Eliminating Fg between Equation B-9 and Equation B-10 results in an 

 expression for the maximum deflection, Yju^x^ associated with the given 

 for a given material. 



= ^PBIe!) (B-II) 



max 384 yCE ' ^'=> ' ■> 



The maximum allowable design stress for 6061-T6 aluminum is cTmax = 

 35,000 psi. Assuming, as before, a design safety factor of 3.5, the 

 maximum stress used in Equation B-11 is 10,000 psi. Setting the value 

 of Jl = 36 inches, E = 10 x 10^ psi, and C = 2.5 inches, the maximum deflec- 

 tion is 



Y = 0.009 inches 



which is quite acceptable for the functional aspects of the tow assembly 

 design. Inserting ^^^^^ into Equation B-9 or using Equation B-10 directly, 

 the required strut cross -section moment of inertia, I, can be found 

 to be I = 5.1 inch^. This moment of inertia value is achieved if the 

 dimensions of Figure B-4B are: Tq = 1.1 inch, r^ = 0.74 inch, t = 0.5 

 inch, and £ = 2 . 5 inches. To check for the possibility of buckling of 

 the strut when under tow, the maximum allowable compressive end load 

 for the particular strut is calculated. From Reference 3, the relation 

 for the maximum end load for column buckling is 



P = 18,000 - 120^ 

 max K 



where P = maximum end load (psi) 

 max 



£ = length of column (in.) 

 k = radius of gyration (in.) 



Using the dimensions of the column strut as determined above the resulting 

 end load for buckling is 



P = 14,580 psi 

 max 



The cross-sectional strut area is 2.98 in. , so the compressive 

 load required to buckle the tow assembly strut is over 43,000 pounds. 

 Since the total tow load as estimated in Table A-1 never exceeds 14,000 

 pounds, failure of the strut by buckling is highly unlikely. 



44 



