Helical bevel gears vs. worm gears | Advantages & disadvantages

The choice between Worm gear units and bevel gear units has a major influence on efficiency and operating costs. In this article we would like to give you the most important advantages of worm and bevel gear units so that you can determine which one is the most suitable for your application. If you still have any questions, please do not hesitate to contact us: Contact form

Further information on worm and bevel gear units.

Frequent applications of angular gearboxes

Worm and bevel gears are often used to transmit motion at right angles or when other properties are required.

  • Conveyor belts
  • Crane
  • Elevators
  • Mixer
  • Many other applications

Worm gear

Helical worm gear
Worm gears. Image source: © roostler – Fotolia. com

A worm gear unit consists of two parts: a worm shaft with worm gears and a worm wheel. The two components are often made of two different materials (steel worm shaft and bronze worm wheel). Worm gears transmit the movement force at right angles via a sliding effect instead of a rolling movement.

Advantages

    • Worm gears are mainly used when a large gear ratio is required. With a worm gear unit, a large overall ratio can be achieved with only a few stages. This means that a smaller, less expensive gearbox can be used.
    • The highest ratio of a worm gear unit is about 100:1.

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    • High self-locking due to the sliding effect of the worm shaft makes an additional brake either obsolete or it is only necessary to install a small, less expensive brake. However, this property depends on the angle of inclination and the friction angle.

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  • More favourable than bevel gear
  • Hollow shaft possible
Schematic diagram of a worm gear unit
Schematic diagram of a worm gear unit

Disadvantages

  • The sliding contact of the gears causes strong friction, which results:
    • one High operating temperature
    • oneLow efficiency
  • High wear on the worm wheel, which is mostly made of bronze. (Only through bronze production a relative efficiency is possible. The friction would be much higher with steel on steel.)

Bevel gears

4 types of bevel gears

  • Spiral
  • Straight
  • Cerol
  • Skew Tooth

Bevel gear sets are composed of two parts, the bevel pinion and bevel gear, which transmit movements at right angles.

Bevel gears use angular gear teeth. As the gears rotate, the entire tooth width of the interlocking teeth is used to transmit the force. In addition, several teeth interlock at the same time. This results in the following advantages.

Advantages

    • Quiet Operating noise (Quiet operation is particularly advantageous in environments such as theatres or airports.)
    • Increased torque capacity compared to worm gears of the same size.

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  • High efficiency (rolling of bevel gears is very efficient compared to the sliding effect of worm gears (98.5%). The metal bevel gear teeth never come into direct contact with an oil film.)
  • Hollow shaft possible
Kegelradgetriebe mit 1:1 Übersetzung
Bevel gearbox with 1:1 ratio. Image source: © roostler – Fotolia.com

Disadvantages

  • High costs.
  • Bevel gears are manufactured in pairs. For maintenance and repair, both gears must be replaced.
  • In order to achieve high efficiency, bevel gear sets must be positioned exactly, so the shafts must be adjusted very precisely.
  • Limited translation range. Maximum ratio of 6:1 per bevel gear set. Spur gear stages are necessary in order to achieve a higher overall gear ratio.
  • Bevel gears are not recommended for high-speed reduction. At high speed, a bevel gear unit generates noise.

Further information

Do you have any questions?

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