CHAPTER XX 



The Tractor Plow Hitch 



BEFORE one attempts to adjust a plow he should know 

 the physical laws that govern the operation of plows. 

 Otherwise he is groping in the dark. It has been the 

 experience of a great many plow experts that the prin- 

 ciples or physical laws underlying the working of plows 

 are not generally understood. For this reason this 

 chapter will treat plow adjustments from the theoretical 

 side (which after all controls the practical), rather than 

 enter into a discussion of how the operator should change 

 the hitch to produce certain results. Another reason for 

 treating the matter from the physical law side is that 

 specific instructions sometimes produce the opposite 

 from the intended results. This happens quite often 

 when instruction books are followed. No writer of 

 instructions can call before his mind all the different 

 conditions that must be met; consequently the best 

 intentions cause trouble by the reader's inability to 

 diagnose conditions correctly. 



The draft laws that control the operation of tractor 

 plows are the same for wheel and walking plows. How- 

 ever, different adjustments are necessary to make these 

 different types of plows conform to the basic law govern- 

 ing proper adjustments. This law stated very specifi- 

 cally is: The shortest distance between two points is a 

 straight line. In tractor plow adjustments one of these 

 points is the "center of power" of the tractor, usually 

 regarded as a point on the rear axle at equal distance 



