EXCAVATING MACHINERY USED IN LAND DRAINAGE. 



25 



SELECTION OF SCRAPER EXCAVATOR. 



In selecting a scraper excavator the purchaser, in addition to 

 choosing the most desirable kind of power and the best means of 

 moving over the ground in his particular case, must determine the 

 length of boom best suited to his needs. 



Figure 2 is a diagram showing the relation between the length and 

 angle of elevation of boom and the effective reach of machine. In 

 this diagram all distances are referred to the heel of the boom. If it 

 is desired to refer horizontal distances to the center of the machine, 

 the correction A must of course be added; this distance varies with 

 the different makes of machine. The distance, B, of the heel of the 

 boom above the ground, likewise varies slightly in different machines. 



10 15 20 25 30 35 40 45 SO 55 60 55 70 75 60 B5 SO 95 100 105 110 115 170 



_L REACH OF BOOM IAI FEET FROM CENTER OF BOOM LUC AT VARIOUS ANCLES. 



To This Disfanc* add 'A" nhcn Disrance from Center of Machine is required. 



Fig. 2. — Diagram of scraper excavator, showing relation between the length and elevation of boom and. 

 the effective reach of machine. 



To determine the maximum clearance of the bucket above the ground 

 for different lengths and positions of boom, the distance B must be 

 added to the vertical heights given on the right-hand margin of the 

 diagram; and from this sum must be subtracted the distance C, which 

 will depend entirely upon the type of bucket used. Thus, for a 

 70-foot boom elevated at an angle of 35°, the horizontal distance 

 from the center of machine to the bucket would be 57 + A; and at 

 that position of the boom the bucket would just clear a waste bank of 

 a height 40 + B - C. 



THE DRY-LAND DIPPER EXCAVATOR. 



Excavating machines employing the same digging principle as used 

 on the floating dipper dredge, but moving on land, either over or in 



