Flexible Couplings

R&D Marine

Part No. 910-001

  • Description
    • Reduce engine noise and transmission vibration.
    • Reduce costly transmission repairs.
    • Fail safe design, both forward and reverse thrust is taken in compression from the steel straps, giving a durable design even in extreme conditions.
    • Fits most major transmission makes and models. For engines 5 to 1,500 horsepower.
    • Under compression load in both forward and reverse.
    • Quick and easy installation.
    • Impervious to salt water, diesel and lubrication oils.

    The R&D Marine Flexible Coupling fits between the transmission output flange and shaft coupling. It is designed to protect a boat's drivetrain. The unit will reduce vibration, compensate for some misalignment, isolate the shaft and absorb shock loads.

    The flexible disc is machined from a resilient and durable polyurethane. It allows the unit to flex, absorbing vibrations and temporary misalignment of the shaft and engine due to movement of the engine or flexing in the vessel's structure.

    The polyurethane disc is backed up by two metal compression straps, one on either side of the flexible coupling. These metal straps hold the system in constant compression whether the drivetrain is in forward or reverse. This feature extends the life of the system dramatically.

    The R&D Marine Flexible Coupling will also absorb shockloads resulting from gear changes, or the propeller striking a submerged object. The polyurethane disk will distort with light shock loads and is designed to be sacrificial in the event of severe shock load, saving on expensive drivetrain repairs. If the disc is destroyed from massive shockload the metal compression straps keep the coupling intact ensuring that the drive system is functional in both forward and reverse.

  • How To Select The Right Coupling For You
    1. Engine horse power and engine speed.
    2. Type of gearbox and reduction ratio.
    3. Gearbox flange details. Diameter of flange. Diameter of register. Pitch circle diameter of fixing holes. Size and quantity of holes. (Pitch circle diameter is the distance between the center of the hole at 12 o'clock position to the center of the hole at 6 o'clock)

    1. Ford 150hp at 2,500 rpm.
    2. Borg Warner Velvet Drive 72C 2:1 reduction.
    3. 5" flange 2,500 diameter register, 4.250 PCD, 4 off holes 0.437 diameter
    To Calculate Power Of Coupling Required:

    Coupling rating needed is 12hp. By looking at the chart below we can determine the coupling required is a 910-009 Borg Warner.

    Flexible Coupling Chart:

    Click to open large version in new window.

  • Installation Procedure For R&D Marine Couplings
    1. Roughly align engine and stern gear without flexible coupling ie. only two rigid half couplings pushed together.
    2. Bolt "R&D Marine" coupling between the two rigid couplings. Tightening details as below.
    3. Check alignment of engine by placing feeler gauges between RED CONE HEADED BOLT and the rigid half coupling. Repeat for the SAME bolt at 90° intervals by rotating the shaft.
    4. If the gap is the same in all four positions, engine is accurately aligned. Recommended minimum to maximum gap difference: 0.010 inch.
    5. Run installation to bring engine compartment to working temperature.
    6. Re-check torque settings.
    Recommended tightening torque:
    • M8 = 20 ft. lbs.
    • 3/8 UNF = 30 ft. lbs.
    • M10 = 45 ft. lbs.
    • 7/16 UNF = 60 ft. lbs.
    • M12 = 80 ft. lbs.
    • 1/2 UNF 75 ft. lbs.
    • 5/8 UNF = 155 ft. lbs.
    • M18 UNF = 250 ft. lbs.
    • 3/4 UNF = 270 ft. lbs.

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