The efficiency of the worm gear set at an interface friction of 0.05 is.

Question

 The worm gear set is designed to have pressure angle of 30⁰ which is equal to the helix angle. The efficiency of the worm gear set at an interface friction of 0.05 is.

                                                        

         (a)   87.9%                      (b) 77.9%

         (c)   67.9 %                     (d) 57.9%