AU2351 AUTOMOTIVE ENGINE COMPONENTS DESIGN

QUESTION BANK

1) Define Spring.

2) Classify springs.

3) State the materials used for manufacturing springs.

4) Define Solid length.

5) Define free length.

6) Write the formula to find Pitch angle of a spring.

7) Define Pitch of the spring.

8) Define slenderness ratio of a spring.

9) Define Stiffness of a spring.

10) Define Endurance stress of a spring.

11) Define Hysterisis of a spring.

12) Define Nipping of a leaf spring.

13) What are the applications of helical springs?

14) Write down the formula used for finding the stiffness of two springs when they are in parallel with their resulting displacements not equal.

15) . Sketch the stress-strain diagram for a ductile specimen and indicate its salient features.

16) Indicate the type of fit used in the assembly of bush in the big-end of the

17) connecting rod of an automobile.

18) Define ‘endurance limit’ in design

19) Indicate the type of fit specified by 120 H7 p6 in a drawing.

20) Mention any two desirable properties of the material used in an automobile piston.

21) Sketch and indicate the salient parts of a flange coupling.

22) Mention the stresses induced in a taper key used in a coupling.

23) What is a ‘bearing characteristic number’.

24) Mention the names of any four theories of failure.

25) Define ‘coefficient of fluctuation of speed’ in a flywheel.

__PART B__

1. A shaft is supported on bearings A and B, 800 mm between centers. A 20^{o} straight tooth spur gear having 600 mm pitch diameter, is located 200 mm to the right of the left hand bearing A, and a 700 mm diameter pulley is mounted 250 mm towards the left of the bearing B. The gear is driven by a pinion with a downward tangential force while the pulley drives a horizontal belt having 180^{o} angle of wrap. The pulley also serves as a flywheel and weighs 2000 N. The maximum belt tension is 3000 N. Design the shaft with proper material of shaft.

2. A mild steel shaft carries two gears, C and D located at distances 240 mm and 380 mm respectively from the centre lines of the left and right bearings. The diameter of gear C is 580 mm and diameter of gear D is 180 mm. The power is delivered to gear C and taken out at gear D in such a manner that tooth pressures Pc and Pd at gear C and D respectively act vertically downward. If the shaft transmits 14 H.P at 100 rpm .Calculate the diameter of shaft. Safe tensile stress is 8 KN/mm^{2} .Gear C weighs 1000 N and gear D weighs 400 N.

3. A shaft is supported by bearing 1000 mm apart. Gear B has 40 teeth and 10 mm module. It is located 400 mm left to the right hand bearing and is driven by gear A directly below it. A belt pulley C, 500 mm in diameter is located 600 mm to the right of left hand bearing and drives another bigger pulley directly behind it. The ratio of tensions is 3:1 with tight side on top. The angle of wrap is 150^{0} .The gear teeth are 20^{o} involute form. The gear transmits 35 KW at 400 rpm. Determine the shaft diameter.

4.The two helical compression springs are placed one inside the other. The outer spring is

made of 38 mm diameter round bar stock with six active terms and has 225 mm outer

diameter of helix. The inner spring is of 25 mm diameter bar with 9 active turns and has

140 mm outer diameter of helix. The free height of outer spring is 19 mm more than the

inner spring. Find the deflection of each spring for total of 90 KN. Also determine the

load shared by each spring and stresses induced in each spring. Modulus of rigidity for

spring material is 85 KN/mm^{2}.

5.Design a spring for a balance to measure 0 to 1000 N over a scale of length 80 mm. The

Spring is to be enclosed in a closing of 25 mm dia. The approximate number of turns is 30.

Also calculate the maximum shear stress induced. Take G = 85 GPa.

6. A helical compression spring of the exhaust valve mechanism is initially compressed with a pre-load of 375 N. When the spring is further compression and the valve is fully opened, the torsional shear stress in the spring wire should not exceed 750 N/mm2. Due to Space limitations, the outer diameter of the spring is not exceed 42 mm. The spring is to be designed for minimum weight. Calculate the wire diameter and the mean coil diameter of the spring.

7.A piston of a reciprocating compressor has a diameter of 60mm. The maximum pressure on thepiston fall is 1.25MN/m2.Assuming the gudgeon pin passing through the small end of the connectingrod can be safely loaded in shear up to 10MN/m2, Calculate the minimum diameter of the gudgeon pin.

8.Design a connecting rod for a petrol engine for the following data:

Diameter of the piston = 68 mm

Stroke length = 80 mm

Length of connecting rod = 160 mm

Maximum explosion pressure = 3.5 N/ mm2

Mass of reciprocating parts = 2.5 kg

Speed = 4000 rpm

Compression ratio = 8 :1

9. The connecting rod of a petrol engine is to be designed for the following

data.

Piston diameter 80 mm

Stroke 120 mm

Weight of the reciprocating parts 15N

Length of connecting rod 240 mm

Max speed 2800 rpm.

Explosion pressure corresponding to 10° of crank angle is 3 MPa.

Factor of safety 6

If the connecting rod is to be made of 40Cr1 Steel, find the dimensions of

the I-section connecting rod.

10.Design a suitable spring for the exhaust valve of a petrol engine. The spring should be capable of exerting a net force of 360N when the valve is open and 220N when it is closed. The maximum inside diameter of the spring is 25mm. The compression in spring is 8mm.

11. Design and draw suitable flywheel for a four stroke four cylinder 133 kW

engine running at 375 rpm. Due to space restriction the flywheel

diameter should not exceed 1.2m

13. A transmission shaft is supported on two bearings which are 1m apart.

Power is supplied to the shaft by means of a flexible coupling, which is

located to the left of left hand bearing. Power is transmitted from the

shaft by means of a belt pulley, 250 mm diameter, which is located at a

distance of 300 mm from the left hand bearing. The mass of the pulley is

20 kg and the ratio of belt tension on tight and slack sides is 2:1. The belt

tensions act vertically downward. The shaft is made of steel with yield

stress 300N/mm2 and the factor of safety is 3. Determine the shaft

diameter, if it transmits 10 kW power at 360 rpm from the coupling to

the pulley.

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