There are two primary categories of gearbox: inline gearboxes and right-angle gearboxes. Both configurations offer different price points, size restrictions, performance, efficiency, and reduction ratios.
This article will discuss the different types of inline and right-angle gearboxes and selecting the right gearbox for your application.
There is no change in orientation between the input and output shafts within an inline gearbox, regardless of being offset from one another. Inline gearboxes may be parallel or coaxial.
Parallel Inline Gearboxes
In a parallel inline gearbox, the input and output shafts offset each other by some amount, but there is no angle between them.
The principal types of gears used in parallel gearboxes are spur, helical, or double helical gears. Spur gears are relatively noisy and, because their tooth surface area is smaller, experience more significant stress, making them typically suited to low-torque, low-speed applications. Helical gears have better tooth meshing characteristics and can transmit far more power at a similar efficiency level with much less noise. Still, the diagonal tooth orientation produces large thrust forces along the shaft, sometimes necessitating special bearings. Double helical gears that resemble two opposing gears side by side help eliminate thrust force while maintaining similar performance.
Because of their efficient use of space, parallel inline gearboxes are ideal for applications where space is limited, such as stirrers in the liquid mixing process.
Coaxial Inline Gearboxes
In the case of coaxial inline gearboxes, the gearbox's input and output share the same axis, such that an imaginary line passing through the center of the input shaft would pass through the center of the output shaft as well.
Coaxial inline gearboxes use planetary gear systems, which offer outstanding performance characteristics. Planetary gear systems are incredibly compact and can handle high torques and high accelerations while experiencing a little backlash. Single-stage reduction ratios are high, and they can easily be connected to achieve extremely high reduction ratios.
Planetary gearboxes have a few downsides, including:
- More complicated to maintain than other gear systems
- Slightly more costly
Input and output axes are at right angles, creating a 90-degree change of direction in the torque transmission. Right-angle gearboxes may be orthogonal or skew type.
Orthogonal Right-Angle Gearboxes
The axes are at right angles and share the same plane, such that two imaginary lines drawn through the center of each axis would meet at the same point.
These gearboxes typically use either straight or spiral bevel gears. Straight bevel gears are standard in many industrial settings, providing good efficiency and power transmission. However, they are noisier and produce significant axial forces, leading to a small efficiency loss. Spiral bevel gears are similar, with better gear tooth meshing characteristics, leading to less noise and higher power transmission capability.
Skew Right-Angle Gearboxes
Skew right-angle gearboxes feature input and output shafts both at right angles and offset from one another, such that the shaft axis never cross the same point. The main gear system types used in these gearboxes are worm gears and hypoid gears.
Worm gears use a screw-like gear to rotate a larger gear known as a worm wheel. Because significant sliding action is involved in this design, worm gears are relatively inefficient and create a lot of heat, making them unsuitable for high-speed or high-efficiency applications. Their advantages include:
- Low cost
- High reduction ratios
- Low noise
- Low vibration
In some cases, they have self-locking capability, meaning that the load cannot drive the worm, and you may need no holding torque or braking system. Their industrial applications include conveyors, hoists, and lifts.
Hypoid gears are similar to bevel gears, except that the tooth alignment is so that the input and output shaft axes sit offset from each other. Because this gear design features very close tooth meshing with a high contact area, hypoid gears have low backlash and are capable of high power transmission. The axis offset between the input and output gears means that bearings can be placed on both sides of the gears, increasing their ability to withstand axially and thrust forces. Hypoid gears have a small amount of sliding action, which has a little impact on efficiency, but this also means they are relatively smooth and quiet.
Which Gearbox Should I Choose?
Now that you know the fundamental types of gearboxes and the gear types they use, you are in a great position to match them to your application's characteristics.
In practice, the choice between inline and right-angle gearboxes usually comes down to the available space for the gearbox and motor combination. Right-angle gearboxes typically create a more compact package when connected to a motor. When the load input shaft faces sideways, a right-angle gearbox allows the motor to be tucked up against the application's side and out of the way. Planetary gearboxes also offer compact size, at least in terms of diameter, which makes them ideal for applications that require minimizing size and weight, such as mobile vehicle and machinery applications.
If saving space is not a priority, the different gearbox configurations and gear types offer distinct strengths and weaknesses. Parallel inline gearboxes are a low-cost option with high speed and torque capability and good efficiency. Simultaneously, their larger surface area improves heat dissipation and makes them ideal for all kinds of everyday industrial tasks. Planetary gearboxes offer exceptional all-around performance. The only downsides are slightly reduced heat dissipation, higher cost and complexity and used when performance and power-to-weight ratio are the highest priority. By contrast, right-angle gearboxes offer slightly less performance, efficiency and relatively low reduction ratios. However, they can be connected to a planetary gearbox to achieve high reduction ratios while transmitting power through a right-angle turn.
The differences between inline and right-angled gearboxes extend far beyond the input and output shafts' orientation, with significant impacts on their performance characteristics and suitability for different applications. Selecting the right product for the job is complex and requires careful consideration of the factors listed above. If you're still not sure what product you need, consult with your trusted gearbox supplier.
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