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Unformatted text preview: ME 3212: Mechanisms Final Exam Fall 2009 This ﬁnal exam has 4 questions. Please do all problems. Also, please put your name at the top of this
page. The exam is open note and open book and has a time limit of 2.5 hours. 1. (20 pts) Two gears having an angular velocity ratio of 3:1 are mounted on shafts that are 136 mm
apart. If the module of the gear is 4 mm and the gears are cut on the 20 degree full depth involute
system, (a) How many teeth are there on each gear? (b) What is the contact ratio of the gears? 2. (30 pts) In a reverted gear train, the input and output axis are collinear. The gear on the output
shaft has 100 teeth and the input gear has 24 teeth. All gear teeth are to be cut with a 20 degree full
depth involute proﬁle. The overall train ratio is such that 20 turns on the input produce 1 turn on
the output. The pitch of all gears is 6 per inch. (a) Specify the distance between the centers of the shafts in inches. (b) Determine the number of gear teeth for all gears. N: 2‘1! N: )00 {\O‘f +0 QCole. 3. (30 pts) Cam follower motion has the following displacement proﬁle: In1t1al Angle Final Angle Type of Motion Parabolic
Dwell Harmonic (a) Sketch the displacement diagram, velocity diagram, acceleration diagram, and indicate where
locations of high jerk are present on the following page. ‘6 (b) When the cam is turning at 300 rpm and the cam is turned at 6 = 30° past the reference point,
what is the velocity of point A on the diagram? (c) When the cam is turning at 300 rpm and the cam is turned at 6 = 300 past the reference point,
what is the velocity of point A on the diagram? 4. (20 pts.) A planetary gear train has the ring gear ﬁxed, the sun gear is the input and the planet
carrier is the output. Determine the train ratio when the ring gear has 127 teeth, the planet gears
have 37 teeth, and the sun gear has 40 teeth. ...
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 Fall '09
 JeremyS.Daily

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