Flexible Shaft Coupling for 5" B/W, Hurth, & Volvo - 25HP/100RPM Capacity

The R & D Marine Flexible Coupling consists of a flexible disc molded with a polyester elastomer. The disc gives clearance for bolt heads and is able to flex freely to take up any temporary misalignment of the engine and shaft due to flexing of the boat structure or the engine moving on its mount. Forward thrust is taken in compression on the disc between the two half couplings, and reverse thrust is retaken in compression on the disc between the two fail-safe straps. In the unlikely event of a severe impact, the steel straps make the coupling fail-safe and ensure the drive is maintained both forward and reverse.

Reduce Engine Noise & Transmission Vibration

Staggered bolts enable the element to isolate vibrations and compensate for some misalignment.

Reduces Costly Transmission Repairs

Absorbs shock loads due to hard gear changes.

Fits Most Major Transmissions

For engines, 5 to 1,500 horsepower It fits brands such as Borg Warner, ZF-Hurth, Twin Disc, Volvo, Yanmar, Technodrive, and more.

Under Compression Load In Both Forward & Reverse

The aft steel strap bolted to the transmission acts as a backing plate to prevent reverse thrust from pulling the element apart.

Quick & Easy Installation

The R & D Marine Flexible Coupling requires no machining and comes supplied with bolts to connect between the two existing shaft flanges.

Extremely Durable

Impervious to saltwater, diesel, and lubrication oils. The Flexible Couplings are made from a polyester elastomer not affected by saltwater, diesel, or lubrication fluids.

Fail-Safe Design

A fail-safe design is incorporated in the R & D Flexible Shaft Coupling that prevents the two couplings from pulling apart in the event of an impact or element failure, whereas other couplings do not. This fail-safe design is accomplished by using two steel straps and thru-bolts going into both the shaft coupling and transmission output flange. The aft steel strap is bolted to the transmission output flange, and the front strap is bolted to the shaft coupling. In the event of an impact, the aft steel strap (bolted to the transmission) will catch the front steel strap (bolted to the shaft coupling) and prevent the drivetrain from pulling apart.

The R & D element will absorb the shock load (reducing or eliminating damage to the transmission) and will maintain contact between the two couplings. The steel straps also keep the R & D Flex-Coupling under a compression load in both forward and reverse operation (the aft strap bolted to the transmission acts as a backing plate).

Machined Not Molded

The Drivesaver is molded, while the R & D Flexible Shaft Coupling is machined. Both designs suggested that you first set your alignment by drawing the two couplings up to each other and then adding the flex-coupling. The machined part will have MUCH tighter tolerance than a molded part.

Checking Alignment

The R & D Flexible Shaft Coupling allows for alignment inspection after the element is bolted in place. There is one bolt head that is machined and painted red. After the R & D Flexible Shaft Coupling is bolted into place, a feeler gauge can be slipped between the red bolt head and the coupling. This process is repeated with the same bolt four times at 90-degree intervals by rotating the shaft. If the gap is within .010" (0.25mm), the engine is accurately aligned.

To calculate the power of the coupling required:

Horse Power of Engine x Reduction Ratio x 100 = HP/100RPM
      Engine Speed  

Example:

• Ford 150 HP at 2500 RPM with Borg Warner Velvet Drive 72C 2:1 Reduction Ratio
• Engine Horse Power is 150 HP, Max Rated RPM is 2500, Reduction Ratio is 2:1
• 150/2500 x 2 x 100 = 12 HP per 100RPM
• The coupling required is 910-009

Specifications:

• Manufacturer: B/W, Hurth, Volvo
• Diameter (inches/mm): 5 / 127
• # of Bolts: 4
• Diameter of Holes (inches/mm): 0.44 / 11.2
• Bolt Pitch Circle (inches/mm): 4.25 / 107.9
• Register (inches/mm): 2.5 / 63.5
• Diameter (inches/mm): 5.63 / 143
• Length (inches/mm): 2.06 / 52.4
• Bolt Diameter: 7/16 UNF
• HP per 100 RPM (hp / kW): 25 / 18.64