steam locomotive in its simplest form, but developed to the utmost, would maintain its position, and there would be a common-sense balance between the various forms of motive power.
W. Cyril WilIiams (90-1) said that the reputation of America had always been to go all out when she felt she was on a good thing. One of the main factors in the adoption of the diesel-electric locomotives by some of its rail roads was trouble with the boilers and fireboxes, principally stays, of such monster steam locomotives as the Southern Pacific with grate areas approaching 150 ft2. The diesel-electric could be divided up into units to reduce the axleload and he was told in the USA that railways wanted to bring it down to something like 28 tons. The duplex was another attempt to lower the weight of reciprocating parts. The lightening of rolling stock was also receiving attention.
Overall cost figures for main line diesel-electrics were not yet available and it would be interesting to examine these. They would presumably take into accqunt the colossal new shops for repairing same that we read about with their equipment not found in the ordinary running shed. Was not it true that at the moment most of the big diesels, apart from shunting engines, were on selected schedules, where they could get big mileages? He could cite, as could many others, instances all over the world where, when the length of haul was right and the traffic there, it was possible to get the same mileage with steam locomotives; it was well known that comparison statistics of operation was one of the most difficult things in the world.
Finally, there was the old question of the loading gauge, which meant that much of what had been done in America could not be done elsewhere. At the same time, we could learn a great deal from America and the notes which the Author had provided and from similar Papers. The cast steel bed seemed to come up frequently at the present time. He was intimately acquainted with engines of. 90,000 lb .. tractive effort which had been running for 20 years With. a well-built bar frame rolled from the slab, with plenty of steel castings, and no trouble had been recorded during this period,
T. Henry Turner (91) said he did not think that the steel casting was needed for steam locomotive frames in this country [Britain]; our narrower loading gauge did not encourage one to use it, unless possibly for gas turbine or diesel locomotives.
The wider loading gauge did not make everything easy for American locomotive designers; they also were limited bv permissible weight, despite the extraordinarily high American axle loads.
The Author had not mentioned the provision made in America for locomotive boiler water chemical control. It would not be possible to obtain maximum efficiency in operating locomotives in this country until locomotive boiler water was tested and accordingly controlled at every.shed. The French had recently progressed a long way In that direction, but he did not think that any other country with the exception of the USA had tried it in such a logical mariner. Every locomotive shed should practice boiler water testing and control as part of its every day and night routine.
Another point, which was not mentioned in the Paper, seemed worth. emphasizing, namely that American engineers use "direct steaming" in their locomotive sheds. It facilitated lighting up and steam raising and probably did more than could be done in any other practical way to reduce the coal smoke nuisance in and near locomotive running sheds.
W.O. Skeat (91-2) noted that certain celebrated British locomotive engineers-the names of Webb, Worsdell and Churchward occurred to himpaid visits to America and in the case of the last-named !n particular, the results were far-reaching, and were especially discernible In the Swindon standardisation programme which was formulated soon afterwards.
Skeat enquired what the present American trends were in terms of cylinder clearance volumes. The opinion in Europe on that matter seemed to be somewhat chaotic; there were opposing schools of thought, and he himself could not see at all which way things were going. At one locomotive works in this country he understood that the present feeling was that cylinder clearance volumes had been much too big in the past and ought to be brought down; on the other hand, In the Paper by E.L. Diamond The Development of Locomotive Power at Speed (Institution of Mechanical Engineers) there were references to extremely large clearance volumes in some of the Chapelon designs. Patrick replied that a clearance volume of about 10 to 12.5% of the swept volume apppeared to be current practice and was considered better than a clearance volume of 8 to 9% which had been tried.
Meeting in Leeds on 24 February 1949 at Great Northern Hotel at 18.45
chaired J.N. Compton who opened the discussion with an observation on mechanical
stokers: in the USA he had travelled on a K4 locomotive a small Pacific
of about 35,000 tractive effort, and was rather surprised that a stoker was
fitted. He believed that it was the law in the USA to use the mechanical
stoker with locomotives over a certain size. They were, of course, not economical
but enabled them to force their boilers. The appalling smoke of unburnt coal
may have a lot to do with the objection to the steam locomotive in built-up
areas. He asked if there was any inter-control of the steam jets with the
cut-off. In other words, did these steam jets only operate between a certain
range of cut-offs. With regard to the combustion chamber, he did not quite
follow how the bottom of the combustion chamber could be Belpaire shape and
how any increase of gas area was obtained. The Author replied that the steam
jets operataing the over the fire air inductors are operated by the fireman.
In response to the Belpaire shape Patrick observed that by pressing the barrel
and firebox to this shape the number of tubes and nett gas area could be
increase without increasing the diameter of the boiler shell.
W.A. Tuplin (94) said that one notable thing was that in comparison with their enormous fireboxes USA locomotives had moderate tube lengths not usually exceeding 25 ft. which was not much longer than some that have been used in locomotive boilers in Britain. Another point was that the figure of 71.3 ihp/ft2. of grate area on the TI class locomotive was not a record as it had been achieved on occasions by British locomotives of various classes, and when running at over 120 mile/h Mallard was producing over 90 ihp/ft2.; Chapelon locomotives had even reached 100 ihp/ft2. Although the TI locomotive of the U.S.A. was remarkable, it was not breaking records in this respect. He was interested, too, in the coal consumption for which figures had been published elsewhere and averaged something higher than 3 lb. per dhp/hr., which is about what is achieved by any good locomotive whether it has piston valves or poppet valves .. The mechanical stoker was naturally essential for a boiler of American dimensions but he could not help feeling that the propulsion of coal for 10 feet or so by jets must result either in heavy steam consumption if the coal is in large pieces, or heavy loss of unburnt coal if it is small. Something of this type might be useful in this country but he would be interested to know how much steam those stokers used. In reply the Author said that it be borne in mind that American locomotives were burning coal of low calorific value as compared with British coal, but mechanical stokers in conjunction with special grates have enabled them to burn low-grade coal with reasonable efficiency. The coal is reduced to small size before being distributed oyer the grate by the stoker jets, and if there is a high proportion of slack there is a considerable loss of unburnt fuel. Also, as mentioned in the Paper, some damage to the boiler occurs due to cinder-cutting when working with low-grade coal at high firing rates. The steam consumed by the stoker jets is approximately 1,400 lb. per hour for an evaporation of 125,000 lb. per hour and the corresponding consumption by the stoker engine is about 900 lb. per hour.
R.I. Vereker (94) said that one point of outstanding note was that on the New York Central 4-8-4 class SI, one of their latest design, the steam pressure dropped to 275 lb. Was it the practice now to have the lower pressure boiler? The Author spoke of syphon tubes and he would like to know if it was better for the design to be taken from the tubeplate or firebox wrapper plate, i.e. longitudinally or laterally with the boiler? In reply to Mr. 'Verener, he said that there was no indication that lower boiler pressures were now being adopted-the trend was rather the reverse. The boilers of the N. Y . C. Class SI" Niagara" were designed for a working pressure of 290 psi and although they were now 'working at 275 psi. the designed pressure may yet be adopted if found advantageous. Thermic syphons are placed longitudinally in a firebox connecting the throat to the crown and promote a very active circulation upwards from this somewhat "dead" area, at the same time providing a very substantial increase in the firebox heating surface. The Author considers this to be the most efficient circulating device in use.
Matthewson-Dick (93) asked about training footplate crews and was informed that firemen must fire for five years before becoming eligible for promotion to driver, and within a certain period of commencement as fireman must pass a series of tests on air brakes, boilers, appurtenances, and rules and regulations. Both drivers and firemen are subject to periodical tests on hearing, vision and colour perception. Important service depots are well equipped with facilities for handling the locomotives and executing routine repairs. Also with plant for hot water washing and direct steaming of boilers. It has now: become a .fairly common practice to clean' tubes by washing with a mixture of air and water under pressure.
Meeting in Birmingham on 2 March 1949 at Queens Hotel at 18.45
chaired E.R. Durnford 98-102
Durnford had asked about the cast steel frames and was informed that the Author had the privilege of inspecting the plant in which the one-piece locomotive frames were cast and machined. A series of large specially designed machines were employed, capable of taking the largest frames. Among the various operations extensive use was made of three-head plano-milling machines with special cutter assemblies. Portable machines were not employed, except for the final boring of the cylinder liners, which were pressed in and finished by the locomotive builder.
H. Lawton (98) had also requested further information on cast steel one-piece frames: the main air reservoirs were cast integral with the frame to save space and to eliminate support brackets. The reservoirs also formed part of the rigid backbone of the casting.
R.C.S. Low requested information on side play in the axleboxes of the 4-4-4-4 locomotives and was told that to accommodate the controlled lateral movement of the axles on the Permsylvania 4-4-4-4 locomotive the rods were designed to float on the outer races of the roller bearings, and the eyes were bored and shaped in such a way as to perrnrt the necessary relative angular movement. Bronze inserts were fitted in the eyes making contact with the roller bearing races.
Oil-fired steam locomotives were still employed extensively in certain States. The burners were of the flat type, and were normally located .at. the front end of the firebox, the whole system being generally similar to that recently introduced on some sections of British Railways.
J.S. Williams (100) was informed that the side play on the coupled axles of the Pennsylvania 4-4-4-4 locomotive was controlled by means of a helical spring arrangement attached to the axleboxes and connected to the main frames. This device was extensively employed on many types of locomotives to provide adequate freedom on curves. !he circulator tubes shown on Fig. 12 were as applied to a coal-burning locomotive. For oil-burning the cross tubes were arched upwards considerably more in the centre to allow for expansion. A considerable number of large American locomotives had double chimneys, and various forms of blast nozzles were in use including multiple-jet nozzles. The steam-turbo-electric locomotive was non-condensing, and the exhaust steam passed through the blast pipe in the usual way.
In reply to Mr. Gillitt, he said that firemen had to serve five years before becoming eligible for promotion to driver, and soon after commencement, had to pass a series of tests on boilers, air brake, appurtenances, and operating rules. All footplate staff had to pass periodical tests on hearing, vision, and colour perception. His Impressions, after a number of footplate trips, were that the men were very competent, physically fit, and keen on their job.
P.K. Dewhurst (99) was informed that the amount of rectification by welding found necessary in the course of machining the large cast-steel frames did not appear to be excessive, bearing in mind the size and complexity of the casting. Such rectification was carried out between roughing and finishing cuts without removing the frames from the machines.
N.W.H. Lloyd (99) was informed that the usual practice with plain bearing axleboxes was to provide cast steel shoes and wedges bearing on bronze guide liners on the axleboxes. Wedges were frequently of the floating type, with automatic spring loaded adjustment. Roller ring axleboxes were fitted with manganese steel liners and on some recent examples these worked on cold-rolled bronze faces inserted in steel shoes, without wedges.
Meeting in Manchester at the College of Technology on 15 March
1949 at 18.30: I.C. Forsyth in chair. 102-4
I.C. Forsyth (103) asked about the drive on the Pennsylvania turbine and was informed that a gearbox was mounted on rhe frames enclosing the second and third axles containing reduction gears and the final flexible drive to each of these axles. The turbines were mounted on either side of this gearbox between the wheels, as illustrated. All-welded locomotive boilers were manufactured only by the American Locomotive Company, and stress-relieving of the complete shell was considered essential and was stipulated by the American Code of Boiler Construction, which also laid down standards regard ing the welding procedure. Manganese steel liners were fitted on all Timken axleboxes. For coupled axle bearings recent practice on some railroads is to fit steel guide shoes having cold-rolled bronze inserts on the bearing faces, dispensing with wedges. For bogie applications the shoes were pressings of manganese steel and in some cases of tempered spring steel.
H. Fowler (103) was told that firebox stays normally of steel having 0.15% carbon and 0.6% manganese, and tensile strength 50,000?? to 60,000 psi were screwed, and frequently seal-welded on the fire side. Fireboxes were of steel and welded throughout.
E.R. Brown (103) was informed that the majority of modern American locomotives were fitted with multiple valve regulators in the smokebox. The Chambers regulator was also common, comprising one pilot valve and one main valve with balancing chamber and is also located in the smokebox. Resistance figures for locomotives were calculated on the usual basis of rail load, number of axles, frontal area, and operating speed. The drawbar pull curve shown on Fig. 21 was for the N.Y.C. Niagara Class locomotive, and offered proof the excellent design of cylinders and srnokebox, and of adequate steaming capacity.
J. Sinclair (103) was informed that fusible plugs are employed, but considerable use is also made of float type low water alarms.
Meeting in Glasgow at St. Enoch Station Hotel on 21 March 1949
at 19.30: R.P. Critchley in chair. 104-8
R.P. Critchley (105) asked if mechanics were employed in repairng the unit while travelling on the railway. The Author, in reply to the Chairman, said a mechanic work- ing on the diesel engines was not a normal part of the crew, but such work was sometimes carried out, as on a multiple-unit locomotive the controls made provision for cutting out anyone engine set at will.
Phillips (105) asked, with regard to the weights on the axles, if the Author could say what rails were used, i.e, the weight per yard, and the approximate sleeper spacings if possible, as well as the type of sleeper adopted; and was informed that flat-bottom spiked rails weighing 127 lb. to 150 lb. per yd. were common and on some sections still heavier rails were being laid. Sleepers were generally wood, but he could not quote the spacing.
He also asked about steam heating on the diesel-electric locomotive, and train crews and was told that fuel used by the boiler was included in the expenditure for coal or oil used when comparing with steam locomotives. Steam heating boilers employed on diesel-electric locomotives are of the Clarkson Automatic type and are oil fired. It was part of the fireman's job to look after these units. Cost of fuel for train heating is included in comparative running costs.
K.R.M. Cameron (105) said one feature interested him and asked the Author if he could say how they fastened the tyres to the wheel. centres. He had had a limited experience with American engmes and found to his horror that the tyres were shrunk on. Slack tyres were quite the rule on heavy freight work partlcularly, and the Americans were apparently accustomed to ehangmg. tyres. m the running sheds by jacking up the offending axle, taking off the coupling rod, heating another tyre, and so the wheel is retyred. The tyre had previously been turned in a lathe to approximately the diameter of the rest, and then shrunk on. Strange to say, It worked. He asked If there was any independent method of fastenmg tyres other than shrinking. The crushing load, such as the 38 tons mentioned, on such tyres, would result in deformation on a scale greater than we have experienced in this country. In reply the Author said the standard practice was to secure tyres by shrinkage only, the shrinkage allowance prescribed being .038 in. for 36 in. centres and .102 in. for 78 in. centres; varying uniformly between and beyond these diameters. Exceptions were the Southern Pacific, who welded short strips to the rim which engage in a groove in the tyre, and the Pennsylvania who used similar but somewhat longer strips each secured by two rivets through the rim. Trouble with slack tyres had been greatly reduced by more rigid control of the type of shims sometimes fitted between tyre and rim as a repair measure, and by regulating the scrapping thickness of tyres. The operation of fitting new tyres without unwheeling is not part of American main line practice, as new tyres are normally fitted and machined to correct profile in the usual way. Regardmg. crews, he had.seen on the American multiple unit the travellmg maintenance engineer clean the unit, check valve clearances, taking readings of temperatures and oil levels and doing other maintenance jobs. The cost of the maintenance engineer's wages is compensated by the fact that the engine is not out of service at the terminus while the examination is carried out.
J.S. Scott (105) was interested in the development of steel castings, equally with regard to steam as with diesel. The diesel had apparently gone back to built up sections and riveted horns. He did not agree with the Author with regard to cheapness of oil on diesel engines in Arnerrca, but they were enabled to build standardised parts by mass production with consequent cheapened costs. With regard to Cameron's points, Scott thought that Bulleid of the Southern took his courage in both hands when he shrunk on a tyre on the Merchant Navy class and put on a very small amount of flange which was riveted over. Replying the Author agreed that fabrication by electric welding was being extensively employed on diesel-electric locomotives, but said this did not apply to the bogie frames which are one-piece steel castings.
J.H. Menzies (106) asked if the Author had any views on the use of the locomotive valve pilot versus back pressure gauges, and whether any examples were seen of the use of the throttle master which also would appear to lighten the task of the engineer. He also desired information on the 4-8-0 shunter of the Norfolk & Western Railroad rebuilt in 1947 and fitted with automatic controls to maintain boiler pressure. Was this successful, and was any extension of the design likely? He also asked for the Author's views on signal foam meters and the various forms of low water alarm. . In reply to Mr. Meneies , he had seen the" locomotive valve pilot" which indicates on a duplex gauge the speed and the Corresponding optimum cut-off for the guidance of the driver and
A. Hood (106) said with regard to the method shown for securing the tyre to the wheel, this was done by welding five small pieces of steel 3 in. long, ¾ in. deep to the wheel centre, overlapping the, rim by 3/8in. or ¾ in. That is what is being done in Australia also, and is more or less American practice. The Author had mentioned thermic syphons and Security Circulator tubes. but Hood thought it had been found the thermic syphon had not proved to be everything it should have been, in spite of the fact that this boiler had been put on the Merchant Navy type. The Russians said when the thermic syphon was introduced that it was no use at all. If you put black blast in the middle of any fire you need additional heating, but these locomotives are equipped with mechanical stokers and there is no question of saving fuel- it is just loaded on as hard as they can. These thermic syphons may be useful in the States, but with the smaller firebox it remains to be seen.
B.C. Bean (106) stated the Author said there was little likelihood of the cast steel main frame coming into force. That is probably true, but we have not the output here to justify expenditure on the plant required. He thought the cast steel bogie, however, was a very excellent thing. The cast steel bogie is made in this country and it is gaining popularity in some of the Colonies. If you can get a bogie made very rigid and flexibility taken up in the springs it is a far better job than being bolted up with plates .and angles. There is absolutely no machining on the bogies. If we could get engineers interested in this country we would find this bogie would do a far better job. He then referred to Cameron's question of the shrinkage of tyres, and said that on the Gold Coast for many years they never did anything else, and so far as he was aware there had been no complaints or disasters.
Journal No. 208.
Borgeaud, Gaston (Paper 484)
The latest development of the electric locomotive in Switzerland - its mechanics and some problems. 121-224.
Fifth ordinary general meeting of the Session 1948-49 was held at the Institution of Mechanical Engineers, London, on Wednesday 19 January 1949 at 5.30 p.m.: Lieut.-Col. Harold Rudgard, President, occupying the chair.
Issue No. 209
Forsyth, I.C. (Paper No. 485)
Some developments in locomotive workshop practice, 1939-1948. 231-83. Disc.: 285-310. 58 diagrams.
Improvements introduced at Crewe Works including shot-blasting, hydro-blasting, steel melting and casting, locomotive cylinder casting in steel, cold sawing, drop stamping, pulverized fuel fired re-heating furnaces in the forge, oxy-acetylene and electric arc welding, automatic continuous welding, stud welding, frame welding, machine tools, finishing of big end and coupling rod bushes and axlebox straps and work inspection.
Issue No. 210
Armand, Louis (Sir Seymour Biscoe Tritton
The influence of the treatment of boiler waters on the maintenance and utilisation of steam locomotives. 328-51.
From a physico-chemical standpoint, the compounds added to the water aim at:
(a) Precipitating lime and magnesium salts in solution in the form of deposits which, combined with an organic substance, form a sludge instead of scale, for each component shows no tendency to coagulate with the others. Special measures must be provided for the anti-scaling effect to be active both in the boilers and in the feeding devices (injector, pumps and pre-heaters) for the conditions in each case are different. In order to obtain that result recourse had to be made to both ordinary chemical reactions, similar to those which are utilised in lime-soda softening plants and to the action of organic products, which through their pseudo combination with the' salts of calcium precipitate them in the form of a pseudo colloid :
(b) Maintaining in the boiler water a sufficient alkalinity so as to avoid ordinary corrosion, without however fearing caustic embrittlement:
(c) Eliminating oxygen from the water in order to prevent certain corrosions:
(d) Finally, by means of deconcentration blow-downs and of the action of certain products, preventing the formation of foaming in the boiler.
Dynamometer car run, Rugby-Manchester (London Road). 353-5.
Run behind Caprotti-fitted class 5 No. 4752 on Tuesday 10th May 1949.
Visit to Messrs. Beyer, Peacock & Co. Ltd. on Thursday 12th May 1949. 358-60.
Demonstration run with dynamometer car and mobile test units Manchester (Central) to Derby on Friday 13th May 1949. 361-5. diagr., table.
5XP class locomotive
Hirst, G.W.C. (Paper No. 486)
The detection of cracks and flaws in axles and crank pins by means of supersonic waves. 367-79. Disc.: 379-85.
Presented in Sydney
Journal No. 211
Williams, W. Cyril
Address by the President. The changing scene: some reflections on overseas railway progress and problems. 394-444.
The early history, later application and development of superheating in locomotive practice. 446-72.
Chairman's Address in New South Wales. Noted that his initial experience with superheaters had been on the GNR in England.
Journal No. 212
Alcock, J.F. (Paper No. 487)
Locomotive limits and fits. 477-502. Disc.: 502-31. 11 diagrs. Bibliography.
Institution of Locomotive Engineers
Locomotive Building Practice, by F. Thompson. Journal No. 47, Paper 91
The Behaviour of Railway Material, by C.W. Ridge. Journal No. 102, p. 577. Paper 280
Locomotive Wheels, Tyres and Axles, by E.S. Cox. Journal No. 128, p. 761 (Paper No. 346).
The Fatigued Strength of Machined Tyre Steels, by T. Baldwin. Journal No. 146, p. 658. (Paper No. 394)
Institution of Mechanical Engineers
British and American Locomotive Design and Practice, by P. C. Dewhurst. Journal No. 3, p. 415.(hopefully corrected and redirected)
Factors Affecting the Grip in Force, Shrink and Expansion Fits," by R. Russell. Vol. 125, p. 493.
Force Fits and Shrinkage Fits in Crank Webs and Locomotive Driving Wheels, by E.G. Coker and Miss R. Levi. Vol. 127, p. 249.
Stress Waves in the Tyres of Locomotives," by E.G. Coker and Mr. Salvadori. Vol. 131, p. 493. "
An Investigation into the Occurrence and Causes of Locomotive Tyre Failures," by C. W. Newberry. Vol. 142, No. 3, p. 289.
Discussion: R.C. Bond (502-) said the subject was one of very great interest and he knew from his own experience as Chairman of the LMS Limits and Fits Committee for some part of the time, how much work had been put into the pioneer Report of the Locomotive Manufacturers' Association Committee.
The whole purpose of limits and fits needed to be kept clearly in mind. As .he saw it there were three main features of importance to those who build and operate locomotives. He was not recording those three features in order of their importance but in the order in which they occurred.
Firstly, there was the question of facilitating manufacture, reducing costs and improving the quality of the product. Those matters, of course, were of vital importance to the locomotive industry and to the railways as manufacturers of locomotives.
Secondly, it was essential to ensure at all times that the running clearances and interference fits, which from long experience of thousands of locomotives the railways knew to be necessary, were achieved in practice.
Finally, and perhaps in some ways most important of all, there was the question of the relationship of limits and fits to repairs and maintenance. There must be strict dimensional control of these parts ·of a locomotive which were not subject to wear but which were attached to or had attached to them parts which were subject to wear and periodical renewal. For those parts there must be complete adherence to standards laid down.
If the above principles were accepted, it was necessary to ask to what extent the last sentence in the Paper was correct. It is stated that "All steam locomotive manufacturers in Britain work to the same limits and fits." Surely the prime objective was to give the railways what they required. As he knew from experience some years ago on inspection of locomotives under construction for the LMS Railway in many of the principal contractors' works, this certainly used to be the case. If that was still the main objective of manufacturers, as he felt sure it was, then he could not help feeling that it was impossible for them to be working to the same limits and fits in all respects.
He would mention piston rings, piston ring grooves and holes in brake hangers, and similar parts into which bushes are pressed, as examples of items which it was vital should conform strictly to limits and fits laid down by the user of the locomotives. Many other items in the same category would, no doubt, readily occur to the members. It was not sufficient for the clearance between piston rings and their grooves to be in accordance with requirements. The piston rings were renewed at running sheds two or three times between classified repairs in main workshops and it was essential that rings manufactured by the railway company in their own shops for stock should be usable at all times. Hence the width of the grooves in the piston heads must conform to the limits laid down by the user.
There were on the other hand limits and fits which were not of particular significance except to the manufacturer for the purpose of improving, or reducing the cost of, his manufacturing processes. Crank pins can be taken as an example in this category. So long as the running clearance between the crank pin and connecting rod or coupling rod bush was correct it does not matter to a few 1,000ths what the size of the crank pin is initially, because on a number of occasions during the life of the crank pin it will be ground to correct inevitable wear, and it was not an economic proposition in this case to reduce the diameter by predetermined stepped sizes. A similar argument applies to the outside diameter of tyres.
The conclusion to be drawn was, he suggested, that so long.as locomotives built in this country were sent all over the world to railways or administrations which had to maintain them, it was fundamental that the railways in question would require certain parts of the locomotives to conform strictly to their own standards.
He could not help feeling that in spite of all the excellent work done by the LMA Committee it was a pity that the British standard limits and fits systems, with some adaptation where necessary, had not been adopted. .
He had intended to give some account of the way in which the LMS Railway had used, and adapted where necessary, the British standard system to their locomotive work. This was, however, no longer necessary as in the current issue of Engineering members would find a full description of the system in summarised form. He could assure the members that this system was in daily use in all main works of the ex-LMS Railway and it was, in fact, the British Standard system with a strictly limited number of adaptations.
It seemed to him that the adoption by the LMA of standard limits, fits and tolerances, irrespective of the size of the parts, must bnng about the need for more gauges than would otherwise have been necessary. Had the British standard system been adopted wherein tolerances and fits bear a definite relationship to the sizes of the parts. it would have been possible to use series of gauges having very wide apphcation.
One of the guiding principles when deciding upon limits and fits to be used in the shops of the LMS Railway had been to allow the widest possible tolerances that experience had proved to be successful. In order to find out what they were, the Committee had been careful to make investigations in the shops and to find out exactly what was being done, and only then to lay down within the framework of the British Standard system, the limits and fits to be adopted in all shops for the future.
The many questions involved in pressing wheels on to their axles all boiled down in the end to the view expressed in one sentence in the Paper to the effect that "it was largely a matter of workshop practice." It was bound to be so and there was no reason at all why it should not be so. Wheels must be tight on their axles and the pressmg on loads must comply with the customer's specification. If this condition was met there would result, in all probability, an mterference fit of from .001 in. to .002 in. per in. of diameter, but there was nothing to be gained by attempting to lay down that each and every works manufacturing locomotives for service anywhere in the world must have their wheels and axles manufactured to identical limits.
While on this question of pressing on wheels, there was one point m the Paper to which he thought he must take exception. The Author had stated that a smooth ground finish on axle wheel seats resulted in too low a pressing on pressure. He entirely disagreed with that. A ground finish does not prevent an adequate pressmg on load being obtained and he suggested that the time for filing wheel seats was past. Wheels and axles can be and are being produced with complete satisfaction straight from the machine tools.
There was one further point in connection with cylinders and crankpins to which he wished to refer the Author had. suggested that cylinders must be bored to the hole basis and crankpms must be finished on a "shaft" basis. He did not agree with these views because the diameter of the cylinders, when scrapped, will be at least ½ in. above the nominal diameter and crankpins .will be probably not less than ½ in. smaller than their ongmal size. Design and stressing of these and other similar component parts must take mto account inevitable wear in service.
In conclusion he desired to express his thanks to the Author for a most interesting Paper. He hoped that what he had said had ~ot sounded too critical. The subject was inevitably most controversial and he was quite sure that the discussion thereon would result in considerable benefit to the locomotive industry and the railways.
Sir William Stanier, (505-8) said that the important thing in the Paper was that it had shown that the locomotive manufacturers in this country had now adopted a universal system and he thought that that was of the greatest importance. Whether it was right or not was a matter for discussion. He agreed with Bond that the B.S.S. specifications could be more rigidly adhered to but he would like to give something of the history regarding this matter.
He remembered in 1912 seing Lelean working out the limits and fits for the Indian Government Railways. He himself had been very interested in what Lelean was doing and he had told him that he had been brought up to think of 1. thousandth of an in. down for a running fit and 1 thousandth ~f an m. up for ~ press fit .which was the general practice on the railways at that time. Again, he remembered the work that Horwich had done on the Lancashire and Yorkshire Railway. When they first put in the go and no-go gauges it was a strong effort to produce standard parts.
He thought it should be remembe.red that improvements made in the grinding machine had made possible fits and limits. One thmg which had horrified him m the Paper was the suggestion made that it was necessary to file a true wheel seat in order to get it to fit. He himself had been warned many years ago that if he put a file on turned work he would go straight to hell! The Author suggested that it was not possible with a ground surface to get a proper pressure in fitting the wheel to the axle. He had been reading only that day in an American mechanical engmeering Journal that they had been making some tests with vanous fimshes and vanous lubricants for wheels. The finish they recommended was a ground finish for the wheel seat with a fine bore hole. (See extract on page 507.)
There was another point in the Paper about a 1 in 500 taper. He was perhaps one of the few who knew how that had arisen. Pearson, when on the Great Western, had been having trouble with carnage axles. They were breaking just inside the wheel seat. On investigation he had found that in pressing the parallel wheel seat into a parallel hole the front part of the axle rubbed off the bore at the inner end so that when the axle was home the hole was bell-mouthed, moisture went in and corrosion occurred. Pearson said that he was grinding wheel seats so that he had a 1 in 500 taper, so the practice of grinding wheel seats 1 in 500 spread to the locomotive works. The LMS had had trouble with crankpins and they thought that one of the troubles was that the fit of the outside of the quarter piece was not sufficiently tight on the crankpin to prevent moisture seeping in. They had changed to a parallel bore hole with a 1 in 500 taper on the pin. That had spread to axles as well eventually.
One of the things which horrified him was that the LMS were bell-mouthing the hole. He did not understand why because it was the amount of tolerance put on the point of the wheel seat of the axle that mattered. When he had left the LMS their practice was a finely bored parallel hole in the wheel and a ground wheel seat with a taper of 1 in 500 on the axle.
On the question of motion holes and pins the Author wondered whether there would be failures when one allowed for casehardened holes and ground pins with a running fit of only half a thousandth for 1¼ in. pin
J.F. Alcock: No, fixed holes, Sir William.
Sir William Stanier: because, having had a good deal of experience with case hardening, his company had found it necessary to allow double the tolerance to that used with bronze bushes. Probably the Author knew that on the LMS they had devised a system of tolerances to limit gauges for turning and boring the bushes and after assembly they finished the hole with a burnishing broach. The broach was sized to limits laid down, giving a mirror finish. The pins were ground to go and no-go gauges. He himself had been responsible for the burnishing broach because he had seen it at the American locomotive works in 1927. He had brought it back and the foreman of the machine shop on the G.W.R. had thought it a good idea and had decided to size the hole as well. That became standardised. and he thought that now there was a standard schedule on the Great Western and on the LMS which covered all sizes of motion parts and which lay down tolerances as well.
He could not understand the statement made by Mr. Alcock that the majority of crankpins had a 1 in 50 taper. He thought that that had been given up when he had served his time.' The Great Western and the LMS did not use it. It must be only the manufacturers! The main thing was that on the Great Western his late chief had had the idea that they should have parallel crankpins and no difference in diameter of the quarter pieces to crankpin. As a result crankpins had broken all over the place after a year and since then it had always been the practice for the part in the quarter piece to be very materially larger than the diameter of the crankpin so that any stress in the crankpin occurred outside the quarter piece and it was possible to see what had happened. He thought that that was better than a taper of 1 in 50.
Extract taken from Mechanical Engineering November 1949
PRESS FITS A Paper discussing the press fit between the railway car wheel and axle was presented by H. J. Schrader, research professor of theoretical and applied mechanics, University of Illinois. Urbana, Ill., during the 1948 ASME Annual Meeting, New York, N.Y.
He pointed out that both the machine shop and mounting practice have greatly improved during the past decade. but the number of wheel loose on axles have not been reduced to a desirable minimum. It may be that the higher speed of both freight and passenger train has a more detrimental effect than the benefit derived from the better machine-shop and mounting practices.
In general, mathematical analyses of the press-fit problem are an extension of Lame's solution of stresses in thick-walled cylinders subjected to internal and external pressure, to cover the special condition of the press- fit problem.
When a thick-walled cylinder is subjected to an internal pressure the body will deform in a radial direction away from the centre; likewise, when a, solid cylinder is subjected to an external pressure it will deform in a radial direction toward the centre. The hub of a car wheel can be considered to be a ·hollow cylinder and the axle a solid cylinder. The internal pressure acting on the hub is equal to the external pressure acting on the axle and when assembled these pressures are equal.
With given diameters of the hub and axle and with the equations for finding the stresses in thick-walled cylinders as developed by Lame, it is possible to determine the pressure that exists between the hub and axle. This solution assumes a uniform pressure between the hub and axle which is true if the axle does not extend beyond the hub faces, or if the shaft does not deform under the pressure. In practice both of these occur, and there will be an increase of stress at the junction of the axle and hub faces.
During a series of mounting tests, ten wheels were tested. The mounting allowance and the lubricant followed AAR standard recommendations, that is, the allowance was 0.0015 in. per in.' of diameter and the lubricant was 12 lb. of white lead to 1 gallon of boiled linseed oil. The speed of mounting was much slower than railroad practice. At each in. of progress, the loading was stopped and a set of strain measurements were taken. With the slow mounting speed the mounting pressures for several of the wheels were below the AAR minimum limits.
Two wheels were mounted on axles with ground wheel seats. These wheels showed considerably higher mounting pressures than those for comparable wheels mounted on turned seats. The bore of the wheels was not ground in either case.
Four wheels were used in repeated mounting tests, two were mounted four times and two were mounted six times. The load required for the second mo'unting was from 28 to 41 per cent. greater than for the initial mounting. With further mountings there was a large increase in the case of one wheel, an appreciable increase for another wheel, and little change for two wheels.
In the foregoing repeated mounting tests the wheels were mounted in about 20 sec. in some cases, and in about 10 min. in others. For the few tests made there seem to be no consistent effects of mounting speeds upon the loads required to press the wheel on to the axle.
Mounting. tests on relatively. few wrought-steel wheels indicate that strains in the hub of the wheel are not always proportional to the mounting pressures. Apparently, small differences or irregularities in the surface finish and slight tapers of the wheel seat or wheel bore, have a great influence on the mounting loads and the wheel strains, and some wheels requiring high mounting loads may pot be subjected to strains as great as those existing in wheels mounted with lower mounting loads.
Some European practices were also discussed by Mr. Schrader.' He said that the main difference is that the Europeans use a wheel centre and shrink on a tyre. The wheel centre is forged of a material which is considerably lower in carbon (0.18' to' 0.20) than is used in wheels for any- American railroads. The mounting allowance, lubrication, and allowable mounting pressures are practically equivalent to U:S. practices.
D.C. Brown (508)
Compton, J.N. (Paper No. 488)
Introduction and development of the pacific type locomotive for the broad gauge in India. 532-50. Disc.: 550-6.
XA,, XB, XC, experimental XP, WL of the North Western Railway and WP classes.
Woollatt, J.S. (Paper No. 489)
A criticism of some aspects of locomotive design. 557-71. Disc.: 572-83. 7 illus., 2 diagrs.
Meeting in Derby at the Midland Hotel on Tuesday 11 January 1949 at 19.00: E.R. Durnford in Chair.
Graduate paper. Since enclosure also improves conditions for the bearings, enclosure of a locomotive valve gear and motion has more advantages than disadvantages.
Another aspect. of mechanical performance is that of the whole locomotive as a vehicle on the track. A smooth riding locomotive will, since lesser forces are imp1ied, wear much better than a locomotive which rides roughly. The subject of locomotive riding is one which has always been shrouded in mystery, and the complete inability of locomotive engineers to come to terms with the problem is illustrated by th,e inconsistency of methods adopted to assist the wheel flanges in their job of constraining the locomotive.
It was found originally that the provision of. a fairly shallow flange was sufficient to keep the engine on the rails, a logical later development being the provision of side-sprung guiding wheels to reduce the side load occurring at the leading coupled wheel flanges. The loading of the side control springs at the guiding wheels has always been decided quite arbitrarily, since the value of the various side forces involved cannot be calculated on account of the variables involved, and, furthermore, would be almost impossible to determine experimentally. It has never been known, consequently, exactly how near a locomotive wheel may approach to derailment in normal service, and on certain designs, the arbitrary method of providing side control has been insufficient since derailments have occurred for no obvious reasons. The position has become so ludicrous that designers have avoided. certain types of locomotives because they doubt their ability to design specimens which will keep on the rails. Examples of this attitude are given by the antipathy of Southern Railway engiqeers towards 2-6-4 tank engines, and the antipathy of everybody since Stroudley towards express locomotives with no guiding wheels at the front. It has to be admitted that the problem is bound to defeat everybody but the theorists.
There are two notable sources af infarmation on this subject. Ubelacker, in 1903, provided a fairly simple method of determining lateral forces on wheel treads and flanges when a locomotive is rounding a curve, but unfortunately the theary begs the questian by assuming that a locomotive rounds a curve smoothly. In other words, he assumes that the side forces existing do not change their magnitude, whereas what actually happens is, of course, that the locomotive at speed is always swaying from side to side on the track.
F.W. Carter, in two Papers written in 1928 and 1930 (years may not be correct KPJ) attempted to find the cause of the oscillation of the locomative and developed a theory arising from the nature of the contact between tyres and rails and also the effect of the coned tread. He showed that if the guiding af a locomotive by side-controlled carrying wheels is correctly designed, the locomotive would have a tendency to. keep to the, rails even without any flanges on the wheels, provided that the wheel treads are coned. The significance of this is that a locomotive so designed would behave very much better on encountering irregularities in the track than one not designed to follow Carter's conclusions. There are many examples af the truth of these conclusions. For, example, he lays down that pony trucks must have an initial side controlling force, so that an ex-L.M.S. 2-6-2 or a Horwich designed 2-6-0 both of which ride well conform to Carter's conclusions, while an ex-L.N.E.R. Class V2 2-6-2, which has a bad reputation, has a type of side control which exerts no initial control on the front or back end of the locomotive. A strong case can be made out for the adoption of Carter's principles, but they appear to have received no attention up to the present.
A slight contribution towards the aim of improving the riding and reducing the derailing tendencies of locomotives concerns the bearing spring fitted. A leaf-type wheel spring in new condition can, by virtue of the friction between 'its leaves, vary the load it exerts from, 10 to 8 tons without changing its deflection. When it was in old condition the load can vary from 10 to 6 tons. Conversely, a wheel which carried 10 tons when weighed might eventually continually vary its load on the rails between 10 and 14 tons.
This effect of continually varyirig wheel load will have a certain tendency to cause a locomotive to roll, but it will not be a serious effect since the friction in the springs will rapidly damp out any rolling. The most serious result of this effect will be that anyone wheel may have a small vertical load on it at the same time as it takes a large lateral load, so that the derailing tendency at that wheel will be great. The reduction in wheel load occurs since the damping effect of the friction in the springs is bi-directional. If damping were provided in the upward direction only, the wheel loading would be allowed to increase on any one wheel but not immediately to decrease. This could be done by using coil springs in conjuction with a uni-directional dashpot at each wheel.
There are other reasons why such an arrangement would be advantageous. It appears that. the conditions of operation of locomotive wheel springs are so arduous that it is impossible to design and manufacture cheaply a spring which will give satisfaction for a long period. After a few months' service a leaf spring acquires a set, presumably because the stresses involved are much higher than anticipated. There is also the fact that no satisfactory method has been evolved for preventing the leaves of a spring from moving in the buckle. Coil springs are open to neither of these disadvantages and are objectionable merely an account of their lacking any damping characteristics. If, therefore, a damped coil spring suspension unit could be used, leaf springs,could be entirely eliminated. The reduced cost of coil springs instead of leaf spring suspension would partially compensate for the cost of a damping unit.
A possible arrangement is shown in Fig. 3, and.would be applied to the coupled axles only, carrying axle springs being undamped. The damping forces needed could best be determined experimentally, and it is probable that on a medium or slow-speed locomotive damping need only be employed on one axle. The arrangement shown employs two coil springs in the conventional position, with the load transmitted via a bridge to faces, in contact but unclamped
E.R. Durnford (572) commented on the leakage of oil from the oil bath on the Bulleid Pacifics.,