Design of Machine elements — Summer 2022

It is required to standardize eleven shafts from 100 to 1000 mm diameter. Specify their diameters.

Differentiate between i. Rigid and flexible coupling ii. Protected and unprotected flange coupling.

Design and draw a protective type of cast iron flange coupling for a steel shaft transmitting 15 kW at 200 r.p.m. and having an allowable shear stress of 40 MPa. The working stress in the bolts should not exceed 30 MPa. Assume that the same material is used for shaft and key and that the crushing stress is twice the value of its shear stress. The maximum torque is 25% greater than the full load torque. The shear stress for cast iron is 14 MPa.

What is nipping in a leaf spring? Discuss its role.

Amechanism used in printing machinery consists of a tension spring assembled with a preload of 30 N. The wire diameter of spring is 2 mm with a spring index of 6. The spring has 18 active coils. The spring wire is hard drawn and oil tempered having following material properties: Design shear stress = 680 MPa Modulus of rigidity = 80 kN/mm2 Determine : 1. the initial torsional shear stress in the wire; 2. spring rate; and3. the force to cause the body of the springto its yield strength.

Apair of straight teeth spur gears, having 20° involute full depth teeth is to transmit 12 kW at 300 r.p.m. of the pinion. The speed ratio is 3 : 1. The allowable static stresses forgear of cast iron and pinion of steel are 60 MPa and 105 MPa respectively. Assume the following: Number of teeth of pinion = 16; Face width = 14 times module; Velocity factor (Cv ) =4.5/(4.5 + v),v being the pitch line velocity in m / s; and tooth form factor (y) = 0.154-(0.912/No. of teeth)Determine the module, face width and pitch diameter of gears. Check the gears for wear; given σes = 600 MPa; Young’s Moudulus for pinion = 200 kN/mm2 and Young’s Moudulus for gear=100 kN/mm2.1

Apair of parallel helical gears consists of a 20 teeth pinion meshing with a 40 teeth gear. The helix angle is 25° and the normal pressure angle is 20°. The normal module is 3 mm. Calculate

the transverse module; (ii) the transverse pressure angle; (iii) the axial pitch; (iv) the pitch circle diameters of the pinion and the gear;

the centre distance; and (vi) the addendum and dedendum circle diameters of the pinion.

What are the difference between Hydrodynamic and Hydrostatic bearings.

Explain the thermal consideration in Journal Bearing design.

The following data is given for a 360° hydrodynamic bearing: radial load = 3.2 kN journal speed = 1490 rpm journal diameter = 50 mm bearing length = 50 mm radial clearance = 0.05 mm viscosity of lubricant = 25 cP Assuming that the total heat generated in the bearing is carried by the total oil flow in the bearing, calculate

coefficient of friction; (ii) power lost in friction; (iii) minimum oil fi lm thickness; (iv) flow requirement in 1itres/min; and

temperature rise.

Enlist causes of failure in rolling contact bearings?

Selection procedure of rolling contact bearing from manufacturer’s catalogue.

What are the different types of wears in gear design? suggest its remedies also.

Explain the aspect of heat generation in design of worm gears.

Explain the step by step procedure for constructing structure diagram for speed box.

Explain various types of ends used for pressure vessels giving practical applications of each.

Explain Clavarino’s and Birnie’s equation for pressure vessels in detail.

Aworm drive transmits 15 kW at 2000 r.p.m. to a machine carriage at 75 r.p.m.The worm is triple threaded and has 65 mm pitch diameter. The worm gear has 90 teeth of 6 mm module. The tooth form is to be 20° full depth involute. The coefficient of friction between the mating teeth may be taken as2 0.10. Calculate : 1. tangential force acting on the worm ; 2. axial thrust and separating force on worm; and 3. efficiency of the worm drive.

What do you understand by 6 x 37 ropes? Explain with neat sketch the different rope section.

What are the different types of ropes used in EOT cranes? How they are designated and selected in the hoisting mechanism.

Discuss the stresses in wire ropes with formulas and explain the step by step procedure for wire rope design.

Describe the basic objectives of material handling system. State the basic principles in selection of material handling equipment.

Explain the different cross section being used for hook design.

Discuss with neat sketches the valve gear mechanism for horizontal and vertical engines. Explain Poppet valve.