Modern conveyors, specially engineered to handle concrete, can place concrete very rapidly and economically. There are three basic types of conveyors. The first is the feeder conveyor, used for rapidly transporting concrete over long distances. Feeder conveyors can carry concrete horizontally at capacities of 60 to 125 cubic yards per hour. The second type of conveyor is the portable unit. These are used for short lift applications such as carrying concrete from the ground level to a second story or over an excavation. The third type of conveyor is the side discharge unit. Side discharge conveyors are used to rapidly place concrete over a large area such as a bridge deck. The essential construction and operating features of conveyors can be summarized as follows: (1) length- most feeder conveyors are about 30 feet long, but they can be made in lengths up to and including 85 feet. (2) Transfer- in a feeder conveyor system, the concrete is transferred from one belt to the next by a baffle hold and shield arrangement which prevents spillage. (3) Elevation- with a normal smooth belts a cohesive concrete mix can be handled through an angle of 20 to 30 degrees without difficulty. (4) Weight- a feeder conveyor unit made of aluminum, complete with motor, need not weigh more than 660 pounds. (5) Belt- belts for handling concrete are commonly made with a two ply, all nylon carcass and a rubber covering of maximum abrasion and alkali resistance. (6) Power- the preferred drive for a feeder conveyor section is an individual 5 horsepower, 220 to 440 volts, 3 phase motor, operating at 1800 revolutions per minute. (7) Operation- feed is normally directed onto the belt of the conveyor unit through a simple directional hopper that prevents spillage.