On June 13, JR Tokai and JR West announced the retirement of the Type 923 electric track test car, known as “Doctor Yellow. Perhaps because of its nickname, it is sometimes referred to as the “doctor of the bullet train,” but it does not perform “medical treatment” while running. So what exactly does this vehicle do?
Laboratory technician rather than a doctor.
As mentioned at the beginning of this article, the official name of the vehicle is the “Comprehensive Electric Track Test Vehicle. In reality, however, the inspection covers much more than just electricity and track. Specifically, they are as follows.
Track (rail and related)
Electricity (electricity supplied from overhead lines)
Signaling (system responsible for detecting train position and preventing collisions)
Communication (radio communication between the train and the ground)
First of all, the rails that support the train, which weighs about 700 tons per train and runs at a high speed of 285 km/h to 300 km/h, are subjected to a commensurate load. This can cause a change in the vertical or horizontal position of the rails. The industry term for this is as follows.
High/low (vertical rail displacement)
Street (displacement of rail in left-right direction)
Level (difference in height between left and right rails)
Flatness (twisting of the plane formed by two rails)
Gauge (change in distance between two rails)
To explain this in a straight horizontal section for simplicity, the distance between the top and inside of the left and right rail heads must be 1435 mm, and the height of the left and right rails must be the same. In reality, however, loads are applied and deformation may occur. The so-called track inspection is used to find this out.
Next is electric power. The power supplied to the overhead lines of the Tokaido and Sanyo Shinkansen is single-phase 25,000 VAC, 60 Hz, and although some fluctuations may occur, these fluctuations must be within the specified range, so the power is actually taken from the overhead lines and checked. In addition, the trolley line (the line that the pantograph comes in contact with) is subject to wear when rubbed by the pantograph, so the condition of the trolley line must also be checked.
Next is signaling. In Shinkansen trains, signal current is passed through the rails to detect the presence of a train. The signal current also sends information to the train on where to slow down and where to stop so that the train does not collide with the train ahead. This is the so-called automatic train control (ATC) system. For safe operation, it is necessary to check whether the signal current is at an appropriate level.
ATC and related functions include point detection. The car body inclination and speed control by ATC, both introduced in the N700 series, are based on the data from this point detection, which is a very important function. Therefore, we will also check the operation of the point detection function.
Finally, communications. On Shinkansen trains, leaky coaxial cables (LCX: Leaky CoaXial cable) are installed alongside the tracks to provide radio communication between the train and the ground. Crew members use these cables to communicate with the control center, and in the past, they were also used for in-train public telephones. We also check to see if this radio communication equipment is functioning properly.
Type 923 trains run on the main line at the same speed as commercial trains, and are inspected and data is collected on these various items.
© Source travel watch
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