Idler spacings

As an ex uTJple, Fig, 4 shows the belt velocities for slip and lift-off as a function of conveying inclination angle for an idler spacing of 1.0 m, an equivalent friction factor of 0.5 and two sag ratios, 0.2% and 0.5%. The adhesive stress between the balk solid and belt surface is taken to be zero. The reduction in sag ratio from 0.5% to 0.2% significantly increases the belt speed before slip and lift-off occur. 

As illustrated in the previous example, idler spacing in relation to sag ratio is an important issue for high speed inclined conveying if spillage is to be prevented. As is usually the case, the contribution of belt stiffness in limiting belt sag is small in relation to belt tension. Hence, the stiffness can be neglected in the sag determination The sag ratio is given by... 

At higher belt speeds, lower sag ratios must be employed. As indicated y Eq. (10), this can be achieved by employing reduced idler spacing. 

With the proper idlers select ed for size and service conditions, the most important step is to locate them properly. For long belts the tension varies considerably, and idlers should be spaced to hold belt sag to reasonable limits along the full length of travel. Too much belt sag can cause a significant power loss, but for most belts of ordinary length it is usu ly satisfactoiy to space idlers fairly closely at the feed... 

Cause of failure Belt has evenly spaced deep bottom cracks from use of substandard backside idler (Figure 58.13). 

A second resonator with a properly chosen length, such that the mode spacing is Av = 8, enhances the signal as well as the idler wave. 

The bandwidth of an OPO depends on the parameters of the resonator itself (specifically the mode spacing Av ode = c/2L for the signal and idler standing waves), and on the line width, power and wavelength of the pump laser. Typical values are Avopo 3 150 GHz. 

Idler sprockets for roller and engineering steel chain drives wear in a different way. There is not much pressure on the working faces of the teeth on an idler sprocket. So idler sprockets usually wear at the bottom of the tooth space. A badly worn idler sprocket for roller chain is shown in Figure 15-2. When the tooth space is worn deeply enough, the chain rollers may bind against the tooth tips as they enter and leave the idler sprocket. 

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