Elastomeric Couplings
Flexible couplings that transmit torque through an elastomeric element — Kop-Flex MAX-C resilient couplings and Morse Morflex driveshaft-style designs. The rubber element absorbs shock and misalignment without lubrication.
Elastomeric Couplings by Category
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About Elastomeric Couplings
An elastomeric coupling puts a resilient element between two hubs, so the drive is carried through rubber or urethane in compression rather than through metal-to-metal contact. That is what makes the group non-lubricated and what lets it absorb shock and torsional vibration. Three lines are stocked here and they suit different jobs. The Kop-Flex ELASTOMERIC coupling uses a split wrap-around element that can be changed without moving either machine. The Kop-Flex MAX-C K2 is a resilient block coupling with high torque ratings for shock-loaded drives. The Morse Morflex carries the drive through neoprene biscuits in a floating center and accommodates the most angular misalignment of the three.
Also known as: elastomeric coupling, rubber couplings, resilient couplings, flexible center couplings, morflex couplings
Series in this category
- Morse Morflex — Stock sizes 252 through 1002, oval-flange through the 352 and round-flange from the 402 up, rated 13 to 725 lb-ft, plus CC spacer plates and replacement centers for the double series.
- Kop-Flex MAX-C K2 — Block sets, flex halves and rigid hubs for sizes 2.0 through 8.0, continuous ratings from 28,400 lb-in for shock-loaded and reversing drives.
- Kop-Flex ELASTOMERIC — Type EE standard hubs with a split, wrap-around rubber element, plus DO drop-out and SS and ES spacer types.
- Elastomeric coupling components — Replacement centers, spacer plates, block sets, end rings and hubs for a coupling already in service.
Related guides: Coupling types compared, Cross-reference help
How to choose elastomeric couplings
- Size on selection torque, not motor horsepower
- Application torque in lb-in is horsepower times 63,025 divided by rpm. Multiply that by a service factor for the prime mover and the driven machine, and the coupling's continuous rating must exceed the result. A smooth motor scores 0 and a centrifugal pump 1, giving a factor of 1.0; a rough engine adds 1 and a rock crusher 3.
- Pick the element for the problem the drive has
- The ELASTOMERIC coupling drives rubber in compression, which carries five to ten times the load of rubber in shear, and its split element comes out without disturbing shaft alignment. MAX-C K2 is built for torque reversals, high momentary torque and start-stop shock. Morflex is the choice where angular misalignment is the issue, with working angles from 1.5 to 10 degrees across the line.
- Check the bore against the hub, not the coupling size
- Each size lists a maximum bore for its rigid hub and a smaller one for its flex hub, and Morflex flanges list a maximum bore with a standard keyway and a stock minimum plain bore for reboring. Morflex is limited to a 3.50 inch bore and 13,300 lb-in, so a larger shaft moves the selection to MAX-C K2 or to a disc or gear coupling.
- Use a spacer type where the pump has to come out
- The DO drop-out spacer lets the center section be removed so a pump can be serviced without moving the hubs or losing alignment, and the single-spacer ES type provides the 3 1/2 inch shaft separation of the American Voluntary Standard for chemical pumps. Close-coupled hubs are for drives that are aligned once and left alone.
- Confirm speed and the operating environment
- Every size carries a maximum rpm, and the MAX-C K2 rating differs between balanced and unbalanced assemblies. The ELASTOMERIC element is rated from -50 to +175 degrees F. MAX-C K2 is not offered for reciprocating engines, synchronous motors or variable frequency drives, which need an engineered MAX-C CB or WB type.
Specifications explained
| Specification | What it means |
|---|---|
| Coupling size | The size designation, such as Morflex 502 or MAX-C 3.5, which fixes the torque rating, the bore range and the hub dimensions. |
| Torque rating | Continuous torque in lb-in or lb-ft. Morflex stock sizes are also rated in horsepower per 100 rpm, from 0.25 to 13.80. |
| Maximum bore, rigid hub and flex hub | The largest shaft each hub can be bored to. On a MAX-C K2 the rigid hub takes a larger bore than the flex hub of the same size. |
| Bore type | Finished bore with keyway, rough or plain bore for reboring, or bushed for a TAPER-LOCK or Q-D bushing on the ELASTOMERIC hubs. |
| Working angle | The angular misalignment a Morflex size is rated for continuously, 1.5 degrees on the 252 rising to 5 degrees on the 502 through 802. |
| Component type | Which part of the coupling a listing is: a center assembly, CC spacer plate, flex half, rigid hub, block set or end ring. |
| Maximum speed | The rpm limit for the size. Morflex stock sizes run from 6,500 rpm on the 252 down to 4,000 rpm on the 1002. |
Common questions
Do elastomeric couplings need lubrication?
No. The drive passes through the rubber or urethane element rather than through sliding metal parts, so there is nothing to grease and no cover to maintain. That is the main reason the group is chosen over a chain or gear coupling on a drive that would otherwise need a lubrication schedule.
Can the element be replaced without moving the motor?
On the Kop-Flex ELASTOMERIC coupling, yes: the element is split at the insert, wraps around the hubs and is fastened to the flanges, so it comes out and goes back without disturbing foundation bolts or alignment. A Morflex center floats between its two flanges and is exchanged the same way. A MAX-C K2 block set needs the clearance listed as its block removal dimension.
How much misalignment will a Morflex coupling take?
Stock sizes are rated for a continuous working angle of 1.5 degrees on the 252, 2 degrees on the 302, and 5 degrees on the 502 through 802, with parallel misalignment allowances of 0.010 to 0.045 inch. The double CC series uses two center members so four sets of biscuits share the misalignment, and the line extends to 10 degrees.
Is a MAX-C K2 suitable for a variable frequency drive?
Not as a stock K2. The manufacturer excludes reciprocating engines, synchronous motors and variable frequency drives from the K2 and UB types, and where a large torsional displacement is required, and directs those drives to the engineered MAX-C CB and WB couplings, which carry rubber blocks selected for torsional stiffness.
