For most pleasure and small boat applications the SigmaDrive SD series is a simple effective solution for noise and vibration issues that are caused by misalignment. SigmaDrive reduces and even eliminates vibrations that originate from an imperfect alignment between the propeller shaft and the engine by adding flexibility to the shaft line. Thrust taken up on the engine from the propeller invariably changes the angle of the shaft line, particularly when the engine uses soft rubber mounts. Using a single SigmaDrive SD coupling will ensure the shaft is correctly aligned at all times, especially under high load. The result, reductions in many cases of around 50% in noise and vibration.
The SigmaDrive SD coupling is able to resist propeller thrust when installed as a standalone coupling directly from the shaft to the output flange on the engine’s transmission. The SD coupling is manufactured from a special bronze alloy and is virtually maintenance free. The internal components are hard-wearing with a long service life. No rubber is used in the construction of the SigmaDrive SD series and its unique design compensates for the movement of the engine when under load from the propeller shaft.
The SD coupling is a direct replacement for a hard coupling such as Buck Algonquin, or flexible couplings such as R&D or Polyflex. The coupling uses a keyless taper lock system to grip the shaft so no modifications are needed to install the unit.
SigmaDrive couplings are available for shaft torques of 185 ft-lbs to 4425 ft-lbs with a range of shaft diameters. The model numbers are SD 55, 100, 150, 225 and 300.