Profile Shifted Internal & External Helical Gear
Profile Shifted Helical gears feature profile adjustment to allow for variations in design such as a non-standard centre distance. The table below provides an example of a helical gear pair and the calculations used to derive the design values.
The following parameters are required as inputs:
Module
Pressure Angle. Usually one of 14.5°, 20° or 25°.
Helix Angle
Number of Teeth, Pinion and Gear
Working Centre Distance.
Coefficient of Profile Shift, Pinion and Gear. Note that the Difference Coefficient of Profile Shift is a calculated value; it is the distribution of this value between Pinion and Gear that is required as a user input.
Height. This is the height of the gear. It is only relevant to calculation of the Axial Contact Ratio.
No. | Item | Symbol | Formula | Pinion Ext | Gear Int |
|---|---|---|---|---|---|
1 | Module | Design Parameter | 3 | ||
2 | Pressure Angle | Design Parameter | 20° | ||
3 | Helix Angle | Design Parameter | 30° | ||
4 | Number of Teeth | Design Parameter | 16 | 24 | |
5 | Working Centre Distance | Design Parameter | 14.000 | ||
6 | Coefficient of Profile Shift | Design Parameter Note #1 | 0.0 | 0.04263 | |
7 | Difference Coefficient of Profile Shift | 0.04263 | |||
8 | Radial Module | 3.46410 | |||
9 | Centre Distance (Standard) | 13.8564 | |||
10 | Involute Function | 0.014904 | |||
11 | Radial Pressure Angle | 22.79588° | |||
12 | Radial Involute Function | 0.022414 | |||
13 | Radial Working Involute Function | 0.026893 | |||
14 | Radial Working Pressure Angle | 24.156° | |||
15 | Centre Distance Increment Factor | 0.04263 | |||
16 | Pitch Diameter | 55.426 | 83.138 | ||
17 | Base Diameter | 51.096 | 76.645 | ||
18 | Working Pitch Diameter | 56.000 | 84.000 | ||
19 | Addendum | 3.000 | - | ||
- | 2.872 | ||||
20 | Whole Depth | 6.750 | |||
21 | Outside Diameter | 61.426 | - | ||
- | 77.394 | ||||
22 | Root Diameter | 47.926 | - | ||
- | 90.894 | ||||
23 | Radial Contact Ratio | Note #2 | 1.735 | ||
24 | Height of Gear | Design parameter | 20 | ||
25 | Axial Contact Ratio | 1.061 | |||
26 | Total Contact Ratio | 2.796 | |||
- #1
The values for are manually assigned and normally sum to equal the Difference Coefficient of Profile Shift (Item 6).
- #2