From Figure B-2 



also, 



2 2 

 a = 4-1 = 3.9 ft 



b = 3.0 ft 



b o 

 tan ((> = — ;. (f) 38 =0.66 rad 



e = cos"'' 4- = 75.5° = 1.32 rad 

 4 



Therefore, arc c=Gr=5.3ft 



B, V, V, , d, A^, and A are the same as for the chain-driven bucket 

 trencher; therefore. 



and 



F,„^m = 864 lb /bucket 

 TOT 



F = 16 lb /bucket 



The number of buckets in contact with the soil 



N, = (arc c) (bucket distribution) = 5.3 buckets 

 b 



F = (P-rnT + ^i-f^)\ = (864 lb + 16 lb) (5.3) = 4,460 1b 

 max TOT lirt b 



T = F (moment arm) = (4,660 lb) (4 ft + 0.82 ft) = 22,000 Ib-ft 

 max max / \ » / v > 



The angular velocity is 



^ ^ tip speed [ 2 ^ rad j ^ 9.1 ft/sec (2 ^) = 2.3 rad/sec 

 TT d y rev I (Tr)(8 ft) 



Then 



hp 



P = T 0) = (22,500 ft-lb)(2.3 rad/sec) 

 max max 



550 ft-lb/sec 



P = 94 hp 

 max '^ 



The forces acting on the trencher are: 



Case 1. Trencher rotating in conventional (upmilling) direction: 



66 



