TORSIONAL COUPLINGS LM TORSIONAL COUPLING SYSTEM 33 LM Couplings The LM torsional couplings are made especially for diesel engine drives. In particular, the LM couplings are highly elastic torsionally, allowing the engine to drive a relatively small inertia load safely from damaging torsional resonance over a wide speed range from low idle RPM to full engine speed. They acomplish this task by shifting the critical speeds far enough below the idle speed to allow full use of the entire working speed range of the engine without limitation. In essence these sophisticated coupl ings effect an attenuated level of stress throughout the whole drive train by reducing vibratory torque to a very low level. How they work A compact, disc shaped elastomeric element lies at the heart of the LM coupling that gives it its high torsional elasticity. This element has moulded cogs or teeth around it’s outside diameter. These cogs make a backlash-free engagement with internal cogs on an aluminium ring which drives it from the engine flywheel. This arrangement pre-loads the elastomer to increase it’s damping and load carrying capacity and gives the coupling the ability to slip together and “blind assemble” inside the engine’s flywheel housing. It also gives the coupling some torque limiting ability to further protect the drive train, as the cogs are able to slip position during rare transient torque spikes, 5 to 6 times rated torque, without damage to the coupling. If these spikes were to occur frequently, only harmless pieces of rubber would shed from the coupling causing no further damage. The shape of the elastomeric element distributes operating stresses equally over its working section, allowing for a large angle of twist, 6° to 12° at nominal torque load depending on size, while minimizing stress. This feature places the LM coupling amongst the highest torsional elasticities of all couplings available on the market. At the thick centre portion near the hub, as well as the cogs, stresses are further reduced to a very low level, providing a very reliable and robust drive. We bond a steel ring to the centre of the elastomeric element that assembles to a steel hub. The centre of this hub is machined to fit the customer ’s driven shaft and is clamped solidly to the shaft at assembly by a tapered split hub, set screws or the L-Loc clamping system. Range of Sizes The LM torsional come in eight different sizes covering a range of nominal torques from 250 to 3800 Nm. This wide range of sizes make these couplings capable of handling applications driven from small single cylinder engines on up to large multi cylinder engines producing in excess of 600 kW. Material Elastomer ic Element Temperature-resistant natural rubber available in a variety of Shore hardnesses to suit individual application requirements. Our natural rubber is suitable for -45°C to +90°C. For unusually high ambient temperature, especially in non-ventilated flywheel housings, we recommend using our special silicone version, rated -45°C to +120°C. Outer Ring High-grade cast aluminium alloy. Inner Hub Steel with minimum tensile strength of 600 N/mm 2. #DriveLineHarmony www.jbj.co.uk/torsional-couplings.html
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