Question: A multiple-drilling machine is used to drill simultaneously six holes in the steel plate shown. Each drill exerts a clockwise couple of magnitude 40 lb? in. on the plate. Determine an equivalent couple formed by the smallest possible forces acting (a) at A and C, (b) at A and D, (c) on the plate.

 Question: A multiple-drilling machine is used to drill simultaneously six holes in the steel plate shown. Each drill exerts a clockwise couple of magnitude 40 lb? in. on the plate. Determine an equivalent couple formed by the smallest possible forces acting (a) at A and C, (b) at A and D, (c) on the plate.

Answer:

a)

Mc = 40 lb-in * 6 holes = 240 lb-in Mc = F*d

240 lb-in = F*12 in

F = 20 lb ---> answer

b)

AD = SQRT(12^2 + 9^2) = 15 in Mc = F*d

240 = F*15

F = 16 lb ----> answer

c)

BC = SQRT(12^2 + 16^2) = 20 in Mc = F*d

240 = F*20

F = 12 lb ---> answer