Trolleybus

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Trolleybus

 

a railless urban surface transport vehicle powered by electrical energy drawn from overhead, or trolley, wires.

Work on the development and use of trolleybuses was carried on in Germany as early as the beginning of the 1880’s. The provision of reliable current collection from overhead wires was found to be the most difficult technological problem in designing trolleybuses. The problem was not solved until asphalt road surfaces were introduced. With these advances, the wide use of trolleybuses became possible. The first trolleybuses in the USSR were built in 1933; trolleybuses started operating in Moscow in 1934. In the 1960’s and 1970’s trolleybus routes were established in many of the major cities of the USSR.

As compared with the trolley car, the trolleybus has the following advantages: no rails (which require a large initial capital investment), better maneuverability, and noiseless operation. A disadvantage of the trolleybus is the need for a more complicated overhead suspension with two trolley wires. In comparison with the motor bus, the trolleybus has several advantages, such as the use of inexpensive electrical energy, the absence of exhaust gases, and simplicity and reliability of operation. The trolleybus, however, requires road surfaces of a much higher quality and is less maneuverable than a motor bus when moving through heavy traffic. In a number of cases, these disadvantages limit the use of trolleybuses.

Most trolleybuses are built as two-axle vehicles with bodies that have either two or three doors. Multiaxle articulated trolleybuses are used on lines with heavy passenger traffic, which follow major urban arteries. Two-axle trolleybuses are generally 10–12 m long, 2.5 m wide, and 3.2–3.4 m high. Present-day trolleybuses can reach speeds of 65–70 km/hr; two-axle trolleybuses can carry 50–70 passengers.

The basic electrical equipment of a trolleybus includes a DC traction motor, an auxiliary electric motor, and lighting and signaling apparatus; the auxiliary motor drives the compressors, fans, and generators and supplies electric power to low-voltage devices. The traction motors may be compound or series motors. Compound traction motors are used in Soviet trolleybuses; such motors operate well both as a traction system and as a generator. Compound motors are suitable for regenerative braking, in which electrical energy is returned to the contact system. The power ratings of traction motors range from 70 to 120 kilowatts for a contact system voltage of 550 volts. The traction motors are controlled by contactors, which switch in the power circuit and are actuated by a controller connected to a pedal near the driver’s seat. Reverse motion is achieved with the aid of an electric reverser, which changes the direction of the current in the armature windings and in the windings of the commutating poles. External lighting and signaling devices are supplied with low-voltage current. Electrical energy from the contact system is supplied through a current collector located on the roof of the trolleybus.

The mechanical equipment of a trolleybus includes the transmission, the running gear, and the controls. The transmission consists of a Cardan shaft and an axle shaft with a differential gear. Bevel gears or worm gears are used in the reduction gear. The running gear, including the spring suspension, axle housings, and wheel hubs, is similar to that of large motor buses and heavy trucks. The braking system includes shoe-type air brakes and a manually operated mechanical actuator for the parking brake. The steering gear and linkage are of the automotive type. The body of a trolleybus is made entirely of metal, with a welded steel frame covered by a thin steel sheet. The frame is fastened to a rigid base that is fabricated as a truss consisting of shaped beams joined by gusset plates.

The use of trolleybuses will be greatly expanded as the overall road system is improved. Furthermore, high-speed trolleybuses can be put into operation as the widths of roadways and the radii of curves are increased and improved pavements are used.

Trolleybuses are used on some interurban routes, such as the Simferopol-Yalta line. The high passenger-carrying capacity of a trolleybus, as compared with a motor bus, makes the operation of trolleybuses highly efficient for lines with a heavy passenger traffic flow.

REFERENCE

Rebrov, S. A. Ustroistvo i teknicheskaia ekspluatatsiia trolleibusov, 2nd ed. Kiev, 1972.
A. A. SABININ