Turbine Shaft

Worm gear mechanisms are commonly used to transmit motion and power between two staggered shafts.

Turbine Shaft

The worm gear and the worm are equivalent to the gear and the rack in the middle plane, and the worm is similar in shape to the screw.

Gas Turbine Instrumentation
Gas Turbine Instrumentation

Basic parameters

  • Modulus
  • Pressure angle
  • Worm diameter coefficient
  • Lead angle
  • Number of worm heads
  • Worm gear number
  • Tip height factor
  • Headspace coefficient

Wherein, the modulus and the pressure angle refer to the modulus and pressure angle of the worm shaft surface, that is, the modulus and pressure angle of the turbine end face, are standard values;

The worm diameter coefficient is the ratio of the diameter of the worm index circle to its modulus.


  1. A large gear ratio can be obtained, which is more compact than the staggered shaft helical gear mechanism.
  2. The two-wheel meshing tooth surface is in line contact, and its bearing capacity is much higher than that of the crossed-axis helical gear mechanism.
  3. The worm drive is equivalent to the screw drive, which is a multi-tooth mesh drive, so the drive is stable and the noise is very small.
  4. Has self-locking.

When the lead angle of the worm is smaller than the equivalent friction angle between the meshing teeth, the mechanism has self-locking property and can realize reverse self-locking.

That is, the worm wheel can only be driven by the worm, and the worm can not be driven by the worm wheel.

For example, in the self-locking worm mechanism used in the hoisting machinery, the reverse self-locking property can serve as a safety protection.

  1. The transmission efficiency is low and the wear is serious.

When the worm gear is meshed and transmitted, the relative sliding speed between the meshing teeth is large, so the friction loss is large and the efficiency is low.

On the other hand, the relative sliding speed is large, causing severe wear on the tooth surface and serious heat generation.

In order to dissipate heat and reduce wear, materials with relatively high friction reducing and abrasion resistance and good lubricating devices are often used, so that the cost is high.

  1. The axial force of the worm is large.

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