USE OF LABOR-SAVING APPARATUS 



75 



While the labor saving is large in connection with opening street 

 pavements, it is even greater in the work of drilling rock for blasting, 

 where two men and a compressor can ordinarily do as much work 

 in a given length of time as 35 to 40 men using hand methods. 



In Fig. 25 is shown another interesting and efficient application of 

 compressed air tools. Compressed air spades are being used to an 

 increasing extent for loosening hard earth instead of doing this work 

 by the usual pick method. A tool of this kind requires very little air 

 and while this particular application is rather new, it is felt that fur- 

 ther study may result in an appreciable saving over hand pick methods. 



Fig. 25 — Pneumatic Spade Replacing Hand Pick Method of Loosening Hard Soil 



Compressed air can also be used to advantage in tamping back filled 

 earth. Under certain conditions, however, it now seems that a 

 suitable mechanically operated tamper will probably show greater 

 economy on all except jobs in congested areas where the underground 

 pipe interference is serious or where the trench or opening extends 

 in a diagonal direction, thus often precluding the use of a rigid me- 

 chanical device. 



The utilization of the portable air compressor is a comparatively 

 recent development undertaken by the telephone companies in co- 

 operation with one of the large air compressor manufacturers. 



