TGV world speed record
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- This article was originally based on material from TGVweb, which is licensed under the GFDL.
The TGV world speed record program was a series of trials by SNCF, the French national railway to test its TGV system to the limits. The aim of the trials was to run a TGV train at its maximum possible speed without any compromise in safety.
Operations TGV 117 and TGV 140, referring to target speeds in metres per second, were carried out by SNCF from November 1989 to May 1990. They came as a follow-up to the previous round of testing, operation TGV 100, which had left off in 1981 with an earlier speed record of 380 km/h (236 mph) set by TGV Sud-Est trainset number 16. The culmination of these test programs was a new world speed record of 515.3 km/h (320.3 mph), set on 18 May 1990.
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[edit] The test tracks
The test runs took place on a section of the Atlantique branch of the TGV network, a few months before the line was opened to TGV revenue service. Strictly speaking, there were no significant alterations of the track or catenary for testing purposes. However, some sections of the line's profile had been planned since 1982 (shortly after the TGV Sud-Est world speed record of February 1981) to allow very high speed running.
Construction of the dedicated tracks of the LGV Atlantique was officially decided on 25 May 1984. Ground was broken on 15 February 1985. The new line was to stretch from slightly outside the Gare Montparnasse in Paris to Le Mans, with a second branch towards Tours. The Le Mans branch was opened for 300 km/h (186 mph) revenue service on 20 September 1989, and the Tours branch opened a year later. The two branches separate at Courtalain, 130 km west of Paris, where movable frog points good for 220 km/h (137 mph) in the diverging route direct trains towards either Le Mans or Tours.
[edit] Location
The test section itself begins on the common branch, at kilometre 114, at the Dangeau siding. It runs past Courtalain and onto the Tours branch of the line. Between kilometre 135 and kilometre 170, the line was designed with progressively wider curves, reaching a minimum radius of 15 km (9 miles) after kilometre 150. These curves were built with larger superelevation than strictly necessary for revenue running at 300 km/h (186 mph). At kilometre 160, the line passes through the Vendôme TGV station. At kilometre 166, there is a long 2.5% downhill stretch into the Loir valley (the Loir is a tributary of the better-known Loire river) and the line crosses the Loir on a 175 m (1100 ft) bridge. This is the area where the highest speeds were expected, and most of the activity was concentrated there.
The Tours branch of the line was tested by special computerized Maintenance of Way equipment, from the Track Research department of SNCF. Just as on all TGV lines, the rails were aligned to 1 mm (3/64 in) tolerances, and the ballast was blasted to remove small, loose gravel. In subsequent testing with trainsets 308 and 325, the track was not significantly affected and required only minimal realignment. This was in contrast to the 1955 world speed record of 331 km/h (206 mph), also set in France, where the track was seriously damaged after the high-speed runs. Strain gauges were placed in several locations, especially at the expansion joint at the end of the Loir bridge.
[edit] Catenary modifications
The catenary was standard TGV style, without any modifications. The only changes were in the tuning. TGV catenary is strung in 1200 m (4000 ft) sections, mechanically tensioned by a system of pulleys and counterweights. Support masts are spaced at 54 m (175 ft) intervals. The catenary (supporting) wire is made of bronze, with a circular cross-section of 65 square millimeters. The contact wire is made of copper, and has a cross-section of 150 square millimeters. The cross-section of the contact wire is circular with a flat section on the contact side.
In general, when a pantograph runs underneath the catenary, it sets up a wave-like disturbance which travels down the wire with a speed determined by the tension in the wire and its mass per unit length. When a train approaches this critical speed, the pantograph catches up with the disturbance, resulting in dangerously large vertical displacements of the wire as well as contact interruptions. The top speed of the train is then limited by the critical speed of the catenary. This problem was very central to the test runs, since it was desired to test set 325 at speeds well above the critical speed of standard TGV catenary. There were two solutions: increase the tension in the wire or reduce its mass per unit length.
Replacing the copper contact wire by a lighter cadmium alloy wire was considered, but dismissed on the grounds of time and cost. The critical speed of the test track catenary was then to be increased solely by increasing the tension in the wire. For the test runs, the usual tension of 2000 daN (4500 lbf) was increased to 2800 daN (6300 lbf) and exceptionally 3200 daN (7200 lbf). For some of the faster runs over 500 km/h (311 mph), the voltage in the catenary was increased from the usual 25 kV 50 Hz to 29.5 kV.
At kilometre 166, catenary masts were equipped with sensors to measure the displacement of the wire. During the 18 May 1990 record at 515.3 km/h (320.3 mph), vertical displacements of almost 30 cm (1 ft) were recorded, and fell within 1 or 2 cm of the predictions made by computer simulations. The critical speed of the catenary for that particular run was 532 km/h (331 mph).
[edit] The test train
In the early stages when operation TGV 117 was still being defined, several criteria were settled upon to focus the preparation of a test train. These were aerodynamics, traction and electrical systems, rail and catenary contact, braking, and last but not least, comfort.
The basic purpose of the test program was to push the envelope of the TGV system, and to characterize its behavior at very high speeds. With this in mind, it only made sense to start with a stock TGV trainset and to modify it as little as possible. Brand new TGV Atlantique trainset number 325 (25th of 105 in the Atlantique series) was arbitrarily chosen to be the starting point of the modifications. It should be emphasized that there was nothing special about this trainset, and that it was returned to its intended state after the test program to enter revenue service. Today, the only distinguishing feature on 325, as compared to other Atlantique trainsets, is a blue ribbon painted across the nose, and bronze plaques bolted to the sides of the two power cars to commemorate the event.
[edit] Trainset 325, first version
In preparation for the first round of testing, modifications began by shortening the train from its usual 10 trailers to only 4 trailers, resulting in a significant increase in power-to-weight ratio. The resulting consist was: power car TGV24049, Trailer R1 TGVR241325, Trailer R4 TGVR244325, Trailer R6 TGVR246325, Trailer R10 TGVR240325 and power car TGV24050. Train length was down to 125 m (381 ft.) from 237 m (777 ft) and weight was down to 300 metric tons from 490 metric tons.
The aerodynamics of a TGV Atlantique are already quite good, and improvements were few. It was decided that 325 would have a "front" and "rear" for the high speed runs, to simplify the modifications. Usually a TGV trainset is symmetric and reversible, but 325's two power cars, 24049 and 24050, were defined as leading and trailing units, respectively. On the roof of lead unit 24049, the pantographs were removed and the roof fairing extended over the opening; the same was done to the 1500 V DC pantograph on trailing unit 24050. Only one pantograph was to be used at high speed: the stock Faiveley GPU unit remaining on unit 24050. As in normal TGV running, the lead unit was to be fed power from the trailing unit through the roof line running the length of the train. Further improvements, such as rubber membranes covering the gaps between the trailers, and a rear spoiler on unit 24050 were considered, but abandoned.
The synchronous AC traction motors on 24049 and 24050 could not be allowed to rotate too fast, because of limitations in the switching frequency of the supply electronics. Technicians had decided upon 4000 rpm at 420 km/h (261 mph) to be the optimal ratio, after testing trainset 325 at high speeds with stock traction equipment. The new traction ratio was achieved by changing the transmission gearing and increasing the wheel diameter. Just as with the 1981 test campaign on TGV PSE number 16, 1050 mm (41 in) wheels replaced the stock 920 mm (36 in) wheels under 24049 and 24050.
To prevent electrical problems, semiconductor components (especially thyristors) were selected with special regard to quality. The main transformers in both power cars were replaced by larger models, each able to handle 6400 kW (8500 hp), or double the usual load, on a fairly continuous basis. Extensive tests were conducted on the electrical systems, to establish how far they could be pushed. The resulting ratings insured that acceptable heat levels would never be exceeded in testing.
Next, the wheel-rail interface was attended to. Axle bearings were unmodified items, broken in for 10,000 km in revenue service on the LGV Sud-Est. Yaw dampers were stiffened, and doubled up on each side for a total of four yaw dampers on each truck, for redundancy in case of a high speed failure. As a result of earlier testing and computer simulations, transverse dampers were stiffened on the power trucks.
The 1981 test campaign provided valuable data and computer models for interaction of the pantograph with the catenary contact wire, and shed light on the very sensitive dynamics. Very large vertical wire excursion (over 30 cm, or 1 foot) had been observed in the 1981 tests, and were blamed on the pantograph catching up with the travelling wave it set up in the contact wire. For this reason, it was not only necessary to modify the catenary to increase the travelling wave speed, but also to fine-tune the pantograph itself.
The pantograph used on 325 was the stock Faiveley GPU. The wiper assembly on this pantograph weighs under 8 kg (18 lb) and is mounted on a vertical shock absorber with 150 mm (6 in) travel. The main structure of the pantograph is constructed of cylindrical tubing, which (Faiveley claims) reduces the pantograph's sensitivity to random variations in environmental factors. The only modifications to the GPU pantograph were an increase in the stiffness of the pneumatic dampers, and a reduced total aerodynamic lift of the structure.
The suspension on the trailers was jacked up by 20 mm (1 in) by overinflating the secondary suspension air bladders and inserting shims, to provide additional suspension travel and to make up for the larger wheels on the power cars.
The brakes on the trailers were tuned to allow a heat dissipation of 24 MJ per disk instead of the usual 18 MJ, with a total of 20 discs.
Many of the modifications listed above, including the synchronous traction motors, were tested at speeds over 400 km/h on TGV Sud-Est trainset 88. In one high-speed test, technicians attempted to provoke a truck into unstable oscillation by drastically reducing the yaw damping, but failed to achieve this.
Finally, most of the seating in trailer R1 was removed and the space was transformed into a laboratory, to process and record test data on vehicle dynamics, overhead contact and dynamics, tractive effort, aerodynamics, interior comfort and noise, and a host of other parameters.
On 30 November 1989, trainset 325 emerged from the Châtillon shops and set out for the test tracks for its first test run. Technicians at Châtillon put 4500 hours of work into the modifications, which was impressive when one considers that their first priority was the routine maintenance of the TGV Atlantique trainsets in revenue service. The first campaign of testing with 325, until 1 February 1990, is summed up in the chronology of the record runs below.
[edit] Trainset 325, second version
On 1 February 1990 at 15:30, 325 returned to the Châtillon shops for the long term. At this time, 325 had set a world record at 482.4 km/h (299.8 mph). Technicians had a 1 March deadline to perform further modifications designed to make possible further data collection and a 500 km/h (313 mph) publicity stunt. This second round of modifications was intended to take direct advantage of the experience gained in the first round.
The axles on 24049 and 24050 were removed and on 2 February, shipped to the Bischheim shops in eastern France for fitting with even larger 1090 mm (43 in) wheels. The lead axle on 24049 was fitted with strain gauges, and returned to Châtillon 8 days after the other axles on 22 February. Initially, the second axle on 24049 had also been scheduled to be fitted with strain gauges, but the 1 March deadline did not allow enough time. To accommodate the bigger wheels, special brake pads had to be manufactured for the brake shoes on 24049 and 24050. With 15 mm (5/8 in) of thickness, only two emergency stops were guaranteed.
On 6 February, the trailers were jacked up and trailer R6 was removed. This brought 325 to the minimum possible consist, since the bar trailer R4 fuctions as the "keystone" of the articulated design of the TGV. 325 now weighed in at 250 metric tons and measured 106 m (348 ft) nose to tail. From 7 to 14 February, the three remaining trailers underwent further modifications. The 25 kV roof supply line to feed the lead unit was replaced by a single cable; this allowed the removal of the insulators supporting the line over the space between trailers, which protruded in the air stream. Rubber membranes were installed to cover the gaps between the trailers, and the Y237B trucks were jacked by 40 mm (1.5 in).
In the gap between power cars and trailers, large airdams were installed. These "snow shields", mounted beneath the couplers, were designed to prevent the formation of a low pressure area between the vehicles, which had induced significant drag in the earlier testing. On the power cars, sheet metal shields were added over the trucks, and the front airdam was extended downwards by 10 cm (4 in) to compensate for the larger wheels. Finally, a removable spoiler was installed on the nose of trailing unit 24050.
The aerodynamic improvements were supposed to yield a 10% reduction in drag. In the previous round of testing, the atmospheric drag force had reached 9 metric tons of force at a speed of 460 km/h (286 mph). On the new version of 325, this magnitude of drag was not expected before 500 km/h (311 mph).
On 27 February 1990, after the trainset was coupled together, 325 rolled out from the Châtillon shops for the second time, 2 days ahead of schedule. This time, 2000 hours of shop labour were required to accomplish the changes. The second campaign of testing, culminating in the standing world speed record of 515.3 km/h (320.3 mph) is summed up in the chronology of the record runs.
[edit] Chronology of record runs
[edit] First campaign: November 1989 - February 1990
Thursday, 30 November 1989
First day of testing. At 7:29, trainset 325 leaves the Châtillon shops behind trainset 308. 325 could not be driven to the test site under its own power, because the 1500 V DC systems had been removed, and several stretches of tracks between Paris and Massy are electrified in 1500 V. Arrival at Massy at 7:49. After testing hot box detectors and the electrical systems, 325 is uncoupled from 308 at 8:21 and leaves Massy. At 8:52, 325 passes the siding at Dangeau, at kilometre 114, and enters the test tracks. Weather conditions are radioed to the crew: temperature, -7 °C (19 °F). Rail temperature, -6 °C (21 °F). Wind, east, 3 km/h (2 mph). Visibility, 500 m (1500 ft). A deer on the tracks delays the first run, and a team is called in to put it to sleep. The second run of the day begins at 12:03, and 325 achieves 391 km/h (243 mph) at kilometre 169, stopping at 12:24 at kilometre 210, the end of the test tracks. Upon returning to Dangeau at low speed, 325 launches into its third run, and hits 407 km/h (253 mph) at kilometre 142.
Friday, 1 December 1989
Weather conditions give trouble, with frost on the catenary. On the first run of the day, video monitors show intense sparking between the pantograph and wire. Testing is interrupted and the catenary grounded while technicians climb on the roof of unit 24050 to inspect the pantograph. The pantograph is adjusted to make firmer contact with the wire, and subsequent runs encounter no trouble. On the third and last run of the day, 325 achieves a speed of 442.6 km/h (275 mph) at kilometre 164.3.
Monday, 4 December 1989
Trainset 308 carries out the usual morning sweep of the test tracks, and reports frost on some sections of catenary, and poor traction at the rail. In spite of slight slippage, 325 hits 463 km/h (288 mph) on its first run, at kilometre 165. Second run, 473 km/h (294 mph). The third run tops out at only 463 km/h (288 mph), due to the main circuit breaker tripping twice. That evening, the decision is made to increase the mechanical tension in the catenary to 2800 daN (6300 lbf) from 2700 daN (6100 lbf) in the faster sections of the test tracks. (The normal tension in the catenary is 2000 daN, or 4500 lbf).
Tuesday, 5 December 1989
The day begins in very cold weather, with a first run at 474.5 km/h (295 mph). 325 returns to the Dangeau siding, and waits for clearance to proceed on the next run. At 11:07, trainset 308 radios that the test tracks are clear, after a sweep at 350 km/h (218 mph). Test director Pierre Delfosse expresses his hope that the next run will be a good one. 325 leaves Dangeau at 11:36 and begins accelerating. kilometre 124.1, 300 km/h (186 mph). kilometre 129, 350 km/h (218 mph). The junction switches at Courtalain are passed at 363 km/h (226 mph) without a jolt. kilometre 149.5, 450 km/h (280 mph). kilometre 154.8, 460 km/h (286 mph). kilometre 163.9, 470 km/h (292 mph). kilometre 166, 480 km/h (298 mph). 600 metres further, at 11:37, the new world record is established, at 482.4 km/h (299.8 mph). At kilometre 169, engineer Michel Boiteau is told to reduce power to zero. The figures for the run are tallied up. From a standing start:
6'15" and 22 km (14 mi) to 400 km/h (249 mph) 8' and 33 km (21 mi) to 440 km/h (273 mph) 9' and 40 km (25 mi) to 460 km/h (286 mph)
At the end of this run, trainset 325 has racked up 337 km (209 mi) at speeds exceeding 400 km/h (249 mph). News footage of the record run is beamed around the world.
6 December 1989 to 29 January 1990
The test runs continue. 325 is called upon to pump out 13 MW (18,000 hp) at the rail, about the same power as a pair of stock TGV-Atlantique trainsets. With trainset 308, 325 undergoes testing of crossings, achieving a relative closing velocity of 777.7 km/h (483 mph). All the test runs go without a hitch, and the conservative safety parametres set at the beginning are never exceeded. The test data from the December 5 record indicates that the limit of the TGV system has not yet been reached. In light of this, it is decided to attempt a second round of testing, to tackle speeds in the 500 km/h (311 mph) range. The test team has to work fast, because the test tracks are scheduled to begin revenue use in September 1990.
Monday, 29 January 1990
For the first time, high-speed runs are attempted on track 2. Running the "wrong" way (on the right-hand track) trainset 325 crosses the leading-point switches in the Vendôme station at 462 km/h (287 mph).
Thursday, 1 February 1990
Last run for this first series of tests. At 15:30, 325 returns to the Châtillon shops. It will stay there for a month, undergoing further upgrades for the second series of tests.
[edit] Second campaign: March - May 1990
First run of trainset 325, version 2, at 408 km/h (254 mph). Upon returning to the Dangeau siding, the crew changes cabins for the second run. When the trainset is powered up again, an electrical malfunction destroys the main transformer in rear unit 24050. This ends the day of testing, and 325 is towed back to the Châtillon shops behind trainset 308. The same evening, the damaged transformer is changed out and replaced by a standard, smaller transformer. Technicians spend all night repairing the electrical system on 24050. Many 1500 V and 72 V circuits had been seriously damaged by 25 kV in the malfunction.
After many slow runs on the shop tracks to fine-tune the new transformer, 325 heads out once more to the test tracks at 10:05. It never makes it; at Saint-Léger, it breaks down once more, and is towed back to Châtillon by 308.
At 6:30, technicians are still busy changing out a traction motor and low voltage electronics. More time is needed to get 325 back into shape. At 19:00, news arrives that SNCF has decided to delay further testing until unit 24050 has its stock transformer replaced with the refurbished transformer from the March 5 incident. With the current smaller transformer, it is doubtful that 325 can generate enough power to tackle 500 km/h (311 mph).
325 is out on the test tracks again, on its second day. The December 5 record is beat, with a top speed of over 485 km/h (301 mph). The 500 km/h mark seems within reach.
A deer on the test tracks delays the first run of the day by over an hour. On the third run, begun at Dangeau at 14:38, 325 makes history and breaks the 500 km/h (311 mph) mark, at kilometre 164.8. At 14:49, 325 reaches a top speed of 506.5 km/h (315 mph), at kilometre 165.9. During this run, over 3 km (2 mi) are covered at speeds above 500 km/h. The fourth run begins with the usual weather condition update. Courtalain: temperature 23 °C (73 °F), rail temperature 32 °C (90 °F). kilometre 166: temperature 24 °C (75 °F), contact wire temperature 25 °C (77 °F), wind, west, 10 km/h (6 mph). The run proceeds as follows:
kilometre 124.4, 300 km/h (186 mph) kilometre 130.1, 360 km/h (224 mph) kilometre 137.0, 400 km/h (249 mph) kilometre 146.6, 450 km/h (280 mph) kilometre 153.0, 480 km/h (298 mph) kilometre 156.6, 490 km/h (305 mph) kilometre 162.0, 500 km/h (311 mph)
At 16:43, after another few seconds, the numbers flash across the screens: 510.6 km/h (317.3 mph). This run is remarkable in that this speed was attained without making use of the hill at kilometre 166. The switches in the Vendôme station were passed at 502 km/h (312 mph).
Flawless first run at 509.9 km/h (317 mph). Second run, not so good. Third run, problem. While running at 300 km/h (186 mph), the pantograph wiper begins to skip on the contact wire. 325 returns to Dangeau at reduced speed, and the catenary is grounded so that technicians can inspect the pantograph. It is suspected that an accelerometre wire interfered with the wiper; the wire is replaced. Fourth run, the wiper again begins to skip on the contact wire. Upon return to Dangeau, the shock absorber on the pantograph is replaced. Fifth run, same phenomenon, at 339 km/h (211 mph). Testing is stopped for the day.
SNCF announces an interruption of the test program, because of a "minor problem" with the pantograph/contact wire interface. After a thorough evaluation of the pantograph, 325 continues test runs despite the bad news, and makes runs at 505 km/h (314 mph) and 508.9 km/h (316 mph).
Delicate tweaking of trainset 325, intended to optimize tractive effort at very high speeds, result in electrical problems. Technicians settle for less ambitious settings to avoid these problems.
A first run tops out at 505.8 km/h (314.4 mph) at kilometre 166.2. Jacques Fournier, president of SNCF and present on 325 today, congratulates the test crew for a new run over 500. Second run: 506 km/h (314 mph). Third run: 510.8 km/h (317.5 mph) at kilometre 166.8. These last two runs are flawless, with none of the electrical problems encountered earlier.
A day of rest for the crew. 325 stays at her home base, the Châtillon shops.
The planned last day of testing. At dawn, 308 backs against 325, and the Scharfenbergs engage. 325 is towed out to the test tracks, with the usual stop at Massy to pick up the technical crew. The equipment trailer R1 has been converted into a studio, since today's runs are planned as a media event. Trailer R10 will be filled with journalists. At 8:08, 308 and 325 arrive at Dangeau and uncouple. Trainset 313 pulls up behind them, and allows France's minister of transport, Michel Delebarre, to board the cab of 325. Trainset 313 proceeds to the Vendôme station with a load of SNCF executives, headed by president Jacques Fournier, and miscellaneous invited dignitaries. At 8:43, a deer is reported on the test tracks. After a short delay for removal of the deer, 325 pulls out of the Dangeau siding at 9:51. Catenary voltage has been increased to 29.5 kV from 25 kV. 15 minutes later, at 10:06, 325 pegs the new world speed record at 515.3 km/h (320.3 mph) at the bottom of the hill at kilometre 166.8. The train comes to a stop a few minutes later at kilometre 210, and the crew and minister celebrate with champagne. Soon after, 325 returns to track 4 of the Vendôme station with lights blazing and horn blowing, and is greeted by hordes of journalists.
