Question

A power train application requires the coupling of a spur gear to a transmission shaft operating at 3600RPM. The coupling must sustain a mean torque loading of 215Nm. There is a 20% torque ripple introduced to the drive line from the load. Select and design a coupling system using either a keyed coupling or an interference coupling such that the section of the transmission shaft at that location is minimized. Assume that the gear is located at the midpoint of the shaft and introduces a steady transverse load of 1000N. The center to center on the bearings is 6.5" (6.5 * 25.4 = 165.1mm)

Answer 1

Design of sleeve coupling

1. max torque = 1.2 * mean torque (as ripple 20%)

                     = 258 N-m

assume diameter 25mm

say 53 N/mm²

Transverse load given = 1000N

center distance = 165.1mm ; radius=82.5mm

Bending moment = 1000* 82.5 = 82.5 N-m

equivalent bending moment =

      M_e =

Torque equivalent=

T_e= 1350 N-m

calculate to verify whether shear stress is in limit

if not diameter should be assumed higher

2. Design of sleeve

D=2d+13;=63mm; L= 3.5d; =88mm

have to check the induced shear stress is less than allowable stress

   

3.Design for key

From design data for shaft diameter width of key is selected

square key

width = thickness

Checking for crushing and shearing is calculated using formula

After finding induced shear stress and crushing stress the value is verified with permissible stress to find the key design safe or not.