Consider how the output is connected In the hydraulic example, the gearbox drives a chain sprocket. That connection imposes a radial load on the output shaft as well as transmitting torque. The calculation uses both the sprocket diameter and its position relative to the shaft shoulder. The initial calculated radial load is approximately 31 kN. After applying the example’ shock and bearing-life factors, the required radial-load capacity becomes approximately 99 kN. Selection therefore includes checks on output-bearing capacity, peak radial load and the combined effect of torque and radial loading on the shaft. The electric example uses a shrink-disc connection and a torque reaction arm. The arm restrains the gearbox casing against the reaction torque generated during power transmission, transferring that reaction to the supporting structure. This arrangement requires consideration of the mounting and reaction forces, together with verification that the shrink disc can transmit the required peak torque. How the gearbox connects to the machine is part of selection from the outset. Establish normal and peak torque Normal operating torque is only one part of the assessment. The hydraulic example includes a possible external static overload of 250% of nominal load. The selected gearbox must be checked against that peak torque requirement as well as the calculated operating requirement. In the electric example, the VFD limits the motor peak factor to 1.6. That specified limit is used when checking peak torque against the capacities of both the gearbox and shrink disc. Knowing how a drive starts, operates and responds to overload helps establish the loads its components must withstand. Account for operating life The required life also influences selection. The examples use output speed and operating hours to obtain gear-life factors. Where external radial loading is assessed, the hydraulic example also applies a bearing-life factor. A gearbox intended for occasional operation over 4,000 hours faces a different requirement from one expected to accumulate 120,000 hours. The required torque rating must take that operating life into consideration.
RkJQdWJsaXNoZXIy NzQyNjQ=