CRUSHING AND PULVERIZING MACHINERY. 



431 



included. The "crackers" have been described quite fully on page 

 239, in dealing with the crushing practice in natural-cement plants, 

 and the Mosser crusher is of essentially the same design as these crackers, 

 though built for heavier work. 



The Gates crusher, shown in view in Fig. 87, and in section in Fig. 

 88, is probably the most extensively used machine of its type. In re- 



FIG. 87. External view of Gates crusher. 



gard to its power requirements, capacity, etc., its manufacturers state: 

 " In estimating power to drive our breakers we have provided 

 for runniftg an elevator and screen also. But it must be borne in 

 mind that no close estimate can be made to cover all sorts of rock 

 and ore; and further, it should be observed that it requires much more 

 power per ton to break rock to \ inch than is required to break it to 

 an inch. The estimates given in Table 176 are intended to cover the 

 ordinary macadam breaking. For fine breaking add liberally to the 

 power. Long experience has demonstrated the reliability of the follow- 

 ing general rule, applicable to breaking the hardest rock to 2^-inch 

 ring, viz.: The Gates breaker will not require over one horse-power 

 per ton of rock broken per hour." 



