Flexible Mounts
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Flexible Mounts Innovation for your future

Flexible Mounts II.2 Flexible Mounting Systems III - FUNCTION OF FLEXIBLE MOUNTING SYSTEM III.3 Various types of flexible mounting IV - DESIGNING A FLEXIBLE MOUNTING SYSTEM IV.1 Determining the centre of gravity 19 IV.2 Determining the load per mount 21 V- INDUSTRIAL RANGE OF ELASTOMERIC MOUNTING SYSTEM MOUNTING APPLICATION GUIDE 28 ENGINE MOUNTING SYSTEMS 67 SUPPORTS AND BUMP STOPS 74 ELASTOMER MOULDED PARTS 87 DISK DRIVE SUSPENSIONS S.L.F® MOUNTS BATRA® RING OTHER MOUNTING SYSTEMS STRUCTURAL DAMPING SYSTEMS STRASONIC ACOUSTIC FOAM VI - NAVY SHOCK MOUNTING SYSTEMS NAVY SHOCK MOUNTING...

I - INTRODUCTION The reduction of noise and vibration has become very important: G The need to improve operating conditions makes it essential. G The increasing mechanisation of industrial and domestic equipment and appliances make it necessary. G The lightness and increasing complexity of equipment demand it. The following pages are dedicated to protection against vibration and shock. They offer design engineers the means to resolve isolation problems using elastomer alone or elastomer bonded to metal supports. The first few pages start, therefore, with a summary of definitions and an...

II - DEFINITIONS II.1 - Flexible mounts II.1.1 - PROPERTIES - Flexible mounts are components which exhibit both flexibility and damping, at the same time and to varying degrees. G - Flexibility is the ability of the mount to deform and recover, with an amplitude approximately proportional to the load. G Damping is a braking force the most important effect of which is the reduction of oscillations. There are essentially two types of damping: - Constant friction (dry friction) which, for a given setting, provides a constant braking force independent of the movement. For there to be movement,...

II.1.4 - CHARACTERISTICS OF ELASTOMERIC FLEXIBLE MOUNTS G Elastic properties These are the parameters which define the ability of the mounting to be deformed in various directions. - The linear stiffness Kx, along the axis Gx is the ratio of the force to the corresponding displacement along this axis. The linear stiffness is expressed by daN/mm. The linear stiffness (Ky, Kz) for the other axes (Gy, Gz)are defined in the same way. - The torsional stiffness (Cx, Cy, Cz) about the three axes (Gx, Gy, Gz) is the ratio of the torque to the angular displacement about the axis. The tortional...

- Maximum amplitude: The maximum offset from the equilibrium position for each cycle. For a forced vibration under constant conditions, the amplitude remains constant. G Sinusoidal vibration x = A sin ωt (shape 1) Amplitude T 2π - Amplitude A - Maximum velocity V = Aω - Maximum acceleration Γ = - Aω2 - Instantaneous amplitude x = A Sinωt - Instantaneous velocity v = Aω cosωt - Instantaneous acceleration ϒ = - Aω2 Sinωt High frequency vibrations (high ω) may, therefore, produce very high accelerations even at low amplitudes. II.2.2 - CHARACTERISTICS OF FLEXIBLE MOUNTING SYSTEMS G Elastic...

- Linear stiffness: Kx along Gx = longitudinal movement Ky along Gy = transverse movement Kz along Gz = vertical movement For each axis, the linear stiffness is the sum of the linear stiffness of all the mounts. Kx = Σ kx Ky = Σ ky Kz = Σ kz - Torsional stiffness: Cx about Gx = roll Cy about Gy = pitch Cz about Gz = yaw The torsional stiffness of the suspension depends on: G The individual stiffness of the mounts, G The position and orientation of the mounts with respect to the centre of gravity G of the machine. G Damping properties Elastomers exhibit viscous damping, the braking force...

Creep characteristics The following formula, which is derived from measurements on samples, gives an estimate of the creep for a load which compresses a Radiaflex mount by 10% of its height at a temperature of 30°C. The creep for an actual mounting also depends equally on its shape. Static deflection at time t = initial static deflection x (1 + Cm x f(t)) where f(t) is the value of the creep from the graph below: Creep f(t) in compression relative to the initial static deflection. 0,2 and Cm is a correction coefficient taken from the table below according to the sample material: Material...

III - FUNCTION OF A FLEXIBLE MOUNTING SYSTEM III.1 - Static function An elastic suspension allows the static load to be more evenly distributed. If a machine rests on more than three points using “rigid” mountings, it is impossible to predict the load on each mounting point and the machine could be unevenly stressed. With elastic mounts having a known stiffness, it is possible to determine (by calculation, or direct measurement) the deflection in each mounting and thus deduce the loading and correct any imbalance. An elastic suspension accomodates minor differences in the distance between...

Free oscillation (natural frequency) a) Undamped (entirely theorical) The machine, having been displaced from its position of equilibrium by a distance A, oscillates sinusoidally. The equation of motion is: z = A sin ωo t ωο Proper frequency Fp = The natural pulsation is ωo = K 2π M The oscillation continues indefinitely with an amplitude A (as shown in shape 1 with ω replaced by ω o). b) Damped In this case, the machine oscillates about its position of equilibrium with a damped sinusoidal motion (see shape 4). The equation of motion is: z = A.e -ε’οω’ο t .sin ω’ t ο ε’o is the damping...

Forced vibration If the machine is now subject to forced vertical vibration induced by a sinusoidal force of frequency ω. The inducing force is F = FM sin ωt. - For a rigid suspension: the inducing force is transmitted directly to the structure the machine is mounted on. ωο - For an elastic suspension with a natural frequency ωο or proper frequency Fp = ____ and damping factor εo: 2π When the inducing force is applied, an oscillation is induced at the natural frequency ωο which dies away rapidly so that, after a short period, only the steady state forced vibration at frequency ω remains...