140 



Indiana University Studies 



ern Indiana, and any estimates based on it will be certain to be 

 high enough. 



Jaw crushers are on the market in all sizes up to the giant 

 Ferrel crusher, which is designed for very coarse breaking in 

 order to eliminate the necessity of sledging. This machine will 

 handle 350 tons per hour crushed to 16-inch size. 



Another recent improvement in jaw crushers to reduce the 

 rock more effectively in a single machine is the machine known as 

 the ''Sturtevant Roll Jaw Crusher". This machine has a grind- 

 ing as well as a crushing effect on the rock, and its output is much 

 finer than that of the ordinary crusher. 



Gyratory breakers are the standard type for work such as 

 grinding rock fertilizer, where a considerable output is to be 

 handled and the mill is to be kept in continuous action. This 

 type of crusher will be found in all the larger crushing plants 

 such as those operated at cement mills and ore plants. The 

 table below, taken with slight modification from Richards' 

 Textbook of Ore Dressing (p. 39), and recommended as correct 

 by the leading manufacturers of today, will give a fair idea of 

 the cost of crushing with crushers of this type,. The figures in 

 the following table are calculated by the same method as that 

 used in the case of jaw crushers: 



Breaker number 



0 



2 



4 



6 



Size of mouth in inches 



4x30 



6x50 



8x68 



12x88 



Tons broken in 24 hours 



Horse-power required 



Cost of breaker 



72 



3 



$375 



228 

 8 



S760 



720 

 16 



11,800 



1 , 500 



32.5 

 $3 , 300 





Operating cost (in cents) per ton 



Oil 



0.020 

 0.169 

 0.541 

 5.556 

 0.971 

 0.308 



0.020 

 0.108 

 0.456 

 1.754 

 0.971 

 0.308 



0.020 

 0.081 

 0.288 

 0.556 

 0.971 

 0.308 



0.020 

 0.071 

 0.281 

 3.267 

 3.971 

 0.308 



Interest and depreciation 



Power 



Labor 



Wear 



Repairs 



Total cost (in cents) per ton 



7.565 



3.617 



2.224 



1.918 



