TORSION 51 



the same material and same section area, in terms of n. Find also 

 their stiffness ratio for the same length. 



488. Solve Problem 487, if the external diameter of the hollow 

 shaft is twice its internal diameter. 



489. A solid shaft 10 inches in diameter is of the same material 

 and section area as a hollow shaft whose internal diameter is 5 inches. 

 Determine the external diameter of the hollow shaft and compare 

 their torsional strengths and stiffness for the same length. 



490. A hollow steel shaft has an external diameter d and an inter- 

 nal diameter - Compare its torsional strength and stiffness with a 



2i 



solid steel shaft of the same length and of diameter d. 



491. A solid shaft 6 inches in diameter is coupled by bolts 1 inch in 

 diameter on a flange coupling. The centers of the bolts are 5 inches 

 from the axis. Find the number of bolts in order that their torsional 

 strength shall equal that of the shaft. 



492. What H.P. can be transmitted with a factor of safety of 6 by 

 a wrought-iroii shaft 4 inches square and making 110 RP.M. ? 



493. Find the H.P. that can be transmitted by a 7-inch cast-iron 

 square shaft making 80 R.P.M., with a factor of safety of 10. 



494. A wooden beam 6 inches square projects 4 feet from a wall, 

 and is acted upon at the free end by a twisting moment of 20,000 

 pound-feet. Find the angle of twist. 



495. What torsional moment can a wrought-iron shaft 10 feet 

 long and 5 inches square withstand, with the angle of torsion less 

 than 1? 



496. A round wrought-iron shaft 3 inches in diameter and 20 feet 

 long transmits 20 H.P. at 100 RP.M. Find the size of a square 

 wrought-iron shaft of equal strength, and the angle of twist for each 

 shaft. 



497. A square wooden shaft 8 feet in length is acted upon by a 

 force of 200 pounds applied at the circumference of an 8-foot wheel 

 on the shaft. Find the size of the shaft in order that the angle of 

 torsion shall not exceed 2. 



498. Determine the factor of safety and the angle of twist per foot 

 of length for a wooden shaft 12 inches square when transmitting 

 24 H.P. at 12 RP.M. 



