How does a trolley car work (what are key components)?
A trolley is an electrically propelled vehicle that runs on rails. Here are typical components and their functions: Trolley pole – a tubular metal pole stretching at an angle from the roof of the car to the overhead wire to draw the 600 volts of DC current that powers the car. Trucks – the wheel assemblies under the car. Contain the suspension that supports and cushions the ride and also hold the electric motors and gearing that propel the car. Controllers – the device on the platform that the motorman (driver) turns to start and control the speed of the car. On cars built before 1935, the controller was normally hand operated. On PCC cars built from 1936 on, the controller was normally pedal operated. The speed is controlled by changing the amount of resistance (in the form of “resistance grids” on older cars) connected in series with the motors, and by changing the motors from pairs of two motors in series to all motors in parallel. Braking system – on traditional trolley built after
