P-01: The Tilting TGV Demonstrator
New high speed lines to reduce trip times to the far reaches of France are very expensive. For this reason, the cheaper possibility of increasing speeds on existing tracks by going to a tilting design was explored in the late 1990s by SNCF and TGV builder Alstom. The P-01 tilting TGV demonstrator was built to study the possiblity of tilting TGVs, which would run without tilt on high speed lines up to 320 km/h and continue on existing tracks, suitably modified for speeds of up to 220 km/h, with tilt.
Why tilt? Faster travel through existing curve radii results in passenger discomfort. By tilting the car bodies into the curve, the centrifugal force is directed downward into the floor of the car, resulting in less sideways force for its occupants. While tilting capability improves passenger comfort, it does nothing to reduce forces at the rail, which increase greatly with higher speeds. Therefore, a good tilting train design must have a low axle loading in order to spare the track and avoid costly and more frequent track maintenance. While the TGV's 17 tonne per axle load is relatively light, it is still significantly higher than that of other tilt trains such as Fiat's popular Pendolino design. This is why a major focus for a next generation TGV design is to reduce axle load to 16 tonnes.
The P-01 demonstrator project (so named after the French term for a tilting train, pendulaire) was launched in 1996 by a team consisting of SNCF, Alstom, and the French government. The budget for the project was 170 million Francs (about 25 million US dollars). In June 1997, TGV Sud-Est trainset 101 was removed from service to serve as the basis for the P-01 demonstrator. This trainset underwent heavy modifications and emerged in April 1998 ready for testing. After a test campaign that lasted into mid 2000, the trainset was returned to the Sud-Est fleet without tilt equipment. The P-01 demonstrator therefore no longer exists, but provided French industry with tilt train experience which Alstom sorely lacked at the time.
The principal intent of the modifications was to add the tilt system, actually two tilt systems, without sacrificing high speed capability. The first was a hydraulic system based on Fiat's technology (Fiat's rail division was subsequently bought by Alstom in 2000), and second an Alstom-designed electro-mechanical system. The tilt system was changed midway through the testing, and had to be packaged into the trailer articulation while leaving room for the SR-10 suspension.
Adding a tilt system to trainset 101 required a few important decisions:
- The power cars would not tilt, because that would entail developing a whole new powered and tilting bogie. This went far beyond the schedule and budget for the project. Instead, the power car suspension was stiffened to maintain the proper alignment of the pantograph in curves, and some improvements were made to cab ergonomics. In particular, a new seat was installed in the cab to make cant deficiencies of up to 260 mm tolerable for the driver/engineer. (Cant deficiency is how much higher the outside rail in a curve would have to be elevated so that no lateral force results at the rail; it depends on speed, radius and superelevation.)
- The end trailers (adjacent to the power cars) would have their motors removed to make room for the tilt system. The resulting one-third loss of power made the trainset incapable of reaching full speed on high speed lines, unless it was coupled to another TGV trainset for testing up to 320 km/h. This limitation came solely from using an old Sud-Est trainset as the basis for the demonstrator, and was deemed acceptable for the purpose of testing.
Modifications were carried out at the Bischheim shops in eastern France and included:
- Installation of inertial measurement equipment (gyroscope and accelerometers) in each power car, with associated control computer to send tilt commands to each trailer's local tilt computer
- Installation of an on-board computer network to link the tilt system's computers
- Installation of hydraulic underfloor equipment on each trailer
- Modification of the bogie design including a tilting transom to which the tilt actuators attached
- Raising of the trainset suspension by 60 mm and extensive body structure modifications to provide adequate clearance for the tilt equipment
- Modification of the trailer articulation to allow 3.5 degrees of differential tilt between adjacent trailers
- Conversion of the interior of trailer R1 to a laboratory (see photo below)
- Conversion of the interior of trailer R3 to a public exhibit on the project
- Installation of the HP (high power) brake and the TVM 430 signalling system for running up to 320 km/h. These modifications were included in trainset 101's midlife overhaul which was completed after the test program, as 101 returned to service in the Sud-Est fleet.
- A Roger Tallon-designed color scheme in dark blue and silver, with red window bands, intended for TGV test trainsets.
This work took 8 months and 30000 hours of labor for 200 people.
TGV P-01 Tilting Demonstrator Technical Data
Top Speed: 220 km/h (or 320 km/h in multiple unit)
Supply Voltages: 25kV 50Hz AC, 1.5kV DC
Traction: 8 DC motors, total continuous power 4300 kW (5770 hp) under 25kV supply, 2070 kW (2770 hp) under 1.5kV supply. Almost twice these figures for 7 minutes.
Length and Weight: 200 m / 385 tonnes
Maximum Tilt Angle: 6.3 degrees from vertical
Configuration: 1 power car + 8 trailers + 1 power car
Spotting Features: New dark blue and silver livery with large red side graphics
Images: [TGVweb] [ERS Picture Gallery]
At left, the relative tilt of the non-tilting power car (left in photo) compared to the full 6.3 degree tilt of the first trailer. At right, the interior of trailer R1 fitted as a laboratory. Both photos copyright Yann Nottara, 1998.
The P-01 demonstrator returned from modifications and static testing to the PSE depot near Paris in April 1998. The first shakedown runs were made on the Melun-Montereau and Meaux-Epernay lines, and were followed by high speed test runs (assisted by a TGV Réseau) at 300 km/h on the LGV Nord between Lille and Calais. Trainset testing and tuning was completed in July 1998.
Testing continued on various lines around France, running the full range from twisty runs in the mountains to high speed LGV runs. Cant deficiency was taken up to 290 mm, and effects on the track were measured. Measurements of safety parameters, track wear and running quality were measured under all operating conditions. Qualitative comfort tests were performed with passengers on board the train.
This testing cycle was repeated after the Fiat hydraulic tilt system was replaced by the Alstom-designed electromechanical system, which was expected to provide higher reliability, lower mass, lower volume and lower cost.
Finally in May 2000, a counter-tilting pantograph was mounted on the roof of trailer R8 to study issues related to tilting power cars.
At the end of the test campaign in the summer of 2000, the P-01 demonstrator returned to the Bischheim shops to undergo the rest of its midlife overhaul and return to service as Sud-Est trainset 101.