R & D Flexible Shaft Couplings (RDD 910-004)

The R & D Flexible Coupling fits between the transmission output flange and the shaft coupling. This resilient polyurethane disk will reduce engine noise and transmission vibration, compensate for minor shaft misalignment, and absorb shock loads.

The disk is backed up by two steel compression straps which hold the system in constant compression whether the drivetrain is in forward or reverse. The coupling will distort with light shock loads and disintegrate in the event of a severe shock load, thus saving on expensive drivetrain repairs. If the disk is destroyed from a massive shockload, the metal compression straps keep the coupling intact, ensuring that the drive system remains functional in both forward and reverse.

• Absorbs vibration - quiets your drivetrain
• Absorbs transmission shock loads caused by high RPM gear changes or the propeller striking a submerged object - helps prevent costly transmission damage
• Dual steel compression straps offer a fail safe design

In the accompanying Specification Table, these are the codes for transmission types: A=Allison, B/W=Borg Warner, P=Paragon, PRM=Newage PRM, T=Technodrive, TD=Twin Disc, V=Volvo, Y=Yanmar, ZF=ZF-Hurth.

Method 1 for sizing your flexible coupling: Use the transmission make, model, and the calculated Power Rating (see below) with the Flexible Shaft Couplings Data Sheet (see link, below).

Method 2 for sizing your flexible coupling: Match the flange diameter, number of flange bolts, the bolt circle diameter (C/C), the register (pilot) diameter, and the bolt diameter, then select a coupling that just exceeds your calculated Power Rating (see below).

Think of the flex coupling as a "torque fuse" - you want it to be strong enough so you don't break it with normal use, but not so strong that it doesn't protect your drivetrain from damage.

The Power Rating (PR) of your drivetrain is a measure of how many HP can be applied to the prop shaft per 100 engine RPM.
Depending on your choice of engine HP, a given transmission may be capable of transmitting different maximum torque loads. For a given transmission, you'll need to match the coupling to the potential torque.
• How to calculate the Power Rating (PR) of your drivetrain: PR = Engine HP x transmission reduction gear ratio (2.5:1, for example, would be 2.5) x 100, all divided by maximum engine RPM