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Series WD-H  
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Series Overview

Please note: Series with these drawing numbers are being discountinued. Available stock needs to be inquired directly.

  • WD-H 0146/3-00020
  • WD-H 0146/3-00027
  • WD-H 0146/3-00022
  • WD-H 0220/3-00019
  • WD-H 0300/3-00040
  • WD-H 0300/3-00054


        Diagram 1: Maximum torque Md max of individual sizes

Limiting load diagrams of individual sizes for “compressive” load
Please refer to the explanations in the Technical Information section of the catalog

Due to the high gear ratio and the large surface contact between worm and worm gear, very high torque values can be transmitted using very small sized Slew Drives (highest power density). Worm gear driven Slew Drives of the heavy series, WD-H, are short-cycle units for rotation and swiveling applications. Use in applications with continuous rotation is not permissible, due to the higher duty. The duty is to be selected so that over-heating around the gearing contact cannot occur. Diagram 2 exhibits maximum permissible duty per minute, depending upon operation torque. When this maximum permissible duty per minute EDmax ’ is exceeded, the permissibility must be checked by the IMO Engineering Department.

The following conditions apply when determining the maximum permissible duty per minute and when verifying the wear characteristic of worm gearing:

  • Output speed: n = 1.0 rpm
  • Wear safety factor of worm gearing: SW = 1.3
  • Observance of the maximum permissible duty per minute EDmax ‘ (see diagram 2)
  • Ambient temperature 68°F

Determining the maximum permissible duty per minute EDmax ‘ :
The maximum permissible duty per minute may never be exceeded

EDmax ': Maximum permissible duty per minute in percent per minute [% / min] (see diagram 2)

fMd:     Ratio of operating torque to maximum torque [-]
Md B:     Operating torque [ft-lbs]
Md max:     Maximum torque [ft-lbs] (see diagram 1)

Diagram 2

Wear characteristics of the worm gear:

Gw: Limit value [h] (see diagram 3)
Bh: Operation time [h]
EDB: Duty [%]
Md B: Operating torque [ft-lbs]

The application is permissible as regards wear characteristics, if the following relationship prevails:

If this relationship is not fulfilled, a high rate of wear must be expected.

Diagram 3

For slew drives with 2 drives, the limit lines for swivel angle ≤170° applies

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