Double Wheel Trolley

a grooved rotating wheel attached to the end of the trolley pole of an electric railway car or bus for making constant rolling contact with the trolley A trolley is an object with wheels that you use to transport heavy things such as shopping or luggage.A hand truck, also known as a hand trolley, dolly, stack truck, trundler, box cart, sack barrow, cart, sack truck, two wheeler, or bag barrow, is an L-shaped box-moving handcart with handles at one end, wheels at the base, with a small ledge to set objects on, flat against the floor when the hand-truck is upright.a wheeled carriage running on an overhead rail or track. 3. chiefly British : a cart or wheeled stand used for conveying something (such as food or booksWheels are added to trolleys to reduce friction. As rolling friction is lesser than sliding friction, adding wheels to trolleys reduces opposition to motion.The word trolley came from the little troller of Daft's system. Trolleybuses had the advantages of electric propulsion (more quiet operation, avoidance of fumes, and faster acceleration) and could load passengers at the curb, but they were less flexible than the motor bus.