STRENGTH OF MATERIALS 



241 



are found in the piston and connecting rods of a locomotive. 

 These parts are always made heavier than would be necessary 

 if they were to remain stationary. 



289. Tables of Strength of Materials. The first thing 

 to know in determining the size of beam or timber is the 

 weight or force load the 

 timber is to support and 

 the location of the load. 



Very careful experi- 

 ments have been made in 

 testing laboratories (Fig. 

 102) to determine the 

 tensile or pulling strength 

 of materials under differ- 

 ent conditions. The re- 

 sults of these experiments 

 have been compiled and published in tabular form, as shown 

 below. Mechanics and contractors can find the strength of 

 any material of any size by looking in the table. 



AVERAGE TENSILE STRENGTH OF MATERIALS IN POUNDS PER 

 SQUARE INCH 



FIG. 102. Testing Machine. 



Metals 



Antimony 1053 



Aluminum: Castings 15000 



Sheet 24000 



Bars 28000 



Brass: Yellow 26880 



Bronze: Cast: Lunken- 



heimer 34000 



Delta metal: 



Cast 44800 



Rolled 67200 



16 



Gun-metal 32000 



Phosphor 40000 



Manganese 62720 



Tobin 78500 



Copper: Cast 22400 



Sheet 30240 



Wire 40000 



Cast Steel: Lunken- 



heimer 80000 



Gold.. ..20384 



