Taking a pair of small gears and large gears meshed by cylindrical spur gears as an example, it is known that the module of the small gears of cylindrical spur gears is 2.5, the number of teeth is 30, the pressure angle is 20 °, and the modification coefficient is 0.35. The module of the large gears meshed with cylindrical spur gears is 2.5, the number of teeth is 65, the pressure angle is 20 °, the modification coefficient is – 0.35, and the addendum coefficient f is 1. The geometric calculation formula and results are shown in the table.
Name | Geometric formula | Pinion | Wheel |
Dividing circle diameter | d = mz | 75 | 162.5 |
Tooth tip circle diameter | da= d + 2m(f + ε) | 81.75 | 165.75 |
Root circle diameter | df= d - m(f - ε + c) | 70.5 | 154.5 |
Addendum height | ha= m(f + ε) | 3.375 | 1.625 |
Root height of teeth | hf= (f - ε + c) | 2.25 | 4 |
Tooth height | h = ha+ hf | 5.625 | 5.625 |
Base circle radius | Υο= mZcosα | 35.2834 | 76.3500 |
Basal node | τi= π mcosα | 7.38033 | 7.38033 |
Circular pitch | τj= π m | 7.8539 | 7.8539 |
Radial clearance | m > 1,c = 0.25m | 0.625 | — |
Center distance | A = m (Z1+ Z2) / 2 | 118.75 | — |