Appendix A 



PLOW RESISTANCE FORCE AND POWER ANALYSIS 



From Reference 36, the static soil resistance for a plowshare moving 

 through a cohesive soil (clay) is given by 



F =SA +SNA^ 

 s us u c f 



where F = Static soil resistance (lb) 



^ 2 ^ 



S = Undrained shear strength (4 lb/in. ) 



u 2 



A = Side area of plow (in. ) 



s 



N = Dimensionless coefficient (2i 10) 



^ 2 



A^ = Plow frontal area (in. ) 



As the velocity of the plow increases, the static soil resistance must 

 be modified by a velocity coefficient, C (Figure A-1), and an inertial 

 term, F , must be added: 



1 2 



Fj = y p Aj C^ V 



2 4 

 where p = soil mass density (O; 3 lb-sec /ft ) 



C^ = drag coefficient (0.7 to 1.5) 



V = velocity (ft/sec) 



The total force, then, is 



F„„^ = C F + F^ 

 TOT V s I 



For the problem at hand, we have plow and feed shoe dimensions (Figure A-2) 



w 



= 



^ in. 



h 



= 



36 in. 



I 



= 



120 in 



C 



= 



1.09 



Thus, 



= 2 h£ = (2)(36 in.)(120 in.) = 8,640 in.^ 



2 

 A = w h = (4 in.) (36 in.) = 144 in. 



54 



