PracticeExam2Solutions

# PracticeExam2Solutions - f(5pt Assuming a bearing load of...

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Problem 3 The 18 tooth pinion is driven 5000 rpm by a motor that delivers 20 lb in of torque. The gears provide a double reduction in speed, with the output taken from the 36 tooth gear. Both the 6-pitch and 9-pitch gears have a 25 o pressure angle. Neglecting the small friction loss in the gears and bearings determine: a) (5 pt) pitch diameters of each gear (including the pinon) b) (5pt) what are the tangential and normal forces applied by the pinion (gear 1) to gear 2 (the one it is driving) at contact c) (5pt) what are the tangential and normal forces applied by the output gear 4 to gear 3 that drives it d) (10 pt) what are the radial loads applied to the countershaft bearing A and B . (Hint: sketch the countershaft as a free body in equilibrium). e) (3 pt) How many rpm does bearing B rotate at?

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Unformatted text preview: f) (5pt) Assuming a bearing load of 100 lbf at bearing B with the speed you calculated in part (e), if you desire a life of 50,000 hours with at least a reliability of 90 percent, what bore size is needed for a deep grove bearing? (be careful on units of force) g) (2 pt) If the gears were helical instead of spur gears, say in words how this would change your bearing design. 25 o Problem 2 Given the diagram below determine the speed (in RPM) and the direction (+ or - y) of the output shaft, n 12 . Problem 3 The shown planetary gear has a sun gear 2 which rotates at 50 rad/sec and arm 6 rotates at 75 rad/sec, both clockwise as viewed from the left. Determine the magnitude and direction of the angular velocity of the sun gear 5....
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PracticeExam2Solutions - f(5pt Assuming a bearing load of...

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