278 



Prof. J. Perry on Struts and 



Without trying to make a rod equally strong to resist 

 bending in the two directions, it is interesting to consider the 

 F or rather w which a coupling-rod will stand when revolving 

 at n revolutions per minute. 



Using (24) and taking 



. Wl Frri* 

 E=3xl0', -j- = 305^, 



d 2 

 /3=6'17 x 10 6 ™ , so that co does not depend upon b. 



If 7=30 and r=12, and 7=20,000, we find for various 

 values of d and n the folio win 2 values of co : — 



Values of 



OJ 



U) 



a> 



n. 



if d=2. 



ifc/=3. 



if d=4. 







20000 



20000 



20000 



100 



16720 



18810 



19090 



200 



11 700 



15455 



16930 



300 



5505 



10690 



13400 



350 



2615 



7880 



11150 



394 













400 







5070 



8800 



450 





2045 



6150 



483 











500 







3400 



557 













Taking as before 7 = 30 and r 

 find :— 



12, but now /= 10,000, we 



Values of 

 n. 





 100 

 200 

 250 

 279 

 300 

 340 

 350 

 394 



ifd=2. 



10000 



8166 



3976 



1490 







if d='6. 



10000 

 8995 

 6185 

 4240 



2010 

 



if 



10000 

 9500 

 8450 



4200 



2050 

 



It is quite easy to make similar calculations on sections 

 of I shape. Rods of this section may be made equally 

 strong to resist bending in the two directions, at much 

 higher speeds than are possible in the case of the rectangular 



