RI 4058 Churrn-Drill Performance

During the period 1937-40 and until peacetime research was superseded in 1941 by wartime activities , the junior author was engaged in studies regarding the relative efficiency of operating methods in quarries producing crushed stone for mineral aggregates . The results of some of these studies were published as reports of investigations in 1939 and 1940 ; / others were discontinued due to war demands on personnel and time . The published reports discussed the efficiency of particular quarry operations with respect to the time consumed and without reference to costs or mechanical factors . • At the time , the field data were collected for the published reports other data were collected relative to the relationship of the numerous variable factors inherent in the operation of a churn drill to the ability of the drill to produce blast holes . The churn drill is essentially a crusher and depends. for its performance upon the foot-pounds of energy it can impart to the cutting edge of its bit . The gravity stamp mill , so well-known in western gold mines , is essentially the same type of crusher . The ratio of foot- pounds necessary to crush the rock , to the total theoretical energy developed by the falling churn- drill tools , affords a good means of evaluating the efficiency of the tool . This does not include to tal over-all efficiency involving the mechanical equipment of the drill itself or its power unit .