STATING that the performance of rear-axle gears depends on both satisfactory gears and suitable mountings, the author describes three laboratory tests for axles.
The first is a deflection test to determine the displacement of the gears and deflections of the differential carrier under load applied by a 20-hp. motor through changeable gear-reduction giving a propeller-shaft speed of approximately 12 r.p.m. Load is applied by means of a prony brake, and deflections are registered on indicators applied at various points.
The second is called the four-square test. In it four axles are set up in a closed circuit, so that the gears and shafts are subject to static torque, and driven by a motor. This gives a high loading with a small expenditure of power. It is a severe wearing test.
The third test is known as the laboratory road-test. In it an axle with heavy flywheels in place of the road-wheels is driven by an automobile engine under conditions simulating road tests.
In addition to these tests, the author describes and illustrates a selective sound-testing outfit developed for the Timken companies by members of the department of engineering research of the University of Michigan. This instrument will measure a sound of a selected pitch after it has been converted into an electric current that will register in volts on a meter. The device was demonstrated at the meeting by Dr. H. B. Vincent, of the University of Michigan.
Most of the discussion has to do with the relative effect of endwise and vertical displacements of the pinion. Discussers agree that vertical movement affects the tooth bearing-area more than does endwise movement, but they do not agree that a larger area of contact results in more quiet gears.
