STREATHAM JUNCTION
19th JULY 1935
Involving
Driver J. Rugman and his Fireman W. Ayers
Depot unknown
extracted & adapted from the report by
On the 19th July between Streatham Common and Balham Stations on the Southern Railway a accident which occurred at about 8.09 p-m. involving the 5.18 p.m. train from Brighton (7.05 p.m. from East Grinstead) to Victoria was travelling at high speed on the up main line, when the coupled wheels of the engine became derailed. Fortunately no further derailment ensued, and there were no complaints of injury or shock from passengers or staff.
The train comprised the bogie coaches weighing 86 tons; it was drawn by tank engine No.2075, Class I.3 super-heater 4-4-2 type, running bunker first, and weighing in working order 76 tons. The engine was fitted with the Westinghouse and brake operating blocks on the coupled wheels only, controlled by the ejector working the vacuum brake on all wheels of the train.
After a few seconds preliminary rolling, apparently unusual at this place, the coupled wheels of the engine left the rails to the left or cess side in quick succession; the train was then brought safely to a stand in about 540 yards, and the adjacent down main line was not fouled. The 18 passengers were de-trained and completed their journey by road transport, all being cleared by 9 p.m.
The engine suffered minor damage only, and after re-railment at 11 p.m., was able to work the stock to the depot at Stewart’s Lane. Damage to permanent way was confined to chairs, keys and fish-bolts, 423 chairs being bro en, 408 on the cess side and 15 only on the six-foot side.
The weather was fine, and had been warm and dry for several days.
1. From East Croydon, the last stop before the derailment, the line runs in a northerly direction for about 1/2-mile to Windmill Bridge Junction, where the Clapham Junction and Victoria line diverges to the left from the line to London Bridge; thence it continues for a proximately 3 miles via Selhurst, Thornton Heath, Norbury , and Streatham Common Stations to Streatham North Junction, where the Mitcham line converges from the west; the point of derailment is about 370 yards, and Balham Junction about 1 1/2 miles further on. The line has four tracks, the up and down main being on the west side, so that the up main, on which the train was running, is next to the cess.
Approaching Streatham Common Station, gradients are falling generally for 3 miles at 1 in 264 to 1 in 100; thereafter through this station the line rises at 1 in 880to 1 in 284 for 3/4 mile, after which it becomes undulating about the site of the derailment, north of which to Balham Junction, gradients are falling at l in 264, and level.
2. Permanent speed restrictions on the up main line are :-
40 m.p.h. through Windmill Bride Junction.
60 m.p.h. through Streatham North Junction
50 m.p.h. through Balham Junction.
At the two latter points the restriction is in force on account of the nmssarily modified superelevation through the connections.
These speed restrictions are included in a special publication which mvers the whole of t!e Southern Railway system, and is issued to all the staff concerned.
There are no speed restriction boards
3 At the site of the accident the line runs in cutting with retaining walls of varying height. Through the trailing connection of Streatham North Junction the up main fine is on a right-handed curve of 40 chains radius; 217 yards further on curvature is again right-handed at 60 chains radius, but on1 for a length of 50 yards. The intervening 217 yards is occupied by leaving and entering transitions separated by a 50 yard length of tangent under Mitcham Lane Bridge. Derailment took place on the 67 yard length of transition immediately following the short 60 chain right-handed curve; beyond this point curvature reverses ta left-handed, again via transition, at radii of 60 to 75 chains.For 60 m.p.h. the superelevation prescribed by the Company's standard rule (85 per cent. of the theoretical) for a 40 chain curve is 4 1/2 inches and for a 60 chain curve 3 ins. In this locality however, on account of the junction and the succession of short curves of varying radii, it has not been found possible to adhere to the rule.
At the “ V “ crossing (1in18) of the trailing points of Streatham North Junction superelevation is therefore only 1 1/4 ins., rising through the lead to 2 ins. at the toe of the switch; thence on the 40 chain curve it varies from 28 ins, to 2 1/4 ins., but owing, probably, to vicissitudes of maintenance the run out now commences on the circular curve before the transition is reached, the greatest variation occurring here. viz., a drop from 2 ins, to 1 1/2 ins. in 30 ft., or 1/720. On the intervening length between the two circular curves superelevation varies from 1 1/2 ins to 1 7/8ins. for the first 85 yards: it then rises partly on the tangent portion, with minor variations. to 2 3/4 ins. on the short 60 chain curve, running out with good regularity at 1/720 on the transition curve where derailment took place; at the actual point of derailment superelevation was 1 1/2ins., and gauge 3/16in. slack.The permanent way was relaid in 1926 with 95 Ibs. R.B.S.material, the 45-foot rails being carried in chairs weighing 46 lbs. each, secured b three coach screws each to 10 ins. by 5 ins. creosoted pine sleepers, 18 per rail length, at standard spacing; the 4-bolt fishplates weight 32 1/4Ibs. per pair. Formation is clay and loam, and since the cutting was drained 6 or 7 years ago there has been no trouble from wet or soft foundation. To ballast is Meldon granite, but this does not extend below the underside of the sleepers, which mainly rest on older “ pebbly “ ballast; no extensive lifting has been carried out over this section in recent years but I understand that lifting on to Meldon ballast is now in hand, as art of s.rear program, other sections of the main line already received attention.
This is the main line between Brighton and the South Cost Towns and Victoria, and carries exceptionally heavy electric and steam traffic ; it is, therefore, placed in the highest class for maintenance purposes. The permanent may appeared to h in good condition; for about 400 yards in rear of the point of derailment, gauge varied from 3/16 in. tight to 3/16 in, slack, the greatest variation in one rail length being from 1/8 in. tight to 1/3 in. slack; sleepers were sound, and fastenings appeared to be holding well, although there was in places slight movement under traffic between chairs and sleepers. Line and level appeared to the eye
to be very good, and I noted that, there was no undue movement of sleepers on their bed under the passage of several trains, both electric and steam, at speeds in the neighbourhood of 60 miles per hour. although some sleepers appeared to be rather heavily packed at the ends, resulting in appreciable deflection under load.
5 The markings on the rail indicated clearly the sequence of derailment; 5 ft. 8 in. beyond be joint immediately preceding derailment a faint abrasion for a length of 7 ft. 5 in. along the running edge of the high (cess) rail was observed, after which there was e flange mark 19 f t .11 in. long, the first derailed wheel thus dropping to the outside 33ft. forward of the joint. A bruise was found on the end of the next rail at about the centre of the head, followed by a flange mark somewhat deeper than the first, crossing to the outside of the rail in 9 ft, where the second wheel dropped over into the cess. It is therefore probable that the right trailing coupled wheel (left leading as running) was first derailed; it broke the fishbolts of the next joint. and the three preceding chairs, allowing the rail to give way outwards under the side pressure of the following driving wheel, the flange of which evidently struck the end of the next. rail, still more or less in its correct lateral position: once the flange was thus lifted to
the head of the rail, derailment of the second wheel followed. It is possible that if the joint had not been released by the breakage of the fishbolts. the driving wheels would have kept to the rails. There was a second and smaller bruise on the rail end at the corner formed by the running edge and the end of the. rail, which was probably due to being struck by a following flange either of the engine bogie or of the train, fortunate without further derailment. If this following flange had struck the end of the rail more squarely the results might well have been serious.
In spite of careful search no object. which might have caused derailment. by obstruction was found on the permanent way.6. Tank engine No.2075. - This (I.3) class of engine has a length over buffers of 40 ft. 11in., and a total length of wheel base of 31 Ft. 2 in. The spacing between the axles of the leading bogie is 6 ft. 3 in., between he bogie centre and the driving axle 10 ft. 8 in., between the coupled axles 8 ft. 9 in., and between the trailing coupled axle and the trailing pony axles ft. 6 in. The diameter of the coupled wheels is 6 ft 7 1/2 in., of the bogie wheels 3 ft. 6in., and of the trailing wheels 4 ft. 0 in. The designed fully loaded weights carried by the bogie: the driving and trailing coupled axles and the pony, are 21 tons 5 cwts.,19 tons 5 cwts.. 18
tons 15 cwts., and 16 tons 15 cm &. respectively. The engine carries in the two side tanks and rear tank 2,110 gallons of water and in the bunker 3 tons of coal. The designed centre of gravity of the engine fully loaded is 5 ft.. fl in. above rail level and at the time of derailment it was approximately 4 ft. 8 in.; its longitudinal position with the engine fully loaded is 2ft, 11 1/2in. forward of the centre of the driving axle.
The leading bogie is swing-link controlled, the setting of links being so arranged that the displacement of the bogie causes the whole engine to take a slight heel towards the inside of a, curve; it has a total side movement. including axle box clearance, of 2. 5/16; in. each way ; axle box clearances of the coupled axles are 1/16in,. and of the pony axle 1/8 in. each way; the main pony casting has a side movement each way of 2 3/4 in. controlled by a single coil spring, initially with a force of 1ton 1 cwt.. increasing to 2 tons 14 cwts. at full travel. With regard to carrying springs, the bogie axle boxes each have two vertical coil springs, but all Four springs of the driving and trailing coupled wheels are laminated, each consisting of 13 plates 5 in. broad.
3 being 5/8 in. and 10 1/2 in. thick; the pony bearing springs are also laminated, with 13 plates 5 in. broad, one being 3/4in: and 12 1/2 in. thick.
There: are: two inside cylinders I9 in. bore by 26 in. stroke, horizontally set,, with the right.-hand crank leading, and piston-valves, operated by Stephenson’s link motion, the working pressure being 180 Ibs. per square inch.
Of the 27 engines in this class, all built for the former L.B. & S.C.R.. the first, No. 21, was constructed at Brighton Works in 1907. It was virtually one of the 4-4-0 tender engines (Class B.4) built as a tank engine by the extension of the frames at the trailing end to carry the bunker over a pair of pony truck wheels end by the addition of side tanks. The remainder, with slight modifications, were built between 1907 and 1913, No.75 (now2075) being put into service in January, 1910. Most of the class mere built as super-heater engines, and the rest were so converted in recent years. When newly built the engines were used on local, as well as the principle express, trains, including through trains between Rugby on the former L. & N.W.R. and Brighton.
Engine No. 2075 wrrs last under general repair in March, 1934, mileage since then being 44,908; bet.ween this general repair and the previous one mileage was 61,316 and the total mileage to the data of the accident was 810,399.
Report and Evidence.7. This train is booked to leave Brighton at 5.18 pm., East Grinstead at 7.5 p-m. and East Croydon at 7.59 p.m. running thence non-stop to Victoria in 16 minutes, representing an average speed of 39.61 miles per hour for the 10 miles 45 chains; the working book passing times allow 7 minutes for the 5 miles 14 chains from Windmill Bridge Junction to Balham Junction, or 44-38 miles per hour. This non-stop timing from East Croydon to Victoria has been in force since January, 1933, prior to which a stop was included at Clapham Junction, but the 7 minute timing, pass to pass, from Windmill Bridge Junction to Balham Junction has stood for over six years.
For the whole of this time the train has been worked from East Grinstead, where engines are changed, to Victoria by a tank engine, and regularly for the last three or four years by an engine of the I3 class, this being the return engine working on the 5.10 pm.from Victoria which arrives at East Grinstead at 6.23 p.m.; 42 minutes are thus available at East Grinstead for locomotive purposes which, I was informed, is sufficient for the necessary routine attention between trips but hardly allows a margin for turning, which can only be done by means of a triangle formed by St. Margaret's Junction at East Grinstead and a connecting goods line, the use of which is restricted to engines of moderate weight (e.g, the I.3 class); there is no turntable.
Driver J. Rugman, who had 36 years' service with the Company and 23 as a driver, worked the 5.10 p.m.train from Victoria to East Grinstead, with engine No. '2075, running chimney first. The engine was generally in very good order and his examination at East Grinstead disclosed nothing amiss before he started on the up journey, bunker first, at 7.5 p.m.
The run was perfectly normal as far as Mitcham lane Bridge. Leaving East Croydon one minute late, he had the regulator barely open, about half the first valve, and the screw reversing gear about 2 1/2 in. out of mid-gear, continuing at this setting until the derailment. Just after passing Mitclmm Lane Bridge at the normal speed of about 55 miles per hour, there were four or five oscillations of a rolling nature followed at once by a grating noise; he thought the first roll was to the left, but was not sure.
Severe oscillation being unusual at this point, he immediately made a moderate application of the brake, not thinking it advisable to brake hard. As sped was reduced the grating sound changed to bumping and he made a full brake application about 100 yards before the train came to a stand.
He described the oscillation as violent but not enough to throw him off his feet; it was soft in character and there was no severe jolt such as might be caused by an axle box striking the horns. He had frequently driven engines of the I.3 class and this was the first time he had felt any serious movement on one of them; they had a reputation for occasional rolling, though they did not ( box or nose). He was emphatic that here was no unusual oscillstion before passing under the bridge and, when the rolling started, he was not alarmed, but took action to steady the speed of the train as he always did when experiencing a roll with a tank engine at speed. He had worked the same train on the previous days of the week with a similar class of engine and with engine No. 2076 on. the Wednesday; in each case the engine was '' chimney first down the line and bunker first up the line ", and bad not experienced any oscillation at this pion t during the week.
At the time of derailment the tanks were approximately half full, and there was about 30 cwt. of coal in the bunker. After re-railment ‘he worked the empty stock with the same engine as far as Clapham Junction and noticed nothing wrong with the engine during this trip.
Fireman W. Ayres. with 18 years' service with the Company and 17 as a fireman, was certain that the oscillation began earlier, between the trailing points of Streatham North Junction and Mitcham Lane Bridge. There was no oscillation through the trailing junction, which he referred to it's a " good junction ". The oscillation was a side to side roll, not particularly severe, and no worse than the normal oscillation experienced at times with this class of engine when running fast, and be did not think there was "anything unusual happening ". The oscillation did not increase, and there were three or four rolls and then bumping as if
the wheels were riding on the chairs; the rolling was soft, without jolt, and he contrasted the motion with that of the 4-4-0 tender engines (B.4class) which " came down with a bang at the end of the roll '. He knew the I3 class of engine well, and had not noticed any difference in the motion whether running chimney or bunker first.
Speed was about 55 miles per hour, it being at this point that the highest speed was attained by non-stopping trains between East Croydon and Victoria; but he had travelled faster here on other trains.
At the time of derailment the tanks were approximately half full, and there was about 30 cwt. of coal in the bunker. After re-railment ‘he worked the empty stock with the same engine as far as Clapham Junction and noticed nothing wrong with the engine during this trip.Fireman W. Ayres. with 18 years' service with the Company and 17 as a fireman, was certain that the oscillation began earlier, between the trailing points of Streatham North Junction and Mitcham Lane Bridge. There was no oscillation through the trailing junction, which he referred to it's a " good junction ". The oscillation was a side to side roll, not particularly severe, and no worse than the normal oscillation experienced at times with this class of engine when running fast, and be did not think there was "anything unusual happening ". The oscillation did not increase, and there were three or four rolls and then bumping as if the wheels were riding on the chairs; the rolling was soft, without jolt, and he contrasted the motion with that of the 4-4-0 tender engines (B.4class) which " came down with a bang at the end of the roll '. He knew the I3 class of engine well, and had not noticed any difference in the motion whether running chimney or bunker first.
Speed was about 55 miles per hour, it being at this point that the highest speed was attained by non-stopping trains between East Croydon and Victoria; but he had travelled faster here on other trains. 8. Driver A. E. Mills and Driver A. Hoper, both experienced drivers, gave evidence as to the steady riding qualities of the I3 class of engine at speeds of 50 m.p.h. and over. On the day in question Driver Mills drove engine No. 2090 (I.3 class) on the 9.30 a.m. train from Tunbridge Wells West to Victoria, the timing of this train between East Croydon and Balham Junction being the same as that of the train concerned in the accident. He noticed no peculiar oscillation at any point in the journey and estimated his speed passing Streatham North Junction as 45 to 50 Driver Hoper on the same day worked the 4.51 pm. from Uckfield toVictoria with engine No. 2004 of the I1 class, a somewhat similar tank engine to those of the I3 class, of the 4-4-2 type, but with 5 ft. 6 in, coupled wheels; he passed the point of the derailment at the usual speed of 55 to 60 m.p.h. and noticed nothing unusual. He remarked that it was unusual to get a roll at that point, although there was generally a slight roll approaching Balham, “ though nothing much there”. There was no difference in motion whether running chimney or bunker first.
Motorman W. J. Packham, with 16 years experience as a driver, and Motorman J. Broadbridge with 24 years, both drove electric trains over this section of line less than half-an-hour before the accident. Neither man experienced any unusual movement and the former said that although he always reported a rough piece of the road, this particular section bad no special reputation for bad riding.
9. Guard S. Emery, with 27 years' service with the Company and 25 as guard, said that he left East Croydon at 8 p.m., one minute late; he was looking through the side look-out of his van, the last vehicle of the train, and estimated that be speed Streatham North Junction at 45 m.p.h., the usual speed. Until his van valve was operated by the driver’s emergency brake application passing through Tooting Bec Road bridge, nothing abnormal had occurred on the journey; he did not notice he the first partial brake application. Although he realised from the emergency braking that something was wrong, he was unaware of any derailment until he met the fireman; after that he took steps to protect the train. He observed no flashes or short circuiting from the conductor rail, and I was informed that the circuit breakers were not affected.
Sigualman W . Nunn, who bad been a signalman for 28 years and for 20 years in Streatham North Junction box, said the train passed his box at the usual speed or 45 m.p.h. and remarked that the Brighton electric trains usually passed the box at about 50 to 60 m.p.h. For a fast train he normally got the " Out of Section " signal from Balham Intermediate signal box in one minute and from 3 Balham Junction box in two minutes when Balham Intermediate was switched out.
He noticed nothing peculiar about the train as it passed him. His evidence was confirmed as to times and usual train speeds by signalmam A. E. English of Balham Intermediate box, who said the train was going quite slowly when it first came into his view. He noticed the time was 8.09 p.m.
Analysis of the signal box timings for this train on the seven weekdays up to and including the day of the accident indicated an average speed of the order of 57 m.p.h. between Windmill Bridge Junction and Streatham North Junction, and rather higher between Selhurst. and Streatham North Junction.
10. Sub-ganger J. Terrell, who had 8 years' service with the Company and 6 years as sub-ganger of the length in question, had been acting as ganger since the ganger’s retirement a week before. He examined the up main line at about 3.30 p.m. on the day of the accident nod found it in condition. At the last general fettling at this point two months ago he had beater packed a few joints, a lift, of perhaps 1/4in. to 1/2in. No joints were attended to on the day of the accident., but there was a joint left unfilled four rail lengths in rear of the point of derailment: this and a few other joints on the length had been shovel packed a month or six weeks previously, and, being “ on the full side “. had been left unfilled to encourage them to settle down. He had experienced little difficulty in keeping the up main in line since the curves were adjusted about five years ago and no more than the usual trouble on a line carrying heavy traffic in keeping the joints and the line generally to a good level. He had not himself gauged the line before the accident, but his predecessor used to do this regularly every six weeks or two months. Permanent-Way Inspector H.A. Gabriel, who had 33 years' service with the Company and over five years as Inspector in charge of this district, confirmed that since the cutting was drained there had been no particular trouble with maintenance on this section; no general lift had been carried out since he had been in charge.There were instructions that Permanent-Way Inspectors should ride over the whole of the lines in their district on the footplate or in the motorman's cab once in every month noting this in their weekly return to the Divisional Engineer’s office, and there was not much difficulty in complying with these instructions. On the 1st July he had ridden over the up main line in the cab of a fast electric train and again on the 23rd July, although it was probably about six months ago that he was last over the line on the footplate of a steam train, the latter being now comparatively few in number. He had ridden on tank engines of the I.3class, and on tender engines of the U class over the up main line and had never noticed any undue movement at this place. He also made a habit of asking drivers if they had any complaints about the road, and he had had none with regard to this section of be.
Assistant Chief Inspector P. King had only had general charge of this section for the last six months; during that time, however he had had no complaints from gangers. He personally gauged the line in rear of the point of derailment about two hours after the accident and found nothing amiss. He gave assurance that no fettling or lifting of the line had been carried out between the time of the accident and my examination of the site other than the necessary repairs to the track in advance of the point of derailment.
Chief Inspector W. Sears, who had been Permanent.-Way Inspector for 20 years and Chief Inspector for six months, had for the last seven years acted as Assistant to the Permanent Way Superintendent of the London (East) Division. He was unable to advance any theory as to the cause of the derailment. He referred to the improvement in stability of the track at this point since the draining operations six or seven years ago, at which time the old “pebbly” ballast was replace by Meldon granite above sleeper bed level. On the 6th June he made an inspection with a view to arranging and additional ballast; this was in fact a continuation of the lift and additional ballast; this was in fact a continuation of the lift already carried out to Selhurst from the north and to Balham Intermediate signal box from the South. There had been a slight increase in the work required to keep the road in order since the electric services to Brighton started in January, 1933, but be had bad no complaints from the gangers or the men on this section with regard to under staffing, the strength of this gang (seven men) complying with the man-power formula for the highest class of line. Neither he nor Inspector King made a regular practice of riding on the footplate. which was left ho the Permanent-Way Inspectors, but he did so when he could. A week before the accident he rode over the up main line on the footplate of an engine of the I3 class, running chimney first; he passed the point of derailment about- 43 to 50 m.p.h. but felt no undue oscillation.
He remarked that the side wear of the rails had become worse since the introduction of the electric services. I noted that whereas the side rear of the high (cess) rail was slight but constant up to a point 50 yards north of Mitcham Lane Bridge, thereafter round the short 60 chains right-handed curve it, varied in waves from negligible to considerable; the waves, however. were not regular, points of maximum wear varying from 17 ft. to 70 ft. apart and of minimum wear 31 ft. to 70ft. 6 ins. In several cases maxima and minima corresponded with the centre and joints respectively of the 45ft. rails. This sudden change from constant (and slight,) to irregular wear in places serious. is noteworthy. I was informed that this type of wear had been noticed since the introduction of the Brighton multiple-unit services and was attributed to the hunting action of the motor-driven bogies.
Wear was not great at the initial point of derailment, and the heaviest side-cutting noted occurred at the middle of a rail 54 yards in rear.
11. Engine No. 2075, less than three months before the accident, under went light repairs, including the following work:-bogie tyres returned, bogie axle-boxes refitted, bogie swing-link bushes renewed, right driving spring renewed washers fitted at.the bottom of the pony springs. The periodical examination of the pony truck was made on 17th December, 1934. and of the tyres and wheels on 20th June, 1935.The engine was examined at Stewart’s Lane depot on the morning after. the accident. by leading fitter F. W. R. Curry, who found no mechanical defect and no parts missing He had the engine weighed on the 23rd July, and the greatest discrepancy was found at the right-hand pony wheel (left leading as running bunker first) namely 7 tons 18 cwt. actual compared with the designed weight-of 8 tons 7 cwt. 2 qrs. With long experience of this class of engine he had noted no particular trouble with their “ running gear ..
Assisted by the Company’s officers, I made a detailed examination of engine No. 2075 at Brighton Works on the 30th July. The flanges of the bogie, and pony wheels were turned to the standard “A'' or thick profile, those of the coupled wheels having the thinner “ G" profile; all were of the standard depth of 1 1/8in. The bogie tyres and flanges were practically unworn having been recently re-turned. Wear of he coupled tyres varied from 1/16 in to 3/32 in, hollow on the tread and, 3/64in. to 1/16 in. at the root of the flange; wear of the pony tyres was similar in amount at the tread. that at the root of the flange being 1/16 in. and 3/32 in. for right, and left-hand wheels respectively.There was considerable scoring and bruising of the treads and flanges of the coupled wheels consistent with the striking of chairs and fish-bolts by the wheels as they ran derailed. but it was not possible to detect with certainty a bruise at the tip of the flange of the right driving wheel to correspond with the bruise on the rail-end referred to earlier in this Report.
The increases from standard will be noted, mileage since the last genera1 repair being 44,908, particularly the 13/32 in. (5/16in. .+ 1/32 in.), increase in respect of the pony axle, allowing a total free movement side to side (including journal clearance) of 27/32in. before the spring begins to exert its controlling force.
After the accident all bearing springs and the pony side control spring were tested for deflection, which in the case of the 8 coil springs of the bogie and of the pony control coil spring did not vary materially from design. The camber of the four springs of the coupled wheels under a test load of 7 tons 10 cwt. varied from 1 3/16in. to 1 5/16 in. as a against 1 in. designed, the sixth late of the left trailing spring being found broken 5 in. from one end. The designed camber of the pony bearing springs under a test load of 6 tons is also 1 in. ; as tested with this load after the accident the camber of the right-hand spring (left, leading, as
running bunker first) was 1 3/16in. and of the left-hand spring practically correct at l in. bare, the top plate of this spring being found broken in the buckle. Except for the two fractures mentioned, the springs were in good condition.
There was no evidence that the axle boxes had been binding in the guides; examination of the axle boxes of the coupled wheels showed in each case that the hexagon-headed set screw, fitted at the underside of the keep to secure the keep pin, had been crushed, corresponding marks being found on the hornstays. Similar damage to these set screws had also been noticed occasionally by Leading Fitter Curry when examining engines of this class; this was not frequent and in his opinion it had invariably resulted from a derailment.
Inspector E. G. Read, attached to the Locomotive Running Department, confirmed this opinion, there being 1 1/2in. normal clearance between the hornstays and the keeps. He knew these engines well both from examining them and from riding on the footplate; they were “ nice engines for riding " and rolled little at high Speed; this would only occur at a soft place in the road and under ordinary conditions he did not think they would ever roll to an alarming extent.
12. On the 2nd August, accompanied by Mr. Sheppey, Eastern Divisional Locomotive Running Superintendent, I travelled on the footplate of an engine of this class, No. 2023, running bunker first when working an up semi-fast passenger train from Oxted to
Victoria, a distance of 20 1/2 miles; Rugman was the driver.
This engine hod worked 52,484 miles since the last general repair in July, 1934, rather more than the mileage of engine No. 2075. The train comprised six bogie coaches and one horse box, weighing approximately 190 tons, and was booked to leave Oxted at 10.09a.m., running the eight miles non-stop to Sanderstead in 13 minutes, an average speed of 36.9 m.p.h.; from Windmill Bridge Junction to Balham Junction, pass to pass, the booking is seven minutes, or 44.36 m.p.h., the same timing ,as that of the train concerned in the accident.
For the first 2 1/2 miles from Oxted speed up the rising gradient did not exceed 35 m.p.h., but on the following falling gradients and reverse curvature to Sanderstead a speed of slightly over 60 m.p.h. was attained; this track is not electrified, and I understand that the up line here has been recently relaid.
Leaving East Croydon 1 noted that the regulator was not opened beyond the first valve. From Windmill Bridge Junction, which was passed at 30 to 35 m.p.h., speed gradually rose down the falling gradients to over 60 m.p.h. at Streatham Common Station.
It was still increasing when the train was steadied by a slight brake application, passing the site of the accident at about 60 m.p.h., after which speed was reduced, Balham Junction (50 m.p.h. speed restriction) being passed at about45 m.p.h.
On the two stretches where a sped of the order of 60 m.p.h. was attained, riding was quite steady, with no appreciable rolling or nosing movement. Rounding the curve of 34 to 53 chains radius at about 50 m.p.h approaching Balham Junction opinion, serious.
My short experience on the footplate leads me to concur in the evidence given as to the good riding qualities of this class of engine.
Conclusion
13 The derailment of a well-balanced engine on track which is intact ( there was no evidence of absence of keys due to high temperature) and maintained to a high standard is difficult to ascribe to any one cause, although the actual sequence of derailment in this case is open to little doubt. To account for this accident, therefore, a combination of factors must be sought, such as speed of the train, the characteristics of the road at the site, and the design and condition of the engine.
The initial derailment to the left of the trailing coupled wheels must have been brought about by heavy side pressure, aided in all probability by temporary relief of weight. on the left-hand wheel. Starting from this premise, the causes which map have led to this state of affairs must be considered.
14. Speed was undoubtedly high at the time of derailment, which occurred at the end of some three miles of falling gradients.
According to driver Rugmam, the engine had been steaming, though lightly, since leaving East Croydon; the load consisted of three bogie coaches only, and this class of engine with 6 ft. 7 1/2 in. wheels and piston valves can freely attain high speed, as I myself observed from the footplate with more than double the load. Furthermore, signal-box timings of the train concerned indicated an average speed of nearly 60 m.p.h. from Windmill Bridge Junction to Streatham North Junction; although such timings should be accepted with reserve as sole evidence of speed over a short distance, they afford confirmation of an estimate arrived at by other means. Allowing for observance of the 40 m.p.h. restriction at Windmill Bridge Junction, this average would involve the attainment of well over 60 m.p.h. at the foot of the gradient. In spite of the estimate of 45 m.p.h. given by guard Emery and signalman Nunn, whose evidence in this respect I discount, I am therefore of the opinion that the speed of the train when the derailment took place cannot have been less than 65 m.p.h. and may well have been higher. Both enginemen thought the speed to be 55 m.p.h., but the existence ot the 60 m.p.h. restriction through Streatham North Junction, of which driver Rugman was aware, should be borne in mind. I do not however, regard the distance run by the train after the derailment, namely, 540yards. as evidence of speed, since driver Rugman wisely made only a light application of the brake on first feeling the unusual movement.
15. With regard to the characteristics of the road, the junction and the succession of short curves of varying radius demand compromise in respect of superelevation. There is a length of tangent of 50 yards under Mitcham Lane Bridge on which superelevation varies from 1 1/2 in. to 2 1/8in., though the highest rate of variation in this length is 1/4in. in half a length of 45 ft. rail. Although this class of engine is not markedly sensitive to tract variations in line or level, I think it is possible that the existence of appreciable superelevation on tangent track, unavoidable at this point, combined with a speed that was certainly high having regard to the varying (though moderate) curvature, initiated rolling of the engine. Although evidence was forthcoming that rolling was unusual ere in spite of moderately high normal speeds. I do not regard this as precluding the possibility of rolling being initiated from this cause on a specific occasion. The reaction of a locomotive to the track at speed cannot obey rigid laws: without the damping effect of a separate tender, a tank engine is inherently more sensitive to track variations and momentary conditions may arise, although perhaps rarely, when contributory factors, such as weight distribution according to the load of water and fuel, surging of water in the tanks (which were about half empty at the time of derailment), spring periodicity, and possibly the phase of them hammer blow, may all be favourable to the building up rather than to the damping out of on incipient roll.
Nevertheless, I do not think that the rolling can have over become really severe; Driver Rugman was not alarmed. and Fireman Ayres, who was a particularly good witness, referred to it as nothing out of the ordinary. The evidence of these two men is conflicting which is understandable, as to the exact point at which the rolling started; although Driver Rugman thought this to be after Mitcham Lane Bridge when it started. Fireman Ayres was emphatic that it began between the trailing junction and the bridge; on the other hand it is significant that the commencement of the rolling was approximately coincident with passage over
the length of tangent immediately following which, it should be noted, the waves of side wear on the high rail were first observed. Although I do not think that the side wear directly contributed to derailment, its presence in this form suggests that a certain unsteadiness in running may have been prevalent at this point, possibly due to the presence of superelevation on tangent track.
16. Although the increase from standard of axle box side play of engine No. 2075 was not abnormal in view of the mileage run, it cannot be overlooked that,9/16 in. wear had taken place between the pony casting and the main frame allowing a total uncontrolled side play to the pony axle, including axle box clearance, of 27/32 in.Initial derailment occurred on a leaving transition from a 60 chain curve; regular displacement of the pony on this curvature would be slight and probably insufficient, with this amount of free play to bring the pony control spring into action. Guiding of the engine would thus devolve on the right trailing coupled wheel of large diameter and less favourably situated in respect of leverage. High flange pressure would result: accentuated by the usual nosing action round the curve although this is not unduly pronounced in engines of the I3class. Once the rolling started, temporary relief of weight would occur on alternate sides of the engine; should a roll to the right have coincided with the upward or negative phase of the hammer blow (2.68 tons at 45 r.p.s. or 64 m.p.h.) of the right-hand trailing anp pled wheel, the combination of heavy flange pressure and relief of load would have set. up conditions favourable to climbing and subsequent derailment. In this connection it, is noteworthy that the spring deflection tests showed that the right.-hand pony bearing spring was appreciably less resilient than standard (1 9/16 in. camber under 6 ton load as against 1 in. designed), which might allow it to assume momentarily more than its share of the load to the further relief of weight on the right trailing coupled wheel.
17. Reference was made by sub-ganger Terrell. who was considered to be a reliable man, to a rail joint which had been left opened out, or unboxed, four rail lengths in rear of the point of derailment, although on my inspection of t be site on the 31st July this joint had been filled in and, with the neighbouring joints. appeared to be of good level. I do not think that this can have had any bearing on the derailment. in view of the independent evidence of two steam train drivers and two motormen of electric trains. all of whom had passed over the site on the up main at hi$ speed on the day in question (the motormen of the two electric trains a few minutes before the accident) and had felt no unusual movement.
Remarks and Recommendations
18. While it is not possible to define with certainty the exact cause of this derailment. I feel that Driver T. Rugman must have been travelling faster than he realised and chat the most likely cause was too high a speed (over 65 m.p.h.) having regard to the two contributory factors, namely the reduced guiding effect of the pony axle, which was leading. and the varying curvature of the track, which necessitated appreciable superelevation on tangent. I do not consider, however, that the maintenance of the track was open to material criticism, having regard to its age and the punishing effect of the heavy multiple-unit traffic.
19. Although the 60 m.p.h. restrict ion through Streatham North Junction, if observed, should preclude the speed at any rate of steam trains, rising appreciably higher before speed is reduced for the 50 m.p.h. restriction at Balham Junction less than 1 1/2 miles further on, I think it is questionable whether speeds of this order through the varying curvature at the site of the accident are not sufficiently high to permit of dangerous oscillation, particularly of a tank engine, when all conditions are favourable to its development.
Furthermore, I doubt whether a speed restriction of 60 m.p.h. through Streatham North Junction is sufficiently below the general level of speed at this point both of steam and electric trains to make much impression on a driver’s mind. The restriction therefore, is probably disregarded in practice, and under favourable conditions, as were present in this case, such as s free running engine, a light train running a little late, and good weather, speed may well rise to an undesirable limit. The Company is carrying out s regular programme of curve realignment some 234 miles of single track having been dealt with since January
1933. The up main line between Streatham North Junction and Balham Junction has not yet been realigned, but I understand this is in hand although a preliminary chord survey does not appear to have disclosed any marks irregularity. I think the Company should consider, in view of all the possible traffic conditions, the desirability of imposing a speed restriction lower than 60 m.p.h. at this place, pending further consideration when this realignment is competed.
Generally, with regard to speed restrictions in the congested suburban area, I consider that the question o€ definition by visual means merits serious consideration. There are six permanent restrictions varying from 30 to 80 m.p.h. in the 10 1/2 miles on the up main line between East Croydon and Victoria; a driver on a routes such as this, where the block sections are short, is fully occupied in observing signals, and it appears that there is a risk that he may consequently overlook speed restrictions committed to his memory, if a visual reminder is not provided.
20. With regard to the diminished guiding effect of the pony truck, this was brought about by wear between the lugs of the engine frame and the retaining washers of the pony control spring; this must have increased the liability to derail of the following coupled wheels, and it important, therefore. that the designed effect of the pony should be maintained in service, and not allowed to diminish through wear. I was informed that it was the practice at running sheds to take up play in the pony casting of engines of this class by the insertion of horse-shoe shaped washers between the lugs of the frame and the retaining washers of the control springs. Lifting is not entailed, but 1 understand that this work is only done when an adverse report is made as to the riding of the engine. This wear had been permitted to develop in engine No. 2075 to the extent of allowing 9/16 in. uncontrolled side lay m the pony casting; in view of the simplicity of method, it appears desirable that attention in this respect should be regular and periodical, rather than occasional as the result of an adverse report from enginemen.Apart from the development of uncontrolled side play due to wear it is questionable whether an increase in the strength of the pony control spring is not desirable in engines of this class. The initial controlling force is 1.05 tons; increase in this initial force would undoubtedly throw more guiding effect on to the pony to the relief of the coupled wheels, and the practicability of this appears to be for consideration.
21. This is a case where the use of deeper flanges on the engine, as is standard practice of one Company, might possibly have had preventive effect. The better angle of contact with the rail of the deeper flange reduces the tendency to begin climbing, or, once climbing has started, the greater depth may delay complete mounting of the rail sufficiently long for more favourable conditions to be established, and so avoid derailment.
22. It is significant that an engine of this class, running bunker first, became derailed in December, 1932, under circumstances which bear a striking resemblance to those of the accident under review. The train was reported to have been approaching Balham Junction on the up main line at a speed of 40 to 45 m.p.h . round the left-handed curve of 34 to 28 chains radius, when the trailing coupled wheels (leading coupled as running) left the rails to the outside of the curve, the pony and the remaining wheels of the engine and train not becoming derailed. No defects in the permanent way or in the running gear of the engine were found that could readily have accounted for the accident, which was attributed at the time to a 5/8 in. stud and nut becoming detached from the rear sand box and falling on to the rail between the left- and pony and trailing coupled wheels, lifting the latter sufficiently to cause derailment; it is understood that this stud and nut, though missing from the engine, were not found on the permanent way, although search was exhaustive. I have discussed this derailment with the Company’s officers, who now think it possible, on account of the similarity of the two cases, that obstruction by the missing stud may not have been the true cause. On account of the remarkably similar circumstances, I cannot avoid the conclusion that these two derailments were most likely due to a similar rare combination. of unfavourable conditions.It appears that under certain conditions the I3 class of engine has a lessened margin of safety against derailment at speed when running with the pony truck leading, particularly when appreciable sloppiness has been allowed to develop; I therefore recommend that the engine workings should be re-arranged so that engines of this class may run chimney first when hauling trains whose booked timings demand maximum speeds of, say, 40-45 m.p.h. and over.
