C-1

A 750-hp 500-rpm motor geared at 1:10 ratio to a hoist having a cylindrical drum 8 ft in diameter is used to raise coal vertically from a mine. At what percentage of full load is the motor operating when raising a 6-ton load at uniform speed? Neglect frictional losses in the hoist.

C-2

Show the arrangement of gears in a simple lathe for cutting screw threads, and calculate proper gear sizes to cut 6 threads per inch, the lead screw having a pitch of 1/8 in.

C-3

An automobile motor has a torque of 230 lb-ft driving the rear axles through a differential having a ratio of 4.11 and an efficiency of 97 per cent. Calculate the tractive effort of the rear wheels, their diameters being 30 in. What rear-wheel horsepower is developed when speed is 40 mph?

C-4

A tensile-testing machine applies the tension through two screws actuating a drawhead or nut, the maximum force on each one being 50,000 lb. The length of the nut in which the screw revolves is 6 in. and the pitch of the screw is 1/2 in. The depth of the flat thread on the screw is 1/4 in. The pressure on the lubricant between threads is 2,000 psi, this assumption being the basis of the calculation. Calculate the mean and root diameters of the screw and the stress on it.

C-5

As shown, a horizontal beam is supported by two rods: one of aluminum 50 in. long and...