Cylindrical worm meshing with helical gear Curved teeth that wrap around the worm Curved teeth and concave worm that wraps around gear High speed-reducer Better shock resistance High shock resistance Light loads Higher load Highest load Reducer selection 1. Load Ratings 2. Service Factors 3. Horse Power 4. Torque 5. Gear Ratio 6. Overhang and bending loads Gear selection 1. Shaft orientation 2. Speed ration 3. Design type 4. Nature of load 5. Gear rating 6. Environment 7. Mounting position 8. LubricationAGMA- American Gear Manufacturers AssociationBacklash- the amount of play between the meshing teeth of two mating gearsFunction of enclosed drives- reduce speed and increase torqueGear trains can be a. Simple Gear Trainsb. Compound Gear Trains.c. Planetary Gear Trainsd. Epicyclic Gear Trainse. Harmonic Gear TrainsSpeed reducers are used to reduce speed, and increase output torque, from the primemover to the driven machine.Gear specifications for replacement:Pitch diameterDiametrical pitchInner and outer radius# of teethBore sizematerialChainsChain application: bicycle, motorcycle, farm implements
Functions of chains: transmission and conveyor Advantages of chains- no slippage, heavy loads with negligible stretch, high efficiency, long life, operate in hostile environments, special materials for special environments, unlimited shelf life, can be easily replaced without machine disassembly, replace damaged links not whole belt Disadvantages of chains- can only be used on parallel shafts, potential for elongation stretch or slack, flexibility limited to a single plane, lower speed limitations, proper maintenance requirements, generate noise, need to replace sprockets Advantages and disadvantages of chain drives compared with belt and gear drives are as follows: 1) Chain drives can be used for long as well as short center distances. They are particularly suitable for medium centre distance, where gear drives will require additional idler gears. 2) Chain drives are used for shafts which are parallel. Some types of gears, like bevel and worm gears, are used for non-parallel shafts.
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- Spring '19
- gear, Gear Trains, Epicyclic Gear Trains, American Gear Manufacturers Association, Planetary Gear Trains, Harmonic Gear Trains