ROCOM Precision Flexible Coupling Design

Rocom’s one piece, double taper, multi overlapping, curved beam flexible coupling is the patented result of years of testing. The beams are double tapered so that they are thick at the OD and thin at the ID in ratio to the circumferential lengths. They are thick at the hub end of the beam and thin at the circumferential center forcing the flexing to the center of their lengths, instead of the end where the highest stress would occur. The thick OD increases strength without sacrificing life.

The space between the beams is calculated and cut to allow the beams to flex without touching each other at their maximum misalignment rating. All thru bore couplings have an inside diameter relief in the flexible area. If the misalignment rating is not exceeded, the shaft cannot touch the flexible beams which otherwise could cause them to fail.
This design is continually self-compensating. When the coupling is in a misaligned condition, one set of three beams flex toward each other without touching, and are at their maximum load capability. On the other side of the coupling, the second set of beams are spread apart to their minimum load carrying capability. The second set of beams are 180° out of phase with the first set. This continually averages the torque load and velocity between all six beams and does not allow the coupling to have a sine wave output on each revolution. Tests by our customers show that when these couplings are installed correctly they have a constant velocity.  

Torque and Torsional Stiffness

The torque rating is based on the buckling point, not on the breaking point of the beam. Once the material exceeds its elastic limits (the buckling point) it will fatigue and fail. The beams are less than 360° long at the ID. Beam length, thickness and height (OD to ID), plus material determines the torque and torsional stiffness. The beam designs can be modified for special requirements.


The method of cutting six short overlapping double tapered curved flexible beams is complex and took several years to develop. Six steel hollow ground jeweler saws must all be bent into exactly the same compound curve, all cut at the same time and hold a tolerance of .025 mm, .001 inch thickness beam to beam. The thickness of the blades range from .20 to .90 mm, .008 to .035 inch, depending on the size of the couplings.


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5957 Engineer Drive, Huntington Beach, California 92649 (714) 891-9922 or (800) 952-FLEX Fax (714) 891-2121 Email: Our Sales Department