Assignment4 (gears)

ASSIGNMENT 4 GEARS 1) Define the following terms: Pressure angle, circular pitch, Diametral Pitch, Module, Clearance, Backlash, Working depth of teeth, Contact Ratio, Gear ratio 2) Compare the cycloid and involute profiles of gear tooth. 3) What do you mean by interference in involute gears? 4) What is the difference between path of contact and arc of contact? 5) What are the different types of gears? 6) Name the four important systems of gear teeth that are commonly used. 7) Define ‘axial pitch’ and ‘normal pitch’ relating to helical gears. 8) Derive expressions for centre distance and efficiency of the spiral gears which connect two shafts. 9) Derive an expression for the minimum number of teeth on a pinion which is in mesh with a rack in order to avoid interference. 10) Prove that the length of arc of contact is equal to length of path of contact divided by cosine of pressure angle. 11) Two involute gears of 20° pressure angle are in mesh. The number of teeth on pinion is 20 and the gear ratio is 2. If the module is 5 mm and the pitch line speed is 1.2 m/s, assuming addendum as standard and equal to one module, find: a) The angle turned by pinion when one pair of teeth is in mesh, and b) The maximum velocity of sliding (Ans. 29.45°, 9.92m/s) 12) A pinion and rack are in mesh. The rack is driven by pinion of 125 mm pitch circle diameter. The no. of involute teeth on the pinion is 20. The addendum of both pinion and rack is 6.25 mm. If the interference is to be avoided, find the least pressure angle. (Ans. 18.43°)