tailieunhanh - Root Cause Failure Analysis Episode 7

Tham khảo tài liệu 'root cause failure analysis episode 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 172 Root Cause Failure Analysis Table 14-1 Gear Characteristics Overview Gear Type Characteristics Attributes Positives Negatives Spur external Connects parallel shafts that rotate in opposite directions inexpensive to manufacture to close tolerances moderate peripheral speeds no axial thrust high mechanical efficiency Noisy at high speeds Spur internal Compact drive mechanism for parallel shafts rotating in same direction Helical external Connects parallel and nonparallel shafts superior to spur gears in load-carrying capacity quietness and smoothness high efficiency Higher friction than spur gears high end thrust Helical double also referred to as herringbone Connects parallel shafts overcomes high-end thrust present in single-helical gears compact quiet and smooth operation at higher speeds 1 000 to 12 000 fpm or higher high efficiencies Helical cross Light loads with low power transmission demands Narrow range of applications requires extensive lubrication Bevel Connects angular or intersecting shafts Gears overhang supporting shafts resulting in shaft deflection and gear misalignment Bevel straight Peripheral speeds up to 1 000 fpm in applications where quietness and maximum smoothness not important high efficiency Thrust load causes gear pair to separate Bevel zerol Same ratings as straight bevel gears and uses same mountings permits slight errors in assembly permits some displacement due to deflection under load highly accurate hardened due to grinding Limited to speeds less than 1 000 fpm due to noise Bevel spiral Smoother and quieter than straight bevel gears at speeds greater than 1 000 fpm or 1 000 rpm evenly distributed tooth loads carry more load without surface fatigue high efficiency reduces size of installation for large reduction ratios speed-reducing and speed-increasing drive High tooth pressure thrust loading depends on rotation and spiral angle Gearboxes Reducers 173 Table 14-1 Gear Characteristics Overview continued Gear Type Characteristics .