Understanding the Various Types of Gearboxes

Common Types of Industrial Gearboxes

The five most common kinds of industrial gearboxes are outlined here.

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Helical Gearbox

Helical gears are a type of cylindrical gear with teeth that are cut at an angle (or helix) to the gear axis. This angled tooth design provides smoother and quieter operation compared to spur gears, which have straight-cut teeth. Here’s a quick overview of what makes helical gears special:

Key Characteristics:

• Angled Teeth: Teeth are set at an angle, typically between 15° and 30°.
• Gradual Engagement: The angled design allows teeth to engage gradually, reducing shock loads and noise.
• High Load Capacity: More teeth are in contact at once, distributing load better than spur gears.
• Smooth Operation: Less vibration and noise, great for high-speed or high-load applications.

 

Types of Helical Gears:

1. Parallel Shaft Helical Gears
   • Shafts are parallel.
   • Used in gearboxes, automotive transmissions, etc.
2. Crossed Helical Gears
   • Shafts are non-parallel and non-intersecting.
   • Compact but lower efficiency due to sliding contact.

 

Advantages:

• Quieter and smoother than spur gears
• Higher load-carrying capacity
• Efficient at high speeds

 Disadvantages:

• Axial thrust: generates a force along the shaft that needs to be managed (e.g., using thrust bearings)
• More complex manufacturing
• Slightly less efficient due to sliding friction

 

The helical gearbox is a very common gearbox utilized when high load carrying capability and efficiency are of utmost importance. Helical gearboxes can be found in various industrial applications or where low noise transmissions are a requirement. Helical reducers are prevalent in the plastics, cement, and rubber industries and other heavy industrial applications

The key benefit of helical gearboxes is the higher load carrying ability and low noise generation. These two features are possible because of the high contact ratio between the teeth and the angle lead of the tooth. In combination this allows for a lower tangential load acting against the tooth and the load to be distributed amongst multiple teeth at any given time.

 

Straight Bevel Gear Gearbox

Straight bevel gears are a type of bevel gear where the gear teeth are straight and tapered, converging at a point (like a cone). They’re used to transmit motion and power between intersecting shafts, typically at a 90° angle, though other angles are possible.

Key Features of Straight Bevel Gears:

• Tooth Shape: Straight, like spur gears but on a conical surface.
• Shaft Orientation: Usually 90°, but can be different.
• Load Capacity: Generally lower than spiral bevel gears due to less gradual tooth engagement.
• Noise & Vibration: Can be noisier and cause more vibration compared to spiral or hypoid bevel gears.
• Manufacturing: Easier and cheaper to manufacture than spiral bevel gears.

Common Applications:

• Differential systems in older or simpler vehicles
• Hand drills
• Industrial machinery where simplicity and cost-efficiency matter

Advantages:

• Simple design
• Cost-effective
• Easy to manufacture

Disadvantages:

• Noisy at high speeds
• Less smooth engagement
• Lower torque capacity

 

Bevel gearboxes are ideal when power must be transmitted between two shafts aligned on a 90-degree angle. A straight bevel gear tooth gearbox is recommended when large shaft misalignments are expected, and the design does not require high levels of efficiency. The straight tooth bevel gear gearbox offers the ability to transfer load between the 90 degrees but limits the amount of design complexity and cost.

Spiral Bevel Gear Gearbox

Spiral bevel gears are a type of bevel gear where the gear teeth are curved and obliquely oriented, allowing for smoother and quieter operation compared to straight bevel gears. They are commonly used in applications that require high torque and smooth power transmission between intersecting shafts—most often at a 90-degree angle.

Key Features:

• Tooth Design: The teeth are curved (spiral) and angled, which provides gradual engagement and better load distribution.
• Efficiency: Higher efficiency due to continuous tooth contact.
• Noise: Quieter operation than straight bevel gears, especially at high speeds.
• Load Capacity: Can handle higher loads because of the larger contact area between the teeth.
• Direction: Designed in pairs, typically with one being a left-hand spiral and the other right-hand.

Common Applications:

• Automotive differentials (transfers power from drive shaft to wheels)
• Helicopter transmissions
• Power tools
• Industrial machinery

Advantages:

• Smooth and quiet operation
• High torque transmission
• Efficient performance at high speeds

Disadvantages:

• More complex to manufacture
• More expensive than straight bevel gears
• Requires precise alignment and installation

 

Similar to straight bevel gears, spiral bevels gear allows load transmission between two non-parallel shafts. But spiral bevel gearboxes are higher in efficiency and generate less noise. Additionally, spiral bevel gears have larger load carrying capabilities. This is due to the helix angle of the gear teeth. The helix angle disperses the load into radial, axial and tangential vectors. The helix angle also permits a larger tooth contact ratio, to better share the load amongst multiple teeth.

A spiral-bevel gearbox is recommended in demanding applications where high load and speeds will be experienced. Also, if the system has demanding vibration requirements, spiral bevels gears are ideal to transfer loads with minimal losses.

Worm Gearboxes

A worm gearbox (also known as a worm gear reducer or worm drive) is a type of gear arrangement that uses a worm (a screw-like gear) meshed with a worm wheel (a gear similar to a spur gear). It’s widely used when you need high torque output and speed reduction in a compact space.

Key Features:

• High reduction ratios in a small size.
• Non-reversible motion: the worm can turn the gear, but the gear typically cannot turn the worm. This provides a self-locking feature in some applications.
• Smooth and quiet operation.
• Good shock absorption.

Common Applications:

• Conveyor systems
• Lifts and elevators
• Gates and doors (garage doors, rolling shutters)
• Packaging machinery
• Automotive steering mechanisms

Advantages:

• Compact and space-saving
• Quiet operation
• Built-in braking (self-locking in some cases)
• Cost-effective for high reduction ratios

Disadvantages:

• Efficiency is usually lower (50–90%) compared to other gear types
• Generates more heat due to sliding contact
• Requires good lubrication

 

Worm reduction gearboxes are ideal for large increases in torque or reductions in speed. Worm gearboxes can carry high loads because of the large thickness of the gear teeth. The worm gears teeth tend to be stubbed, reducing the cantilever type bending. Like bevel gears and helical gears, the angle teeth provide less tangential loading of the teeth. This transfers loads in the axial and radial directions making worm gearbox teeth less vulnerable to bending failures.

The one down fall is worm gearboxes do not experience the same efficiency as other the gearbox options mentioned on this page. High sliding velocity experienced between the teeth generates frictional losses. Worm gear systems should be evaluated closely when high speeds are of interest.

Epicyclic Gearbox

An epicyclic gearbox (also called a planetary gearbox or planetary gear system) is a type of gear system that consists of one or more outer gears (called planet gears) revolving around a central gear (called the sun gear). This setup is often enclosed within an outer ring gear (the annulus or ring gear) that has internal teeth. The planetary gears are typically mounted on a rotating carrier that holds them in place as they orbit the sun gear.

Main Components

1. Sun Gear – The central gear.
2. Planet Gears – Gears that rotate around the sun gear.
3. Planet Carrier – Holds the planet gears in position and can also rotate.
4. Ring Gear (Annulus) – Outer gear with internal teeth that mesh with the planet gears.

 

How It Works

Depending on which part is held stationary, which is the input, and which is the output, you get different gear ratios and functions:

• Input: Sun gear, Output: Carrier, Ring gear fixed → Speed reduction.
• Input: Carrier, Output: Sun gear, Ring gear fixed → Speed increase.
• Input: Sun gear, Output: Ring gear, Carrier fixed → Reverse direction.

 

Advantages

• Compact size, high power density.
• Multiple gear ratios in a small space.
• High torque output.
• Used for automatic gear shifting (like in automatic transmissions).

 

Common Applications

• Automatic transmissions in vehicles.
• Robotics.
• Wind turbines.
• Aerospace and industrial machinery

Epicyclic gearboxes are very useful in many applications. These gearboxes provide in-line shaft connections, permit high gear ratio combinations and operate at a high level of efficiency. The gearboxes are arranged with a large outer ring gear, a centered sun gear and multiple planet gears. The system’s advantage comes from the multiple planet gear arrangement. Unlike a single gear on gear mesh where the load is one to one from the first gear to the second.

In a multiple planet gearbox arrangement, the load is divided between the number of planet gears. This allows for an improved load carrying capability. Epicyclic gearboxes also benefit in application with their ability to be in constrained locations. There’s a reason these types of gearbox systems are used in automotive transmissions.