FARM MACHINERY 201 



it be not too great. With the proper amount of suction a 

 plow will run evenly, as far as depth is concerned. To test 

 for suction, lay a straight- X - - ~_, 



edge on the underline of ^^^^A- ,__ ^ 



the landside when the 



plow is turned bottom Fig HO. Illustrating method of 



. . ..... , . using a straight-edge to determine 



Side Up. It there IS an whether a plow has the proper "suc- 



opening of about % of an 



inch between the straight-edge and the landside at the 

 joint between it and the share, the suction is about correct. 

 To lift and bend the furrow slice, a certain amount of 

 pressure must come upon the outer corner, or wing, of the 

 share. To resist or carry this pressure, a certain amount 

 of surface, or "bearing," is provided to rest upon the bottom 

 of the furrow as the plow is drawn along. If this bearing 

 is too great, the plow will be continually tending to turn out 

 from the land, and if insufficient will turn in the opposite 

 direction. The amount of bearing, or the width of surface 

 at the corner of the share, varies with the condition of the 



soil, but 1}4 inches is 



* |0ffiB0 rjfcj^^ about correct for a 16-inch 



< plow. The bearing sur- 



face is triangular in shape, 

 and is usually about 3 

 inches long. 



Steel-beam walking plows have an advantage in clearance, 

 and for this reason are more satisfactory in plowing under 

 trash and weeds. On the other hand, wooden-beam walking 

 plows are slightly lighter. 



Sulky or Gang Plows. Riding plows with moldboards 

 may be divided into two classes, frame and frameless, and 

 are constructed with and without tongues. The frameless 

 and tongueless plows are of the cheaper construction; but, 



