80 



<;I:KI-:X\V MACHINK. 



acting at a leverage of 112 to 1 ; or the maximum load the 

 machine can exert is 



1000x112 _ n . 



= 50 tons. 

 2240 



Any or all of these weights can be used. If the carriage and 

 scale plate alone are used, the range of load is from 



Oto50xll21b. 



or from up to 2| tons ; or by putting on the full comple- 

 ment of 1,000 Ib. the range is increased, and becomes 

 from to 50 tons. Any intermediate range can be used 

 according to the size and material of the specimen tested. 



The graduation of the weighing lever in all the Green- 

 wood machines is in numbers representing the "mechanical 

 advantage " of the load which is being used. For instance, 

 in the present machine the maximum mechanical advan- 

 tage or leverage is 112 to 1 ; so that the lever is graduated 



FIG. 31. 



from 1 to 112 with intermediate divisions. If the travelling 

 weight which is being used is 500 Ib., and the pointer 

 on this weight indicates, say, the figure 60 on the scale, the 

 meaning is that there is a load of 500 Ib. acting at a 

 leverage or mechanical advantage of 60. The load on the 

 specimen will therefore be 



500 x 60 = 30,000 Ib. 



Thus, to obtain the load on the specimen the travelling 

 weight must be multiplied by the mechanical advantage. 



