Figure 2-37.—Typical cable guides.from rubbing against nearby metal parts. They arePressure Sealsalso used as supports to reduce cable vibration in longstretches (runs) of cable. Figure 2-37 shows sometypical cable guides.FairleadsFairleads maybe made of a solid piece of materialto completely encircle cables when they pass throughholes in bulkheads or other metal parts. Fairleadsmay be used to reduce cable whipping and vibrationin long runs of cable.Split fairleads are made foreasy installation around single cables to protect themfrom rubbing on the edges of holes.GrommetsGrommets are made of rubber, and they are usedon small openings where single cables pass throughthe walls of unpressurized compartments.Pressure seals are used on cables or rods that mustmove through pressurized bulkheads. They fit tightlyenough to prevent air pressure loss, but not so tightlyas to hinder movement of the unit.PulleysPulleys (or sheaves) are grooved wheels used tochange cable direction and to allow the cable to movewith a minimum of friction. Most pulleys used onaircraft are made from layers of cloth impregnatedwith phenolic resin and fused together under hightemperatures and pressures. Aircraft pulleys areextremely strong and durable, and cause minimumwear on the cable passing over them. Pulleys areprovided with grease-sealed bearings, and usually donot require further lubrication.However, pulleybearings may be pressed out, cleaned, and2-26
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