Boardwork no.1 and 2 - Comprehensive Examination in Machine Design, Engineering Materials and Shop PDF

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Boardwork no. 1 1. A 90 inches long shaft rotates at about one end at 12 rad/sec. It starts to accelerates at 12 rad/sec2. How long in-sec will the velocity of free end reach 150m/s. Solution:

2. If the ultimate shear strength of a steel is 42,000 lb/in 2. The force to punch two 3in. diameter hole in a 5/8 steel shaft is. Solution:

3. An oil cylinder, closed at both ends contains oil at a pressure of 200 psi. The inside diameter of the cylinder is 30 in. If the yield point of the material is 38,000 psi and a safety factor of 4 is used. The wall thickness should be. Solution:

4. Compute the line shaft diameter that transmits 40 kW at 1200 rpm. The ultimate shear stress is 81.95 MPa and safety factor is 10. Solution:

Solving for D,

5. What is the decrease in lateral dimension due to and axial tensile force of 100,000 lbs in a steel bar 3.5 inches on each side of 20 ft. long. Solution:

Solving for strain,

6. A steel rod 4.0 cm in diameter and 1000 mm long has an elongation not to exceed 7 mm, find the allowable load in kN. Solution:

7. Two springs, one of force constant k, and the other of force constant k 2 are connected end-toend. If k1=10 N/m, and k2=15 N/m, find k. Solution:

8. A spur pinion 6 inches in diameter has a torque of 4,500 in-lb applied to it. The spur gear in mesh with it is 12 inches in diameter. The pressure angle is 200. Determine the separating force.

Solution:

9. A hollow shaft with outside diameter of 14 cm and wall thickness of 0.80 cm transmits 200 kW at 400 rpm. What must be the angular deflection of the shaft if the length is 5 meters? Take G=12,000,000 psi. Solution:

Solving for J,

10. The shaft is subjected to a steady load of 40,000 lb at a shear stress of 12,000 psi. Compute the diameter of the said shaft in inches. Solution:

Boardwork No. 2

1. A pair of gear and pinion having a ratio of 5 with a circular pitch of 0.5 inch, compute the center distance, in inches, between the gear of 70 tooth and pinion. Solution:

Solving for D1

Solving for D2

Solving for C,

2. Design a safe shaft diameter for a power transmitting shaft to transmit 40hp at a shaft speed of 205 rpm. Solution:

3. What would be the diameter in millimeter of a main power transmitting steel shaft SAE 1040 to transmit 150kW at 900 rpm. Solution:

4. Compute for the circular pitch in inches, of a pair of a gear and pinion with a ratio of 5. The center distance indicated is at 18. The gear has 90 teeth and the pinion has 18 teeth. Solution:

Solving for D1,

Solving for Pc,

5. Find the center distance, in inches, of a 90 teeth gear meshing with 18 teeth pinions or having a circular pitch of 0.545. Gear/Pinion ratio is 5. Solution:

6. A 60 inch diameter steel pipe, 3/8 inch thick, carries water under a pressure head of 550 ft. Determine the hoop stress in the steel. Solution:

Solving for hoop stress;

7. Determine the length of the belt needed for a two flat belt pulleys having a diameters of 70 cm and 30 cm. The center distance is 400 cm and pulleys rotate in the same direction. Assume power transmitted is 10 hp at 200 rpm. Solution:

8. A gear set having a gear ratio of 3 is to be used at a center distance of 254mm. If the gear has 60 teeth, what must be the circular pitch? Solution:

Solving for D1,

Solving for Pc,

9. A round steel bar 12 inches long is to withstand a dead load of 40,000 lb in compression. The rod must not shorten more than 0.004 inch and have a factor of safety of at least 10. Assume the ultimate strength of the material to be 110,000 psi and modulus of elasticity to be 15,500,000 psi. Determine the diameter of the rod. Solution:

10. Compute the line shaft diameter that transmits 40kW at 1200 rpm. The ultimate shear stress is 81.95 MPa and safety factor is 10. Solution:

Solving for D,...