Trolley Collector for Overhead System:
This consists of a grooved gun metal wheel or grooved slider shoe with carbon insert carried attached to the end of a long pole provided on the top of the car. Other end of this pole is hinged to a swiveling base fixed to roof of vehicle. Necessary upward pressure for the pole and current collector is achieved by means of springs. As two trolley wires are required for a trolley bus a separate trolley collector is provided for each wire, the bases being mounted side by side. The pressure for wheel is approximately 10kg and for a carbon insert slider is approximately 17kg. The main drawback of trolley collector is that it has to be rotated through 180° for reversing the direction of motion of the vehicle. Another drawback is that there is poor contact between the wheel and trolley wire which gives rise to high current density. Suitable for comparative low speed (say 22 to 30 kmph).