Figure 1: (a) spur gear test rig (b) schematic Diagram of the spur Gearbox Rig (Components of interest contained in dotted box) [7] In this test rig, the single stage gearbox (in this case a spur gear set with 1:1 ratio and 32 teeth on each gear) is driven primarily by a 3-phase electric motor, but with circulating power via a hydraulic pump/motor set. The input and output shafts of the gearbox are arranged in parallel and each shaft is supported by two double row ball bearings (Koyo 1205). The flywheels are used to reduce the fluctuations of the input and output shaft speeds. The couplings are flexible in torsion and without stiffness in bending, making them very helpful for the attenuation of the shaft torsional vibration. The bearings under test (Fig 2) were double row self-aligning (Koyo 1205) with a contact angle of 0o, a ball diameter of 7.12 mm and a pitch diameter of 38.5 mm. Fig 2: Bearing under test (Koyo 1205) [1] Fig 3: Extended inner race fault [2] An extended fault was inserted in the inner race of the bearing by grinding one eighth of the circumference (length 22 mm) as shown in Fig. 3. The elasto-hydrodynamic effect of the oil film was not taken into account. In the simulation model an extended rough profile was programmed into the bearing’s S-function to simulate the vibrations generated from the test rig as a result of the extended inner race faults [2]. The tests both in the experiment and in the simulations were carried out at a 10 Hz shaft frequency. The ball pass frequency of the inner race at this speed is roughly 71.1 Hz. 3. Lumped Parameter Model (Internals) Different mathematical models [7-9] have been developed to study the dynamic effects on the transmission error (TE) of the UNSW gearbox. These were lumped parameter models (LPM), which assume that each shaft mass and inertia is lumped at the bearings or at the gears. In all these models, rolling element bearings (REBs) were modelled as a single degree of freedom (mass-spring) system with 401
RkJQdWJsaXNoZXIy MTMzNzEzMQ==