1. Experiment 11
Gearing

2. Involute Curve

5. Forming of gear

8. Nomenclature and definitions
Also called base circle
Number of teeth
Diameter pitch, teeth per length
Pitch diameter
Module
Circular pitch

10. Pressure angle

11. Example 1
A gear set consists of a 16 tooth pinion driving a 40 tooth gear. The module is 1. the gear are cut using a pressure angle of 20o.
Compute the circular pitch, the center distance, and the radii of the base circles.
In mounting these gears, the center distance was incorrectly made 2 mm larger. Compute the new values of the pressure angle and pitch-circle diameters.

12. Sol.
Circular pitch
pitch diameter of pinion and gear

15. Gear train

16. Force analysis

17. Wt

20. Strength of Gear Teeth

21. Lewis form factor

23. AGMA Stress Equations

24. Geometric Factor YJ(J)
             Reprinted with the permission of E. I. DuPont de Nemours and Co.; see Ref. 8.

25. Surface strength geometric factor ZI(I)
Elastic coefficient ZE
mN=1, For spur gear
Speed ratio

27. Dynamic coefficient Kv

28. Over load factor

29. Example 2
A steel 20o spur pinion with 20 teeth and a module of 2.5 mm transmits 120 W to a 36 tooth gear. The pinion speed is 100 rpm, the gears are grade 1, 18 mm face width, manufactured to a No. 6 quality standard, and considered to be of open gearing quality installation. Find the AGMA bending and contact stresses and corresponding factors of safety. The allowable strength of the gear tooth is 654Mpa. Contact strength is 1260MPa.

30. Sol.

32. Experiment
Rotating speed 1750 rpm, and power 2.5 kW

33. The structure of a simple transmission is shown in previous slide
The structure of a simple transmission is shown in previous slide. If the power transfer to lay shaft is 2.5kW at 1750 rpm. The gear and the pinion is made by a material of allowable bending strength 650 Mpa, the allowable contact strength is 1200MPa. If the two reduction ratio 0.75 and 0.5 are required, please select the proper pinion and gear for this system.