How to Determine Which Bevel Gear Design is Right for Your Application
Simple gears are used to transfer power from one shaft to another, but when the shafts intersect at odd angles, they don’t intersect at all, or you need to change the rotational direction of a shaft, things become complicated. It takes a bevel gear to keep things moving. Bevel gear design is commonly used in many industrial applications as well as in all types of vehicles.
On a standard gear, the pitch surface (that carries the teeth) is cylindrical. On a bevel gear, the pitch face is conical. The angle formed by the pitch pace and the axis on which it’s mounted is called the pitch angle. Often, bevel gears work at right angles, but they can be designed to function at any pitch angle. A hand drill is an example of a tool that uses a 90o bevel gear.
Bevel Gear Examples
Bevel gears are classified by their geometry, and each type of bevel gear offers its own specialty or advantage. Here are a list of bevel gear examples:
- Straight Bevel Gear. On a straight bevel gear, the teeth are straight but they taper toward the apex of the cone-shaped surface. This is the most common type of bevel gear. It functions well, but operation can be noisy, especially at high speeds or under heavy loads.
- Spiral Bevel Gear. On a spiral bevel gear, the teeth are curved and set in a spiral so they contact their counterparts more gradually. This smoother operation eliminates the noise (and higher risk of tooth breakage) of a straight bevel gear.
- Zerol Bevel Gear. A zerol bevel gear also has curved teeth, but they are not angled in a spiral, so the teeth align with the axis.
- Hypoid Bevel Gear. On a hypoid bevel gear, the pitch angle is hyperbolic instead of conical and the pinion can be offset–either below or above the gear center.
By nature, bevel gear design is highly complex–even intricate. So it takes meticulous planning to design and manufacture to achieve the desired operational result.
Which Bevel Gear for Which Application?
Bevel gears are used in vehicles of all types as well as industrial applications such as wind turbines and cooling towers, steel manufacturing, and printing presses. If your application requires high rpm, high torque, and/or many load cycles, spiral bevel gears will be the best choice. Spiral design is also recommended for reducing speed. If your application requires transferring power to two shafts which are spinning at different speeds–a vehicle differential, for instance–the best choice is a hypoid bevel gear.
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