nine the first critical speed by the Dunkerley equation. shown in F'ig. 8-17 below. Ans. 1480 rpm 320 lb

International Edition---engineering Mechanics: Statics, 4th Edition
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Chapter4: Coplanar Equilibrium Analysis
Section: Chapter Questions
Problem 4.8P: The figure models the handle of the water cock described in Prob. 4.9. Draw the FBD of the handle,...
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110
CRITICAL SPEEDS OF SHAFTS
SUPPLEMENTARY PROBLEMS
11. A shaft simply supported on two bearings 20 in. apart carries an 80 lb flywheel 7in. to the right of the left
bearing. The static deflection curve shows the following:
Distance from left bearing, in.
2
6
8
10
12
14
16
18
20
Deflection, in.
.001 .003 .005.007|.008 .009|.008 .006 |.002
Estimate the critical speed.
Ans. 2400 rpm approximately
12. A steel shaft 40 in. long is simply supported at the ends and has diameter 3 in. over the mid-20 in. of length.
The remainder of the shaft is 2.5 in. in diameter. Masses weighing 300 lb each are attached at the two loca-
tions where the diameter changes. Neglecting shaft mass and using the Rayleigh-Ritz equation, estimate the
first critical speed.
Ans. 81 = 82 = 0.00425 in., w,= 30 rad/sec
13. Determine the critical speed for the steel shaft shown in Fig. 8-14 below. Neglect shaft mass.
Ans. 1900 rpm
14. The shaft shown in Fig. 8-15 below is to be made of stainless steel (E = 26 × 108 psi). Determine a safe di-
ameter to insure that the first critical speed be no less than 3600 rpm.
Ans. d = 2 in.
14"
- 5"
500 lb
10'
1300 lb
26".
20"
Fig. 8-14
Fig. 8-15
15. For the steel shaft shown in Fig. 8-16 below estimate the first critical speed using the Dunkerley equation.
Ans. 1800 rpm
16. For the shaft of Fig. 8-10 of Problem 5, determine the first critical speed by the Dunkerley equation.
Ans. 442 rad/sec
17. Determine the critical speed of the steel shaft shown in Fig. 8-17 below.
Ans. 1480 rpm
500 lb
800 lb
/ 320 lb
10
15
40"
18"
Fig. 8-16
Fig. 8-17
9.
Transcribed Image Text:110 CRITICAL SPEEDS OF SHAFTS SUPPLEMENTARY PROBLEMS 11. A shaft simply supported on two bearings 20 in. apart carries an 80 lb flywheel 7in. to the right of the left bearing. The static deflection curve shows the following: Distance from left bearing, in. 2 6 8 10 12 14 16 18 20 Deflection, in. .001 .003 .005.007|.008 .009|.008 .006 |.002 Estimate the critical speed. Ans. 2400 rpm approximately 12. A steel shaft 40 in. long is simply supported at the ends and has diameter 3 in. over the mid-20 in. of length. The remainder of the shaft is 2.5 in. in diameter. Masses weighing 300 lb each are attached at the two loca- tions where the diameter changes. Neglecting shaft mass and using the Rayleigh-Ritz equation, estimate the first critical speed. Ans. 81 = 82 = 0.00425 in., w,= 30 rad/sec 13. Determine the critical speed for the steel shaft shown in Fig. 8-14 below. Neglect shaft mass. Ans. 1900 rpm 14. The shaft shown in Fig. 8-15 below is to be made of stainless steel (E = 26 × 108 psi). Determine a safe di- ameter to insure that the first critical speed be no less than 3600 rpm. Ans. d = 2 in. 14" - 5" 500 lb 10' 1300 lb 26". 20" Fig. 8-14 Fig. 8-15 15. For the steel shaft shown in Fig. 8-16 below estimate the first critical speed using the Dunkerley equation. Ans. 1800 rpm 16. For the shaft of Fig. 8-10 of Problem 5, determine the first critical speed by the Dunkerley equation. Ans. 442 rad/sec 17. Determine the critical speed of the steel shaft shown in Fig. 8-17 below. Ans. 1480 rpm 500 lb 800 lb / 320 lb 10 15 40" 18" Fig. 8-16 Fig. 8-17 9.
No.1
Three masses A, B and C are placed on a balanced disc as shown at radii of
120 mm, 100 mm and 80 mm respectively. The masses are 1 kg, 0.5 kg and 0.7
kg respectively. Find the 4th mass which should be added at a radius of 60 mm in
order to statically balance the system.
1000
300
No.2
Find the mass and the angle at which it should be positioned in planes A and D at
a radius of 60 mm in order to produce complete balance of the system shown.
C
Plane D
Plane A
'B
600
Radius B is 75 mm
Radius C is 50 mm
Mass of B is 5 kg
Mass of C is 2 kg
200 mm
300'mm
375 mm
Transcribed Image Text:No.1 Three masses A, B and C are placed on a balanced disc as shown at radii of 120 mm, 100 mm and 80 mm respectively. The masses are 1 kg, 0.5 kg and 0.7 kg respectively. Find the 4th mass which should be added at a radius of 60 mm in order to statically balance the system. 1000 300 No.2 Find the mass and the angle at which it should be positioned in planes A and D at a radius of 60 mm in order to produce complete balance of the system shown. C Plane D Plane A 'B 600 Radius B is 75 mm Radius C is 50 mm Mass of B is 5 kg Mass of C is 2 kg 200 mm 300'mm 375 mm
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