ME 302 -MACHINE DESIGN II SEMESTER 6 DESIGN OF A BELT DRIVE SYSTEM Problem: A belt drive system is to be designed for a Power Transmission System used in a small workshop. According to the lay-out given below, two lathe machines are driven by an electric motor via an overhead line shaft. Power is transmitted from the motor to the line shaft by a Vbelt drive and from the line shaft to the machines by independent flat back drives. 3m Fig 1- Belt drive system Data: 1. Line shaft is 2.0 m. above the centre line on the Motor and Machine shafts. 2. Speed ratio of Motor/Line shaft is N1 3. Speed ratios of Machine/Line shaft are N21 and N22 4. Power of Machines are X1 and X2 kW 5. Losses through the transmission, Bearing efficiency factor =0.99 Efficiency factor of V-belt drive =0.98 Efficiency factor of Flat-belt drive =0.95 6. Type of electric motor, 4- pole induction motor How to obtain individual data: 1. Speed ratio of Motor/Line Shaft N1 Divide student se. number by 3, if the remainder =0 =1 =2 then N1 = 1.5 = 2.0 = 2.5 2. Speed ratio of Machine/Line Shaft N21, N22 2.1. Machine No. 1 N21 = 2.0 for all ODD student se. number = 2.5 for all EVEN student se. number 2.2. Machine No. 2 N22 Divide student se. number by 4, if the remainder = 0 then N22 =1 =2 =3 = 1.5 = 2.0 = 2.5 = 3.0 3. Power of Machine X1 and X2 Divide student se. numbers by 6, If the remainder Example; 1. = 0 then, =1 =2 =3 =4 =5 3. X2= 3.5 kW = 4.0 kW = 4.5 kW = 5.0 kW = 5.5 kW = 4.0 kW Let student se. number 54 Speed ratio Motor/Line Shaft N1 54/3 2. X1= 4.0 kW, = 4.5 kW = 5.0 kW = 5.5 kW = 6.0 kW = 6.5 kW remainder= 0 then, N1 = 1.5 Speed ratios Machine Shaft/Line Shaft 54 is an EVEN number, then N21 = 2.5 54/4 N22 = 2.5 remainder = 2 then, and Power of Machines 54/6 remainder = 0 then X1 = 4.0 kW and X2 = 3.5 kW Time Duration: 6 Sessions (4 Calculations and 2 Drawing sessions) Format of the Design Drawing Drawing Sheet : Size A2 Time Duration: Two drawing sessions 1. Representation of all the details with one, two or three main views. 2. Part drawings for each and every component. 3. Assembly or sub assembly drawing as necessary. 4. A sketch of application set up. 5. Tables for; Selected and design components as necessary, Problem data, Material data, System specifications, Machining or manufacturing details etc. Format of the Design Report (Sections to be included) 1. Date 2. Title 3. Problem 4. Introduction 5. Notation 6. Data Problem data, Material selection data, Design data 7. Design Calculations Where ever possible please provide sketches, figures as necessary to illustrate various parameters used in your calculation 7.1. Power, Torque calculations using given data and considering losses through the transmission 7.2. Selection of motor using given standard catalogues 7.3. Design of V-belt drive (one drive) 7.4. Centre distance, speed ratios, Pulley diameters, length of belts, standard nominal length, selection of belt section type, number of belts required, and check for service level. 7.5. Design of Pulleys for the V-belt drive (two pulleys). Face width of pulleys, outer diameter, size of the boss, width of the hub, number of arms and cross section, check for the failure in arms (bending shear), check for failure in rim (critical speed etc.) 7.6. Design of Flat Belt Drives (two drives) Centre distance, speed ratios, Pulley diameters, and length of belts, length correction, selection of belts and belt materials, size of the belt (cross section), check for belt tension, and selection of face width of the pulley. 7.7. Design of Pulleys for Flat Belt Drives. Face width, Pulley dimensions, size of the boss, width of the hub, number of arms and cross section, checks for failure in arms (shear, bending) checks for failure in rim (critical speed etc.) 7.8. Design of the line shaft Diameter of line shaft, Estimation of masses of pulleys on the line shaft, power through each drive, Belt tensions, Torque at each pulley, Torque diagram, Force diagram through each drive, Force due to self weight of pulley and belt tension, Components in horizontal and vertical directions, Bending moment diagram for vertical and horizontal directions, Maximum bending moment and resultant maximum bending moment, Maximum combined stresses(torsion and bending), Check for the diameter of the shaft. 7.9. Design of key and key ways Keys for motor shaft, Line shat and machine shafts. Key section, Type, Cross section and length, Check for failures 8. Results Results in tabulated form, List of components, System specifications, Material and Manufacturing details of components. Mech/E05/Jan/2009