1 TORSIONAL COUPLINGS INTRODUCTION Torsional Couplings Lovejoy Torsional Couplings solve torsional vibration problems typical of those found in diesel engine applications. The torsional coupling dampens torsional vibrations and tunes the system to have critical speeds outside the operating range. Our application engineers can analyze the application with our computer programme and determine the exact coupling needed for almost any application. The LF family is a rubber-in-compression coupling designed for a wide range of applications such as generators, pumps, compressors, front power take-off, etc. The largest size, the 400, can transmit up to 5,000 Nm of torque. These are available in a range of shore hardness. The is one of the most versatile LF LF couplings available, it can be adapted to many configurations such as shaft-to-shaft, engine flywheel mounts, or floating shaft. It not only provides torsional protection but also absorbs shock loads and can tolerate misalignment. For direct-mounted, diesel-driven hydraulic pumps, the coupling in Hytrel® and a coupling are available. These are very stiff couplings designed to shift LF LK critical speeds well above the operating range. When the inertia of the driven (hydraulic pump or pumps) is small compared to that of the driver (the diesel engine), a stiff coupling such as the Hytrel® or is required. Hydraulic LF LK pump drives are a fast-growing segment of the market, particularly in smaller diesel engine drives. Applications include crawler tractors, manlifts, compactors, skid steer loaders, excavators and forklift trucks. Both the LF Hytrel® and the have many thousands of hours of successful service in a LK wide variety of applications around the world. Torsional couplings are designed primarily to fit standard installations such as those specified by . SAE jbj Techniques has design and application engineers with many years of experience to custom design a torsional coupling to fit special applications. We can solve torsional vibration problems. Also if necessary, our engineers can analyze coupling failures. LF Torsional Coupling System Overview The LF Torsional coupling system consists of six basic models or configurations. Each model is designed to satisfy user requirements in a particular area of application and is available in a wide range of torque sizes; 10 - 5000 Nm. Flexible elements of various materials and durometer hardness may be substituted for each other in each size without complicated and uneconomical changes in coupling hardware or design. No other coupling design has achieved this versatility and economy from common components. #DriveLineHarmony www.jbj.co.uk/torsional-couplings.html System Torsional Vibratory Load = critical resonance speed of the system (rpm). nR = dynamic torsional stiffness of the coupling. CTdyn = mass moment of inertia for the drive side. JA = mass moment of inertia for the load side. JL = number of oscillations generated per revolution. i n =R 2 • i 60 C • Tdyn J • J A L J + J A L CTdyn JA JL The coupling will be modelled as the spring controlling torsional oscillations of the engine and the flywheel on one side and the driven equipment on the other: Use the dynamic torsional stiffness values (C ) from the performance data tables which are found in representative coupling catalogues. Mass Tdyn moment of inertia values may be obtained from the respective engine and equipment manufacturers. Note: System steady-state operating speeds should be 1.5 to 2 times the major critical speed for safe, low-resonance operation. Critical speed due to resonance: Select coupling stiffness so that the system does not run at high resonance as well as the normal running and idle speeds are not at or near critical speeds. Crtical speeds are related to the system natural frequency and the number of pulces or excitations generated per revolution (order). For analysis, if ‘I’ possible, reduce the application to a 2-mass system and apply the following equations:
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