Flexible couplings for rotating components

Glossary of Terms

ROCOM Catalog Data

The data in this catalog is given at its worst condition. Moment of inertia was calculated for each of the customer’s largest B1 bore combined with the smallest B2 bore shown for each size coupling. Torque and torsional stiffness tests were performed at the maximum misalignment ratings, not in a straight line.

The torque rating is the buckling point of the beams, not the breaking point. If the buckling point is exceeded, the beams have gone beyond the elastic limits and will fail.

These ratings have no safety factor. We want you, the customer, to know what the worst conditions are that can be expected. You decide what safety factor is needed for your application.

Glossary of Terms

Torsional Deflection, Torsional Stiffness, Torsional Rigidity and Wind-Up are all synonymous. Windup occurs when torque is applied and the rotation of one end of a shaft is greater than the other end. The ratings in this catalog are shown in arc minutes per newton meters and per pound inch at their maximum misalignment rating NOT WHEN THE SHAFTS ARE IN PERFECT ALIGNMENT.

Hysterisis or Lost Motion
This occurs when the driven shaft side of the coupling winds up after the drive shaft side has decelerated to zero RPM. When the direction of rotation is reversed it unwinds and rewinds before driving the driven shaft.

The motion between two or more parts of one component or two components connecting two shafts such as two gears, some belts and pulleys, and some take apart flexible couplings.

Static Torque
Torque applied while in a non-rotating condition. Rocom static torque ratings are below the buckling point of the flexible beams. If the beams are run in a buckled condition or have exceeded the torque rating, the coupling will fail.

Please note: The correct dynamic safety factor should be determined by the customer in accordance with the system’s requirements.

Total Misalignment

The sum of the maximum machined, molded, stamped or bent sheet metal tolerances, the bearings and shaft tolerances, the expansion and contraction of different materials plus the distortion that can occur to the assembly.

Angular Misalignment

When the center lines of the shafts extend and form an obtuse angle. The intersection of the obtuse angle should be at the center of the flexible beam area.

Angular misalignment

Parallel Misalignment

The extension of the center lines of the shafts are in parallel planes. When the coupling is installed, there should be two equal obtuse angles within the coupling.

Parallel misalignment

Skewed Misalignment

The combination of angular and parallel misalignment. The shaft’s center lines extensions are not parallel or intersecting. There can be two obtuse angles of varying degrees. These angles should be centered as nearly as possible within the flexible coupling.

Skewed misalignment

Axial Motion

The motion in the direction of the center lines of the shafts. This motion is created by expansion and contraction, unrestrained shafts in sleeve bearings or other similar unrestrained members. The flexible coupling must be able to accept the maximum axial motion without damage to the bearings or the coupling.

Axial motion

Prop. 65 Warning for California Residents

WARNING: These products may contain chemicals known to the State of California to cause cancer, birth defects, or other reproductive harm.

Rocom Couplings Corporation

2727 Skyway Drive, Suite A
Santa Maria CA 93455

(805) 862-4424

Toll Free 1-800-952-FLEX

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