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TORQUE-SET method to set tapered roller bearing clearance

by:JNSN     2022-03-16
The TORQUE-SET method for setting tapered roller bearing clearance is based on the following principle: The torque in a preloaded bearing increases directly with the applied preload, which is a function of the latter (usually measured by dimensional preload) ). Laboratory tests have shown that the torque change of the new bearing is very small, and the bearing torque can be effectively used to predict/measure the dimensional preload clearance. A load pre-test is required to determine this relationship between preload and torque (Figure 14). The required bearing clearance, either axial clearance or preload, is achieved by adding or subtracting shims after measuring the initial torque of the bearing. Shim tables are generally used to help select the final shim set for each unit (Figure 15). The steps required to implement the TORQUE-SET method are summarized as follows: 1. Assemble the device using a reference (constant thickness) shim set, making sure the system is preloaded (16). NOTE: The bearing preload results produced by each assembly are not actually the same, depending on the cumulative tolerance of each component. 2. Measure the torque of the bearing (fig. 17). 3. Select the final shim pack thickness from the pre-drawn shim table (Figure 15). 4. Install the final shim set, install all bolts, and complete the assembly (Figure 18). Bearing torque is affected by rotational speed and lubricant used. In any application using the TORQUESET method, the lubricant and speed should remain the same. The most common method of measuring bearing torque is with a torque wrench. Sometimes a socket that fits the size of the nut on the shaft end can be used, if not, a special adapter can be made to fit the size of the shaft end. If the bearing seat can be rotated, a torque wrench can be fitted to the bearing seat to measure the torque. If a torque wrench is not available, a spring balance can be used to measure bearing torque. Wrap the rope around a gear or wheel and use a spring balance to record the pull required to keep the assembly turning. Torque is calculated by multiplying the pull force by the radius of the gear or wheel on which the rope is wound. If there is a gasket table, then this step can be omitted. The gasket table indicates the size of the gasket group corresponding to the tension. When measuring bearing torque, rotate the shaft as slowly as possible while maintaining smooth rotation. Special considerations for the TORQUE-SET method: 1. To be able to measure torque. The design must facilitate measurement of bearing torque. If other components such as seals, piston rings, etc. contribute to the torque, these torque values u200bu200bmust be identified and separated from the bearing torque. For example, in the case of axial clearance, record the drag torque of the shaft and seal; in the case of preload, add the required bearing torque. 2. Can the tight fitting components be reset. When a tight-fitted component is used for bearing adjustment, it must be attempted to reset or back-compress the component after the TORQUE-SET load has been applied and the final shim set has been determined. 3. Bearing rotational torque is affected by rotational speed and lubricant used. These must remain constant across measurement units. The most common way to measure rotational torque is with a torque wrench. During torque measurement, rotate the shaft as slowly as possible (approximately 3.5 rpm) while maintaining smooth rotation. 4. The TORQUE-SET method cannot be used if the load is unbalanced (such as caused by heavier components, clutch discs or caliper brakes). This results in a change in torque during rotation. 5. For field operations the TORQUE-SET method cannot be applied to previously operated (eg run-in) bearings. A new set of bearings or an alternative method must be used. Typical TORQUE-SET Application The TORQUE-SET method has been successfully applied in various industries and automobiles. Typical applications include drive gear shafts, differential shafts, transmission shafts and gearbox shafts. Advantages of the TORQUE-SET method Usually no special jigs or other tools are required. All that is required is a torque wrench or a simple spring balance No need to measure shim clearance. The purpose of changing the shim set is simply to obtain the correct clearance. This method is particularly useful on equipment where manual methods are impractical or very difficult in practice. However, it is not practical for very large equipment. The TORQUE-SET method can be used on-site when installing new bearings.
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