Answer the following questions in detail.
Question 1) Write down the advantages and drawbacks of worm gear drives. Suggest materials for worm wheel and worm with proper justification.
Question 2) Load on the journal bearing is 180 kN due to turbine shaft of 300 mm diameter running at 2000 rpm. Find out the following:
(i) The Length of a bearing if the allowable bearing pressure is 1.6 N/mm2, and
(ii) Amount of heat to be removed by the lubricant per minute if the bearing temperature is 60°C and viscosity of the oil is 0.02 kg/m-s and the bearing clearance is 0.25 mm.
Question 3) Write down the step-by step procedure for the selection of flat belt from manufacturer's catalogue for given application. Give all other information and recommendations required in selection.
Question 4) A pair of worm and worm wheel is designated as 3/60/10/6. The worm is transmitting 5kW at 1440 rpm to the worm wheel. The coefficient of friction is 0.1 and the normal pressure angle is 20°. Find out the lead angle, torque and component of gear tooth forces acting on the worm and worm wheel.
Question 5) Pair of spur gears with 20° full-depth involute teeth consists of a 20 teeth pinion meshing with 41 teeth gear. Module is 3 mm whereas the face width is 40mm. The material for the pinion as well as for the gear is steel with the ultimate tensile strength of 600 N/mm2. The gears are heat treated to a surface hardness of 400 BHN. The pinion rotates at 1450 rpm and the surface factor for the application is 1.75. Assume the velocity factor accounts for the dynamic load, and the factor of safety is 1.5. Find out wear strength, effective load, torque, beam strength and rated power of gears. Suppose lewis form factor as 0.32 for 20 teeth.
Question 6) A V-belt drive is needed for a 15 kW, 1440 rpm electric motor, that drives a centrifugal pump running at 360 rpm for a service of 24 hours per day. From space considerations, centre distance must be approximately 1m. Find out:
(a) Belt specifications
(b) number of belts
(c) correct centre distance, and
(d) pulley diameters
Question 7) A concentric spring is used as the valve spring in the heavy duty diesel engine. It contains two helical compression springs having same free length and same solid length. The composite spring is subjected to a maximum force of 6000 N and the corresponding deflection is 50 mm. The maximum torsional shear stress induced in each spring is 800 N/mm2. The spring index of each spring is 6. Suppose same material for two springs and the modulus of rigidity of spring material is 81370 N/mm2. Diametrical clearance between the coils is equal to the difference between their wire diameters. Compute:
(a) The axial force transmitted by each spring
(b) Wire and mean coil diameter of each spring
(c) Number of active coils in each spring.