168 POWER AND THE PLOW 



Moldboard engine gangs may be divided into hand-lift and 

 power-lift types. Those of the hand-lift type may again be 

 divided in two general classes : 



(1) With bottoms combined into a rigid frame, which is 

 raised and lowered as unit by one lever. 



(2) With bottoms attached either singly or in pairs to one 

 independent frame, each bottom or pair of bottoms being 

 controlled by a separate lever. 



The former are known as "solid" gangs and the latter as 

 "flexible hitch" gangs. The term "flexible," however, is used 

 also to distinguish from a rigid frame of the latter type one 

 which is jointed to adapt it to work in uneven ground. Engine 

 gang plows, especially the flexible types, are usually more effi- 

 cient than horse plows. The point of hitch is lower, and the 

 distance from the point of hitch to the centre of resistance 

 greater. The line of draft is thus more nearly parallel with 

 the base line and there is less loss of power through the opposi- 

 tion of forces. From the point of hitch on the drawbar to 

 the centre of resistance of an engine gang plow is frequently 

 from twelve to eighteen feet, with a descent of only eighteen 

 to twenty inches. From the point of a horse's shoulder to 

 the ground is about fifty inches, and from that point to the 

 centre of resistance only eleven or twelve feet; hence there is 

 greater tendency to lift the point of the plow from its true posi- 

 tion. This tendency must be overcome by giving it, either 

 through suction or the curvature of the beam, a natural incli- 

 nation to run into the ground. The more nearly the centre of 

 resistance moves along the line of draft the more easily the 

 plow will "swim," and the fewer will be the undulations left 

 on the bottom of the furrow from jumping. Unfortu- 

 nately, the majority of engine gang, plowmakers seem to 

 have overlooked this point and simply transferred the horse- 

 plow bottom to the engine gang without correcting the 

 unnatural, but perhaps necessary, curvature of beam and 

 landside. 



