Plain bearings

Plain Bearing Sheaves Roller Bearing Sheaves ... 

In these tables, the K factor for sheave friction is 1.09 for plain bearings and 1.U4 for roller bearinfrs. Other K factors can be used if recommended by the equipment manufacturer. 

This type can be illustrated by reference to the conditions existing in a properly designed plain bearing. If the two bearing surfaces can be separated completely by a fluid film, frictional wear of the surface is virtually eliminated. Resistance to motion will be reduced to a level governed largely by the viscosity of the lubricating fluid. 

Specific application for machines with combined hydraulic and plain bearings, and lubrication systems where discontinuous or intermittent sliding (stick-slip) at low speed is to be prevented... 

Dial indicators Figure 54.15 shows a common dial indicator, which is also called a mnout gage. A dial indicator is an instmment with either jeweled or plain bearings, precisely finished gears, pinions, and other precision parts designed to produce accurate measurements. It is possible to take measurements ranging from one-thousandth (0.001 inch or one mil) to 50 millionths of an inch. 

All plain bearings also are referred to as fluid-film bearings. In addition, radial plain bearings also are commonly referred to as journal bearings. Plain bearings are available in a wide variety of types or styles and may be self-contained units or built into a machine assembly. Table 60.8 is a selection guide for radial and thrust plain bearings. 

Table 60.8 Plain bearings selection guide (a) Journal bearings...

As indicated above, dissimilar metals with low frictional characteristics are most suitable for plain bearing applications. With steel shafts, plain bearings made of bronze or Babbitt are commonly used. Bronze is one of the harder bearing materials and is generally used for low speeds and heavy loads. 

A plain bearing may sometimes be made of a combination of materials. The outer portion may be constructed of bronze, steel, or iron to provide the strength needed to provide a load-carrying capability. The bearing may be lined with a softer material such as Babbitt to provide the sacrificial capability needed to protect the shaft. 

In plain bearings, the lubricating fluid must be replenished to compensate for end leakage in order to maintain their load-carrying capacity. Pressure lubrication from a pump-or gravity-fed tank, or automatic lubricating devices such... 

With plain bearing surfaces of steel, a great improvement can be obtained by phosphating and impregnating the layer with oil. The inherent porosity of the phosphate films provides minute reservoirs for the oil. Should it be necessary to operate a bearing dry, then either a bonded film of MoSj or p.t.f.e. (polytetrafluoroethylene) can be used to advantage. Both materials have excellent frictional and wear characteristics. 

Fig. 12.1. Incipient fatigue cracks in an experimental Al-20%Si plain bearing alloy (a) optical, lOx objective (b) 0.73 GHz (Ilett etal. 1984). 

Fig. 8. Design of angular circular extrusion head with rotating core for manufacturing of tubes and hoses 1 — Single-screw extruder 2 — Adapter 3 — Core holder 4 — Separable core tip 5 — Alignment bolts 6 — Rotating core 7 — Plain bearing 8 — Stop flanging 9 — Head casing 10 — Electric heaters 11 — Place for installation of thermocouples...

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