54 PROBLEMS IN STRENGTH OF MATEEIALS 



is brought by a belt and ^pulley at the middle, what H.P. can be 

 transmitted with a maximum shearing stress of 8000 pounds per 

 square* inch? 



518. Compute the maximum unit-stresses for a steel shaft 3 inches 

 in diameter, in fixed bearings 12 feet apart, which transmits 40 H.P. 

 at 120 K.P.M., and upon which a load of 800 pounds is brought by a 

 belt and pulley at the middle. 



519. Find the diameter of a steel shaft, in fixed bearings 8 feet 

 apart, to transmit 90 H.P. at 250 R.P.M., if there is a load of 480 

 pounds at the middle and the maximum allowable unit-stress is 7000 

 pounds per square inch. 



520. Determine the factor of safety for a wrought-iron shaft 3 inches 

 in diameter, resting in bearings 12 feet apart, when transmitting 25 

 H.P. at 100 K.P.M., and bearing a load of 200 pounds at the middle. 



521. A hollow structural steel shaft, 17 inches outside diameter 

 and 11 inches inside diameter, with ends fixed in bearings 18 feet 

 apart, is to transmit 15,000 H.P. at 50 R.P.M. Find the maximum 

 unit-stresses, considering the weight of the shaft. 



522. A steel shaft 4 inches in diameter, with ends fixed in bearings 

 10 feet apart, carries a pulley 14 inches in diameter at its center. If 

 the tension in the belt on this pulley is 250 pounds, and the shaft 

 makes 80 E.P.M., how many H.P. is it transmitting, and what is the 

 maximum unit-stress in the shaft ? 



523. Find the factor of safety for a vertical wrought-iron shaft 

 4 feet long and 2 inches in diameter, if it weighs with its loads 6000 

 pounds, and is subjected to a twisting moment of 1200 pound-feet. 



524. Find the maximum horizontal shearing unit-stress in a canti- 

 lever beam 6 inches wide, 8 inches deep, and 10 feet long, if it sup- 

 ports a weight of 1000 pounds at its free end. 



525. A simple wooden beam 4 inches wide, 12 inches deep, and 

 14 feet span bears a load of 12,500 pounds at the middle. Find the 

 maximum horizontal shearing unit-stress. 



526. A wooden, built-up simple beam 6 inches wide, 12 inches 

 deep, and 10 feet long is formed by bolting together three 4x6 inch 

 beams. When the beam supports a load of 2000 pounds at its middle 

 point, find the maximum unit-shear in the planes of contact and the 

 total horizontal shear on the bolts. 



