134 



RESISTANCE OF MATERIALS 



233. The cylinder of an hydraulic press is 12 in. inside diam. How thick must 

 it be in order to stand a pressure of 1500 lb./in. 2 if it is made of cast steel and 

 the factor of safety is 10 ? 



234. A high-pressure cast-iron water main is 4 in. inside diameter and carries 

 a pressure of 800 lb./in. 2 Find its thickness for a factor of safety of 15. 



235. The- water chamber of a fire engine has a spherical top 18 in. in diameter 

 and carries a pressure of 250 lb./in. 2 It is made of No. 7 B. and S. gauge copper, 

 which is reduced in manufacture to a thickness of about .1 in. Determine the fac- 

 tor of safety. 



236. A cast-iron ring 3 in. thick and 8 in. wide is forced onto a steel shaft 10 in. 

 in diameter. Find the stresses in ring and shaft, the pressure required to force the 

 ring onto the shaft, and the torsional resistance of the fit. 



NOTE. Since the ring in this case is relatively thin, assume an allowance of about half 

 the amount given by Moore's formula. Then, having given Z) 2 = 10 in., D s = 16 in., and 

 having computed the allowance K, we have also D l = D z K, and, inserting these values 

 in the formulas of article 82, the required quantities may be found, as explained in 

 problem 217. 



237. The following data are taken from Stewart's experiments on the collapse 

 of thin tubes under external pressure, the tubes used for experiment being lap- 

 welded steel boiler flues. Compute the collapsing pressure from the rational 

 formula for thin tubes, given in article 81, for both the average thickness and least 

 thickness, and note that these two results lie on opposite sides of the value obtained 

 directly by experiment. 



238. The following data are taken from Stewart's experiments on the collapse 

 of thick tubes under external pressure. The ultimate compressive strength of the 

 rhaterial was not given by the experimenter, but from the other elastic properties 

 given it is here assumed to be u c 38,500 lb./in. 2 Compute the collapsing pres- 

 sure from the rational formula for thick tubes, given in article 81, for both average 

 and least thickness, and compare these results with the actual collapsing pressure 

 obtained by experiment. 



