For a stub tooth spur gear with 24 teeth, a face width of 48 mm, a module of 4 mm, and a material with an endurance strength of 270 MPa, what is the allowable endurance load?  (could you please explain where you got the lewis number? thank you)

If in a gear design problem, the required hardness of steels per allowable gear bending strength is: HB = 158; while the required hardness of steels per allowable gear contact strength is: HB = 256.  Which material HB hardness will be used for gear material specification?     256     158     120     400

a single-start, square-threaded power screw with the following parameters: PARTS A - D circle final answers for each part A -  A weight of 1500 N must be lifted. What is the total required torque necessary to lift this weight? Give your answer in units of N m. Part B - if the available power to drive the screw is 1,011 Watts, determine the fastest speed at which the weight can rise. Give your answer in units of mm/s, Part C - The efficiency of the preceding power screw (expressed as a number between 0 and 1, not as a percentage) is ? Part D - Suppose a high-quality thrust bearing was used to eliminate the collar friction. The efficiency of the screw would now be?

Choose the correct option