Lo-Rez SOFT-MOUNT Package
The image above shows a typical engine and integral reduction gear mounted on Lo-Rez type BR-T steel-spring vibration isolators and filtted with an RT coupling. In some cases it is necessary, because of hull framing and gear case protrusions, to utilize a hollow spool-spacer between the reduction gear and the coupling.

The BR-T vibration isolators have special thrust-carrying devices which permit them to carry full-load propellor thrust without 'locking up' or becoming 'bound' so that they are capable of providing effective isolation of the engine-generated vibration over the entire speed range. The lateral flexibility of the RT coupling assists in this function.

The BR-T isolator series includes the BR4-TELS, TLS and TMS sizes. Each of these incorporates a limit stop to prevent excessive vertical motion and rocking motion. The neoprene bumpers can be easily adjusted to accommodate the actual working height of the isolator as well as to limit the random motions to any desired degree. The central leveling screw and the two additional cap screws securely fasten the engine and gear box to the top of the isolator. As with all Lo-Rez isolators there are neoprene dampers inside each end of the isolator to withstand lateral (including crash) forces - so obviating need for any external chocks. The main load-carrying springs are seated in rubber cups, so that there is no metal-to-metal path within the isolator. 'Noise' pads below the isolator are not required.

The Lo-Rez RT (Reverse Thrust) elastomer flexible coupling was designed primarily for use in the low-speed shafting of geared propulsion systems; particularly those systems in which the engines and gear boxes are mounted on highly-flexible vibration isloators, and where both vibration control and noise control are paramount requirements.

RT couplings can be provided with a variety of elastomeric elements which vary in hardness and also in damping properties. For standard elements, the dynamic magnifier for RT couplings if 6.5 and for high-damping rubber, this dynamic magnifier is 3.5.

The dynamic stiffness factors are based on the respective rated torque levels. For smaller values of transmitted torque, the dynamic stiffness values vary linearly with torque, reducing at zero torque to approximately 75% of the values for full rated torque.

As in mechanical (viscous) damping, the acoustic attenuation properties can be varied by changes in the rubber mix and by changes in the material and weight of the metal components. Tests on actual propulsion systems fitted with Lo-Rez 'soft mount' systems show noise level reductions of from 13 to 20 dB.

The RT coupling driving and driven flanges, or coupling halves, are coupled togther by a set (usually 12) of 3 tiered cylindrical elastomeric elements which are preloaded in compression by articulating bolts and end caps. This configuration results in a combined shear and compression loading of the elements and tensile loading of the articulating bolts when the RT coupling is transmitting torque.

This configuation and loading geometry provide the RT coupling with several important characteristics:

  • two-directional (propellor) thrust capability
  • two-directional torque capability
  • low torsional, angular and radial stiffness for torsional tuning, nisalignment and shock absorption
  • excellent noise-attenuating properties
  • good mechanical damping level
  • open design, facilitating inspection and maintenance and providing for cool operation
  • equal axial (longitudinal) stiffness for forward and reverse thrusts
  • non lubricated
  • A.B.S. approved
  • shock tested to U.S. MIL spec. MIL-S 901C (MOD.)

Lo-Rez RT Flexible Coupling Lo-Rez BR-T Vibration Isolator

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