Disk Friction and Flexible Belts

The sliding surfaces are present in most machine components and it is desirable to minimize the friction in order to reduce energy loss and wear. In contrast, clutches and brakes depend on friction in order to function. The function of a clutch is to permit smooth, gradual connection, and disconnection of two elements having a common axis of rotation. A brake acts similarly except that one of the elements is fixed. In pivot bearings, clutch plates, and disk brakes there is friction among circular surfaces under distributed normal pressure. In the design of belt drives and band brakes the impending slippage of flexible cables, belts, and ropes over sheaves and drums is important. This chapter presents a drum subjected to the two-belt tensions T 1 and T 2 , the moment M necessary to prevent rotation, and a bearing reaction R . The forces acting on the differential element are calculated using the equilibrium of the element. The tension increases from T at the angle θ to T + dT at the angle θ + dθ .