There are many components used in belt power transmission systems that are critical, but some may not be as readily apparent as others. An example is electric motor mounting bases.
While motors can be bolted directly to structures by their mounting feet, this does not always allow for necessary movement and adjustability. Adjustable motor bases are commonly used to secure motors while providing a means of positional adjustment. While types, designs, and methods of adjustment vary with brands and size, the best designs adjust with large linear screws.
Focusing on belt drive systems, adjustable motor bases are used to shift motor positions for belt removal and for new belt installation. They are also used to shift motor positions for belt pre-tensioning. Another critical function of adjustable motor bases is adjusting and maintaining motor shaft position for alignment with driven shafts. Accurate shaft alignment is very important for good belt performance, especially with synchronous belt drive systems.
Figure 1 – Single Screw Adjustable Motor Base
Figure 1 illustrates an adjustable motor base utilizing a single adjustment screw. While screw adjustment is superior to bases that only slide, side forces exerted by belt drives on motor shafts generate torsional forces. Single screw adjustment bases often deflect resulting in non-parallelism between motors and driven components. Correction with single screw designs can only be accomplished by applying external forces to motors and bases, which becomes difficult with increasing motor size. Single screw adjusting bases are used mainly for their economics, but do not generally maintain adequate shaft alignment nor belt tension.
Figure 2 – Duel Screw Adjustable Motor Base
Figure 2 illustrates an adjustable motor base utilizing duel adjustment screws. While motor bases of this type generally have fairly heavy duty designs, small torsional deflections can be compensated for fairly easily while applying pre-tension to belts. Adjustments to shaft alignment and belt tension levels are easy and accurate with this type of motor base design.
The design and condition of adjustable motor bases can have a critical effect on belt drive service and performance. When performing maintenance operations, replacing belts or converting V-belt drives to synchronous drives, consider upgrading inferior and insufficient motor bases to heavy duty duel adjusting screw types.