Helical Gear
Helical gears are gears with teeth cut at an angle to the axis of the gear. This angled tooth design allows smoother and quieter operation compared to spur gears. Helical gears are commonly used where high-speed and heavy load transmission is required.
Characteristics
- Teeth are inclined to the gear axis.
- Smooth and quiet operation.
- Higher load carrying capacity.
Applications
- Automobile gearboxes
- Industrial machinery
- Heavy-duty power transmission systems
Herringbone Gears
Herringbone gears consist of two sets of helical teeth arranged in opposite directions on the same gear. This design eliminates axial thrust and provides smooth power transmission.
Advantages
- No axial thrust.
- Smooth and quiet operation.
- Suitable for heavy load transmission.
Applications
- Marine engines
- Heavy machinery
- Industrial gear systems
Bevel Gearing
Bevel gears are used to transmit power between shafts that intersect at an angle, usually 90 degrees. The teeth are cut on a conical surface.
Uses
- Automobile differential systems
- Machine tools
- Right-angle power transmission systems
Spiral Bevel Gearing
Spiral bevel gears are similar to bevel gears but have curved teeth. These curved teeth provide smoother engagement and quieter operation.
Advantages
- Smoother and quieter operation.
- Higher load carrying capacity.
- Better efficiency.
Hypoid Gearing
Hypoid gears are similar to spiral bevel gears but the shafts do not intersect. Instead, the axes of the shafts are offset. Hypoid gears provide smooth and quiet operation in high-speed applications.
Applications
- Automobile rear axle drives
- Heavy machinery
Pinion and Rack
The rack and pinion mechanism converts rotary motion into linear motion. The pinion is a small circular gear, while the rack is a straight gear with teeth cut along its length.
Applications
- Steering systems in automobiles
- Machine tools
- Linear motion systems
Worm Gearing
Worm gearing consists of a worm (a screw-like gear) and a worm wheel. It is used to transmit motion between non-parallel and non-intersecting shafts.
Advantages
- High reduction ratio.
- Smooth and quiet operation.
- Self-locking capability in some cases.
Applications
- Conveyors
- Lifting machines
- Speed reducers
Velocity Ratio of Worm Gearing
The velocity ratio of worm gearing depends on the number of threads on the worm and the number of teeth on the worm wheel.
Velocity Ratio = Number of Teeth on Worm Wheel / Number of Threads on Worm
This allows large speed reduction in a compact system.
Repair of Gear Teeth
Damaged gear teeth can be repaired instead of replacing the entire gear. Two common methods are used for repairing gear teeth.
Building Up Method
In this method, metal is added to the worn or damaged gear tooth using welding. After welding, the tooth is machined to restore its original shape.
Advantages
- Cost-effective repair method.
- Restores the original shape of gear teeth.
Dovetail Method
In the dovetail method, the damaged portion of the gear tooth is removed and replaced with a new metal piece shaped like a dovetail. The new piece is fixed firmly in the slot and machined to match the original gear tooth profile.
Advantages
- Strong and reliable repair.
- Suitable for large gears.
Conclusion
Various types of gears such as helical, bevel, spiral bevel, hypoid, worm gears, and rack and pinion systems are used in power transmission systems. Proper maintenance and repair techniques like building up and dovetail methods help extend the life of gear components and maintain efficient machine operation.