Design of Machine Elements 3rd. Edition by Bhandari, V.B. | 9780070681798 | 70681791 | Holooly

Design of Machine

Design of Machine Elements [EXP-45116]

355 SOLVED PROBLEMS

Question: 20.3

1 kW power at 720 rpm is supplied to the worm shaft. The number of starts for threads of the worm is four with a 50 mm pitch–circle diameter. The worm wheel has 30 teeth with 5 mm module. The normal pressure angle is 20°. Calculate the efficiency of the worm gear drive and the power lost in

Verified Answer:

\text { Given } k W=1 \quad n=720 rpm \qua...

Question: 20.4

5 kW of power at 720 rpm is supplied to the worm shaft, as shown in Fig. 20.10. The worm gear drive is designated as, 2/40/10/5 The worm has right-hand threads and the pressure angle is 20°. The worm wheel is mounted between two bearings A and B. It can be assumed that the bearing A is located at

Verified Answer:

\text { Given } \quad k W=5 \quad n=720 rp...

Question: 23.5

A 25 × 50 mm bar of rectangular cross-section is made of plain carbon steel 40C8 (Syt = 380 N/mm^2 and E = 207 000 N/mm^2). The length of the bar is 500 mm. The two ends of the bar are hinged and the factor of safety is 2.5. The bar is subjected to axial compressive force. (i) Determine the

Verified Answer:

Given For bar, cross-section = 25 × 50 mm.

...

Question: 23.3

A 6 × 19 wire rope with fibre core and tensile designation of 1570 is used to raise the load of 20 kN as shown in Fig. 23.7. The nominal diameter of the wire rope is 12 mm and the sheave has 500 mm pitch diameter. Determine the expected life of the rope assuming 500 bends per week.

Verified Answer:

Given W = 20 kN number of bends = 500 per week For...

Question: 15.11

A ball bearing is operating on a work cycle consisting of three parts—a radial load of 3000 N at 1440 rpm for one quarter cycle, a radial load of 5000 N at 720 rpm for one half cycle, and radial load of 2500 N at 1440 rpm for the remaining cycle. The expected life of the bearing is 10 000 h.

Verified Answer:

\text { Given } L_{10 h }=10000 h

...

Question: 15.14

A ball bearing is subjected to a radial force which varies in sinusoidal way as shown in Fig.15.14 and discussed in Ex. 15.13. The direction of force remains fixed. The amplitude of the force is 1500 N and the speed of rotation is 720 rpm. Determine the dynamic load capacity of the bearing for

Verified Answer:

\text { Given } P_{\max }=1500 N \quad n=7...

Question: 15.16

A ball bearing, subjected to a radial load of 5 kN, is expected to have a life of 8000 h at 1450 rpm with a reliability of 99%. Calculate the dynamic load capacity of the bearing, so that it can be selected from the manufacturer’s catalogue based on a reliability of 90%.

Verified Answer:

\text { Given } F_{r}=5 kN \quad n=1450 rp...

Question: 12.11

A band brake working on the back-stop principle is shown in Fig. 12.25(a). The width of friction lining perpendicular to the axis of the drum is 75 mm. In normal operating condition, the drum rotates in clockwise direction. Calculate: (i) the minimum value of coefficient of friction between the

Verified Answer:

\text { Given } w=75 mm \quad p_{\max .}=0...

Question: 24.10

A beam of circular cross-section is subjected to pure bending moment M and the bending stresses are given by the following equation: σ = 32 Mb/πd^3 where d is the diameter of the beam. It has been observed that the diameter (d) of the beam is a normally distributed random variable with a mean of

Verified Answer:

\text { Given } \mu_{d}=50 mm \quad \hat{\...

Question: 8.14

A beam of rectangular cross-section is welded to a support by means of fillet welds as shown in Fig. 8.34. Determine the size of the welds, if the permissible shear stress in the weld is limited to 75 N/mm^2.

Verified Answer:

\text { Given } P=25 kN \quad \tau=75 N / ...

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