Along CA and DB, on the same side of MN, take MA' = CA, NB' = DB; and join A'B'.
Similarly, rs = W (x +a) 11 is the shear on DB.
The links AB and CD are equal in length and are centred respectively at A and C. The ends D and B are joined by a link DB.
The resistance to slipping of a flat belt on a pulley may be obtained by considering the equilibrium of a small arc of the pulley surface subtending an angle dB at the centre, and having tensions T and T+dT at its extremities.
Then the intersection of EB and DB' determines a point P on the (true) curve.
