Track Indicator

a railroad car that continuously monitors the condition of tracks, including the gauge, the alignment of the rails’ level and the uniformity of their plane, any sag in the rails, and the existence of horizontal or vertical shocks. The first track indicator for mechanically recording rail flaws on tape was built in 1887 by the Russian engineer I. N. Livchak. The first track indicators in Russia were used in the early 20th century.

A passenger car serves as the frame of a track indicator. The monitoring apparatus, installed under the car, consists of rollers that are pressed against the railheads by springs. Widening or narrowing of the gauge causes the rollers to shift horizontally. This motion is transmitted to the car by a system of cables and pulleys and automatically plotted on a tape, which is set in motion by the wheels’ axle.

Vertical measurements are made with the aid of a pair of the car’s wheels. The motion of these wheels is compared with the reference reading of a gyroscope or physical pendulum located in the car. Irregularities are transmitted to the automatic recorder by a system of cables and pulleys.

Track recorders have considerable weight, with the pressure on the axle reaching 17.5 tons, and move at high speeds ‘(100–120 km/hr). The cars thus have a strong dynamic impact on the tracks. This makes it possible to record elastic deformations of the rails and hidden shocks that occur when the train is in motion. Track indicators that operate at higher speeds (to 180–200 km/hr) utilize methods of contactless measurement with the aid of such inductive components as electromagnets and selsyns.

Light, manually operated track-indicator handcars travel at speeds of up to 5 km/hr and weigh about 20 kg. They are used to measure the rail gauge and rail alignment within a maintenance section. The measurements are recorded on a tape.