Question

1. The countershaft shown in the Fig QI has two spur gears mounted on it with teeth cut with a 20 pressure angle. The shaft (grooved) is to be made of cold-drawn AISI 1040 steel having Sut= 779 MPa and S,-593 MPa, an elongation of 19% and HB-262. You are asked to size the shaft for safe operation according to DE-Eilliptic criterion by using a factor of safety of 2.5 and a reliability of 99 percent. The stress-concentration factors for the grooves, Kt and Ko, are 2.14 and 1.75 respectively for a fillet radius of r 2 mm. The shaft is supported by two cylindrical roller bearings at D and C, which have bore diameters of dp-40 mm and dc-55 mm. a) Find the reactions at points D and C and draw the shear force, bending moment and torque diagrams for xy-plane. (8 pts) b) Do the same as in a) for xz-plane. (7 pts) c) Determine the safe diameter da for the shaft at A. (10 pts) d) Determine the safe diameter ds for the shaft at B. (10 pts) Dimensions in millimeters. 12 kN 20 Gear 3, 700 D Gear 4, 350 o. 20 450 250 450 9

Answer 1

iiven dr mm Sy 543 MR 18 262 Sheaf 3X12 : 0.23 Cb)

nl dia of A-400m means 62.3510良3 3.S

d) C- ae 3 so Safe diameer da ogart at B 2- Iucm らJ.