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Method of automatically setting bearing clearance

by:JNSN     2021-12-25
In addition to preset bearing components, Timken has developed five commonly used methods for automatically setting bearing clearance (ie SET-RIGHT, ACRO-SET, PROJECTA-SET, TORQUE-SET and CLAMP-SET) as manual Adjustment options. Refer to Table 1-Comparison of methods for setting clearance of tapered roller bearings. The various characteristics of these methods are explained in the form of a table. The first row of this table compares the ability of each method to reasonably control the installation clearance range of the bearing. These values u200bu200bare only used to illustrate the overall characteristics of each method in setting the clearance, and have nothing to do with whether the clearance is set as the target of preload or axial clearance. For example, under the SET-RIGHT column, the expected (high probability interval or 6σ) clearance change may range from a typical minimum of 0.008 inches to 0.014 inches due to specific bearing and housing/shaft tolerance control. The clearance range can be divided between the axial clearance and the preload to maximize the performance of the bearing/application. Refer to Figure 5-Application of automatic setting bearing clearance method. This figure uses the design of a typical four-wheel drive agricultural tractor to illustrate the general application of the method of setting the clearance of a tapered roller bearing. We will discuss in detail the specific definitions, theories and formal processes of each method application in the following chapters of this module. The SET-RIGHT method obtains the required clearance by controlling the tolerances of the bearing and the mounting system, without the need to manually adjust the tapered roller bearing. We use the laws of probability and statistics to predict the effect of these tolerances on bearing clearance. Generally, the SET-RIGHT method requires stricter control of the machining tolerances of the shaft/bearing seat, while strictly controlling (with the aid of accuracy grades and codes) the key tolerances of the bearings. This method believes that each component in the assembly has critical tolerances and needs to be controlled within a certain range. The law of probability states that the probability that each component in an assembly has a small tolerance or a combination of large tolerances is very small. And follow the normal distribution of tolerances (Figure 6). According to statistics, the superposition of all parts size tends to fall in the middle of the possible tolerance range. The goal of the SET-RIGHT method is to control only the most important tolerances that affect the bearing clearance. These tolerances may be entirely internal to the bearing, or they may involve certain mounting components (ie, the widths A and B of Figure 1 or Figure 7, as well as the shaft outer diameter and the inner diameter of the housing). The result is that, with a high probability, the bearing installation clearance will fall within an acceptable SET-RIGHT method. Figure 6. Normally distributed frequency curve variable, x0.135%2.135%0.135%2.135%100% variable arithmetic Average 13.6% 13.6%6s68.26%sss s68.26%95.46%99.73%x Figure 5. Application frequency of automatic setting bearing clearance method, front-wheel engine deceleration device, rear-wheel power take-off, rear axle center articulated transmission Axial fan and water pump input shaft intermediate shaft power take-off clutch shaft pump drive device main reduction main reduction differential input shaft intermediate shaft output shaft differential planetary reduction device (side view) steering knuckle steering mechanism tapered roller bearing clearance Setting method SET-RIGHT method PROJECTA-SET method TORQUE-SET method CLAMP-SET method CRO-SET method preset clearance component range (usually the probability reliability is 99.73% or 6σ, but in the production of higher output , Sometimes 99.994% or 8σ is required). No adjustment is required when using the SET-RIGHT method. All you have to do is to assemble and clamp the machine parts. All dimensions that affect the bearing clearance in the assembly, such as bearing tolerance, shaft outer diameter, shaft length, bearing seat length, and bearing seat inner diameter, are considered as independent variables when calculating the probability range. In the example shown in Figure 7, both the inner ring and the outer ring are installed with a conventional tight fit, and the end cap is simply clamped on one end of the shaft. s u003d (1316 x 10-6)1/2u003d 0.036 mm3s u003d 3 x 0.036u003d0.108mm (0.0043 in) 6s u003d 6 x 0.036u003d 0.216 mm (0.0085 inch) 99.73% of the assembly (range of probability) possible interval u003d 0.654 mm (0.0257 inch) 100% of the assembly (for example) choose 0.108 mm (0.0043 inch) as the average clearance. For 99.73% of the assembly, the possible clearance range is zero to 0.216 mm (0.0085 inch). †Two independent inner rings correspond to an independent shaft variable, so the axial coefficient is doubled. After calculating the probability range, the nominal length of the axial dimension needs to be determined to obtain the required bearing clearance. In this example, all dimensions except the length of the shaft are known. Let's take a look at how to calculate the nominal length of the shaft to get the appropriate bearing clearance. Calculation of the length of the shaft (calculate the nominal size): B u003d A + 2C + 2D + 2E + F[ [2 where: A u003d average width of the housing between the outer rings u003d 13.000 mm (0.5118 inches) B u003d average shaft Length (to be determined) C u003d average bearing width before installation u003d 21.550 mm (0.8484 inch) D u003d increase in bearing width due to average inner ring fit* u003d 0.050 mm (0.0020 inch) E u003d increase in bearing width due to average outer ring fit* u003d 0.076 mm (0.0030 inch) F u003d (required) average bearing clearance u003d 0.108 mm (0.0043 inch) * converted to equivalent axial tolerance. Refer to the 'Timken® Tapered Roller Bearing Product Catalog' Inner Ring and Outer Ring Coordination Practice Guide chapter.
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