Does anyone help me to solve this problem in the attached file? When I solved this problem, I got wrong answers. Attached file is the image file with the problem and answer. (Question No.3) I think I have to find allowable shear stress of Pin A to find the safety factor of this pin, since its ultimate shear strenght is already given. (vertical height is 500mm) However, My allowable stress for Pin A is 431.5MPa, which is far more than its ultimate shear stress. I took moment at B and C to find the shear force of Pin A. (and Pin A is in double shear) so I used the formula " shear stress = shear force / (area of shear plane) * 2 " to find the shear force, and I got the answer above(431.5Mpa) while its ultimate shear stress is 350MPa. I still don't get what is the problem.. (I think there are logical errors on my thought). Please help!