Lovejoy S-Flex Endurance 8S Elastomeric Coupling

Lovejoy S-Flex 8S is the size 8 S Type flange of the S-Flex Endurance elastomeric coupling: two cast-iron flanges and a toothed EPDM, Neoprene or Hytrel sleeve that carries torque in shear. With a 1.938 in (49 mm) maximum bore and a nominal 1,475 in-lb (166.66 Nm) rating with the EPDM sleeve, it is a mid-size choice for motors driving pumps, fans and conveyors.

A shear-type sleeve that needs no lubrication

The S-Flex Endurance design is three parts: two flanges with internal teeth engage an elastomeric sleeve with external teeth, and the teeth lock together under torque without clamps or screws. Misalignment and torsional shock are absorbed by shear deflection in the sleeve, which Lovejoy describes as very well suited to impact loads. The coupling is low maintenance, needs no special tools to install, and offers double engagement for reliability.

The reformulated EPDM sleeve is the headline of the 2026 catalogue: at least three times the life of the previous design, at least 30 percent more torque rating, and a possible product downsize in 50 percent of applications, according to Lovejoy testing. Thirteen sizes cover 60 in-lb to 72,480 in-lb.

Technical specifications

Sleeve ratings for size 8

S-Flex Endurance sizes 3 to 16

EPDM rated torque and maximum RPM for the full size range:

Selecting and ordering size 8

Calculate nominal torque, apply the application service factor from the catalogue chart, and read the EPDM, Neoprene or Hytrel column of the rated-torque table. Check that the shaft diameters fit the maximum bore. A complete coupling is two flanges and one sleeve, ordered with the 685144 UPC prefix: for size 8 the catalogue lists a 1-3/4 in bore flange with 3/8 x 3/16 keyway as 36145, metric bores of 24, 28, 30, 32, 38, 42, 45 and 48 mm (for example 48 mm, 14 x 3.8 keyway, 41568), and sleeves JE 35572, JES 36707, JN 36402, JNS 36881, E 36419, N 36421, H 36514 and HS 40072.

Hytrel sleeves transmit about three to four times the power of an equivalent EPDM or Neoprene sleeve, but they can only be used with S or SC flanges and should not replace EPDM or Neoprene sleeves directly.

Installation and operation notes

Hytrel sleeves are not recommended in high service factor applications. Keep shaft alignment within the sleeve limits, avoid sudden shock loads at start-up, and inspect the sleeve shortly after first operation, then periodically. Axial movement of about 1/8 in is accepted without passing thrust to equipment bearings, and the sleeve minimises radial loads on bearings under parallel misalignment.

Where it is used

Typical drives are motors to centrifugal pumps, fans and blowers, conveyors and mixers; the SC Type spacer version suits pump spacing. For comparison with a gear solution see the Flender RUPEX pin and bush coupling. Sleeve chemical resistance for oils and solvents is tabulated on catalogue page SF-24.

Operating notes for Oman and the GCC

S-Flex 8S couplings are widely used on pump and fan drives in water treatment, desalination and HVAC plants in the region. The sleeve material decides the limits: EPDM is the general choice, Neoprene is used where oil contact is possible, and Hytrel carries more torque but accepts less misalignment and cannot be used as a direct replacement for the softer sleeves. In outdoor or hot plant rooms, check the sleeve temperature limit against the real operating temperature near the motor, keep a spare S-Flex 8S sleeve in stock, and recheck alignment after the first few weeks of running, when foundations and pipework settle.

Information to send with an enquiry

• Motor power and speed, and the driven machine
• Shaft diameters and keyways on both sides
• Sleeve material and flange type
• Shaft separation if a spacer is needed

Frequently asked questions

What does an S-Flex Endurance coupling consist of?

Two flanges with internal teeth and one elastomeric sleeve with external teeth, with no clamps or screws between sleeve and flanges.

Which sleeve materials are available for size 8?

EPDM (standard, black), Neoprene (black with green dot) and Hytrel (orange, 8H) in one-piece, split or two-piece forms.

How much misalignment can size 8 accept?

The EPDM and Neoprene sleeves accept up to 1 degree angular, up to 0.062 in parallel and about 0.125 in axial movement; Hytrel accepts 0.25 degree and up to 0.035 in parallel.

What is new about the EPDM sleeve?

Lovejoy states the reformulated EPDM sleeve lasts at least 3 times as long as its previous design and has at least 30 percent more torque rating; Neoprene and Hytrel are unchanged.

Can a sleeve be changed without moving the shafts?

The two-piece E and N sleeves and the split JES and JNS sleeves are designed for small shaft separations where a one-piece sleeve cannot be fitted over the flanges.

Documents and quotation

The S-Flex Endurance catalogue (11181 Rev C, June 2026) is hosted on this page. See Couplings and Shaft Locking Devices. Seven Star LLC is an independent supplier in Muscat; send flange bore sizes, sleeve material and quantity for a quotation.