ENGINEMAN 1 & CKeep a record of the end play measurementsand refer to them when checking the main thrustbearing. The normal wear of a pivoted shoe-typethrust bearing is negligible even with years of use.However, when a thrust bearing is new, there maybe slight settling of the leveling plates. If younotice any increase in the end play, examine thethrust shoe surfaces, and make all necessaryrepairs.In most cases, the main thrust bearing capmust be removed for inspection. The opening isof such size that it will permit the withdrawal ofthe pair of ahead and astern thrust shoes locatedin line with it.C H E C K I N G E N D P L A Y W H I L ERUNNING THE SHAFT.—The simplest methodof checking end play is to use a suitable measur-ing instrument on any accessible part of thepropeller shaft while running the shaft slowlyahead and astern. This is normally done at theend of a run when the ship is maneuvering to ap-proach the pier before the machinery and shaftare cold. Although the speeds should be slow toavoid adding deflections of bearing parts andhousing to the actual end play, these speeds shouldbe sufficient to overcome the rake of the shaftand to ensure that the full end play is actuallytaken up.End play is measured with a dial indicatormounted on a rigid support close to any con-venient coupling flange. Occasionally a shaft mayhave a shoulder turned on it for the sole purposeof applying a dial indicator. Make sure that theflange surface is free from paint, burrs, and rustspots. The flange surface should also be welloiled in order to prevent damage to the dialindicator.JACKING ON THE SHAFT FLANGE.—Ifit is not feasible to measure the end play of a shaftwhile running, your next choice is to jack the shaftfore and aft at some convenient main shaft flange.Use a dial indicator make certain that the shaftmovement is free, and guard against overdoingthe jacking force. The main difficulty associatedwith the use of the jacking methods is in findingsuitable supports to ensure that no structuraldamage will be incurred when jacking is doneagainst a main shaft flange coupling.MAIN PROPULSION SHAFTBEARINGSYou will be required to watch and maintainthe main propeller shaft bearings. These bearingssupport and hold the propulsion shafting in align-ment. They are divided into two general groups:the main line shaft bearings (spring bearings), andthe stern tube and strut bearings.MAIN LINE SHAFT BEARINGS(SPRING BEARINGS)The main line shaft bearings (spring bearings)are of the ring-oiled, babbitt-faced, spherical seat,shell type. These bearings (figure 4-3) are designedprimarily to align themselves to support the weightof the shafting. In many of the older, low-powered ships, the bearings are not of the self-aligning type and consist only of bottom halves.The upper half of each assembly consists only ofa cap or cover (not in contact with the shaft)designed to protect the shaft journal from dirt.The spring bearings of all modern naval ships,however, are provided with both upper and lowerself-aligning bearing halves.The brass oiler rings (figure 4-3) hang looselyover the shaft journal and the lower bearing half,and are slowly drag fed around by the rotationof the shaft. The upper half of the bearing isFigure 4-3.—Main line shaft bearing.4-8
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