Laboratory Testing of Back Axles
Page 57
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TORQUES up to 10,480 lb.-ft. can be
applied to any type of rear axle on a test rig built by Heenan and Fronde, Ltd., Worcester, for British Timken, Ltd., Northampton. The rig will enable data to be collected in the laboratory regarding bearing performance, casing deflections, and so on, very much quicker and more thoroughly than could be done by operational testing alone.
The maximum torque quoted is applied at a speed of 0.625 r.p.m. to 1.875 r.p.m. to an axle having a reduction ratio of 8 to 1. The torque available is, in practice, sufficient to test any production axle to destruction. Test
readings will include measuring the strain between points some distance apart with micrometer gauges and evaluating local stresses by means of strain gauges. The test data provided is thus of inestimable value.
The main components of the rig include a 12.5 h.p. reversible electric motor, the drive from which is taken through a Heenan Dynamatic slip coupling which. provides a variablespeed drive, and a Dynamaticslip brake, to a worm gear with a reduction ratio of 90 to 1. The drive to the axle is taken through a jointed propeller shaft.
Speed-increasing gears with a ratio
of 1 to 50 at both ends of the axle arc connected by a common external shaft to a two-speed step-up gearbox. from which the drive is taken to a Heenan Dynamatic Mk. 1 eddy-current dynamometer. Adjustments can easily be made to the location of the assemblies tc facilitate the testing of different .types of axle.
'fhe dynamometer, slip brake, and slip coupling are all electrically excited, and the controls can therefore be conveniently mounted on a single panel. Safety devices ensure that the rig cannot be damaged by failure of the current or of the flow of the cooling water supplied to the dynamometer.