HOW does optical alignment set a shaft line? Optically precise targets are set in holders that fit the bearings. The optical alignment telescope sits in a stand that adjusts the height, horizontal position, and the angular position of the scope. The scope lines up to the centers of the targets, and becomes an extension and representation of the shaft line. A machined fixture fits on the output coupling, and holds an optically precise mirror with crosshairs. The crosshairs on the target are compared to the crosshairs in the scope- this is how the vertical/horizontal center of the marine gear output coupling relates to the shaft line.

    THE angular relationship is established through a procedure called 'auto-reflection.' The scope has a fitting to accept a light source, and that light projects on the mirror, and the mirror reflects the light back to the end of the scope, which has a special target, which the operator sees as another set of crosshairs. The position of this secondary set of lines establishes the angular position of the coupling. With the angular position and the vertical/horizontal center set, perfect alignment is achieved.

    OPTICAL ALIGNMENT establishes the correct shaft line, and is unaffected by gravity or any other outside influences. Optical alignment sees a straight line, and adjusts the engine angular position relative to that perfect shaft line. Optical alignment quickly and accurately provides the yard with a snapshot of the drive train- in this case, it is quickly demonstrated that the grounding has indeed bent the port aft strut, and that the engine is low.

    THE REMEDIAL work can now be planned and carried out in an efficient and organized manner. Generally, on this type of boat, the strut is dropped, the mounting surfaces prepped, drilled for jacking screws, and reset to the shaft line. The engine alignment will be adjusted after the strut is reset, and now the port side turns easily, smoothly, and shows no vibration underway. The angular position of the engine now matches the shaft line, and the boat runs perfectly.

    THERE ARE many different types of bearing systems, and drive trains, and shafting systems, and an optical alignment specialist has to be familiar with all manner of construction. Some vessels require absolutely perfect alignment- there are systems that don't have the tolerance that flexible mounts and rubber cutless bearings build into a boat. Still, the major benefits of optical alignment- accuracy, efficiency, speed- apply to almost any project. A vibration analyst, a skilled team at the boatyard, and an optical alignment specialist can create a smooth-running boat each and every time.

    Michael Bartlett is a specialist with Quantum Alignment and travels extensively in his work. You may reach Michael at mbartlett@quantumhydraulic.com, or at 954-205-5547.

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