Machine Design ME 3180
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This 0 page Study Guide was uploaded by Chloe Reilly on Monday November 2, 2015. The Study Guide belongs to ME 3180 at Georgia Institute of Technology - Main Campus taught by Staff in Fall. Since its upload, it has received 46 views. For similar materials see /class/234258/me-3180-georgia-institute-of-technology-main-campus in Mechanical Engineering at Georgia Institute of Technology - Main Campus.
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Date Created: 11/02/15
MEElgo Some suggestions for the exam 0 Read the entire exam 4 problems rst 0 When answering the questions be as complete as possible 0 Clearly state all your assumptions 39 Win 0 And remember I cannot give credit for empty pages so attempt all questions Problem 1 On the following pages a description is given of a socalled overdrive unit for an automobile As I have told you in class these overdrive units are planetary or epicyclical gear systems which are mounted behind a regular transmission in order to provide additional gearing An exploded view of the overdrive unit is shown in Figure 613 In Figure 612 a sectional view of the overdrive unit is shown In Figures 610 and 611 the working principle of the overdrive is shown and explained in the accompanying text Please note that the planet carrier is the arm and the annulus is the ring gear In a nutshell the working of the overdrive is as follows In Fig 610 the transfer of the input to output motion is shown when the overdrive is not in use If the overdrive is not in use there is a 1 to 1 direct drive ratio between the rotation of the input shaft the so called third motion shaft and the output shaft which transfers the rotation and power to the differential of the car The rotation from the input shaft is transferred to the output shaft by means of a unidirectional clutch item 5 Fig 610 which completely bypasses the planetary gear system In Figure 611 the overdrive unit is shown in the engaged state Ifthe overdrive is in use the sun wheel remains stationary with respect to the housing by means of a brake ring item 2 Fig Fig 611 The planet carrier is directly connected to the input shaft and starts rotating with the same rotational speed as the input shaft The transfer of the rotation through the planet wheels causes the annulus ring gear to overrun the uni directional clutch and give an increased speed to the output shaft ie overdrive Problem 2 Your next task is to determine the bearings required to support the output shaft of the overdrive unit from Problem 1 In the overdrive unit of Problem 1 a number of ball bearings can be identi ed supporting the output shaft that is items 77 and 81 in Figure 613 see also Figure 612 One of the bearings supporting the output shaft is a SKF deep groove ball bearing The axial and radial load on this single ball bearing is as follows Fa 200 lbs Pr 300 lbs The overdrive unit is to last for at least ve years while operating 10 hours a week with an average speed of 2000 revolutions per minute Furthermore the bore of the bearings should be 50 mm normal clearances are used and we would like to minimize the weight of the bearing Question Which SKF bearing designation would you recommend to be used for this hearing 15 points Note Use the SKF bearing data given in the pages following this problem Do not use the tables in your textbook 3 III528 Fig 610 Overdrive pomru39ain overdrive not in ueeSec11 Fig 611 Overdrive power train overdrive in use8eo11 7 Spring plessure 4 Cone clutch 1 Hydraulic pressure 4 Planet carrier 2 3rd motion shaft 5 Unidirectional clutch 2 Brake ring 5 Annulus 3 Sun wheel 3 Planet wheel 5 6 8 9 10 11 12 I 7 v1 1 r I f l 5 41 i 1 i l 2 7quot quots I v quotgm4 4gt 39 AND 176lt3Ie221 y quot 91 lelleummkaJs lt4 mmka 1 quot39 IE5 I r I V quot l s m 1 1 1 quotII no u I m 115411 19 18 171615 14 13 Overdrive unit type D sectional view Upper half shows overdrive disengaged lower half shows overdrive engaged The separate detail is of the operating cylinder Sec 11 1 Nonretum valve 6 Clutch spn ng 17 Speedometer driving gear lb Planet carrier 2 Grub screw pump body 7 777mm bearing 2 Spacer 7 7 Planet Wheel 3 Pump plunger 8 Sun wheel 13 Shim 18 Brake any 4 Malnshaft 9 Cone clutch assembly 14 Needle roller bearing 19 Oil inlet 5 Cam 70 Annaus 15 Un directione clutch I Fig 613 Overdrivemit WI D exploded View See 12 Operating piston 2 Main casing assembly Brake ring Intermediate casing Filter Sealing plate Magnetic rings Side cover plate Gasket Drain plug Washer Plug Washer Spring Plunger Steel bell Operating valve Operating valve lever assembly Mills pin Mills pin Oring Cover solenoid Gasket Solenoid Selflocking nut Gasket Plug Washer Pump plunger Pin Pump body Pump plunger spring Nonretum valve body Steel ball Screw Clutch assembly Bearing housing quottrust bearing Plate Bolt Spring Circlip Circlip Gasket Oring Bridge piece 3 Lockwasher Sun wheel assembly Planet canier Locating ring 3rd mo on shaft Inner member unidirectional clutch Cage unidirectional clutch Roller unidirectional clutch Spring for clutch Cimip 9CEEf P Og cM Oil thrower imst bearing Annaus assembly Bearing Inner bearing Speedometer driving gear Bush 7hrust washer Bearing Oil seal Steady bush 3rd motion shaft On39ng Pin Locking screw Speedometer drive bee ng assemny Speedometer driven gear Oil seal speedometer bearing M 39 n a a eh 39139 39 v u w v e LAAA Deep groove ball bearings Equivalent dynamic bearing load For single bearings and bearing pairs arranged in tandem PF PXFYFa when FaF s a when FaF gt e The X and Y factors required for the cal culation of the equivalent bearing load of deep groove ball bearings are dependent on the ratio of the axial load F to the basic static load rating Co They are also in uenced by the magnitude of the radial internal clearance increased clearance enables heavier axial loads to be carried If the bearings are mounted with the usual tits tolerance is to n6 depending on shaft diameter and J7 for the housing the values of e X and Y given in the upper table opposite can be used to calculate the equivalent load For bearing pairs in tandem the values given under 03 clearancequot should be used If a greater clearance than Normal is chosen because a reduction in clearance will be obtained in operation for example as a result of strong heating of the inner ring then the values of the factors under Normal clearance should be used For bearing pairs in tandem Fa and F are the forces acting on the bearing pair For bearing pairs arranged backtoback or facetoface F Y1Fa when FaF g e P 075 Fr Y2Fa when FaF gt e F and F are the forces acting on the bearing pair The values for factors 9 Y and Y2 for different values of FaCo are given in the lower table opposite Equivalent static bearing load For single bearings and bearing pairs in tandem P0 06 F 05 Fa When Po lt F P0 F should be used For paired bearings F and Ft are the forces acting on the bearing pair For bearing pairs arranged backtoback or facetoface P0 F 17Fa F and F are the forces acting on the bearing pair Axial load carrying capacity If deep groove ball bearings are sublected to a purely axial load this axial load should generally not exceed the value of 05 CO Small bearings and light series bearings Diameter Series 8 9 0 and 1 should not be subjected to a load greater than 025 Co Excessive axial loads can lead to an appreciable reduction in hear ing life 5 r t v EKF 5 mm39mm39hm WWMWMM um we e x1 v ifoia 39rx v e x quotv quotx 0025 022 4 175 39 4 044 5 142 004 7 024 162 042 o44 136 1 001 p 021 148 044 to 4 127 r 013 031 13 043 044 f 116 h 025 5 037 114 53 0 105 Mgro 1 e o441 j l lt t V 5mmswapagate 39 immmwmmpmmm Bwbupahumadbadrbbackamtace 55133941 x av talc a r v I quotI j 1 39 i all 2 153 1lflii 52 v mmz quot awn wequot 3 i 3 i39ajlz r39 a 39 wr
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