Midterm Exam By signing below, I acknowledge that I am aware of and will comply
ID: 1766578 • Letter: M
Question
Midterm Exam By signing below, I acknowledge that I am aware of and will comply with UNT academic dishonesty policy. I understand and will comply with the class calculator policy provided in the course syllabus and understand this exam is closed book, notes, intermet. 1-phone etc. Any deviations from the policy will result in a zero assignment grade. Explain all work for credit. Name: For problems 1-4, match the terms with their definitions. a) Ratio of number of teeth to pitch diameter b) The direction of all forces in a gear set c) The location at which all forces are applied d) The distance from one tooth to the next Circular Pitch 2) Pitch Point ) Diametrical Pitch 4) Line of Action For problems 5-8, match the terms with the direction they indicate. S Axial Force 6) Radial Force 7.-Tangential Force 8) Normal Force a) Parallel to the shaft b) Parallel to the radius of the gear c) Direction of rotation d) Perpendicular to the teeth face 9) For non-parallel shafts where a low gear ratio is desired, which gear set would be best to use? a) Helical Gears c) Spur Gears b) Bevel Gears d) Worm Gears 10) How does the Diametrical pitch of two meshing gears compare? a) The Diametrical pitch of the pinion is larger c) They are equal to each other b) The Diametrical pitch of the Gear is larger d) Depends on the direction of rotation 11) Which of these is the Train Ratio? b) NG/Np d)relro c) de/dp 12) When does interference occur? b) One tooth touches another below the base circle a) The two gears are not aligned b) The two gears have different circular pitches d) Only in spur gears 13) An Idler gear a) Doesn't transfer forces c) Doesn't spin b) Doesn't add or remove torque d) Affects the gear ratio of a simple gear train 14) An important difference between helical gears and spur gears is a) There is an axial load c) The speed and cost of the helical gears is usually higher b) The teeth engage more smoothly d) all of the above 15) What is true about Brinell failure a) Usually occurs before Spall failure c) Is due to static forces b) Is due to dynamic forces d) none of the aboveExplanation / Answer
1-4)
1) Circular Pitch: The distance from one tooth to the next
2) Pitch point: The location at which all forces are applied
3) Diametrical pitch: Ration of number of teeth to pitch diameter
4) Line of action: The direction of all forces in a gear set
5-8)
5) Axial force: Parallel to the shaft
6) Radial force: Parallel to the radius of the gear
7) Tangential force: Direction of rotation
8) Normal force: Perpendicular to the teeth face
9) a) Helical gears: Used for parallel shafts
b) Bevel Gears: Used for non parallel shafts. Gear ratio can be low compared to Worm gears
c) Spur gears: Used for parallel shafts
d) Worm gears: Used for non parallel shafts. And depending upon the number of teeth on worm wheel very low gear ratios can be acheived
10) Option C is right. The diametrical pitch for a pair of gears should be same.
11) Train value: is the ration of the speed of the drien or follower to the speed of the driver. Option (b)
12) Out of the options given, the suitable options are B and C
If the tooth of one gear/pinion touches another pinions/gears below the base cirle.
And if the two gears have different circular pitches
13) Idel gear is used to transfer the motion and to change the direction of the motion. It can not affter the gear ration of simple gear train. It is a rotating gear. It transfers the motion also. SO the option is b i.e., it can not add or remove torque
14) all statements are correct