Types of gear drives

1. T ypes of gear drives BY PRATIK SUDRA GOVERNMENT ENGINEERING COLLEGE,VALSAD

2. Gear drives A gear is a toothed wheel with the teeth cut on the periphery of a cylinder or a cone. Gears are mounted on the shafts with key. There are two gears mounted, one on each of the driving and driven shaft. Therefore the teeth of one gear is mesh with the teeth of the other gear. The rotation of gear will cause rotation of the other in the opposite direction.

3. Advantages of gear drives Positive drives. High transmission efficiency. High velocity possible, even up to 60:1 Velocity ratio will remain constant throughout. Used for low, medium and high power transmission.

4. Disadvantages of gear drives Require lubrication. At very high speeds, produce noise and vibrations. Manufacturing of gears is costly. The large number of gear wheels in gear trains increased the weight of machine. Not suitable for shafts having large centre distance.

5. Terms used in gears Pitch circle Pitch circle diameter. Pressure angle or angle of obliquity. Circular pitch. Module.

6. Types of gears Spur gears Helical gears Spiral gears Bevel gears Worm and worm wheel gears Rack and pinion gears

7. Spur gears Teeth of the spur gears are cut on the circumference of the cylindrical discs. Can transmit higher power because of the contact between the mating gears is along lie. Use transmitting power between two shafts when the axes of driving and driven shafts are parallel & co-planar. Machine tools and automobile gear boxes.

8. Helical gears Teeth are cut in the form of the helix around the gear. Teeth are not parallel to the shaft axis. Two moving gears have identical helix angle but opposite hand. Use Transmitting power between two parallel ,non parallel, non-intersecting shafts. Smooth and quiet running at high speeds is required. Automobile power transmission.

9. Spiral gears Same as helical gears and cut along helical path. Point contact while curvilinear contact in case of helical gear drive. Point contact in spiral gears are more suitable for transmitting less power. Use: Transmit power between two non-parallel non-intersecting shafts.

10. Bevel gears Cut on conical surfaces. Teeth are varying in cross-section along the tooth width. The axis of two moving gears are inclined in the bevel gear. Use Transmitting power between two shafts, when the axis of two shafs are inclined and intersect each other. Widely use in automobiles.

11. Worm and worm wheel gears A worm has one or more number of helical threads of trapezoidal shape cut on it. Gear wheel with tooth profile consists of a small segment of helix with engages with the worm. Use Transmitting power between two shafts having the axis at right angle and non-coplaner. Machine tools like lathe, milling ,drilling machines.

12. Rack and pinion gears Rack is a rectangular bar consist of a series of straight teeth cut it. Rack is a spur gears infinite diameter. Rack is mesh with another small gear known as pinion . Use Convert rotary motion into linear motion. Machine tools like lathe, drilling, planning machines. Measuring instruments.

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