Code No: R05320305Set No. 1 III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008 DESIGN OF MACHINE MEMBERS-II ( Common to Mechanical Engineering and Production Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. Design a journal bearing required to resist a radial load of 8kN. The oil used has a viscosity of 0.0087kg/m-s at the operating temperature of 800 C. Shaft speed is 720r.pm. Bearing diametral clearance may be assumed as 0.00025mm per mm diameter, and ambient temperature is 300 C. If heat radiating capacity of the bearing is 150N-m /sec/m2 of projected area of bearing per 0 C; determine whether artificial cooling is necessary? 2. Design a connecting rod of I cross section for an automobile diesel engine of the following specifications. Diameter of cylinder=100mm Stroke length =125mm Maximum combustion pressure =2.8MPa Maximum engine speed=2000rpm Weight of the reciprocating parts =1.1kg Length of connecting rod between centers=31.5cm Assume an allowable crushing stress =3000kg/cm2 . [16] 3. Design a piston, piston rings and gudgeon pin for a single four stroke engine for the following given data : Cylinder bore = 150mm Stroke = 130mm Maximum gas pressure = 6MPa b.m.e.p = 0.7MPa Fuel consumption = 0.15kg/brake kW/hr Speed = 2000rpm [16] 4. (a) Figure 4a shows a crane hook with trapezoidal section. Determine the stresses at the points, P and Q. 1 of 3 Code No: R05320305 Set No. 1 Figure 4a (b) What are the assumptions made in Winkler-Bach Theory. 5. (a) Name the type of stresses induced in the wire ropes. [12+4] (b) Design a wirerope for a vertical mine hoist to lift a load of 50kN, from a depth of 250 m. rope speed of 8m./s is to be attained in 18seconds. Take factor of safety as 6. Assuming suitable data if necessary. [4+12] 6. (a) Prove tan ϕn = tan ϕ cos α in case of helical gear where ϕn ϕ α carry usual meaning. (b) A bronze spur gear is used with mild steel pinion. The gear ratio is 2.5:1. The pressure angle is 200 stub. The number of teeth on pinion. The safe static stresses for bronze and CS are 80MPa and 110MPa. Design the pair. [6+10] 7. (a) How does the helix angle influence on the efficiency of square threaded screw? (b) A load of 12kN is raised by a screw, with single start square threads of 50mm mean diameter and 12mm pitch. The screw is operated by a hand wheel, the boss of which is threaded to act as a nut. The load is resisted by a thrust collar, which supports wheel boss, and has a mean radius of 30mm. The coefficient of friction is 0.15 for the screw, and 0.18 for the collar. If the tangential force applied by each hand on the wheel is 120N; determine the diameter of hand wheel required. [4+12] 8. Briefly explain the procedure of speed diagram. 2 of 3 [16] Code No: R05320305 ⋆⋆⋆⋆⋆ Set No. 1 3 of 3 Code No: R05320305 Set No. 2 III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008 DESIGN OF MACHINE MEMBERS-II ( Common to Mechanical Engineering and Production Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. A 407 radial ball bearing ,with inner race rotation, has a 12 seconds work cycle as mentioned below: For 3 seconds Fr =5kN Fa =2kN Speed=900R.P.M Light shock For 9 seconds Fr =3.5kN Fa =0 Speed = 1200 r.p.m steady load If the basic dynamic capacity of the bearing is 42500N, determine the expected average life of the bearing. Take X=0.56 and Y=1.43. [16] 2. Design a Connecting rod for a slow running four-cylinder engine. Rod is made of a material of ultimate strength 450Mpa and factor of safety of 9 is used for design. Following additional data are available: Diameter of piston, = 98mm Weight of reciprocating parts/cylinder = 1.82kg Length of connecting rod = 300mm Stroke =140 mm Speed =2,000rpm Compression ratio =4 Maximum explosion pressure =2.35Mpa Density of material of connecting rod =0.008kg/cm3 L/d ratio for big end bearing =1.3 L/d ratio for small end bearing =2.00 Use Rankine formula for finding the cross section of the rod, in which take σc =315Mpa and factor of safety=5 for calculating buckling load. Allowable Stress in big end cap and bolt materials is 85 MPa and allowable pressure of 7MPa and 14MPa may be used for big end bearing and for wrist pin respectively. [16] 3. Design an aluminum alloy piston for a single acting four stroke engine for the following data: [16] Cylinder bore = 0.3m Stroke = 0.375m Maximum gas pressure = 8 M Pa Break mean effective pressure = 1.15MPa Fuel consumption = 0.22kg/kW/hr Speed =50rev/min. 1 of 2 Code No: R05320305 Set No. 2 4. Starting from fundamentals derive an expression for radius of neutral axis of a Tsection curved beam. [16] 5. (a) Classify the chains. (b) A roller chain operating under steady load conditions, transmits 4kW from a shaft rotating at 600rev/min to one operating at 750rev/min. i. ii. iii. iv. Determine Determine Determine Determine the the the the chain required using at least 15 teeth in the sprockets. sprocket pitch diameters. shortest advisable centre distance. number of links of chain required. [4+12] 6. Design a pair of helical gears to transmit 50kW power at a speed reduction ratio of 5:1. The input shaft rotates at 3000rpm. Take helix and normal pressure angles equal to 25 degree and 20degree. Both pinion and gear are made of steel (the following data is given) Name of the part Permissible BHN Pinion 55MPa 340MPa Gear 40MPa 300MPa The number of teeth on the pinion may be taken 20. [16] 7. (a) Differentiate between a compound screw and a differential screw. (b) A cross-bar of a planar, weighing 10kN is raised and lowered by means of two square threaded screws of 40mm nominal diameter and 6mm pitch. The screw is made of steel and the nut of phosphor bronze, with 42mm height. A steel thrust collar, with 36mm mean radius, takes the axial thrust. The coefficient of friction at the threads and the thrust collar may be taken as 0.15 and 0.12 respectively. Determine the force required at the radius of 125mm of a hand wheel, to raise and to lower the load. Also, determine shear stress induced in the nut, and bearing pressure induced on the threads. [4+12] 8. Briefly explain the procedure of speed diagram. ⋆⋆⋆⋆⋆ [16] 2 of 2 Code No: R05320305 Set No. 3 III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008 DESIGN OF MACHINE MEMBERS-II ( Common to Mechanical Engineering and Production Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Explain the various types of lubrication? (b) A 310 deep groove ball bearing has a work cycle with 1000r.p.m for one-third of the time, 2000r.p.m for the next one third of the time, and 4000 r.p.m for the last one-third of the time. The outer race of the bearing rotates. Assume light shock condition. The radial load is 3.5kN and axial load is 2kN. Determine the expected average life in hours, if the basic dynamic capacity of the bearing is 47kN. [4+12] 2. Design a connecting rod of I cross section for an automobile diesel engine of the following specifications. Diameter of cylinder=100mm Stroke length =125mm Maximum combustion pressure =2.8MPa Maximum engine speed=2000rpm Weight of the reciprocating parts =1.1kg Length of connecting rod between centers=31.5cm Assume an allowable crushing stress =3000kg/cm2 . [16] 3. Explain the following piston troubles and under what conditions they will be experienced : (a) Burning of piston crown (b) Seizure of piston (c) Cracking of piston crown and side walls (d) Breaking of piston rings (e) Stocking of piston rings (f) Excessive lib oil consumption (g) Scuffing of piston rings and cylinder liners. [16] 4. A crane hook carries a load of 6 kN, the line of the load being at a horizontal distance of 32.5 mm from the inside edge of a horizontal section through the center of curvature, the center of curvature being 40 mm from the same edge. The horizontal section is a trapezium whose parallel sides are 15 mm and 30 mm and perpendicular distance apart by 32.5 mm. Find the greatest tensile and compressive stresses in the hook. [16] 5. (a) Name the type of stresses induced in the wire ropes. 1 of 2 Code No: R05320305 Set No. 3 (b) Design a wirerope for a vertical mine hoist to lift a load of 50kN, from a depth of 250 m. rope speed of 8m./s is to be attained in 18seconds. Take factor of safety as 6. Assuming suitable data if necessary. [4+12] 6. (a) Define the terms of Module and Circular pitch. (b) Design a spur gear drive required to transmit 45kW at a speed of 800rpm. The velocity ratio is 3.5:1. The teeth are 20degree full depth involute with 18 teeth on the pinion. Both the pinion and gear are made of steel with a maximum safe static stress of 180MPa for the material of the shaft and key. [2+14] 7. (a) The magnitude of torque considered to design the screw and the handle are not the same. Why? (b) A sluice valve, used in water-pipe lines, consists of a gate, raised by the spindle, which is rotated by the hand-wheel. The nominal diameter of the single-start square threaded screw is 36mm and the pitch is 6mm. The inner and outer diameters of the friction collar are 40mm and 60mm respectively. The coefficient of friction at the threads and the collar are 0.15 and 0.20 respectively. The weight of the gate is 9kN, and the frictional resistance for operating the valve, due to water pressure is 2.5kN. Using the uniform wear theory for collar friction, determine, i. the torque required to raise the gate, and ii. the overall efficiency of the system. 8. Explain the following: (a) Design of drives (b) Force analysis of lathe guide ways. ⋆⋆⋆⋆⋆ [8+8] [4+12] 2 of 2 Code No: R05320305 Set No. 4 III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008 DESIGN OF MACHINE MEMBERS-II ( Common to Mechanical Engineering and Production Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Explain the principle of hydrodynamic lubrication. (b) Select a single row deep groove ball bearing for a radial load of 4000N and an axial load of 5000 N, operating at a speed of 1600r.p.m for an average life of 5 years at 10 hours per day. Assume uniform and steady load. [6+10] 2. (a) What is the piston rod and the connecting rod. Mention their applications? (b) With neat sketch, Write the design procedure for connecting rod. [4+12] 3. Design a Cast iron piston for a single acting four stroke engine for the following specifications. Cylinder bore = 100mm, Stroke = 120mm, Maximum gas pressure = 5N/mm2 , Break mean effective pressure = 0.65N/mm2 , Fuel consumption = 0.227kg/kW/hr, Speed =2200 rev/min, Assume suitable data. [16] 4. A crane hook has a trapezoidal cross-section as shown in figure 4. Determine the maximum load to be carried by the hook if the working stress is 1.50 × 105 N/ mm2 . [16] Figure 4 1 of 2 Code No: R05320305 Set No. 4 5. (a) Derive the expression for length of open flat belt drive. (b) In a crossed belt drive: the diameter of the drive and follower pulleys are 200 mm and 400mm respectively. The centre distance of the drive is 2m. The driver pulley rotates at 400r.p.m. Find the angle of contact between belt and both the pulleys, and the length of the belt required. [8+8] 6. (a) What is the difference between involute and cyloidal gears. (b) In a spur gear drive the diameter of pinion is 100mm and the centre distance 220mm. the power to be transmitted is 6.5kW at 900 rpm of pinion. Using 200 full depth teeth and material for pinion steel with permissible static stress of 200MPa and for gear a steel with a permissible static bending stress of 150MPa, determine the necessary module and width of the teeth using Lewis equation only. [4+12] 7. (a) Differentiate between pitch and lead of a screw. (b) The nominal diameter of a square threaded screw is 50mm, and pitch of the threads is 10mm. A load of 20kN is lifted through a distance of 150mm. Find the work done in lifting the load and the efficiency of the screw, when i. the load rotates with the screw, and ii. the load rests on a swivel cup, which does not rotate with the screw. The inner and outer diameters of the bearing surface of the swivel cup are 20mm and 60mm respectively. The coefficient of friction for the screw threads and the bearing surface may be taken as 0.12. [4+12] 8. Briefly explain the procedure of speed diagram. ⋆⋆⋆⋆⋆ [16] 2 of 2