170 THE OLIVER PLOW BOOK 



lines one a vertical line of draft (or force) tending to 

 pull the plow out of the ground and the other, the line of 

 side draft, which has to do with keeping the plow oper- 

 ating straight ahead determine plow adjustments. 

 The line through which these forces neutralize (or the 

 resultant force) is the true line of draft from a practical 

 standpoint. All plow adjustments must be made to 

 keep this line straight, because this line will straighten 

 theoretically regardless of how the plow or the tractor 

 operates. 



When we understand these laws and what is necessary 

 to keep the line between these two points straight, that 

 is, between the center of power and the center of draft, 

 we can readily see why it is necessary to have the plow 

 beams and a vertical adjustment to take care of the 

 penetration of the plow, as well as a horizontal adjust- 

 ment to take care of the side draft. 



In Fig. 5 is illustrated the vertical line of draft. C is 

 the center of draft of weight. CX is the theoretical line 

 of draft. B represents the center of power of the 

 tractor. BGC then represent the line of draft passing 

 through the clevis on the front of the beam of the plow 

 at G. If the line BGC were angled as BHC and the 

 resistance at point C required more power than the 

 force necessary to straighten the line, it is evident that 

 the line BHC would assume the position BGC before 

 the plow would move. Hence the bottom would rise 

 until BHC reached the position BGC. 



Obviously this would lessen the depth of the plow 

 regardless of the fact that there may be a wheel at the 

 rear and one at the front. If the front wheel happened 

 to be the controlling factor of a power lift, the lift would 

 refuse to work because of the lack of weight to hold the 



