Journal of the Institution Locomotive Engineers
Volume 34 (1944)
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Journal No. 177
Alcock, G.W. (Paper No. 444)
Development of the locomotive poppet valve gear in America. 5-25. Disc.: 25-61. 19 figures (illus. and diagrs.)
Third Ordinary General Meeting of the Session 1942-43 held at the Institution of Mechanical Engineers, London, on Thursday, 10 June 1943, at 5.30 p.m., O.V.S. Bulleid, President, occupying the chair.
The Franklin System of Steam Distribution marks a step forward in the scientific development of the steam locomotive. This system stems from two important developments: the use of horizontal poppet valves of a design very similar to that applied to a great many British built locomotives ; and an entirely new design of valve gear developed by the late William E. Wood[w]ard, for many years Vice-president in Charge of Design of the Lima Locomotive Works.
The Franklin Railway Supply Company undertook a major research programme to develop an entirely new system of steam distribution, which would bring to the American locomotive the full potential advantages possible with poppet valves. The objectives of this research programme were 'as follows :-
Increase mean effcctive pressure to be obtained by a separation of the valve events so that the admission and cut-off, release and compression would be controlled independently, at the same time providing large passage areas for both inlet and exhaust and improved steam flow.
Increase cylinder economy to be obtained by reduced clearance volume, the independent control of the valve events, and by a substantial decrease in back pressure.
Increased mechanical efficiency to be obtained by reduced weight of moving masses, reduced friction and elimination of carbonization.
Reduced maintenance to be obtained by the use of light-weight parts, the entire mechanism to be fitted with anti-friction bearings, running in an oil bath. Absolutely fixed valve events at all speeds and all cut-offs.
Journal No. 178
Poultney, E.C. (Paper No. 445).
Locomotive power. 66-103. Disc.: 103-45. 23 diagrs., tables. Bibliog.
Paper mentioned in Locomotive Mag., 1943, 49, 166. The object of this Paper is to put before members a method which the author has evolved for determining the probable power output of simple expansion steam locomotives as measured by the power available at the coupling between the locomotive and the train. During the last few years much attention has been given to this subject, which is, of course, of great interest and importance. A perusal of the technical journals, and more especially those devoted to railway matters, will establish the truth of this statement, and a list of some of the more important contributions dealing with the evaluation of steam locomotive power which have appeared during recent years will be found at the end of the present Paper. No attempt will be made to discuss the various means which have been suggested at various times and by numerous authorities to establish means whereby the power of a steam locomotive may be estimated. This has been very well dealt with comparatively recently in a series of articles by E. L. Diamond, contributed to The Railway Gazette, and to which attention may usefully be drawn. As Iresult of tha study the author has been able to give to the problem the conclusion has been reached that it is best and most convenient to separate entirely the boiler and the engine performance and estimate locomotive resistance by some formulac which includes engine friction and the rolling and air resistances. The means proposed for estimating pulling power throughout the usual operating speeds obtaining in either passenger or freight service is therefore as follows. Four distinct processes are involved. These are the determination of :-
I. The Tractive Force.
2. Boiler Steaming Capacity.
3. The mean effective pressure in the cylinders from which
4. Resistance of the Locomotive.
is calculated the Indicated Tractive Force.
I. The Tractive Force depends entirely on the dimensions and the number of the cylinders, the diameter of the driving wheels, and the steam pressure, the mean pressure (maximum) being dependent upon the initial pressure and the full gear cut off.
Boiler capacity is taken to be proportional to the grate area, and is determined by the firing rate and the heat value of the coal fired.
The available mean pressure in the cylinders depends upon the steam supplied to the engines per unit of time. This is governed by the boiler capacity in relation to that of the cylinders.
Locomotive Resistance is a function of the total weight, the size of driving wheels, the number of coupled axles, and the head-on air resistance.
Without going into a lot of detail the above shortly sets out the factors governing locomotive power. They are accepted by the author as being fundamental, and form the basis of the proposed method for arriving at the performance of any given steam locomotive of normal type and design, a delineation of which followed:
Discussion:. Mr. E. S. Cox (104-6) remarked that the author, particularly in his conclusions, rather disarmed any criticism of his Paper by pointing out the tentative nature of some of the information on which his calculations were based, and by emphasising his desire to avoid complication. It was possible, howcver, to over-simplify so difficult a subject as locomotive performance, and personally he would like to draw attention to two places wherr he thought that the conclusions given in the Paper might be a little misleading. The author gave a diagram (Sheet 2) illustrating the evaporation of a boiler as it was affected by changes in the calorific value of the coal. That, of course, was something which it was very necessary to study in the design of a locomotive, and especially in the design of a freight locomotive, which had to do its booked work with any kind of coal which might be available. But it was not only calorific value which affected the evaporation ; the quantity of ash and the amount of clinker formed by a coal might also, by artificially restricting the effective grate area as it accumulated, affect the evaporation to a greater extent than a consideration of the calorific value alone might lead one to imagine.
To illustrate that, some time before WW2 some tests were carried out on the L.M.S. Railway with a modern freight engine with modern valve events and a good steaming boiler (presumably 8F 2-8-0), in which trains of some 1,000 tons were taken between Toton and London day in and day out under very uniform conditions of running. The steaming was good, time was kept, and the only factor which was changed was the coal; a succession of different kinds of coal were tried, ranging all the way from the best supplied to locomotives to the worst with which they had to put up. The calorific value of the best was 14,500 B.Th.U. per-lb., and in passing it might be mentioned that all engine testing on the L.M.S., where quality of coal did not enter into it, was carried out with -coal from one colliery alone having the B.Th.U. value. The worst coal had a calorific value of 11,150 B.Th.U. The water consumption-the demand on the boiler made by the engine was very uniform throughout the whole series of tests, but the coal consumption varied from 2.73 lb. per d.b.h.p. hour to 4.12 lb. per d.b.h.p. hour, whereas pro ratu to the drop in calorific value alone the lowest consumption should have been only in the region of 3.j lb. per d.b.1i.p. hour. The difference between that figure and the actual heaviest of 4.12 was accounted for by the factor of the restriction of effective grate area which he had already mentioned. The highest and lowest average evaporations were 8.75 and 5.8; lb. of water per lb. of coal, and the average combustion rates throughout the runs were 39.5 and 67.9 lb. per square foot of grate area per hour respectively.
There was another point which came out of those tests, and which confirmed the authors method of dealing with the subject by separating the cylinder portion of the engine from the boiler. It was quite clear in those particular tests that the cylinders on the engines concerned had no idea ot what was going on in the firegrate, and they continued to demand steam at a rate which required from 23 to 24 lb. of tender water per d.b.h.p. hour throughout the whole series. The boiler was able to supply that quantity irrespective of the quality of the fuel. It was true that at the tail end of the trips with one or two of the worst coals some falling off in steaming was apparent, but otherwise steam production was fully adequate and working pressure was maintained.
That led to the conclusion that a well-designed engine working within its designed capacity and in good working order did not have its performance affected by quality of coal, within very wide limits ; it simply used more of the coal as the quality declined. Bad coal seemed to affect performance only if it was very bad indeed or if the engine was run down or if it was obviously overloaded. Indeed, if that were not so it was difficult to see how the locomotives in this country could grapple with war-time conditions as they were doing to-day. That was just one more example of the extreme flexibility of the steam locomotivo to meet fluctuating conditions.
Another instance of where it was not easy to agree with the author's rather simplified conclusions was where he said that steaniing power was proportional to the size of the fire-grate and was independent of the heating surfaces, within the limits set by normal boiler proportions. That might be true if the word "ideal" were substituted for the word "normal," and it could, of course, be conceded that heating surface simply expressed in square feet was now discarded as a suitable comparative measure of boiler capacity ; but unless each tube was so proportioned that it would give up the maximum amount of heat with the minimum resistance, and unless the total cross-sectional area through all the tubes was sufficient as an index of the capacity of the whole tube bank to boil water, then the steaming power would be restricted, whatever the grate area. It might be said that all modern boilers should have ideal proportions in that respect as a matter of course, but unfortunately such was not the case. Factors such as weight and loading gauge restrictions, the quality of uater used, the individual ideas of designers and the wish to standardise sizes of tubes had their influence in preventing the theoretically best values for those factors being adopted, and the maximum steam production rate had to be discounted accordingly.
Turning to the specific examples of performance curves given in the Paper, he thought that the author had been too much led away by the desire to correlate his characteristic curves with actual details of engine performance, and had also rendered the comparison rather more difficult by drawing his curves to cover a particular running condition, namely, running on level tangent track, whereas variable-speed dynamometer car tests, with which he was trying to make the comparison, were carried out on British railways under every variety of curve and gradient. To be of general use, it would seem that a locomotive characteristic performance curve must be done for the maximum performance of which the engine and boiler was reasonably capable at each speed expressed in terms of performance at the rim of the wheel, so that the data provided could be applied, with suitable allowance for engine and train resistance, to every successive variation in running conditions which the engine \voultl encounter in service. The best way to obtain each point on such a curve was by constant speed tests on the line with the particular locomotive, but in the absence of means to do thisand hitherto means for carrying out constant speed tests had been available only one the L.N.E.R., and there only recentlyit was possible to produce the curves, but more tentatively, from theory combined lvith the published results of constant speed tests.
The authors curves, however, suffered from an artificial restriction in the imaximum steam production capacity of the boiler, because the author had selected rates corresponding to the average throughout a test run in which speed, cut-off, rate of combustion and rate of steam production had varied widely. It was in fact impossible to use the average figures from the variable speed dynamometer car test to fill in the points on a characteristic curve, because such tests were tests of trains rather than engines, and even the maximum recorded power output on such runs might be well below the maximum of which the engine was capable, but it was none the less adequate for the schedules of the trains being tested. The two series of tests on the L.M.S. referred to in the Paper, Sheets 13 antl 14, did, however, involve very nearly the niaximum output of which the engines were reasonably capable for one or two individual parts of the run. Taking Sheet 14, the test of the Pacific engine, first, the three steam-flow rates on which the curves were based were far below the sustained capacity of the boiler to produce steam. On the particular runs on which the top curve was based, giving an average steam flow of 29,600 lb. per hour, ;I maximum rate of steam production of p,soo Ib. per hour was atctually attained.
None the less that was a maximum power of which the engine was capable, and corresponded to a rate of comhustion of about 13.5 lb. per square foot of grate per hour. The corresponding recorded d.b.h.p. was 2'510 at 44 m.p.h. No indicator cards were taken, but as a result of careful calculations the i.h.p. was estimated at 3,350. It would be seen, therefore, that the true characteristic curve of that engines performance was very much higher than the author indicated; and, while the above figures were on that particular run translated into a load of 600 tons and an average speed of 55 m.p.h. over the very severe road betwccn Crcwe and Glasgow and return, the same high power output was always available if needed to deal with a heavier train or at it higher speed and more level route. In the case of the 4-6-0 cngine, Sheet 13, this was nearer the maximum of which the engine was capable, but there again the recorded sustained maximum, on the particular runs selected by the author, gave 1,232 d.b.h.p. at 57 m.p.h. and 1,208 d.b.h.p. at 69 m.p.h., with calculated i.h.p.s of 1825 and 1863 respectively. The maximum steam production of that boiler was in the region of 27,000 lb. per hour, at a combustion rate of 150 lb. per square foot of grate per hour.
It was very necessary, of course, not to confuse maximum power output with maximum thermal efficiency. The rates of output just mentioned were not, of course, those at which the highest thermal efficiency was obtained, but they were liable to be attained at any time on short severe sections within the length of a run whose average figures would bc very much less. 'lhey were moreover short of the point at wllich the curve of consyniption per d.b.h.p. hour steepens sharply towards an uneconomic level. They gave high operating efficiency in representing the reserve capacity available to meet maximum conditions oi spcetl, gradient and load on a given run.
In conclusion, he would like to say a word about the L.M.S. curves for train and engine resistance to which the author referred, and which were published in Sir William Stanier's address. The curves were drawn as the result of many dynamometer car tests over a long period of time, and, though they appeared to be low and were lower than the curves which the present author had given, they none the less seemed to be very close to the true values for modern engines and stock. It was interesting to note that the L.M.S. resistance curve for rolling stock was very close to the curve based on the formula given in the American press at the time that tests were being made in America with very heavy trains at 100 m.p.h.
F.C. Johansen (107) said that he ventured to make one or two remarks with regard to points in the Paper which dealt with the subject of train resistance.
In the first place, as a matter purely of historical precision, he thought that it was correct to say that resistance formula2 of the type R-8 +BI'+ CV2 actually dated from Mr. Scott Russell, who proposed that type of formula in the year 1846 It had subsequently been used by many engineers, and was firmly established as the most rational form of train resistance forniulce by Carus Wilson's masterly analysis of the subject in 1907. He (the speaker) knew and respected both Mr. Lawford Fry ancl Mr. Dendy Marshall well enough to be sure that neither of them would wish to claim to have originated that type of formula. The term which concerned thc resistances which were independent of speed was not quite so simple as would appear from the author's description. Would it not br truer to say that resistances denoted by the A term were proportional, not simply to the diameter of the driving wheels. but rather to the ratio of thc diameter of the driving wheels to the diameter of the journals upon which they revolved ?
He deplored the tendency which was evident in the Paper to perpetuate the idea of air resistance being associatecl with the weight of a locomotive. It had been accepted for a long time that the air resistance of the locomotive was associated with its size and shape, and had nothing whatever to do with its weight. Any apparent connection between air resistance and weight was purely fortuitous. He would like to suggest that it was convenient to associate the head-on air resistance of a locomotive with what he would call the silhouette cross-sectional area, and that that was a good deal more accurate and precise than the method which the author had adopted. To support that viewpoint the following table showed a variation of about 50 per cent. in the weight of the five locomotives there referred to, and, corresponding to that weight. there was a marked variation of the order of 35 per cent. in the value of the coefficient R/WV2 , which the author had taken as his basis of air resistance measurement. The coefficient R/AV2 however, based on the silhouette area, was practically constant for locomotives of markedly different types, including the U class of -the Southern Railway and the L.M.S. '' Princess Royal " Pacific type, weighing half as much again. The cross-sectional outline of locomotives was usually available along with other information, and it seemed just as easy and far more accurate to use that form of expression for the air resistance rather than to Inse it irrationally on weight.
R=Air resistance in still air (lbs.) A=transverse "silhouette" area (sq. ft.)
V= Train speed (m.p.h.) W=Weight of locomotive (tons)
|L.M.S. 4-6-0 No. 6100 Royal Scot||139.5||96||0.198||0.00142||0 00206|
|L.M.S. 4-6-2 No. 6207 Princess Royal||159.2||101.5||0.206||0 00129||0 00203|
|L.N.E. 4-6-2 No. 4472 Flying Scotsman||148.7||96||0.192||0 00129||0 00200|
|S.R. 2-6-0 U Class||104.7||90||0.183||0.00175||0 00203|
|S.R. 4-4-0 V Class||109.5||92 5||0.189||0.00173||0 00204|
|L.M.S. 4-6-2 No. 6220 Princess Coronation (streamlined)||164.5||101.5||0.094||0.00057||0 00092|
In much the same way as the author had commented upon the fact that
the older types of resistance formulae indicated higher values for resistance
than represented the facts nowadays, he considered that the author's expression
for air resistance as given in Table 2 , Sheet 9, was decidedly on the high
side. It would perhaps be true to say that almost any type of British locomotive,
so long as it was of conventional design, with a chimney, dome, cab and so
on, and provided it more or less filled up the loading gauge, could be regarcled
as having an air resistance of about 2,000 lb. at 100 m.p.h., closely
proportional to the square of the speed. That was a convenieat figure to
remember, and was quite as accurate as was required for the author's and
similar purposes. For an unconventional type, however, such as a well streamlined
locomotive, the air resistance was very considerably less than for a comparable
locomotive of convcntional type. If, as was apparently the case, the data
on page 79 and Sheet 14 referred to an L.M.S. streamlined Pacific, the factor
.002V'2 for the air resistance per ton of locomotive weight was
excessive, and if it had been used the drawbar pull at 60 m.p.h. had probably
berm over-estimatecl by something of the order of 10 to 20 per cent. 109
D.R. Carling (109) thought Mr. Poultney's formulae would appear to offer a reasonably accurate method of estimating the power output of locomotives, for any given rate of working, provided that the locomotives compared were not too dissimilar in type, the fuels not markedly different in quality and the conditions of working reasonably alike.
The method did not, however, give any indication of a particular locomotive's ability to maintain any assumed rate of cornbustion, or what the maximum rate might be expected to be for any type. It would not, for example, give any indication of the phenomenal steam raising capacity of the boiler of a Chapelon 4-8-0, reaching over 50,000 lbs. per hr. when being fired at the rate of 245 Ibs. of coal per hr. on each of the 40½ sq. ft. of grate area, or of some Pennsylvania types, with wide fireboxes, to consume coal at rates up to 220 or even 240 lbs. per sq. ft. per hr. That capacity for a high maximum power output was a most important factor in assessing the usefulness of a locomotive to the operating department.
Turning to details of the Paper, he said there was a noteworthy omission of any reference to the steam demand for the heating of passenger trains, which might, with heavy trains on moderate schedules over an easy road, reach 10 per cent. or even 15 per cent. of the steam generated, necessitating an even larger increase in the rate of cornbustion, due to lower efficiency. It was not a safe proceeding to take simple averages from a variable speed dynamometer car run, as the variable quantities did not vary simultaneously, and average results might be very misleading if severe gradients were involved. It was better only to make use of selected portions of such runs, over which conditions were nearly constant, to make power output estimates, while coal consumption figures obtained on such runs were only comparable with those obtained on other closely shnilar runs. :lny attempt to obtain train resistance [ormula from dyn;imometer car records was a matter of great difficulty, because oC the varying conditions of gradient, curvature, state of track, speed wind direction and velocity, wet or dry weather, temperature, etc. The figures obtained indicated not only a formula for mean resistance, but also the extent to which departure from the mean was liable to occur. No doubt similar variations were likely with locomotive resistance. It would seem reasonable to adjust thc resistance formula according to the proportion of the total weight on the coupled wheels. One would not expect the same resistance per ton for 2-6-0 with a six-wheeled tender and a 4-6-4 with a twelve-wheeled tender, but both were " six-coupled." 'The same resistance formula could be used safely only where the conditions of both track and rolling stock were similar.
Great care would have to be taken in making a comparison if any of the factors involved varied widely, and such methods could not be applied without intelligent adaptation as circumstances required.
Misleading results might be obtained if a direct coinparison were made between a British 2-8-0 using, say, best Welsh steam coal and a 2-8-8-4 using Brazilian coal and running on a metre gauge earth ballasted track. If it was known that a coal with a high content of clinker forming ash had to be used, as might be the case in the Indian example quoted in the paper, it would, pvrhaps, be preferable to assume that one quarter of the grate was blocked and combustion taking place at an increased rate on the other threequarters.
K. Cantlie, (110) said they all knew thc commoner systems of power computation. Stephenson, D.K. Clark, and others had laid a foundation on which others had built. Cole, of the American Loco. Co., had, however, started what was almost a fresh era in power computation, and his work had been brought up-to-date by Brandt, Kiesel, and Lipetz. These, in turn, had drawn freely from Fry, Schmidt, Chapellon, Henschel, and other sources, and their collective work was a guide to all loco. men. He supposed that the majority of locomotive engineers used, like himself, some combination or modification of the various fornulae set out by these gentlemen.
The question was, therefore, how the Authors system compared with existing systems. He felt that the fact that dynamometer tests, mentioned by Mr. Cox, had established highcr maxima for certain locomotives than had the Authors calculations, was hardly a fair criterion, for any formula or system must be conservative, allow for unfavourable average conditions, and his firing rate was in any case limitcd to 120 lbs. per sq. ft. of grate.
His own vicw was that the Poultney system suffered from over simplification. Examples of this seemed to him first, the assumption that the stcaming power was proportional to the grate area and firing rate, and second the assumption of a standard degree of superheat.
He felt that though the Author was theoretically right in adopting Lawford Frys heat balance principle, there were many features about a boiler that, in practice, militated against the reliability of a system which assumed that a certain quantity and quality of coal fired per sq. ft. of grate area necessarily produced a given quantity of steam. Limitations of weight and loading-gauge frequently caused compromises in boiler design which resulted in their having insufficient gas-area, tube-spacing, or firebox volume, and insufficient depth of throat-sheet or distance from fire-bed to tube-plate. In addition, not only the front end arrangements, but the hardness of the feed-water and above all, the ash-content of the coal, were of the greatest importance ; for where the coal, however high in B.T.Us., had a really high ash-content, as was frequent overseas, a rate of firing even as high as the Author proposed, was often impossible. A thick fire with such coal could not be maintained, and the higher the firing rate, the thicker the fire.
He therefore felt that Cole's system, based, as it was, on the estimated steam production of firebox and tubes, did something to eliminate one set of variables, provided, of course, that one accepted Cole's estimates, based on the Altoona tests. By taking Cole's figures, one could always check back to ascertain that the firing rate was not excessive for the coal fired. To assume that 100°F. of superheat would be standard for all superheated engines ignored, it seemed to him, the enlarged and more efficient superheaters now widely used. The latest forms of Type A and Type E superheater were intended to give 200° to 250° of superheat, and their use notably decreased the weight of steam used per I.H.P. hr.
The Poultney system, therefore, seemed to him better for providing loco. men with a working estimate of performance once the boiler's efficiency had been established, than in assisting in establishing the maximum performance of which a locomotive was capable-and it was the latter figure which most loco. men required. For the maximum hauling power at speed was dictated by the maximum steam-rate, and in consequence his own view was that the boiler horse-power method was superior in this respect, as it took in the time factor for steam supply as the Kiesel formula did for steam consumption.
As to rolling resistance of locomotives, he agreed with Mr. Poultney that the rolling resistance of locomotives, on straight tracks at least, was often over-estimated, and recollected seeing a publicity stunt in which two damsels pushed a Chicago and North Western 4-8-4 fitted with roller-bearings, along the track by pushing on the front buffer-beam. The engine weighed over zoo tons. He noted that the Author had not mentioned the usual figure of 28 lbs. per ton of adhesive weight at all speeds. This, with Schmidt formula for carrying and tender wheels, and the Alco air-resistance tables, had given reasonable results in his experience.
There were several other points that he must omit owing to lack of time, including the use of .85 B.P: for tractive effort, and one or two typographical errors in the Kiesel formula. He must end on a note of admiration for Mr. Poultney's enterprise and knowledge, and looked forward to hearing what he was sure would be convincing replies by the Author to the two points that he had raised.
Mr. M. A. Crane (M.) said that at some time or other most locomotive engineers had dreamed of being able to gather all the particulars of the locomotive together and put them into a hat and shake them together, and so produce the performance of the locomotive. He thought, therefore, that the author had done some service to the profession by putting forward his ideas and clarifying the methods for obtaining the results in question. Many locomotive engineers at one time or another had attempted to produce such curves, and had found, with the many other duties which fell to them. that a considerable amount of work was involved. The The second point was the degree of superheat. author had now done much of the work required, and no doubt many engineers would wish to test the method outlined in the paper. There may be those amongst us who carry these formuk in their minds and can always in a few moments produce the curves, but for others the authors Paper would be used as a work of reference. The Kiesel formula had been used on many occasions before. Some people had even used it in its original form to ascertain the tractive force of the locomotives then running on their railways, and an arbitrary figure was chosen for the speed, which gave results quite as unsatisfactory as the ordinary indicated tractivc force. Manj, years ago, Vincent and Lipetz sent a memorandum to thr International Railway Congress in which they clarified the idea, in view of the misunderstandings which existed, and gave some more information on the use of the Lipetz formula. The present author had brought these ideas together and simplified them, so that locomotne engineers might usv them or criticise them as they thought fit. *.
He regretted that the author had not in his examples o f thc complete curves shown cases where there wak a considerable tlifference between different classes of locomotives in the power curvc when the boiler had taken
The President (O.V.S. Bulleid: 116-118) said he always enjoyed a Paper by the author, but whenever he read a Paper he always asked himself, What practical use am I going to get out of this? A locomotive, after all, was a hauling machine, purely and simply, and the author had described how to arrive at its drawbar capacity. Personally, he had once had the onerous task of re-loading the whole of a railway companys engine power, and, being young and enthusiastic, he studied every locomotive resistance formula that he could get hold of and, having made one or two simple tests, he took one of Ivatts Atlantic engines to find out, by coasting, what sort of resistance a 4-coupled engine would have. Running down from Stoke, they found that if they ran at 49 m.p.h. the engine pulled herself down to 31, and if they ran at 20 m.p.h. she pulled herself up to 31, so that they took 11.2 lb. per ton as representing the resistance of an Atlantic engine, which was just as good as any other figure.
When they worked out the loading, which they did at considerable length, they quickly realised that when loading trains over gradients of 1 in 50 in the West Riding of Yorkshire, 1 in 100 on other routes, and 1 in 200 on the main line, and when they had to add 22 or 44.8 lb. per ton to every ton of the engine and the train, it was really of very little moment whether the resistance of the engine became 12, 15 or even 20; and from that day onwards he had always used a rough and ready calculation, taking the goods train at 6 lb. per ton and the locomotive at 12. He found that as a rough and ready approximation, which did not even call for the use of the slide-rule, he could get a very fair approximation by taking the engine resistance at 12 lb. per ton plus the gradient and deducting that from the tractive effort of the engine, which gave him R very crude but workable figure for the tractive effort available behind the engine; and if he divided into that the figure obtained for the train he got the weight of the train behind the engine, as closely as he wanted it. That had one undesirable consequence ; very often it bought him back to the difficulty he had to face as a young engineer when confronted with the fact that some of the older engines could in fact haul more than some of the more modern ones, which was a very awkward stumbling-block when one was young, to find that the latest was not necessarily always the best. They confirmed their train resistance formula in a very striking manner. They were working the Cock o the North (which, it would be recalled, was a poppet-valve engine originally), and she was undoubtedly, as he had said on a previous occasion, an extraordinarily free-running engine. On one occasion they passed Potters Bar with about .500 tons behind the tender at 70 m.p.h., and they then pulled the engine up into mid-gear, so that all the poppet valves were off their seats; and, having begun that 12-mile stretch, mostly downhill at 1 in 200, at 70 m.p.h., they found, when they began to slow down to stop at Kings Cross, that they were doing 72 m.p.h.! He concluded, therefore, that anybody who talkcd about the high friction resistance of a locomotive was confusing the machine friction of the locomotive and its compression resistance. That was a point to notice, because obviously that engine was rolling down the 1in 200 very nearly as freely as the passenger rolling stock. Those were two interesting experiments which they made, which confirmed the figures as to train resistance in a very practical way.
A good deal had been said about coal, and the Institution was very indebted to Mr. Cox for the information he had given about the experiments he had described. Personally, he thought that that information was the most interesting addition which had been made in the course of the discussion to the Paper. To him, however-, bad coal did not mean coal of 11,000 or 12,000 B.Th.U. What most of the Southern drivers called bad coal was coal which preferred to go straight up through the chimney rather than burn at all, and which remained as a solid slab in the bottom of the tender, because it was so fine and so packed that they could hardly handle it. It was not, therefore, altogether a question of B.Th.U., but of the wretched stuff which one had to try to hold 011 the grate, That was why the figures on the Southern, using South Wales coal which had been shattered by putting it through a coaling plant, were a great deal higher than one liked ta see published. The Paper was very interesting, but he did not like the authors short cuts with grate area. If the author would reflect for a moment on certain recent locomotives which had come into this country, he would perhaps think again and decide that grate area alone was not the measure of a good locomotive boiler. Personally, he had always thought that locomotive firebox volume was the critical factor.
He would like someone to tell him whethcr steam was genetated instantaneously. Did steam just happen in that way because one wanted it, or did it in fact take a time? He had never been sure about that. He thought that the author was quite wrong in taking Kiesels formula and saying that it was devised twenty years ago. Locomotive engineers had not been standing still for twenty years, and locomotive proportions, steam-pipe size, volume of steam in the steam-chest and so on had made great progress, and so, too, had the exhaust arrangements. Mr. Kiesel had been very remarkable at the time, but was surely a little antiquated now.
The President added the author was, unfortunately, in indifferent health, and he was sure members would understand if he preferred to reply to the points raised in writing.
Mr. H. Holcroft (113) suggested that the author had rather 01 er-eniphasised the importance of the nominal tractive effort of a locomotive based on 85 per cent. of the boiler pressure and had assumed that it was the actual force available. Whether it was taken at the cylinders or measured at the rim of the driving wheels it was only a nominal figure and was analogous to the Treasury rating for motor cars, and had just about the same use. That is to say, it was a measure of comparison between one engine and another, but it represented no real value. When an engine started from rest all superheat was lacking, there was a good deal of conclcnsation, and lubrication was imperfect, so that nothing like the " paper " figure was ever obtained in practice.
In passing, he would like to draw attention to the author's remarks upon the exhaust steam injector on page 72, and, although it ~7as not strictly relevant to the paper, he would point out that as much steam would pass through some cylinders at 15 per cent. cutoff at 60 m.p.h. as at, say, 30 per cent. at 30 m.p.h. As regards loss of exhaust pressure it should be remembered that the exhaust steam injector was a form of ejector-condenser, and it would work with steam at atmospheric pressure if necessary, and therefore always had a head of 14.7 Ib. per sq. in. at the least. If there were two or three pounds of exhaust pressure available the injector simply operated on 16.7 or 17.7 Ib. instead of 14.7. It should be observed that after an engine started with a very heavy load and when there were long intervals between the heavy exhaust beats the injector would continue to work during the intervals, though it " sang " as it went along. Due to the length of the pipe connecting cylinders to injector and the low density and wetness of the steam there was a loss in head of exhaust pressure and variations in pressure at the cylinders had only a partial effect on the delivery of the injectors. With regard to locomotive resistance, he remembered that in his apprenticeship days he used to study the coal consumption figures on sheets which were exhibited in the locomotive depot and was impressed by the fact that the single-wheel engines were invariably at the top of the list in order of merit, while the 4-wheelcoupled engines, which shared some of the wark with them in the same link, were always 4 or 5 lb. per mile heavier in coal consumption, although of very much the same dimensions. He also noticed that when an engine was towed after the coupling rods had been taken off engines the crank pins soon got out of step, and therefore he concluded that the small amount of friction in the crank pins alone could not account for heavier coal consumption, but that it was simply due to the fact that the coupled wheels were never of quite the same diameter, and therefore a certain amount of slip had always to take place, which resulted in a drag transmitted through the crank pins. Additional friction was also set up if the crank pins were not accurately spaced, and in those days the quartering of the crank pins was not always done with the precision now possible by means of quartering machines. He thought that on the whole there had been a reduction in the friction of coupled engines simply due to better quartering, and there was less disparity in diameters of coupled wheels resulting from improved machining methods and callipering. This may account for present day estimates of locomotive resistance being lower than those formerly in vogue.
The question of locomotive resistance had always interested him very much, and after studying the authors curves, he arrived at the same conclusion as Mr. Johansen had, that the component CV2 should not be proportional to the engine weight. It was quite illogical to make it proportional, because that component was mainly concerned with head-on air resistance and almost all modern engines filled the loading gauge and had the same cross-section, and therefore the value of CV2 should not be expressed in pounds per ton of engine weight, and should be the same in each case. As an experiment, he had equated the part of the L.M.S. curve between 30 and ;o n1.p.h. to the simple formula A+BV2 and had found the constants that would fit in with the curve. On the assumption that A represented a constant total resistance varying with each engine and that BV2 was the air resistance common to all, he took a large number of types, from 0-6-0 and light and heavy 4-4-0 type locomotives up to Pacifics, and multiplied the weight on the coupled wheels by the arbitrary figure of 15 Ibs. per ton and the weight on the tender and carrying wheels by 3 lbs. per ton, and then he added to the sum the same amount for air resistance in each case, assuming it as o.+Vz, and thus obtained a set of figures for the total resistance of all the different types ; and then finally he divided the results by the engine weights and so got the equivalent resistance in Ib. per ton. On plotting the results he found that the figures followed the L.M.S. curve fairly closely for all types, which suggested that the splitting up of a resistance diagram into separate curves for 4-, 6- and 8-coupled engines was quite wrong.
Anyone who cared to repeat the experiment would find it most illuminating, because all the engines came out at about 10 or 11 lb. per ton at 30 m.p.h., and at 70 m.p.h. the long, heavy engines, like the Pacificr, gave the lowest figures in Ib. per ton, whereas the light 4-coupled engines came out higher. On consideration, it would be agreed that that was right, because their weight in relation to the frontal air pressure was much less. No claim was made that the values obtained by means of the experiment correctly represented locomotive resistance because the constants assumed were purely arbitrary. Nevertheless, in view of the known inconstancy meoMoTIvE POWER. "5
of this resistance due to variables and accidental causes they were probably sufficiently near the mark. On page 81, dealing with the " King Arthur " engine, the author gave the weight of the locomotive as 138 tons, but the particular engine in the trial had a tender of only 4,300-gallon capacity, and therefore the weight should be 129 tons, and a correction was necessary for this. Turning to Sheet 17, which also dealt with the " King Arthur " class engine, the acid test of the author's suggestions was how his estimate compared with actual results. Personally, having had a great deal to do with those engines, he could say, with regard to that diagram, that for the i.h.p. shown, of just over 1,000, those engines would operate trains of more than 400 tons in weight over the same road at 55 m.p.h., and therefore the figure was excessive in the case of the 314 tons which the author had taken. For a 314-ton train, the horse-power would be a little under 900 at that speed, and would correspond to'a train resistance of about 10.7 Ib. per ton and an engine resistmce of about 21.7 lb. per ton against the slight uphill gradient. On that basis, the coal per i.h.p.-hour worked out at 2.2 lb. and represented a thermal efficiency of about 8 per cent., and the water was about 17 lb. per i.h.p. hour. The author estimated a steam flow of 15,900 Ib. per hour, which represented an evaporation of 8.1 j lb. of water per lb. of coal of 14,000 B.T.U. calorific value. Actually, from test results, making an addition for water returned by the exhaust injector and deductions for train heating and safety-valve losses the water consumption was 14,900 lb., as compared with the author's estimate of 15,900 Ib., which was about 7 per cent. on the high side. In the upper portion of the diagram, Sheet 17, the author showed a water rate of about 26 Ib. per d.b.h.p. hour and a coal rate of 3 lb. per d.b.h.p. hour, whereas it should be approximately 4 lb. and the water about 31 Ib., which was quite a normal result for modern locomotives; The conclusion to which he came was that the method suggested in Sheet 3 for taking the water evaporated in accordance with the weight of coal fired per square foot of grate per hour might apply very well to American locomotives of the wide firebox type in which all the proportions were more or less standardised, but it did not seem to fit in with other cases, such as boilers having narrow fireboxes. Papers had been presented to the Institution previously in which the boiler proportions in relation to its output were discussed very carefully, and it was thought necessary to make calculations involving the fourth power of absolute temperatures, mean hydraulic depths, and logs. of logs. to obtain the required results, but the author had suggested a very short cut of arriving at the same result by means of a diagram, a method which seemed to be too good to be true !
Journal No. 179
Fairburn, C.E. (Paper No. 446)
Maintenance of diesel electric locomotives on the L.M.S. Railway. 212-58. includes folding diagram (side elevation).
Worked three shifts and either six or seven days per week: weekly mileage 200-250. Outlines modifications made to the design.
The original requirements laid down for Diesel electric shunters proved to meet traffic requirements very satisfactorily and the various designs of locomotive which have appeared have all given good service. A point to be emphasised is the need for a motor with forced ventilation and a double reduction drive. An engine with a nominal rating of 350 h.p. has proved sufficient for a locomotive of 30 tons service weight. The last jackshaft drive locomotives, which exceeded this figure by nearly 5 tons, were considered rather too heavy and the new design with two axle hung motors is better in this and certain other respects. The service weight included over 2½ tons of fuel which was sufficient for a fortnight's running in the most heavily worked yards, and if a month's operation without a visit to the maintenance depot is to be obtained, provision would have to be made for carrying more fuel. The question of the weight of the fuel and its tanks therefore assumes some importance, and it seems that if more fuel is to be carried an attempt will have to be made to reduce the locomotive weight in other respects.
The original control system with four fixed engine speeds was satisfactory, but it gave only ten main running positions, and a vernier auxiliary controller to give finer graduations was found desirable for hump shunting. The system was in fact somewhat complex and expensive, and the new arrangement with continuous variation of engine speed is expected to give a degree of control sufficient to meet all likely circumstances by rather simpler means. Engine lubrication had received close attention and the present arrangement with by-pass filtration and the temporary installation of a magnetic filter in the main circuit after overhaul maintains the lubricating oil in good condition at all times and gives an appreciable saving as compared with the policy of frequently changing the engine oil, even if the oil is subsequently reclaimed. The filtering of the ventilating air has been effective in keeping the locomotive cleaner and in reducing general maintenance costs, and the double cleaning of the air entering the engine should assist in reducing rates of wear.
With lengthened experience the amount of examination and adjustment called for by the maintenance schedules has been reduced to about one half without any reduction in .the st~ndard of maintenance. Although one engine has now been in service for ten years and overhaul procedure is fairly well established, there are a number of items about which further experience. will be needed before final limits of wear can be laid down. It was, how ever, clear that the rates of wear are very moderate and that engines can be kept in service for at least 30 years on an economic basis as regards overhaul costs. This had been achieved by taking advantage of the ability of the shunting locomotive to carry a relatively heavy engine with only moderate mechanical and thermal loadings on the various parts. The low load factor, too, assists engine life in some respects, but its results were not all advantageous. In other applications of the Diesel engine to traction work where weight is usually a factor of importance, the result could not be obtained by this method and it would seem, on the basis of general experience and published statements, that the user in such. cases may have to be reconciled to an appreciably shorter engine life. The methods of overhaul and of reconstructing worn parts which are becoming established do not make as much use as might perhaps have been expected of the various special techniques for depositing new metal which have, of late, been coming into greater prominence. The reason for this is largely the low rate of wear experienced, for example, If. crankshaft wear were higher it would not be possible to true bearings by grinding alone, but it would. would be necessary also to build them up in diameter. The present shunting locomotive, therefore, meets th.e service for which it was designed and presents no serious maintenance difficulties. The current maintenance methods have been arrived at cautiously and the general immunity from serious failure seems to have justified this course. The position can never be regarded as static and it is expected that coritrnuous but not dramatically rapid progress will be made. Similarly, no great changes of basic design appear imminent, but the progress of the supercharged engine is being watched and it would seem that uruts of this type will ultimately come into general use for traction purposes.
Journal No. 180
Cox, E.S. (Paper No. 447)
Locomotive axleboxes 1944, 34, 275-317. Discussion: 317-40:1945, 35, 221-38: 1946, 36, 171-6+ 3 folding plates. 21 diagrs., 8 tables.
In 1939, the last pre-WW2 year, there were 87, 914 axleboxes on the 7,508 steam locomotives in stock on the L.M.S. Railway, and 43,476 of these were coupled axleboxes. The design, manufacture, operation and maintenance of this large number of bearings is an important part of the work of the Mechanical Department, especially in the case of the 50% of the total represented by coupled boxes, which are subject to such a variety of fluctuating forces as to render them something quite apart from journal bearings as normally understood in engineering practice. The service given by these axleboxes is one of the major controlling features in locomotive availability.
There are three principal factors which directly affect such a\ ailability so far as axleboxes are concerned :
1. Rate of wear.
2. Number of failures in traffic--almost entirely in the.....
3. Time taken for repairs.
These factors are in turn affected by:
(a) Inherent characteristics such as loading, design, choice of material and lubricating oil, method of lubrication, repair procedure, etc. ; and
(b) Incidental failure in individual cases due to human element, defective material or accident.
The greater part of this Paper is devoted to group (a) above. Unless otherwise stated the experience and practice referred to is that of the L.M.S. Railway and, in view of the many abnormal features of wartime operation, it is confined with one or two exceptions, to the period before the present war. Very extensive precis in Locomotive Mag., 1944, 50, 106-8 and 122-4
Previous part of precis pp. 106-8. Very extensive precis of Paper 447 in Volume 34. The four types of coupled axleboxes in use on L.M.S. locomotives were illustrated and the following comments made on them.
The steel with pressed in brass was standard on the old L.N.W., but bearing performance was below standard due to insufficient size, excessive loads and inadequate oiling arrangements. The box of this type, now standard on all new L.M.S. construction since Sir William Stanier's advent, derived more from G.W. design and contained features which have 'raised locomotive bearing performance to a very high level. These are:
Generous bearing and radiation surfaces and low unit loading.
Thin white metal lining unbroken by brass strips or oil grooves.
Deep underkeep with large oiling pad.
The liability of anyone of the engines so fitted to run a hot coupled bearing is once in ten years per locomotive, so that the bogey of the hot bearing has been practically exorcised.
When. however, this design of box has been applied to engines having high loads with inadequate bearing size, it has not been especially successful.
The steel or wrought iron box with loose brass was a specialitv of the old Midland Railway: it has little virtue. The additional surfaces increase the places where wear can and does occur. and the heat transfer away from the bearing is poor.
The object of the manganese bronze box was to obtain good thermal conductivity without the disadvantages of the solid brass box. After many years of experience, however, its disadvantages seem to outweigh its advantages. As the manganese bronze is too soft to take a pressed in brass and is not itself a bearing metal. it is necessary to confine the white metal by bronze strips dove-tailed into the parent metal. These strips, even if carefully fitted into their grooves, and suitably located with pegs, tend to come loose in time and disturb the white metal. Where inside collars are fitted to the axles, this is particularly likely to happen, and where an engine is a heavy one with big sIde thrusts on the boxes disintegration is inevitable. '
The example may be quoted in this respect of the 70 Royal Scot engines, built with this type of box in 1927-30. In 1932 there were no less than 102 hot boxes. They were replaced by steel boxes WIth pressed m brasses to the original overall dimensions and to the same design as the Stanier engines m 1934, the collars being at the same time turned off the axles. In 1939 'the total number of hot boxes was six. The conversion was thus successful where unit loading was low. Where heating occurs manganese bronze boxes often become deformed, and in such circumstances they have to be scrapped.
In the case qf solid bronze boxes, since this is a bearing metal no strips or white metal are needed on the flat surfaces when the box is new, and it gives also most excellent thermal conductivity. It has been stated that such a box will run at 10°F lower temperature than a non-ferrous box otherwise identical. 'Where high bearing pressure is inevitable this may offer real advantage. On the other hand, high capital value is permanently locked up by its use, and after a few reboring's from a higher centre line the whole box must be scrapped and replaced, which is a waste of man hours even although the bulk of the material is recoverable. It is also weak mechanically unless it is made very heavy.
After referring to the composition of the white metal used on the L.M.S. in peace-time conditions, * the author dealt with the disposition of the bearing metal. Whatever the general design -of the box, the arrangement of the bearing surface itself regarding the extent and thickness of the white metal lining can be independently varied. For many years the deep pocket shrouded with brass all round held the field. This deep pocket allowed the brass to be rebored from successively higher centres a considerable number of times be- fore the white metal eventually became too thin . -On the other hand, it was not customary to machine the bottom of the deep cast-in pockets, so that bondmg of the white metal to the brass was -often poor, with subsequent failure of the bearing.
In 1932, Sir William Stanier brought on to the L.M.S. the conception of the thin layer of white metal not shrouded at the sides, but only at the ends, thus allowmg the brass to be machined before the metal was applied to ensure a perfect bond. To give increased surface for effective bonding this machining took the form of serrations, six to the inch.
The shrouding all round previously necessary to prevent the thick white metal from spreading under load was no longer necessary since tendency to :spread almost vanishes if the metal lining is made sufficiently thin.
This arrangement brought with it the further advantage that with suitable adjustment of the oil supply arrangements the actual bearing surface could be made to consist of an unbroken white metal surface. This design has proved entirely satisfactory where bearing pressures have. been reasonable, although at the cost of increased machining hours.
Some controversy has, however, surrounded its application to the heavily loaded bearings, the claim bemg made that as the metal wore thin under the constantly repeated blows of the piston load effect, the presence of the serrations initiated disintegratlon of the metal. This, however, is very difficult to prove or disprove, many white metal surfaces '.'caught m the act" showing crumbling in lines at right angles to the serrations.
Improvements in bonding due to research in methods and control do, however, seem to avoid the need for serrations altogether, and the latest L.M.S. arrangement is with 1/8 in. thick metal bonded to a plain machined surface.
Actually it is necessary to allow an upwards tolerance on this value. There are practical reasons why this upper limit should be as high as possible, and a point on which information is still sought is what is the maximum thickness such an unshrouded lining can attain before the metal begins to flow and extrude along the length of the bearing under the effect of load.
Dealing with lubrication, the author stated that the main points are: ~
(a) Quality of oil.
(b ) Method of supply, i.e., trimming feed or mechanical lubricator.
(c) Method of application to journal. .
Particulars were then given of the five oils used on the L.M.S. in recent years.
The first of these oils was and still is the general standard which has proved satisfactory with all. normally loaded bearings, and is the oil associated with the good bearing performance given by the modern steel boxes with pressed in brasses. The use of this oil compounded with free fatty acid instead of rape was undertaken as a precautionary measure so as to have a ready alternative should there be any interruption in supply of rape under war-time conditions. With mechanical lubrication it can be said to have given fairly satisfactory results, but with trimming feed some adjustment in the number of trimmings was found desirable since this compound has not in general such good syphoning properties.
The next two oils described were attempts to deal with the problem of the overloaded bearing where a greater film strength and degree of that elusive property "oiliness" was obviously desirable to withstand the pulsating and heavy loads on the large inside cylinder engines.
The use of superheater cylinder oil may seem an unusual approach. Although open to criticism as a bearing oil, it was, introduced on to the 0-6-0 Cl. 4 freight engine at a time when heated bearings were becoming especially troublesome arising from a variety of factors. It was in fact successful in arresting the upward trend, although it produced no actual improvement. It could, of course, only be used with a mechanical lubricator, and has now been superseded.
A welcome reduction in hot boxes on overloaded bearings has, however, resulted from the introduction of oil which not only was compounded with 15 per c~nt. of rape, but was specially produced by the oil companies to meet the particular conditions of the case, and was based on investigations onginally carried out by the L:N.E.R. This oil is now standard for certain classes of engine, but is more expensive than the other oils. Straight mineral oil is used on engines wholly engaged on shuntmg where runs are very short and average box temperature are probably low, even although with a high degree of full gear working , resultant box loadings are high.
Without going any further into this very controversial subject, it seems probable that beanng performance improves within limits with improvement in quality of oil, and indeed provision of the best oil obtainable seems to be the only palliative in the case of overloaded bearings. Rape oil is the most satisfactory compounding medium and is especially desirable when trimming feeds are used because it promotes ready syphoning. It also undoubtedly assists in providing continuity of lubrication where the oil film tends to become broken down by reciprocating loads. Whether the modern moderately loaded bearings would run satisfactorily on straight mineral oil is a debatable point. There seems no reason why they should not.
In dealing with the pros and cons of mechanical and trimming feeds, the author pointed out that two railways employ the former in their latest designs, one employs the latter, and the remaining company uses neither, nor indeed any type of feed external to the axlebox itself. The G.W.R. has dispensed with upper feed entirely on its modern engines and relies solely on underkeep and pad for coupled axlebox lubrication, the pad in this case being of felt. That railway has, however, a preponderance of outside cylinder engines with generous-sized bearings. The felt or worsted underpad, like the trimming, is subject to variation of feed depending on vis- cosity and any variations in quality of oil and textile as delivered. If this .is relied on alone to lubricate the bearing it is probable that a higher standard of control and periodic inspection of these items is necessary than in the case of the mechanically-fed engine.
A possibility which has not been explored very far is that of conducting heat away from the bearing by circulation of an excess volume of oil, by means of an axle-driven pump contained within the keep itself. There is a proprietary brand of American axlebox which takes this idea a certain distance.
The maintenance of boxes was dealt with at some length, and mileages between shoppings quoted for various classes, after which bogie, pony truck and tender bearings came in for notice. As the author pointed out, the only available alternative to the plain bearing is the roller bearing, and locomotive engineers are viewing this with considerable interest, having regard to its increasing use in the U.S.A. in all types of axle box, both carrying, coupled and tender. The bearings of this type fitted to the L.M.S. Turbomotive were then illustrated and described.
The paper, which was well illustrated by drawings and photographs, and contained many useful tables and graphs, was summed up by six conclusions as follows:
(1) Bearing pressure arising from combination of static weight; piston thrust and the area of bearing surface is the most important factor in performance and should be as low as. possible.
(2) The large inside cylinder engine as normally designed is the most unfavourable type from this point of view. Moving the coupling rod crankpins on such engines through 180 deg. will give improvement at a certain cost in other directions. The outside cylinder arrangement allows of the lowest unit pressures obtainable for given conditions of piston thrust and static weight.
(3) The design of axle box should include generous dimensions, thin white metal lining and well lubricated underkeep. Above all it must provide for rigidity, as loose strips and loose brasses give trouble whatever the axlebox size and loading.
(4) Given the conditions in (1) and (3) above, considerable variations in class of oil and white metal, and in method by which oil is fed to the bearing seem possible without much variation in performance.
(5) By suitable design in new engines the hot box problem for the plain bearing can be said to have been solved, with a recorded liability of not more than one hot box per engine in ten years. The potential mileage of such boxes before wear requires shopping is about 70,000 miles on the average, with in- dividual performance both above and below under different conditions of service.
(6) There seems little hope of bringing the bearing performance of the inherently over-loaded types anywhere near the above level, whatever design of plain bearing is, adopted. Use of the best quality of oil procurable with a 15 per cent. rape content is the best palliative so far discovered.
Discussion: Stanier opened the discusssion (p. 317) noting that there was not a great deal that he could add to what was contained in the Paper. He had been associated with the Author in the work which had been done, and the Paper contained a very clear and complete account of the troubles and experiences which the L.M.S. Railway had had during the time for which he had been associated with it so far as locomotive axleboxes were concerned.
The Great Western Railway, in his younger days, built a class of engine known as the " Badminton " class which had the coupling rod cranks in line with the inside cranks, and they ran for quite a number of years in that way, but the ''Atbara" class, a development of the ''Badminton" class, reverted to the outside crank being opposite to the inside crank.
One of the greatest difficulties which the L.M.S. Railway had experienced with its modern engines was to keep dust and ashes and water away from the trailing axlebox of a 4-6-0 engine, which came under the middle of the ashpan. It was yery difficult to keep the ashes and the water from surrounding and smothering the axlebox and causing excessive wear, particularly on the boss face of the wheel and the axlebox face against it and in the horn guide surfaces. It was found that on the axlebox in that position pegged on bronze liners were hopeless. It was largely as a result of the experimental work done on the axlebox in that position that there was evolved the solid bronze liner on the horn itself, bolted on and retained top and bottom with lugs, and the hardened steel face on the axlebox. That, however, was only a palliative, and the position was still one which gave a great deal of trouble. In India a great deal of trouble was experienced from sand and wear on axleboses, and a tremendous number of experiments had been carried out with dust shields of all kinds, but he had not yet learned whether the problem had been solved. He thought that the problem had still to be solved, and he was happy to think that the time had come when he was going to watch how other people did it. He thought that the Institution had been very fortunate in obtaining such a complete record of experiments carried out over a series of years on what was a very important problem
D.D. Gray (318-20) said he had been asked at short notice to give a brief description of the axleboxes used on the L.N.E.R., and particularly of the axleboxes used on the 2-8-2 locomotive which underwent tests at the Vitry testing plant. On the L.N.E.R. there had been very little trouble so far as their modern outside cylinder locomotives were concerned, but the heating of the boxes of the larger inside cylinder engines still frequently caused considerable trouble. At one time or another almost all the recognised forms of installing and lubrication had been used for the driving boxes of those engines, but their latest design, and one which seemed to be giving good results, was a box with a machined oil groove gin. wide and gin. deep in the crown of the box on the vertical centre line. The white metal is in pockets, leaving r$n. of bronze at the back and front above the horizontal centre h e , and there was an inch bronze bar in which the oil-way was cut on the vertical centre line. Mechanical feed for the oil was used, and all boxes were provided with an Armstrong pad in the tray, giving an auxiliary under-feed lubrication.
Their larger oil boxes, previously mentioned, are normally of the type which have three white metal pads keyed to serrations machined right across the box. The pads are divided by bronze bars at 45' to the vertical centre line. Each bar is provided with a machined oil groove, the back groove being fed by mechanical lubrication and the front bar by an auxiliary syphon feed. In service those boxes gave no trouble, but it was with regard to that type of box that the President had expressed the view that it would be of interest to show some slides dealing with the hot boxes experienced on the Vitry testing plant.
The boxes were 9½ by 11 inches, and the first slide showed the bronze box with the two.oil grooves. The engine had done a very substantial mileage in England before being placed on the plant, and from the time of leaving the works in England to going over to France not one hot journal bearing had occurred. On trials in this country speeds of over 80 m.p.h. had been recorded, and special load capacity tests had been made in Scotland. On the stationary testing plant, however, the heating of the boxes was a constant anxiety, and many days which could have been spent in obtaining test data were lost while overhauling took place. Furthermore, b.h.p. tests were carried out between Paris and Orleans at a period half-way through the stationary tests, .while some adjustment was made on the testing plant, and on those road tests there were no signs of heating.
On the test bed oils brought from England were first used, but trials were also made with pure rape oil and with the oil used by the French railways. Standard qualities of white metaI were used as well as metal provided in France. The boxes started with the standard bronze bars, but boxes were also tried with a white metal crown. The next slide showed one with a single oil groove at one side, the other being filled up with white metal. The following slide showed one with a solid white metal crown. The oil-ways were gradually being filled up with white metal. It all went to show, he thought, that there were very definite limits to theorising about what really happened within the lubricating film on a locomotive axlebox, and, valuable as theory might be, it was experience in running under traffic conditions which must be the final criterion. The next slide showed a box with the lubrication slots cut in the fop of the box and at one side, which did not prove very satisfactory. The white metal did not function very well. The very bad markings shown in the last slide were put down to hydraulic action between the axlebox guide and the horns.
J.E. Spear (320-1); Graff-Baker (321) Bulleid (325-7): lubrication of Merchant Navy class.
Second Ordinary General Meeting of the Birmingham Centre was held at the
Midland Hotel, on Wednesday, 28 February, 1945, at 7.30 p.m., the Chair being
taken by Mr. E. J. Larkin. (actually contained
within Volume 35)
The 1945 Meeting was held in Birmingham on 28 February 1945 and was chaired by E.J. Larkin (his remarks in Volume 45 pp221-2); D.W. Sanford (222-3)noted that the Stroudley method of arranging the cranks reduced the load on the axlebox, but increased the stresses on the crank axle; R.G. Jarvis (224-5) showed axlebox force curves and noted that outside two-cylinder locomotives tended to develop knock more noticeably on the left-hand side; G.M. Rickards (225) observed that heavy collar work has a greater affect upon bearings than speed;
A.H. Edleston (226) requested the size of the axleboxes on the SR Q1 0-6-0 and was refered to Journal 166 (1942) where it is stated that they were 8¾ inches in diameter; There they had an engine with an ample boiler, and providing it steamed as well as it appeared capable of on paper, the pistons should receive steam at the designed working pressure continuously. Was the Author in a position to say how these axleboxes, as originally designed, were standing up to their heavy task in service?
The Turbomotive had been mentioned in the Paper; he saw the engine when stripped down at Crewe Works. The roller bearing axlebox housings, in which the outer roller races were housed, had become slightly oval, and in order to restore them to their original diameters to suit the races, the axleboxes had a layer of hard material deposited on the worn surfaces by means of welding. The material used appeared to be a nickel alloy, and the work was carried out by an outside firm, but the machining was done in the Crewe Shops. He understood difficulty was experienced in finding the right tool (angle and rake, etc.) to machine this material, but after trial it was successfully accomplished and the races put in again.
Would this same process be of any value in restoring to their original dimensions, axlebox guide and axlebox faces of the orthodox type which have become badly worn, because as far as he knew the Turbomotive axlebox housings have given very little trouble since being treated in this manner.
Major H. E. Neale (Visitor) statedN.E. Neale (226-7) observed that the 8F locomotives in Persia did good work when lubricated with castor oil and also observed that the Hennessey lubricator fitted to the USA 2-8-2s worked well. R.G. James (227) noted that the 8F class in Turkey were lubricated with oil distilled from coal (which he called a form of creosote); F.G. Carrier (227) noted that the 4F 0-6-0s were the worst offenders with their steeply inclined cylinders. H.S. Hanson (227) noted that the load varied greatly on idividual axleboxes on the 4F class. C.E. Peake (227-30) submitted a written communication; J.W. Caldwell (230-2) commented on the Cannon type fitted to the LMS turbine locomotive (Turbomotive) and was appreciative of the GWR under pad form of lubrication. C.W. Clarke (236-8) recorded the difficulty of using non-ferrous alloys in India.
Meeting in Manchester on 28 February 1946
(actually contained within Volume 36)
H.H. Saunders chaired the meeting
J. Hadfield: (36-171-2)
was surprised that axlebox materials were still being
discussed, but... of the correct bearing to suit any given set of conditions
had been reduced to a matter of merely consulting a book of tables. It was
useful to learn that the London, Midland & Scottish Railway had now
standardised on the cast steel type of axle box body with pressed-in horse-shoe
brass and he considered that they had every reason to be proud of the results
achieved by their later designs. .
Regarding the substitution of solid bronze axleboxes for steel axleboxes it was frequently stated that the cost of the bronze box was prohibitive, but this was by no. means certaain. The raw materials for the bronze box were certainly more expensive, but the cost of machining and fitting brasses, side ,and face liners, etc., to steel axleboxes practically eliminated that difference and many large railways now used solid bronze axleboxes, as standard practice. He asked the Author what effect the different methods of spring suspension had on the wearing qualities of the axlebox , The L.M.S.8F class for example had under hung springs with short compression links, and it would be interesting to know whether the axlebox wear on these engines differed in any way from that on engines with spring links in tension or on engines with overhung springs.
H. Fowler (36-172}: Arising out of this most interesting Paper there is one point that occurs to me regarding hot boxes. I do not know if the Author has any information which would show whether an engine which has been lifted at a Running Shed is more prone to heated bearings than one which has received attention at a Main Works.
The L.M.S. have gone to an enormous amount of trouble and expense in perfecting the finishing of axle boxes in their Main Works, but it is not possible to work to the same degree of fine finish in a Running Shed which is not equipped with the same high class plant, and I would like to ask the Author whether he has found that there is any great difference between the number of cases of hot boxes on engines turned off Running Sheds compared with those coming out of the Main Works.
D. Patrick (36-172-3): After reading and hearing this excellent Paper on Axleboxes as used on the L.M.S. I can only wish that they had also been using grease lubrication and had been able to conduct the same painstaking investigation regarding grease lubricated axleboxes.
With reference to the large number of L.M.S. 8F class. engines which were in service in Egypt during the war, I should. be interested to know whether the Author could supply any information as to how the extensive use of white metal on all faces stood up to the operation under desert conditions. Also whether the oil pads in the keeps continued to function satisfactorily without becoming clogged and glazed with sand and dust.
On the Tirnken Axleboxes of the L.M.S. turbine locomotive, the lateral thrust is taken on a circular spigot on the steel casting, and one would expect a high rate of wear on the limited surface presented.
There is a reference in this paper to the Bengal Nagpur Railway and the method of lubrication used. The oil used was actually "solidified oil" which is incapable of being syphoned and appeared to be very satisfactory. The latest "Beyer-Garratt" engines which were built for that railway had this arrangement fitted and the axle-box was of solid bronze. A series of fins were provided in the recess in the top, with the object of assisting in heat dissipation.
Journal No. 181
Lynes, L. and Simmons, A.W. (Paper No.
Brake equipment and braking tests of Southern Railway C.C. electric locomotive. 345-76. Discussion 376-95. 36 figures (mainly diagrams)
Sixth Ordinary General Meeting of the Session 1943-44 held at the Institution of Mechanical Engineers, London, on Wednesday, 31 May 1944, at 5.30 p.m.: Mr. O.V.S. Bulleid, President, occupying the chair.
The brake trials carried out with the S.R. Mixed Traffic Electric Locomotive Type C.C. brought some problems when introduced to traffic were unique. Further, the Authors intend, in order not to prejudice any paper which may yet be read to this Institution, to deal exclusively with the brake on the locomotive, giving a brief description of the essential parts of the brake apparatus necessary to the subjec
In pursuance of the investigations, it was decided that brake tests should be made with the following trains:
80-wagon empty freight trains, unbraked and loosely coupled.
1,000 ton (approx. 75 wagons) loaded freight train, unbraked and loosely coupled.
80-wagon empty freight train with up to 15 wagons at the head of the train, vacuum braked and closely coupled, balance of train unbraked and loosely coupled.
1,000 ton (approx. 75 wagons) loaded freight train with up to 15 wagons, at the head of the train, vacuum braked and close coupled, balance of train unbraked and loosely coupled.
16-coach passenger train, vacuum braked and closely coupled throughout.
40-vehicle freight fast train, vacuum braked, closely coupled.
The locomotive was equipped with:
straight air brake
automatic air brake
automatic vacuum brake & combined straight air barke
The information obtained during the brake trials and practically applied is an illustration of the care taken by railway companys chief officers to ensure that innovations in rail transport would function reliably for the services intended. It is with satisfaction to be able to state that the various problems presented by the introduction of a very powerful electric locomotive in the braking of heavy fast goods trains, partially braked and unbraked, by straight air brake, automatic air brake, including Deadmans applications, and also fast passenger trains fully vacuum braked, by automatic vacuum service brake and passenger communication applications, were brought to a successful conclusion.
Discussion: W.J.A. Sykes (376-7) re training of motormen in starting very long and heavy trains. Since those tests were made, the motormen who had been engaged in driving the locomotive at the head of long and heavy freight trains had been suitably coached, and very excellent starts had been made. As proof of that, after the locomotive had been running for some months on a certain freight service a guard came up and complained to the driver that he had had a bump at a certain junction, adding that no other drivers had ever given him any bumps and that he hoped there would be no repetition of the incident. That showed that the control af the trains by the drivers had been good, mainly as a result of the facts discovered in the course of the brake tests described in the Paper.
R. T. Glascodine (377) said he was very much interested in the tumbler shock instrument shown in Fig. 14, and would like to have some information as to the exact speeds at which the pieces of steel tipped over. To say that a certain number went over was not so useful as an indication of the speed at which any particular piece went over. He noticed that the Wimperis accelerometer was found to be useless beyond a speed of deceleration of 6 ft. per sec./per sec., and that, of course, might be expressed as a blow of just over onethird of the weight. He had been very much interested in trying to find out what was the blow which did damage in a stoppage with a sudden bump, and he had been trying to ascertain what was the critical speed at which damage could be said to be done, what rate of deceleration was really harmful. He was not able to get very much information from the various diagrams in the Paper because they were drawn out on a scale of I cm.= j secs., and any stoppage which took multiples of 5 secs. was not very much use from his point of view ; he was more interested in stops taking something of the order of 0.1 .sec. If the Authors could give more detailed information about the forces which occurred, it would be useful. It was interesting to hear that the damagewas more likely to be done with slow trains than with fast rains, but that, he believed, was a matter of common knowledge and experience. When drawbars were broken it was usually at a stoppage between I m.p.h. and rest, and not when coming dopn from veq high speeds.
W.S. Graff-Baker (377-8) remarked that while many tributes had been paid to the excellence of the Paper, which was beyond question, no one had so far referred to the courage of those who devised the equipment described and who had brought it to perfection. It had been said that the difference between the difficult and the impossible was that the impossible took a little longer. He did not know how long it took to get the braking system in question to harmonise as well as it now appeared to do. Lesser people would have put a vacuum brake as well as an air brake on the locomotive and have done with it. That might have saved many headaches, but he appreciated that it would have interfered considerably with the design of the locomotive. The combination adopted was something in the nature of a triumph of mind over matter-not only to combine a vacuum brake with an air brake, but also to combine the possibilities of braking passenger stock and fitted, partially-fitted and unfitted wagon stock, to give the locomotive its maximum universal value. He had always held that if a thing was complicated in proportion to its function it was wrong, but in the present case the function was complicated, so that one must expect the apparatus to be fairly complicated also. He would be interested to have some information later on how much trouble it gave under normal service conditions, and whether in fact it would require a very high degree of maintenance. The problem to be met was very different from that which he had to face, but one could always learn a great deal from the technical operating results of such equipment.
E.S. Cox (378) pointed out that an attempt had been made in the case described to do something over and above what had usually been attempted in steam practice-namely, to produce a locomotive which was capable of performing every function which fell to the lot of a locomotive, and to provide on the one vehicle braking equipment to suit all circumstances. It might be ignorance on his part, but he could not understand why the brake equipment on the locomotive was stated not to be available for use in connection with the usual Westinghouse automatic brake system on Westinghouse-fitted trains. He did not see what feature there was in the braking layout which rendered that impossible. At the end of the Paper the Authors said they were unaware whether similar steps, in the matter of starting trains very gradually, were in use with steam-hauled trains. An example of that kind which might be cited was that of the Garratt loconiotives which hauled loose-coupled freight trains of something like 1300 tons between Toton and Brent. The trains were so long that they sometimes covered portions of the line including several gradients, and the method used by the drivers in such circumstances was the extreme of gradualness. The engine was put into mid-gear and the regulator fully opened, and then the engine was slowly and steadily wound down so that the train could be picked up wagon by wagon until all the couplings were taut, and then the real get-away was commenced
T. Henry Turner, M.Sc. (380), asked whether the Authors could add to the most interesting data they had already given, the chemical composition of the brake blocks and tyres, and also the chemical composition and hardness of the rails over which the trials were run. There were many sorbitic rails on the Southern Railway and some of them might have hardnesses approaching those of the Continental martensitic rails on which wheels readily skid. There were some unusual American brake blocks now on locomotives in this country, and they were producing strange results in wear on tyres ; but he assumed that in the Authors case ordinary grey cast iron brake blocks had been used. Both the chemical composition and the hardness of brake blocks, tyres and rails should therefore be added for completeness of the record if possible. He was very interested in the simple tumbler shock recording instrument described in the Paper. He did not remember having seen anything like it before, and if it was new, perhaps the Authors would say who invented it. As for the noise of vehicle impacts on braking, this was not a good advertisement for the railways, as anyone who slept within sound of goods trains bumping their wagons together would be well aware. Perhaps one day a Noise Abatement Society would force the railways to abolish the three-link coupling, even if nothing else could do so. The damage to freight of such noiseycreating bumping was often overlooked, but the department with which he was concerned frequently had to investigate cases where either rough shunts or abnormally hurried stoppages at signals caused damage to valuable freight. That point should he borne in mind by anybody who was trying to develop better braking systems. There was need for improvement in the whole of the train, and he hoped that the Authors, spurred on by Mr. Bulleid, would not stop at the locomotive, but would go on to deal with the continuous braking of freight trains.
P.W. Bollen (385) referred to the Authors remark that it is necessary to state before detailing the tests that the satisfactory functioning of the brake on the locomotive under normal service conditions was not in question, and said he did not think that that opinion was held in the early days of the design stage, when it was thought that a bogie vehicle with small wheels would not give such good braking as a steam locomotive with coupled wheels. A preliminary test was therefore made with a coal train of about 500 tons with Bn express motor coach at its head. The motor coach was put there for the purpose of conducting the braking tests and not for tractive purposes, the train being pushed by a steam locomotive in the rear. The steam locomotive pushed the train to the top of a grade, and then the braking was done by the electric bogie vehicle. The result showed that the fears which had been felt were not well founded, and that the bogie vehicle could give quite a good braking effect.
The Authors stated that at 10 m.p.h. the coefficient of friction was i j per cent. greater than at 40 m.p.h., but that did not seem to he borne out by Fig. 27, for instance, when one looked at the retardation (ft./sec./sec.). At the start it was nearly 1, and just before the stop it was about 2. In the first 20 seconds there was only 15 lb. brake pressure in the cylinders, which was about one quarter of the maximum, and no vacuum brake at all on the train ; whereas in the second half of the period there was full braking on the locomotive and about 10 in. of vacuum in the vehicles. He That was of some historical interest. wondered what the effect would be of continuing the vacuum right down to zero instead of stopping at about 8 to 10 inches ; he thought that by the time the vacuum had got down to 10 inches the train should be sufficiently bunched up to prevent any serious shock. The Authors stated that they gave signals from the start of the test by flashing an electric bulb. As that was visible from the guards van it would be of interest if they could include in their graphs some indication of when the first shock was felt in the guards van after the commencement of the test.
On the penultimate page of the Paper reference was made to the starting of trains. He believed that it was the regular practice with main line goods trains for the driver to open the regulator slightly for a short period, and then close it and then open it again, repeating the process about three times until the train was fully stretched out before putting on full power.
Journal No. 182
Address by the President. Looking forward. 403-13.
The opening Ordinary General Meeting of the Session 1944-45 held at the Institution of Mechanical Engineers, London, on Thursday, 26 October, 1944, at 5.30 pm.,
As the advantages of electrification decrease, the case for diesel electric- or the retention of the steam locomotive improves. In any case, the job cannot all be done at once and first things should come first.
Stage 1 .-Electrifying suburban services plus such parts of the main line as present clear advantages;
Stage 2.-Gradually replacing main line steam locomotives on unelectrified sections by diesel electric locomotives, using the gradualness of the change to gain technical and operating experience ;
Stage 3.-Gradually electrifying the remainder of the main lines by sections, applying the experience gained under stages 1 and 2; and
(a) Abandoning branch lines and substituting road
(b) Developing specialised branch line vehicles and motive
(c) Continuing the use of steam locomotives on branch or a combination or selection of any or all of these according to circumstances.
In the development of main line diesel electric locomotives it may well be practicable and certainly desirable for such :ilachines to operate from the electric power supply as electric locomotives when working in urban electrified areas and-in the interests of smoke and noise abatement-to run on the diesels only outside the cities. Such locomotives could be converted to all-electric at a later date when opportune and have a continuing life after the transition from Stage 2 to Stage 3.
What form is the passenger rolling stock of the future to take? The answer is largely independent of the means of traction. There are two kinds of vehicles used generally in the world-saloon cars and compartment coaches. America uses saloon cars exclusively, but in Europe compartment coaches form by far the majority of passenger vehicles. It is to be noted that of late the saloon car has increased in number in this country, while it is also to be noted that many persons like to get into a dining-car and stay there. Incidentally, the Pullman car in its British manifestation, regarded as a luxury train, retained the saloon form. The Blue Trains and the Golden Arrows were saloon car trains. It seems perhaps reasonable to suggest that there will be a further turn over from compartment to saloon type vehicles.
Editorial comment (very anti-non-steam traction) in Locomotive Mag., 1945, 51, 15..
Young, Harold (Paper No. 449)
Some notes on the C.38 class 462 type locomotive in service on the New South Wales Government Railways. 418-43. Disc.:443-50.. 17 figures (illus. & diagrs.)
Joint meeting of the Institution of Locomotive Engineers and the Institute of Engineers (Australia) held at Science House, Sydney, on Wednesday, 15 March 1944.
The heaviest passenger trains ol 500 tons then operatcd on the N.S.W. Railways with two 4-6-0 type locomotives of the C.36 class. It was considered that a Pacific locomotive (4-6-2 type) could be designed to give better locomotive proportions, greater power with a relatively small increase in weight on the driving wheels, less destructive action upon the track and eliminate double heading on all grades other than the 1-40 or steeper. Therefore, the C.38 class locomotive, of the two-cylinder simple Pacific type, illustrated in Fig. 1 , was designed by the Mechanical Branch, N.S.W. Railways, and constructed by the Clyde Engineering Company, Sydney, to railway working drawings, specifications and inspection and certain important components were completed at Eveleigh and supplied to the company. The first of a series of five was placed in service on 22 January, 1943, and has performed to expectations. Fig. 2 gives outside dimensions and weight distribution.