tailieunhanh - Industrial Machinery Repair Part Episode 2 Part 4

Tham khảo tài liệu 'industrial machinery repair part episode 2 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Gears and Gearboxes 309 Where TF tangential force Stf separating force TTf thrust force hp input horsepower to pinion or gear Dp pitch diameter of pinion or gear rpm speed of pinion or gear Ộ pinion or gear tooth pressure angle Ằ pinion or gear helix angle Herringbone Gears Commonly called double helical because they have teeth cut with right and left helix angles they are used for heavy loads at medium to high speeds. They do not have the inherent thrust forces that are present in helical gear sets. Herringbone gears by design cancel the axial loads associated with a single helical gear. The typical loads associated with herringbone gear sets are the radial side-load created by gear mesh pressure and a tangential force in the direction of rotation. Internal Gears Internal gears can only be run with an external gear of the same type pitch and pressure angle. The preload and induced load will depend on the type of gears used. Refer to spur or helical for axial and radial forces. Troubleshooting One of the primary causes of gear failure is the fact that with few exceptions gear sets are designed for operation in one direction only. Failure is often caused by inappropriate bidirectional operation of the gearbox or backward installation of the gear set. Unless specifically manufactured for bidirectional operation the nonpower side of the gear s teeth is notfinished. Therefore this side is rougher and does not provide the same tolerance as the finished power side. Note that it has become standard practice in some plants to reverse the pinion or bullgear in an effort to extend the gear set s useful life. While this 310 Gears and Gearboxes Table Common failure modes of gearboxes and gear sets THE PROBLEM THE CAUSES Gear failures Variations in torsional power Insufficient power output Overheated bearings Short bearing life Overload on driver High vibration High noise levels Motor trips Bent shaft Broken or loose bolts or setscrews Damaged motor Eliptical gears Exceeds