COMPRESSED AIR 251 



One of the recent special applications of compressed 

 air power is the invention of a railroad man, Mr. T. W. Younger, 

 master mechanic of the Southern Pacific railway at Portland, 

 Ore., known as the Redfield pneumatic saw. An outfit usually 

 consists of a traction engine to which are attached two West- 

 inghouse air pumps supplying the air to the pneumatic en- 

 gines operating the same. The size and capacity of these 

 engines are as follows : 



Weight, including frame, 150 pounds. 



Length of stroke, 30 inches. 



Diameter of piston, 2^ inches. 



Air pressure required, 75 pounds. 



Capacity, 50,000 feet in logs per day. 



The main feature in connection with light weight of 

 engine is the valve, which, it is claimed, is of new design and 

 is perfectly balanced under all conditions, thus permitting 

 the engine to work in any position. The valve motion and 

 running gear are very simple and easily repaired, therefore has 

 no complication of valves and ports. The tubular valve 

 is actuated by a rocker arm that receives its motion by two 

 cams fastened to the guide rod. 



The saw used is the ordinary Kell}^ five or six foot drag 

 saw and test has proven that one of these saws will cut through 

 a pine tree five feet in diameter in five minutes. A gang 

 numbers seven men in place of 14, as required when hand 

 methods are in vogue, and when the compressed air plant 

 has been transported to the desired location the saws are 

 connected up. One saw is generally used with two frames, 

 thus permitting the removal of the engine and saw blade 

 to the w^aiting frame immediately after the first cut has been 

 completed. Two men using a saw with frame adapted for 

 felling trees immediately start to work preparing material 

 for the remainder of the gang to cut up to the desired dimen- 

 sions. In cutting up the fallen logs two men generally oper- 

 ate one saw and an extra frame or frames, as may prove de- 

 sirable. The frames are first placed in position on the log, 

 then the cut is started in the first frame; moving the engine 

 and blade to the second frame after completing the first cut 

 and continuing in this manner, one man arranging the frames 



