larger outside diameter than metallic hard to balance assembly some types do

Larger outside diameter than metallic hard to balance

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larger outside diameter than metallic, hard to balance assembly, some types do not have a good overload torque capacity, speed is a problem Compression types: include jaw, donut, and pin & bushing Driving and driven rotate in same plane with parts of the driving hub pushing parts of the driven hub through elastomeric elements positioned as cushions between them Torque transmitted → elements are compressed Parallel misalignment accepted via compressive distortion of elastomer material Angular misalignment accepted via sliding ot distortion of elastomer material Advantages: Elastomers in compression have higher load capacity than shear → higher torque and tolerate overload Offer a greater degree of stiffness Jaw couplings: driving and driven have 2 seven jaws formed around their circumferences pointing to the opposing hub; hubs brought together, jaws from hubs mesh; sometimes space between hubs is filled with elastomer molded into a spider and the legs of the spider are the cushions; design is called Fail-safe > surface area = > torque rating Straight side type: offer several alternatives in spider constructions in addition to the basic asterisk-shaped solid spider or open-center spider spiders (the alternatives are collar, ring-in-groove, block, and in-shear) Collar - fitted w/ elastomer elements installed and removed externally; take form of linear spider → legs are molded in single strip that is wrapped around coupling; collar held in place by 3 screws Ring-in-groove - “snap-wrap”; similar to collar but wrap around spider held in place with a Spiralox retaining ring that snaps into a groove that is molded into spiders perimeter; only available in NBR and max speed is 1750 RPM Compression block - heavy duty applications that have requirements beyond standard capacity; large diameters; transmit torque through independent blocks of elastomers in cube, oval, or wedge shape; shape inserted between jaws and held in place by steel collar; easy to change stiffness In-shear - newest; axially twice as wide as standard spiders for straight sided jaw hubs; instead of intermeshing hubs in same plane, they push hubs apart so the jaws rotate in separate planes → causes removable elastomer to transmit torque through a combo of shear and compression method; spider held in place with floating steel ring; easy removal and replacement of spider Benefits: simple maintenance, non-failsafe operation, greater angular misalignment capacity of 2 degrees, greater softness, only used for electric motors Bore capacities = ⅛” - 2 ⅞” → light to medium duty Max torque = 6228 in-lb Angular misalignment = ½ degree - 1 degree Curved Jaw Type: Main difference in geometry of jaws and spider legs; the intermeshing faces of a radial curvature provides built in encapsulation of the spider legs by the hubs The corresponding spider legs are crowned
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Benefits: higher speed ratings, greater angular misalignment capacity of 1.3 degrees, greater strength
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