300 APPLIED SCIENCE 



1 -r- diametral pitch, we can make a formula for the outside diameter 

 which will read : 



or, adding up, we will have O = D + - 



P 



where = outside diameter, P = diametral pitch, and D = pitch 

 diameter. 



Questions 



1. State some advantages and disadvantages of the transmis- 

 sion of power by individual drive. 



2. What is the mechanical principle involved in pulleys trans- 

 mitting power by belting? 



3. What is the property of matter that allows the belt to turn 

 the pulley? 



4. What kind of motion is illustrated in a rotating pulley? 



5. Explain how Babbitt metal reduces friction. 



6. Is frictional electricity ever generated by the belt going over 

 the pulley? 



7. Why is it necessary to have shafting of different diameters? 



8. Explain two forces at work on a rotating shaft. 



9. Is leather belting stronger than canvas? 



10. Why is a pulley "crowned"? 



11. Explain the difference between a pulley and a gear. 



12. When is transmission by gearing preferred to transmission 

 by pulley and belt? 



13. Name the common types of gears and explain their uses. 



14. Explain the meaning of the following terms used in gearing: 

 diametral pitch, circular pitch, diameter of pitch circle, whole 

 diameter, bottom diameter, number of teeth, working depth of 

 tooth, velocity of gear, distance between centers of teeth, whole 

 depth of tooth. 



Problems 



1. One gear has 200 teeth and another 50 teeth. What is the 

 ratio of the diameters of their pitch circles? 



