Anti vibration mounts are often installed beneath vibrating machines, this way vibrations and structural noise can be successfully isolated.

Diesel engines, compressors, generators, fans or pumps may be connected with belts, chains or even elastic couplings. It is a common mistake to install each element with anti vibration mounts, this often leads to making strong conical effect on the mounts wearing them out quickly.

In order to avoid these conical effects, anti vibration mounts are often installed inclined, but mechanical wear makes them change their stiffness causing a loose of tension on the belts.

Anti vibration mounts installed in the inclined position is a common practice, but belt pulling forces make the mounts work in a conical angle. This type of work changes the stiffness of the anti-vibration mounts as time goes by.	Anti vibration mounts under a common frame, help avoid uneven belt tensions. Mounts can be installed beneath the common frame without being subjected to conical tensions. Anti vibration mounts offer vibration control and provide great longevity.

Common frames provide stable installations that offer low wear on anti-vibration mounts.

Other common practice is to use mounts that are too stiff in order to reduce the oscillating movement of the suspended element. But as the stiffness increases (k), the natural frequency also raises, leading to a lower vibration isolation or risk of approaching to the resonant frequency of the system.

Being on this point many engineers try to find a compromise between stability and isolation. Finding this balance between isolation and stability not durable and very dependent on the stiffness tolerance of the anti-vibration mounts.

Positioning of the mounts and stiffness ratios of the mounts (horizontally stiff mounts) can help finding a stable and correct vibration isolation level, as shown on the picture below. AMC-Mecanocaucho application engineers may be a point of help in order to predict the movement and vibration isolation.

Should you be interested in this topic do not hesitate to contact our applications engineers. They will be able to help and provide input. Contact form AMC-MECANOCAUCHO® Applications engineers.

Anti vibration mounts are often installed beneath vibrating machines, in many cases where there is a fixing hole on a frame. Although this may be a practical and fast way of installing the anti vibration mounts, special caution must be considered so the frames do not “hang” causing cyclical bending moments that can lead to noise or ruptures caused by fatigue.

An easy way to solve this situation is by placing the anti vibration mounts at each corner of the frame. This way we will assure that frames are not swinging at its own natural frequency. If the distance between mounts is greater than 5 feet/1,5m. we often recommend installing mounts in between. This measure helps the stability and avoids frames from twisting or bending avoiding supplementary noise that can cause disturbance.

AMC-MECANOCAUCHO has developed an online tool that allows engineers to make their own calculation and have direct access to our application engineers. This calculation software provides estimations of vibration isolation efficiency requiring simple information such as:

1. 1. Total load.

2. 2. Centre of gravity position.

3. 3. Position of mounts.

4. 4. Disturbing frequency.

The user and password can be obtained easily by clicking on this link.

An example of this online calculation software for vibration isolation can be seen below.

Should you be interested in this topic do not hesitate to contact our applications engineers. They will be able to help and provide input. Contact form AMC-MECANOCAUCHO® Applications engineers.

Anti vibration mounts are often installed beneath vibrating machines, in many cases where there is a fixing hole on a frame. Although this may be a practical and fast way of installing the anti vibration mounts, special caution must be considered so the stability of the suspended is assured.

An easy way to solve this situation is by placing the anti vibration mounts at the height of the centre of gravity. This way we will assure that the suspended element will not be its own natural frequency.

AMC-MECANOCAUCHO application engineers can help by making 6dof calculations, where the optimum position of the mounts can be found, and simulations of displacement can be obtained.

In order to make this calculation, AMC-MECANOCAUCHO application engineers will require the following information:

1. 3D drawing.

2. Total load.

3. Center of Gravity position.

4. Possible position of mounts.

5. Disturbing frequency.

6. Shock magnitude, duration and sense.

Should you be interested in this topic do not hesitate to contact our applications engineers. They will be able to help and provide input. Contact form AMC-MECANOCAUCHO® Applications engineers.

Anti vibration mounts are often installed on the engine brackets and below the crankshaft. Although this may be a practical and fast way of installing the anti vibration mounts, special caution must be considered so the stability of the suspended is assured.

An easy way to solve this situation is by placing the anti vibration mounts at the height of the crankshaft and equidistant to the center of gravity. This way we will assure that the suspended element will not be its own natural frequency.

Raising the mounts to the height of the crankshaft improves the stability and vibration isolation.	Brackets allowing the mounts receive equal load helps provide more stable suspended elements.

AMC-MECANOCAUCHO application engineers can help by making 6dof calculations, where the optimum position of the mounts can be found, and simulations of displacement can be obtained.

In order to make this calculation, AMC-MECANOCAUCHO application engineers will require the following information:

1. 3D drawing.

2. Total load.

3. Center of gravity position.

4. Possible position of mounts.

5. Disturbing frequency.

6. Shock magnitude, duration and sense.

Should you be interested in this topic do not hesitate to contact our applications engineers. They will be able to help and provide input. Contact form AMC-MECANOCAUCHO® Applications engineers.

Akustikabsorber® noise attenuating composites are often installed in industrial machinery to absorb, insulate and damp airborne noise.

VIbrabsorber+Sylomer ® spring anti vibration mounts are often installed beneath industrial machinery to isolate structural noise.

When it concerns airborne noise insulation, the installation principle consists of encapsulating the machine as shown in the figure below.

Fig 1: General overview of encapsulation within a Noise and vibration generating machine.

In order to achieve the optimum results the below advices should be followed:

1. Install the machine on the stiffest part of the frame.

2. Place the machine on anti vibration mounts that provide vibration isolation following a calculation, according to the percentage of isolation that is required. More information click here.

3. It is recommended to use belts or roller drive systems which provide less noise than gear trains. Rigid piping and stiff wiring can act as an acoustic bridge, therefore use flexible hoses and wiring instead.

4. Apply vibration damping materials which have high mass and viscosity. Rubber plates such as MP-5 / MP-10 can be placed on the surfaces exposed to the greatest vibration, this will help to reduce noise.

5. Install an Akustikabsorber that provides the highest transmission loss and absorption coefficient to reduce noise build-up inside machine.

6. Avoid all mechanical contact between the cabinet and the machine chassis, as this can act like as an acoustic bridge.

7. Seal openings at the base and other parts of the cabinet to prevent noise leakage. In fact, when a sound wave encounters an obstacle or an opening which is comparable in size to its wavelength, the sound will bend around the obstacle or squeeze through the opening with little loss of energy, as shown below. The amount of sound energy that passes through a small hole or hairline crack in a wall is far greater than one would predict based on the size of the crack. This points out how important it is to caulk or seal all cracks or openings in walls, doors, etc., which separate areas where privacy is desired.

Fig 2: Diffraction of noise when passing a small hole of a wall.

HOW TO CONTROL SOUND DIFFRACTION WHILE ALLOWING THE CORRECT ENGINE COOLING PERFORMANCE.

The cooling system serves three important functions. First, it removes excess heat from the engine; second, it maintains the engine operating temperature where it works most efficiently; and finally, it brings the engine up to the right operating temperature as quickly as possible.

When the transfer of thermal energy occurs via heat conduction, a thermal flow is required, this is to say an entrance of cold air and an extraction of hot air. For this purpose, forced ventilation with axial fans may be required.

Since noise diffraction can occur through a hole where an axial fan is placed, it is advisable to follow some advice, so noise insulation is achieved whilst hot air is extracted.

Fig 3: General overview of an encapsulated machine with a cooling flow of air.

Additionally to the advice given in Fig 1 the below advice can be also useful for those installations where cooling and noise insulation is required.

1. Any entry and exit holes created for ventilation should be covered with Akustikabsorber® materials that provide good transmission loss and absorption coefficient.

2. Applying vibration damping materials which have high load and viscosity. Rubber plates such as MP-5 / MP-10 should be placed on the surfaces exposed to the greatest vibration, this will avoid metallic plates responding to vibration and generating noise.

3. Position the air inlet/outlet to an area/direction which is outside humans hearing presence. Ideally outlets should be pointing upwards to an area which has a large air volume.

4. Install anti vibration mounts to suspend the axial fan , this avoids radiation of structural noise and secondary airborne noise.

5. Seal openings at the base and other parts of the cabinet to prevent noise leakage.

6. Solid constructions which are generous in mass (concrete/metal) provide better results than light construction structures (wood/plastic).

7. Install double walls covered with Akustikabsorber® materials for optimum sound insulation.

Do not hesitate to contact our technical department if you require help on this topic.

Akustikabsorber® noise attenuating composites are often installed in industrial machinery to absorb, insulate and damp airborne noise.

Vibrabsorber+Sylomer® spring anti vibration mounts are often installed beneath industrial machinery to isolate structural noise.

This article aims to inform people of the expected typical improvements in noise reduction per frequency band of industrial machinery. For a more detailed view on reduction figures an acoustic engineer should be contacted.

Let’s imagine that we have a rotating machine that generates a noise level as seen below.

If we add Vibrabsorber + Sylomer® anti vibration mounts which provide a low natural frequency suspension and also assume that the ground is infinitely stiff , we will correct the noise level within the low frequency band. This is demonstrated on the graph below.

If we have no anti vibration mounts in place and add only an enclosure that is rigid and correctly sealed, we will correct the higher frequencies but have almost no impact/improvement on the low frequencies.

Combining the Vibrabsorber+Sylomer® anti vibration mounts and the sealed enclosure we will reduce both the high and low frequency bands as shown below.

Within the same enclosure if we add Akustikabsorber® soundproofing composites, we will further increase the noise insulation at higher frequencies.

If we provide a secondary step of isolation (double mass isolation system) comprising of an additional layer of Vibrabsorber+Sylomer® and Akustikabsorber, we can expect a further reduction of low, mid and high frequencies as shown below.

This kind of installation must be correctly studied taking in account the stiffness and damping per axis of the mounts. It is also important to consider the weight of the intermediary frame as this plays a key role in achieving good results. More information on this topic can be found on the following article: VIBRATION ISOLATION ON INDUSTRIAL MACHINERY.

Do not hesitate to contact our technical department if you require help on this topic.

VT Spring mounts are often installed in industrial environments to isolate vibration of suspended machinery. Correct installation of these anti vibration mounts will optimize soundproofing results.

VT spring hangers from AMC-MECANOCAUCHO® are installed to reduce noise and vibration in industrial environments, typical applications include HVAC equipment, silencers, airducts, fans, compressors and even suspended ceilings. Their architecture allows the connection of two components with an elastic element between them, this provides a low natural frequency to the suspended system.

From one side, this anti vibration mount is installed to the vibrating element and from the other to the structure or frame.

Each installation is different, and complexities of each work must be studied and measured. Spring hangers provide flexibility on the way that they can be installed. Below are shown 2 types of installation possibilities.

Fig 1. Vibration source fixed to the spring. Metal hanger frame installed to the structure.	Fig 2. Vibration source fixed to the metal hanger frame. Spring installed to the structure.

Both of installations are acceptable. Figure 1 installation will be preferable as the metal hanger frame is installed to the point where there is more mass. There is no possibility for a long stud to resonate.

Figure 2 is still acceptable as the stud is short and has a high stiffness, it is unlikely that the metal stud will interfere with the main disturbing frequencies of a machine (often 4 to 200Hz).

If it is unavoidable and long studs must be used there is a possibility that high frequencies could interfere with the length of the stud, in this case we would recommend filtering these frequencies using a Sylomer® pad as shown in the images below.

Fig 3. Accelerometers placed on SRS+Sylomer® acoustic hangers.

As part of its service to customers AMC-MECANOCAUCHO® supervises installations to ensure correct fitment, vibration measurements are also taken to verify the vibration isolation results. The process consists of installing accelerometers at different points of the installation to determine the vibration transmission.

Correct Alignment of studs

It is important to maintain the concentricity of the studs to avoid any metal to metal contact, and a resulting acoustic bridge.

The below image shows a correct installation of a VT spring hanger anti vibration mount.

Fig 4. Correctly aligned studs on a VT hanger.

Although the VT acoustic hanger from Mecanocaucho incorporates a rubber cup to avoid a metal to metal contact, it is preferable that the stud has no contact with the rubber rim.

Fig 5. Misaligned studs lines should be avoided.

Equally loaded and deflected

Ensure that VT spring hangers can be equally loaded and deflected, hangers with very uneven deflections will alter the natural frequency of the system and could reduce the performance of the suspended installation. Using the height adjusters can allow a correct levelling, the below image shows the preferred installation method.

Fig 6: Duct suspension installing the metal frame to the Steel beam.

Installing the metal frame to the source of vibration is a less preferred installation method. Studs should be kept to the lowest dimension possible in order to avoid a frequency response of the stud itself.

Fig 7. Installation of the metal frame to the source of vibration. (Less preferred installation method). Studs should be kept to the lowest dimension possible.

Correctly Installed VT hangers on inclined ceilings

Inclined ceilings are often a challenge for the installation. An option to achieve a robust installation is by means of using beam clamps and “U” shaped metal parts that are fixed to channels.

AMC MECANOCAUCHO manufactures metal parts to suit your installation needs so do not hesitate to contact our technical department if you require help on this topic.

Motion control must be considered as this creates an effect on the vibratory force of the isolated mass.

The below image shows several options which can be seen for introducing anti vibration mounts on industrial machinery.

1. a) Machine sits on an inertia block. Depending on the flexibility of the floor the main supporting structure will to some degree be isolated from the machine vibration.

2. b) Machine sits on anti vibration mounts, the level of transferred force that is reduced will depend on the dynamic stiffness of the vibration isolators.

3. c) Machine supported with mounts on an inertia block. If the floor is flexible the introduction of the inertia block produces a compound spring system. If the natural frequency of the floor/inertia block is greater than the disturbing frequency of the machine, problems should not occur.

4. d) Machine sits on an inertia block supported with anti vibration mounts. Satisfactory degree of vibration isolation will be achieved if the dynamic stiffness of the anti vibration mounts is adequate, whilst the effect if the inertia block will be to reduce the motion of the isolated machine due to the effects of rotary or reciprocating action.

Fig. 2: Different mounting options of anti vibration mounts.

Inertia masses are usually made of concrete with reinforced bars. They are normally used for the following reasons:

1. 1. To Increase the stability of the system.

It is usual to find machines that incorporate fixation holes that are too close together. If we want to provide adequate stability correct spacing of the mounts is advisable. Concrete bases or steel rails can be used that set a distance between the mounts can be used. Fig 3 and Fig 4 show examples of how this can be achieved.

Fig. 3: Boiler supported with Vibration isolators on Vibrabsorber+Sylomer® spring mounts.

Fig. 4: Single cylinder diesel engine isolated on AMC-MECANOCAUCHO BRB mounts with distancing frame.

2. 2. To lower the Centre of Gravity.

Mounting industrial machinery on a substantial concrete base has the effect of lowering the centre of gravity of the complete assembly. This adds to the improvement of the stability provided by extending the width of the base, but also has the effect of reducing the likelihood of a rocking motion. A typical section through such a base is illustrated on Fig.5



Fig. 5: Machine with T section Foundation block to Effect on Centre of Gravity mounting.

3. 3. To give a more even weight Distribution.

Often industrial machinery is much heavier at one end than the other. This means that, if they are mounted directly on anti vibration mounts, very different arrangements are needed at opposite ends of the equipment to cope with uneven weight distribution. If the machine is mounted on a concrete block, the weight distribution will be more even and, providing the block is heavy enough, it may enable symmetrical mounting arrangement to be used. Figure 6&7 illustrates an example where not only uniform loading of the vibration isolators is achieved, but also a better method of supporting the pipework.

Fig. 6: Pump plus Elbow extended to the inertia block.	Fig. 7: If the concrete inertia is thick even if the elbow is at one of the corners, the stability is not compromised. Courtesy picture of 2 AMC 500+Sylomer® under concrete inertia block on the HVAC system on a shopping mall in France.

4. 4. To minimize the effect of External forces.

Although the use of an inertia block does not improve the transmissibility for a given static deflection, it does not mean that a much stiffer vibration isolator can be used for the same static deflection. This is to say if the mass of the installation is doubled, the stiffness of the anti vibration mounts must also be doubled. This means that the equipment is far less susceptible to the effects of external forces such as fan reaction forces and transient torques due to changes in speed or load.



Fig. 8: Installation of a Genset on FZH+Sylomer®jack up mounts embedded on a concrete block on a rooftop of a building. Courtesy picture of BBVA bank headquarters in Lima, Perú.

5. 5. To provide or replace rigidity

An inertia base can be used to provide rigidity for the mounted equipment in the same way that a steel base is used. This consequently leads to reduced wear.

6. 6. To reduce problems due to coupled modes.

A tall piece of equipment will have two rocking sideways coupled frequencies, these may occur at two to three times the frequency of the vertical natural frequency which can lead to resonance problems. Adding an inertia base has the effect of lowering the rocking natural frequencies which helps to avoid this problem.



Fig. 9: Installation of washing machines on a concrete block using Sylomer® SR-11 in 37mm of thickness.

In order to avoid problems of coupled modes, the machine can be installed on a stepped foundation block. In this case, the center of gravity of the system is lower, closer to the plane of the vibration isolators. This results in decoupling of the rocking modes and high levels of movement can be avoided.

Fig 10, shows an example of a large Vee twin piston compressor installed using this stepped inertia mass as this avoids the movement of the pipe connections on the inclined cylinders.

In order to model this system AMC-MECANOCAUCHO applications engineers can help by making a mathematical model of the system using multibody calculation software as shown on the article Vibration isolation of industrial machinery.

Contact form to get in touch with applications engineers of AMC MECANOCAUCHO.



Fig. 10: Piston compressor installation on a stepped inertia block.

7. 7. To minimise the effects of errors in estimated positions in the equipment’s centre of Gravity.

When vibration isolators are being selected, it is necessary to calculate the total load on each anti vibration mount so that the appropriate vibration isolator can be chosen. This normally has to be done before the equipment is available and estimated positions of the centres of gravity of each item has to be used. If this information is inaccurate, the estimated loads may be considerably different from the ones which occur in practice. This may lead to anti vibration mounts being grossly under or overloaded, or to the equipment sitting at an unacceptable tilt. The latter problem becomes increasingly likely as the vibration isolators with high static deflections are used. If a concrete inertia base is used the centre of gravity of this is normally known and accurate and, if the mass of the inertia block is comparable with the mass of the rest of the equipment, it means that, even if the equipment information is not accurate, the possible inaccuracies in the final estimated centre of gravity are small. This reduces the possible errors per vibration isolator loading and reduces the likelihood of a tilted installation. The probability of a tilted installation is also further reduced due to the stiffer springs that will be required to carry the additional weight of the inertia base.



Fig. 11: Installation of a full surface Sylomer SR-11-25. Concrete will be poured so several HVAC machines can sit on top of the inertia Block. The application is on the rooftop of a Shopping Centre.

8. 8. To act as a local acoustic barrier.

When very noisy equipment is mounted directly on the floor of an equipment room, the floor directly under the equipment may be subject to very high sound pressure levels in the immediate vicinity. This local area where the floor is exposed to these high levels may cause problems of noise transmission into the room below. A concrete inertia base can act as an effective barrier, protecting the vulnerable areas of the floor.

Interesting measures to adopt when inertia bases cannot be used.

1. 1. Installing mounts equidistant to the centre of gravity and if possible, on the points where lowest vibration is felt. (nodes).

The position of the antivibration mounts determines the vibration modes of the suspended ensemble. An even load distribution over all the vibration isolators is advisable. One easy way of obtaining this is by installing the antivibration mounts equidistant from the Centre of gravity of the suspended equipment. Following Fig.11 shows the position of the Cog of a machine and the mounts with the position A and B in respect to the centre of gravity. Achieving an equal distance between A and B will help to achieve this goal.

Fig. 11: Equidistant mounts to the center of gravity is achieved when a=b.

Mounts installed at the height of the Centre of gravity provide more stable suspensions and avoid excessive movement of the suspended element, particularly in mobile applications.

If the vibration mounts are positioned at the points where less vibration amplitude is found (nodes), they will be subjected to the lowest vibratory force, this leads to optimized vibration isolation.

Fig. 12: Nodal points expressed as red rectangles on a diesel engine installation.

1. 2. Using anti vibration mounts with high damping (energetic dissipation) devices.

When concrete mass/blocks cannot be installed, the alternative can be to use mounts that incorporate a damping system. The use of additional damping can allow stable solutions. The energetic dissipation often achieved by the transfer of a viscous fluid from one cavity to another as shown on the below video.

Fig. 13: Explanatory video of the process of energetic dissipation using the Vibrabsorber+Sylomer Antiseismic Visco mounts under a dynamic test bench.

AMC-MECANOCAUCHO produces a wide variety of anti vibration mounts that use hydraulic systems to provide additional damping. These vibration isolators can use spring+Sylomer or rubber, maximum load capacities range from 20Kg (44lbs) to 50 tons (112.000Lbs) of load. Their damping system can be adjusted by the viscosity of the fluid and by the orifices where the liquid must flow through. For the case of the Vibrabsorber+Sylomer Visco, this mount incorporates a “MAX-MED-MIN” adjustable damping system, that regulates the passage of flow of viscous fluid. More information can be found by clicking here.

Fig. 14: Vibrabsorber+Sylomer antiseismic Visco.

Fig. 14: Vibrabsorber+Sylomer Visco incorporates an adjustable damping device and a restricted displacement device as shown on this link.

Fig. 15: AMC-MECANOCAUCHO Hydraulic mounts.

Fig. 16: AMC-MECANOCAUCHO Hydraulic cones.

In the below video a stamping press is installed without a concrete inertia block. The video on the left shows the press being installed without a damping system where as the video on the right shows the Vibrabsorber+Sylomer antiseismic visco. The energetic dissipation produced inside the fluid chamber, provides a more stable and safer environment for the worker.

Fig. 17: AMC-MECANOCAUCHO ANTISEISMIC VIBRABSORBER+SYLOMER VISCO SPRING MOUNTS are anti vibration mounts that incorporate an energy dissipation device. This device provides damping to eccentric machinery that requires quick stabilization for proper functioning.

Fig 18 and 19 below shows how hydraulic mounts can be used in 3 cylinder engines. Optimum results are achieved when the mounts are equidistant to the centre of gravity and at the height of the Crankshaft (or centre of gravity).

Fig. 18: Hydraulic mount medium from AMC-MECANOCAUCHO supporting a 3 cyl engine.

Fig. 19: Hydraulic mount medium from AMC-MECANOCAUCHO supporting a 3 cyl engine.

1. 3. Using anti vibration mounts with restricted displacement due to integral snubbers.

Anti vibration mounts can be equipped with different elastic steps. A linear elastical range of load provides the stiffness required for the vibration isolation of the machinery. In the event a high traction or compression forces occurs, the mounts architecture provides a secondary stiffness step. Normally this is achieved with metal parts that enter in contact with a section of the rubber that acts as a snubber/buffer.

Fig. 20: Pattern of elasticity of an AMC-MECANOCAUCHO CB mount.

Fig. 21: Cross section of a CB 76 mount, where the internal architecture is shown.

The progressive stiffness section is achieved when rubber is bulked filling the hollow areas of the anti vibration mount. Figure 22 shows the FEM process of loading of an AMC-MECANOCAUCHO CB mount.

Fig. 22: Loading process of a AMC-MECANOCAUCHO CB mount.

1. 4. Using stabilizers on the highest amplitude points of the suspended element.

Installing stabilizers on the highest amplitude points can be used, nevertheless special care must be taken so this point does not transmit excessive vibration to the adjacent supporting members (Frame). The part should only work when the machine is exposed to shocks, whilst under normal operation this point should have very little contribution, i.e have the lowest stiffness possible. Fig 23 shows a mobile genset installed with a CB mount acting as a multiaxial buffer, on the point where highest mobility is registered.

Fig. 23: Extreme mobility genset using CB mounts as multiaxial stabilizers

AMC MECANOCAUCHO manufactures anti vibration mounts and has a team of application engineers to help your installation needs so do not hesitate to contact our technical department if you require help on this topic.

The correct selection of anti vibration mounts is key for achieving good vibration isolation values on HVAC equipment. However, if the installation of the vibration isolators is wrong, the expected isolation results may not be reached. In this article we will describe good practices for installation, with examples of what has to be done and what has to be avoided to ensure we don’t face expensive surprises.

Each work is different and has inherent complexities, in fact there are many variables that can affect the vibration transmissibility. For example the materials used in the structure (wood or concrete), the position of where the machinery has to be installed (ground level or rooftop) and also the type of room that is adjacent to the machine room (sensible or not sensible).

Even if it is hard to define all problems that may happen we will show here some common ones and we will describe how they can be avoided.

1.- SUBFRAME STIFFNESS WHEN USING SPRING MOUNTS

The air handling unit manufacturer must prove that its frame is sufficiently rigid to be supported on specific supports. We recommend in all cases to reinforce it by creating a frame in IPN 120 beams fixed at least over the entire periphery. The Spring mounts will first be placed at regular intervals under the equipment frame, the deflection of the spring mounts must then be checked to ensure the installation is flat and level. If the deflection of the vibration isolators is not even across all mounts then the position of them must be adjusted, this can be done by increasing the density of the anti vibration mounts in the most deflected areas.

Fig. 2: Representation of how an additional IPN beam can be added under the frame of an HVAC equipment.

2.- STIFFNESS OF THE BRACKETS

The stiffness of the brackets must be at least 10 times more rigid than the antivibration mounts. If the brackets are softer, their stiffness may affect the vibration isolation of the System and may damage the anti vibration mount.

Fig. 3: Installation of DRD 130 mounts on an HVAC equipment, where the brackets used are weak than the rubber itself.

3.- WIDTH OF THE METAL BASE ON ROOFTOPS

The metal bases used above and below the anti vibration mounts must be correctly dimensioned to ensure adequate support. The complete contact area of the metal interfaces must be supported, this avoids the possibility for uneven loading and damage to the vibration isolators as a result.

Fig. 4: Installation of DRD 130 mounts underneath HVAC equipment, where the metal bases used are thinner than the base of the baseplate of the anti vibration mount. The fixation deforms and damages the anti vibration mount.

4.- WIDTH OF THE BRACKETS WHEN USING TSR ANTI VIBRATION MOUNTS

It is important to recall that the load must be distributed over the entire surface of the elastomer pads. This is crucial to ensure that the elastic properties are achieved, if the contact area is too small it will be necessary to provide a steel distribution plate of sufficient thickness, so that it does not deform when loaded.

Fig. 5: Representation of an HVAC equipment with correctly dimensioned bases for TSR Anti vibration mounts

5.- INSTALLATION OF PIPING FOR HIGH VIBRATION AMPLITUDES

When experiencing high levels of vibration for piping installations, the amplitude can be reduced by adding damping to the system. A good way to achieve this is by adding an inertia base that is fixed on to anti vibration mounts as shown in the image below. This way the vibration energy is decreased and the suspended element is damped. Using Sylomer® bands on the perimeter of the piping and on the base of the anti vibration mounts will help to diminish the transmissibility of high frequecies.

Fig. 6: Representation of a high amplitude vibration pipe on an inertia base with Vibrabsorber+Sylomer® vibration isolators.

6.- INSTALLATION OF HVAC EQUIPMENT WITH A HIGH POSITION OF CENTRE OF GRAVITY

Machines that have the Centre of gravity located at a high position tend to be unstable. The first reaction by the design engineer may be to change the anti vibration mounts and replace them with ones that have a higher stiffness. Althought this may resolve the problem of the stability, the increased stiffness will in turn increase the natural frequency of the system and lead to a decrease in vibration isolation.

A simple way to resolve this problem is to use stabilisers. Stabilisers can be installed at points where the highest amplitude is achieved, however special care must be taken so this point does not transmit excessive vibration to the adjacent supporting members (Frame). The part should only work only when the machine is exposed to shocks adding the lowest stiffness as possible when the machine is working.

Fig. 7: Shows a HVAC installation with a CB anti vibration mount acting as a multiaxial buffer.

Another possibility is to use spring mounts with integrated buffers. The Vibrabsorber+Sylomer® antiseismic anti mounts have rubber based buffers on the side walls that can provide a silent rubber to metal contact when exposed to lateral movements of the HVAC equipment. If additional stability is required, the VISCO version of these mounts can provide additional stability through hydraulic damping.

Fig. 8: Video of the Vibrabsorber+Sylomer® antiseismic working on an HVAC installation.

Fig. 9: Cross section of a Vibrabsorber+Sylomer® antiseismic version. Click here to see videos of how these vibration isolators work.

Fig. 10: Figure of a tall machine with integrated buffers on the Springmounts. 2 VSH Vibrabsorber+Sylomer® antiseismic mounts are installed on a low position.

These anti seismic mounts are easy to install, the below video shows the simple process.

Fig. 11: Video of installation of Vibrabsorber+Sylomer® anti seismic mounts.

7.- SUSPENDING HVAC MACHINERY WITH ACOUSTIC HANGERS

Fig. 12: Elastically suspended HVAC equipment with SRS+Sylomer ® acoustic hangers

It is important to maintain the concentricity of the studs to avoid any metal to metal contact, and a resulting acoustic bridge. Although the SRS+SYLOMER® acoustic hanger from Mecanocaucho incorporates a rubber cup to avoid a metal to metal contact, it is preferable that the stud has no contact with the rubber rim.

Fig. 13: Correct and incorrect installation representation of SRS+Sylomer ® acoustic hangers

If you are interested in getting further information on this topic, more information can be found in CORRECT INSTALLATION OF SPRING HANGERS TO OPTIMIZE ACOUSTIC INSULATION RESULTS.

8. ELASTIC SUSPENSION OF PUMPS WITH ANTI VIBRATION MOUNTS

For pumps, since the dynamic load is often greater than the static load, during stops and starts, the suspended assembly tends to move on these vibration isolators if it is not attached to an inertia block. Consequently, to avoid significant movements during transient phases and therefore to avoid mechanical failures, it is necessary to implement inertial masses under the pumps, this ensures the dynamic loads are relatively low compared to the static.

For further information on this topic, you can click on the following article. “Vibration isolation of machinery, Controlling motion”.

AMC MECANOCAUCHO manufactures anti vibration mounts and has a team of application engineers to help your installation needs so do not hesitate to contact our technical department if you require help on this topic.

The purpose of an anti-vibration mount is to attenuate vibrations. The design of the vibration isolator is key to achieve the targeted stiffness and load capacity.

This article aims to answer some of the recurrent questions about the design of anti-vibration mounts.

How do you know the max rubber to metal bond Stress?

An anti-vibration mount is expected to last for many years, environmental conditions such as exposure to direct sunlight, oils or other deteriorating agents can cause the bond to weaken prematurely. In absence of these parameters certain maximum allowable bond stresses are used and should not be exceeded.

Compression 750 psi

Tension 150 psi

Shear 150 psi

A vibration isolator should have no region of high localized stress, particularly at the interfaces of the metal and rubber. Sharp changes in profile can cause high stress points, this might be caused by boltheads, boltholes, or indentations. Below are some examples:

For obvious reasons AMC MECANOCAUCHO prefers designs of anti-vibration mounts that incorporate a flat surface for bonding, as they provide lower regions of high localised stress.

How does the temperature affect the creeping of the anti-vibration mount?

At 60º C (140ºF) the rubber creep is from two to nine times greater than at 25ºC (80ºF) depending on the compound.

How does the shape of the stiffness curve change according the type of loading on the rubber?

Anti-vibration mounts use rubber bonded to the metal to achieve an elasticity. However, depending on the type of loading the mounts receive they can exhibit different stiffness values.

	TYPE OF LOADING	LOAD-DEFLECTION (L/D) CHARACTERISTICS
(A) Compression
(B) Shear
(C) Torsion
(D) Tension
(E) Buckling

Compression Loading

The word compression is used to indicate a reduction in the dimension (thickness) of an elastomeric element in the line of the externally applied force. The stiffness characteristic of elastomers stressed in compression exhibit a nonlinearity (hardening) which becomes especially pronounced for strains above 30 percent. Compression loading is frequently employed to provide a low initial stiffness for vibration isolation and a relatively high final stiffness to limit the dynamic deflection under shock excitations. Because of the nonlinear hardening characteristics of compression loading, it is the least effective type of loading for energy storage and therefore is not recommended where the attenuation of force or acceleration transmission is the primary concern. (The energy stored by any spring is the area under the load-deflection curve.)

Shear Loading

Shear loading, illustrated in the above figure, refers to the force applied to an elastomeric element so as to slide adjacent parts in opposite directions. An almost linear spring constant up to about 200 percent shear strain is characteristic of elastomer stress in shear. Because of this linear spring constant, shear loading is the preferred type of loading for vibration isolators because it provides a constant frequency response for both small and large dynamic shear strains in a simple spring­mass system. Shear loading is also useful for shock isolators where attenuating force or acceleration transmission is important, because of its more efficient energy storage capacity when compared to compression loading.

Tension Loading

Tension loading refers to an increase in the dimension (thickness) of an elastomeric element in the line of the externally applied force. Elastomers stressed in tension exhibit a nonlinear (softening) spring constant. For a given deflection, tension loading stores energy more efficiently than either shear or compression loading. Because of this, tension loading has been occasionally used for shock isolation systems. However, in general, tension loading is not recommended because of the resulting loads on the elastomer-to-metal bond, which may cause premature failure of the material.

Buckling Loading

Buckling loading, occurs when the externally applied load causes an elastomeric element to wrap or bend perpendicular to the applied load. Buckling stiffness characteristics may be used to derive the benefits of both softening stiffness characteristics (for the initial part of the load­deflection curve) and hardening characteristics (for the later part of the load­deflection curve). The buckling mode thus provides high energy-storage capacity and is useful for shock isolators where force or acceleration transmission is important and where snubbing (i.e., motion limiting) is required under excessively high transient dynamic loads. This type of stiffness characteristic is exhibited by certain elastomeric cushioning foam materials and by specially designed elastomeric isolators. However, it is important to note that even simple compressive elements will buckle when the slenderness ratio (the unloaded length/width ratio) exceeds 1.6.

Combinations of the types of loading described above are commonly used, which result in combined load-deflection characteristics. Consider, for example a compression type isolator which is installed at an angle instead of in the usual vertical position. Under these conditions, it acts as a compression-shear type of isolator when loaded in the vertical downward direction. When loaded in the vertical upward direction, it acts as a shear-tension combination type of isolator.

How does the rubber profile shape affect the stiffness of the anti-vibration mount?

The moulded shape of the rubber section of the vibration isolator has a great impact on the load deflection curve of the mount. Below are some examples of how the shape and design of the mount affects the stiffness of the anti-vibration mount.

Shape	Force-travel characteristic curve	Notes
Symmetrical angled spring In top mount/wedge mount		Frequently used on rubber-metal mounts. Depending on the spring angle: degressive under compression to progressive with a steep angle. In the x direction, hard with a flat angle to soft with a steep angle. The spring rate in the y direction is always softest.
Conical spring (section)		Frequently used on hydromounts. Behavior as for cup springs: linear to degressive, progressive at transition to cylindrical hollow spring. Radial spring rate variable, depending on core height and angle.
Cylindrical hollow spring (section)		Frequently used as inner spring on hydromounts with intermediate ring. Degressive under tension, progressive under compression. Very soft and degressive in the radial direction.
Rectangular spring		Frequently installed with bonding on one side as a stop or torque support buffer. Degressive under tension. Progressive under compression. Very soft and degressive in the transverse direction.

Shape	Force-travel characteristic curve	Notes
Cylindrical (section)		A standard article, bonded on both sides. Sometimes installed with one side used as a stop or torque support buffer. Degressive under tension, progressive under compression. Very soft and degressive in the transverse direction.
Bushing (section)		Rubber between two tubes, standard catalog article. On engine mounts, mainly used as the small eye of pendulum mount. For good durability, the rubber must be radially preloaded (calibrated) The bush is considerably softer in the axial direction than in the radial direction.
Loop (section)		Loops are special shapes used to close the working chambers of hydrobushings and box type mounts. They are also often used for setting the expansion spring rate.

Should you be interested in this topic do not hesitate to contact our applications engineers. They will be able to help and provide input. Contact form AMC-MECANOCAUCHO® Applications engineers.

The correct position of the mounts will affect the vibration modes and reduce the natural frequencies of the suspended element, therefore increasing the vibration isolation.

Key factors to consider are:

• 1. All the mounts should withstand a similar static load. In the longitudinal direction, the mounts should be installed symmetrically around the total COG.

• 2. To achieve the lowest natural frequencies possible and to improve dynamic load distribution, the mounts should be installed symmetrically around the total COG in the transverse direction.

• 3. To minimize the dynamic forces transmitted by the mounts, it is recommended to install the mounts on the imaginary Neutral Torque Axis (referred to as the NTA), this connects the front & rear mounts with the total centre of gravity.

• 4. If the mounts are soft (to minimize the transmitted forces) and they are installed on the NTA, the dynamic forces can be effectively isolated.

It is recommended to install the Hydraulic Mounts in the upright vertical position. If they are installed in an inclined position, the weight of the suspended equipment would create a static radial load. This could result in the internal piston directly contacting on the internal wall of the hydraulic chamber, this would dramatically increase the mounts stiffness and therefore reduce the vibration isolation.

Another effect of an inclined installation is that it can create an unwanted hammering effect, due to the piston hitting the internal wall of the hydraulic chamber.

Due to this, AMC recommends installing Hydraulic Mounts in the upright vertical position, so the weight of the suspended system acts in the axial direction of the mounts.

It is important to keep the alignment between the anti-vibration mount and the fixation brackets. Fastening the mounts misaligned can result in the internal piston of the Hydraulic Mounts touching the internal wall of the hydraulic chamber, dramatically increasing the mounts stiffness and therefore reducing the vibration isolation. It can also produce a hammering effect.

Furthermore any misalignment in the installation is absorbed by the rubber element itself, this places additional unwanted stress on to it.

The slotted holes help to accommodate the position of the Hydraulic Mounts to keep the alignment correct.

Once aligned, the flange of the Hydraulic Mounts can be fastened:

During the fastening of the top screw, it is important to not twist the rubber. Twisting the rubber unnecessarily increases the stress on the rubber and can introduce damage to the bonding surfaces. This might lead to premature appearance of cracks or premature failure of the adhesion between the rubber and the metal parts.

To avoid the twisting of the rubber, there are several methods:

1. 1. Sometimes the friction between surfaces is enough to avoid twisting the rubber.

1. 2. Hold the top washer with a hook type wrench, using the slots of the top washer.

1. 3. Tighten the top screw using a pair of wrenches. While one wrench holds the bolt, the other can tighten the nut.

1. 4. The Hydraulic Mounts Large are provided with pin holes. Using them prevents the twisting of the rubber.

The Hydraulic Mounts can also be installed upside down, providing that they are still working in compression. However it is important to note that the damping fluid inside the hydraulic chamber will tend to go downward due to the gravity. Although this factor is not critical to the mounts performance, it might somehow reduce the damping level provided by the mount.

Do not hesitate to contact our application engineers for more information on the installation of Hydraulic Mounts.

INTRODUCTION

This article aims to inform people about the importance of the floor flatness and levelness values of a concrete slab, mostly known as FF and FL numbers.

The FF and FL numbers are calculated based on the standard ASTM E1155, the American Concrete Institute presents the acceptable range levels in the Guide for Concrete Floor and Slab Construction, ACI 302.1.

But what are F numbers?

F numbers are used to measure and improve the flatness and levelness of concrete floors.

• Floor Flatness (FF): FF numbers evaluate how flat the floor is on concrete slabs. It also controls the irregularities in the surface of the floors, including their bumps and undulations. F numbers go from zero upwards, so the higher the F number, the flatter the floor.

• Floor Levelness (FL): FL numbers evaluate elevation differences along a sample line at short intervals, either from the slope or from some specific plane on a surface. The higher the FL number, the more level the floor is.

When we talk about FF and FL numbers, two different sets of values can be provided: Specified Overall Values (SOV) as well as Minimum Local Values (MLV).

Specified Overall Values refers to the entire slab while Minimum Local Values refers to each section of slab. Minimum Local Value criteria will often be lower than Specified Overall Values allowing a margin of error during the placement of the concrete.

Classification of Flatness and Levelness numbers on concrete floors

Based on the standard ACI 117, random-traffic concrete floors are classified as follows:

Super flat floors require special skill and equipment to achieve those values and should only be used for the most critical of concrete floors.

Acceptable FF and FL Numbers

Many architects and builders are faced everyday with the situation of defining the flatness and levelness of the concrete slabs in different projects. But what values are considered acceptable?

According to the standard ACI 302.1 published by the American Concrete Institute, the following FF and FL values are acceptable.

Problems with floating slabs with low flatness values on the structural concrete floor

Non-flat concrete slabs could lead to very critical situations, below some cases are shown which can be found in different constructions.

Non-levelling slabs

CASE A

For non-levelling slabs with plywood systems, the supports that are at a higher-level will be receiving all of the load.

The supports at the lower level would be working only when the weight is applied to the wood floor which could lead to possible cracking on the floor.

CASE B

In case of having a concrete slab above the plywood, the supports at the lower level will support more load than the rest which can lead to internal stresses and strains on the isolated slab which can lead to cracking.

Levelling-slabs

CASE C

For levelling-slabs, the supports that are at a lower level lead to have a higher load than the supports on a higher level. Therefore during the process of elevating the concrete slab, it is necessary to remove part of the concrete in order to access to the supports at the lower level.

As in CASE B, this situation can lead to internal stresses and strains on the isolated slab, which can lead to cracking.

SOLUTION

For giving a solution for these critical situations, the installation of a high compressive strength levelling compound is carried out.

This is a solution at the time of installation. Nevertheless, it is better to take the time previous the start of the work to ensure that the structural floor meets all the requirements in order to assure a proper installation of the different isolations systems.

AMC MECANOCAUCHO® manufactures anti vibration mounts and has a team of application engineers willing to help with your installation needs, do not hesitate to contact our technical department if you require help on this topic.

INTRODUCTION

This article is applicable to all types of rubber mounts regardless of the brand or type of support. The elastomer degradation process occurs in all types of mounts in a similar way.

In this article the reasons and the degradation process of the elastomeric compound in rubber mounts are emphasized. By knowing how and why the elastic properties of a mount degrade over time, this article can help to determine which practices are correct to extend the life of support.

We will start first with the mechanics of elastomers. It does not matter the type of rubber, hardness or color since all elastomers are composed of polymeric chains. The term polymer comes from the Greek "poly" which means many and "mer" which means parts. Natural rubber, as well as other rubber compounds, is a polymer, a long-chain shaped molecule that contains repeating subunits.

Fig 1: Representation of a subunit of natural rubber

We can make use of the analogy of a tangled spaghetti plate representing a mass of polymer. The individual spaghettis represent a single polymer chain. The long length of the chain allows for tangles. With the discovery of vulcanization, a structure could be formed with sulfur bonds linking individual polymer chains in a three-dimensional network. Chains now have extensibility allowing for tension support and retraction upon release of tension. Our spaghetti analogy just changed from disconnected spaghetti holders to a fishnet structure like in vulcanized rubber.

Fig 2: Representation of sulfur cross-links between blue and green natural rubber strands

So in a simplistic way, we can say that elastomers are made up of a huge set of chains, as shown in the image below.

Vibrations can occur for various reasons or origins such as unbalance or misalignment of shafts in rotating elements, amplification due to resonance with the rotation frequency, etc. The vibrations create stress on the rubber, as you can see in the fatigue test video below.

This stress and strain creates a stress on the polymer chains. The stress in the system is shown in the following FEM image.

Polymer chains are subjected to many cycles of strain over the years. The polymer chains will break depending on the number of cycles.

Figure 3 shows a graph of load versus deflection of two rubber mounts, one new and the other used. As indicated above, the continuous stress caused by dynamic loads and vibrations in the elastomer, leads to the breaking of the polymer chains. Therefore, the rubber mount due to use and the passage of time shows fewer polymer chains to support the same load. This affects the deflection of the mount. As can be seen, over time, the deflection of the rubber mount goes from S1 to S2. This is because the remaining polymer chains have held out as long as they could, but have obviously become more deformed.

Fig 3: Load-Deflection curve of a new and a used support

From an insulation point of view, we must understand that the stiffness of flexible mounts plays a key role in insulation. But what is stiffness? Stiffness is the ratio of force to displacement. That is, the amount of force that is needed to cause a certain displacement or deflection. Stiffness is represented by a brown dotted line, showing the proportion or slope of the curve at a given force (F1). The stiffness 0 is the stiffness of a new support and the stiffness 1 is the stiffness of a used support. The stiffness of a used bracket is greater than that of a new bracket.

Rigidity plays an important role in the insulation of a suspended machine. Determine the resonant frequency of the system. The higher the stiffness of the suspension, the higher the natural frequency, so the lower the insulation.

Fig 4: Natural frequency formula where K is the stiffness of the mounts and M is the mass of the system.

So, in other words, even if the system moves more and shows more elasticity, you might think that the system is better insulated against vibrations, but the case is quite the opposite. The vibrations are higher than ever.

SUMMARY

The degradation of elastomers occurs in all rubber mounts, its degradation depends directly on the load cycles and their magnitude. The degradation comes from the loss of polymer chains. The lower the polymer chains that we have in the frame, the more elastic the system will be. The more elastic the bracket, the more movement the suspended element will show, as well as damaging other elements of the system and unwanted noise. This will cause increased stress on the mounts causing the remaining polymer chains to break, creating self-powered degradation.

In all suspended assemblies where anti-vibration mounts are present, with use and years of service the characteristics of the mounts can be affected and even damaged. This in turn has a negative effect on the vibration isolation performance and the correct operation of the system.

It is therefore important to know how to detect when the anti-vibration mounts of a machine or a suspended element require replacement. In the following article we show some recommendations and give advice about the need to replace an anti-vibration mount.

REPLACING ANTI-VIBRATION MOUNTS: SIGNS OF A WORN OR DAMAGED MOUNT

During the operation of a machine or suspended element, there are different signs that can appear when a support is worn or damaged. Below we list some of the symptoms that anti-vibration mounts can present and that will allow us to recognize if they need a replacement:

1. Increase of the vibration levels in the system

If the vibration levels of the system are higher than usual, this may be a sign that the anti-vibration mounts are worn and may need to be replaced.

2. Excessive movement of the suspended element

If a support is worn or damaged its mechanical properties may be affected, this therefore may also affect the dynamic behavior of the system, for example reducing the overall stability of the assembly. If a greater than usual movement is observed in the suspended assembly this would indicate that the anti-vibration mounts are damaged or worn.

3. Impact noises

A worn mount can often lead to knocks or bumps within its environment. This is due to the suspended assembly moving more than normal and making contact with other components. This can cause impact sounds that become quite noticeable.

4. Reduction of its initial height

With use and time, the internal polymeric chains of the rubber can become damaged due to repeat loading cycles, this results in fewer supporting chains which must carry the same load. Therefore, if it is observed that the installed height of the mount is lower than when it was initially installed, this is a sign that the piece may be worn. A good visual indication of this can be if the distance between the metallic elements is close and about to make unwanted contact.

5. Visual appearance of the support

If there are signs of significant corrosion, cracks or high permanent deformations, wear will be occurring on the rest of the support. Below we have made a visual overview of the different areas we need to focus on to assess whether or not the mounts should be replaced.

1. Loss of adhesion between bonding of metal to rubber

2. Presence of oil, diesel,… on the mounts

3. Excessive corrosion on metal parts

4. Visible cracks in the rubber section

5. Visible damages

6. Very low height on the mounts

6. Other factors to take into account

There are other factors that can also compromise the life of the mount, and therefore cause damage or premature wear on the mounts. Some of the most common are:

1. Incorrect installation of mounts.
2. Aging / hours of use.
3. Shocks or excessive dynamic loads that can damage the supports of the suspended assembly.
4. Incidents/accidents that have caused damage or moved the anti-vibration mounts of the suspended assembly.
5. Liquid leaks (oil, diesel,...) on the supports, contaminating the elastomer.

If you experience any of these signs or suspect that any of the above reasons may be relevant to your application, we recommend to check your mounts and consider replacing them.

AMC MECANOCAUCHO® manufactures anti vibration mounts and has a team of application engineers willing to help with your installation needs, do not hesitate to contact our technical department if you require help on this topic.

INTRODUCTION

Noise and vibration isolation is necessary throughout a wide range of applications. These can range from static applications (such as small compressors or refrigeration units) in which the anti-vibration mounts will only have to withstand the loads corresponding to the weight of the system itself, to the suspension of engines or cabins for off-road vehicles in which the anti-vibration mounts must withstand important dynamic loads

Due to this variety of applications several types of anti-vibration mounts are required, each with the aim of adapting to the needs of each case.

Anti-vibration mounts can be classified according to several characteristics (type of anti-vibration mount, union between the rubber and the metal elements, materials ...). This article aims to discuss two ways of classifying these elements, these are fail-safe anti-vibration mounts and non-fail-safe anti-vibration mounts.

NON FAILSAFE ANTI-VIBRATION MOUNT

This type of anti-vibration mount is one that does not maintain its integrity in the unwanted event of failure of the elastic element. The integrity of the mount depends on the adhesion between the rubber and the different metal parts of it.

Some examples of this classification of anti-vibration mount would be for example, cylindrical mounts, VD or DRD/DSD type mounts. Below we will analyze the adhesion zones on which the integrity of each of the mentioned anti-vibration mounts depends.

Analyzing the cylindrical anti-vibration mounts, its structure would consist of a rubber section adhered on both sides to two circular metal plates:

Analyzing the VD anti vibration mounts, its structure would consist of a rubber section adhered to the upper and lower metal components, on which the suspended element and the chassis will be joined:

Finally, considering the DRDs, its structure would consist of a rubber section adhered to the base at the bottom and a disc-nut at the top, this also adhered to the rubber section:

In the case of large dynamic loads and deflections, if the anti-vibration mount is subjected to these frequently and for long periods of time, it could be the case that this adhesion is compromised. In extreme cases separation from the rubber could occur, at which point the suspended element would no longer be secured in place.

Therefore, this type of mount is not recommended for applications with large dynamic requirements. Its field of applications usually extends to mostly static machines such as compressors, rotary pumps, air conditioning equipment, small groups of motor pumps or fans.

FAILSAFE ANTI-VIBRATION MOUNT

This type of anti-vibration mount has a fail-safe system that guarantees its integrity even if there is a failure in the elastic element, so the integrity does not depend on the adhesion, but on the mechanical resistance of the metal components.

Within this group of anti-vibration mounts would be included a large part of the catalog anti vibration mount of AMC Mecanocaucho®.

As an example we will review the bell type anti vibration mounts, such as the anti-vibration mounts of the BRB, BSB or marine anti-vibration mounts. These would have a structure that would consist, as in the previous case, of a rubber section adhered to the base. Unlike the previous case they also contain a central boss metal with a larger diameter at the bottom than the diameter of the central hole at the base.

In the event that the anti-vibration mount is installed in an application with large dynamic loads that cause the rubber element to fail, the suspended element would still be mechanically captive since the geometry of the metal components prevent it from coming apart.

Another example can be seen in the anti-vibration mounts that are installed with washers, such as cone type anti-vibration mounts or symmetrical anti-vibration mounts (such as CB or TF).

In these anti-vibration mounts the washers act as a fail-safe system, since they cannot move through the outer metal component of the anti-vibration mounts, so the suspended system would not be free due to failure of the elastic element.

In the case of symmetrical mounts, these are installed through a hole in the frame or in the bracket of the suspended element as can be seen below.

A similar type of anti-vibration mount would be the families of the SCB, SCH (and their reinforced versions) and the cabin mounts, which are also installed through a hole and by means of a washer at the top and bottom.

In the case of cone mounts, these are installed through a hole in the chassis and secured via the holes in the flange of the outer metal (either in 2 or in 4 points, depending on the type of cone). After that, the washers are installed at each of the two ends as can be seen below.

This type of mount is typically recommended for applications with dynamic requirements. Its field of application is more diverse, it can be used to isolate almost all types of vehicle elements (engines, cabins, transmissions ... ) as well as generator sets or compressors, both mobile and static.

Below is a summary of the main fail-safe products available within the AMC Mecanocaucho range of anti-vibration mounts.

BRB
BSB
MD
Marine mounts
Hydraulic mounts
Hydraulic cones
Cones

Tf Mounts
CB Mounts
Cabin Mounts
SCB/SCBR Mounts
SCH/SCHR Mounts
Bushings
NP Mounts

CONCLUSIONS

As discussed, each of the two types of anti-vibration mount is designed for a specific field of application. Fail-safe anti-vibration mounts the most recommended for applications with high dynamic demands while the non-fail safe anti-vibration mounts would be considered for applications that are mainly static.

AMC Mecanocaucho® has developed a calculation tool to assist with the selection of anti vibration mounts. This calculation tool is called Vibration Isolator Pro.

This tool has been developed to perform anti-vibration calculations in a simple and effective way using basic input data such as the equipment mass and number of mounts.

It is accessible as a web version on Mecanocaucho.com and also via our mobile app ‘Vibration Isolator Pro’ which is available for Android and IOS environments.

If you are interested in this matter, please do not hesitate to contact our application engineers. They will be able to help you and offer you their point of view.

Contact form for AMC-MECANOCAUCHO application engineers®.

Elastomeric isolators may be designed in both bonded and semi bonded configurations. For the bonded isolator, metal elements are bonded to the elastomer on all load-carrying surfaces (Fig 1). For a semi bonded or unbonded isolator, the elastomeric load-bearing surface rests directly on the supporting structure (Fig. 2).

Bonded parts are typically more expensive due to the special chemical preparation required to achieve a bond with strength in excess of the elastomer itself. A bonded part is generally the preferred option since they can allow a higher level of stress for a given deflection, with this higher stress they provide higher spring constants and higher elastic energy storage capacity.

Fig. 1		Hydraulic mounts, Hydraulic cone mounts ,Cone mounts, Cone with fixation flange, CB, TF, cabin mounts, Marine type in V, VD mounts, AT anti vibration mounts, V shaped anti vibration mounts, DSD, DRD ,Bushings, Sandwich mounts, AN mounts, NP mounts, SN anti vibration mounts
Fig, 2		SCH, SCB mounts, TFS mounts, SPS mounts

Bonded isolators can be designed to provide the correct load distribution in shear, compression, tension, or combination loading. More information on this topic can be found through this link. A more uniform stress distribution in the elastomer is obtained by bonding inserts on all the load-bearing elastomer surfaces, these inserts reduce the unit stress by distributing it more uniformly throughout the volume of the elastomer. In contrast, semi bonded parts usually fail to distribute the load uniformly, resulting in local areas of stress concentration in the elastomer body which can shorten the life of the isolator.

A significant difference between bonded and semi bonded elastomeric isolators relates to how elastomers behave under load. When an elastomer pad is compressed under load its volume remains constant, only its shape is changed. The rubber "bulges" under load. When this ability to bulge is controlled the load-deflection characteristics of the isolator are also controlled. In a bonded isolator, the load-carrying surfaces have a fixed degree of bulge because the elastomer cannot move along the bond line, and so it remains in a fixed position regardless of the load or environmental conditions.

In a semi bonded isolator this is not the case. The ability of the elastomer to bulge depends to a considerable degree the amount of friction present at the interface of the rubber and its supporting structure. When all surfaces are clean and dry, the difference between the ability of a bonded and a semi bonded isolator to bulge is negligible. However, if oil or sand can work its way into the elastomer-to-metal interface of the semi bonded isolator, the ability of the elastomer to bulge is greatly affected. Consequently its original load­deflection characteristics no longer exist. The isolator can exhibit load-deflection characteristics that are 50 percent less than when it was new, in many cases, this can cause the isolator to malfunction.

Thus, where consistent Load-deflection characteristics are required for the life of the equipment, bonded isolators should be used. Although the initial cost of a semi bonded isolators is lower, in many applications the cost of extra machining of the support structure and the reduced service life may well make semi bonded isolators a poor selection.

Status of a semi-bonded vibration isolator similar to our SCH mounts, on an application where a high ratio of Dynamic Load / Static load was present.

According to the technical parameters of your application and the requested budget or natural frequency requirement, several types of antivibration mounts can be selected.

Industrial machines can be installed on platforms where several elastic steps are present. Wheels or frames depending on their construction have their own elasticity. This elasticity will affect the natural frequencies of the system. In theory, in order to have precise vibration isolation calculations we should take all the elastic steps in consideration.

Since this level of input data is very hard to achieve, simplified mathematical models can be used to provide us with a good guidance value. Calculations that take into consideration the suspended element as a solid (rigid body) and take into account the 6 degrees of freedom are AMC-MECANOCAUCHO®'s preference. This kind of vibration isolation calculation will be able to provide us the 6 natural frequencies of the system, knowing the input vibration we can then understand the expected vibration isolation performance of the suspended system.

In the image below we show an example of this type of calculation.

Our technical team will review this information to make the most appropriate product selection, taking into consideration the following key points:

1. Load capacity

Depending on the geometry of the support, and the hardness of the rubber we can have different load capacities for each anti vibration mount. Therefore, the first stage of the selection would be to narrow the options to the products with the required load capacities. For this, we must know the weight per support.

As a standard default range, and to ensure a good durability throughout the product life, AMC Mecanocaucho® does not recommend loading the anti-vibration mounts over 85% of their load capacity.

2. Type of application

Industrial machinery has different utilities and therefore a different type of work.

Generally, the different applications can be divided into two large families, static applications, and dynamic applications. It is advisable to keep this in mind when reviewing the different families of anti-vibration mounts.

• Static applications: these are cases in which the equipment/object to be suspended does not move. For this reason, stability and safety against failure is an issue that is not as important as in dynamic applications when selecting the appropriate support. In these cases, we could go with soft rubber harnesses, and load the mounts to 70-85% of their load capacity.

  The frequency of the input vibration can differ and be variable for each type of machine. Therefore, the natural frequency of the suspended element is studied and tuned in order to achieve good stability and also optimum vibration isolation levels. For this purpose, AMC-MECANOCAUCHO applications engineers will be able to help and give you recommendations.

• Dynamic applications: these are applications that present movements, dynamic loads, shocks, etc. In these cases, we need to select fail-safe supports (integrated security) and analyze the stability that we obtain with the different solutions. The hardness of the rubber and the damping coefficient offered by each type of support is of great importance. As we can have dynamic loads, it is necessary not to load the supports excessively, in order to have a load margin for the most demanding moments.

These are the load ranges recommended by AMC for each type of application:

Some machines are exposed to transient shocks, such as inputs from the terrain they are driving on (speedbumps, potholes etc.) In these kinds of cases the frequency is generally low, therefore low stiffness anti vibration mounts are preferred. This property allows the mount to reach low natural frequencies of the system and reduce the accelerations reaching the machine.

Low natural frequency is achieved through low stiffness anti vibration mounts, this is good for vibration isolation however soft anti vibration mounts can lead to unstable suspended elements. In order to add stability to the system anti vibration mountings with damping systems can be introduced, this allows the suspended element to stabilize faster as shown in the graphic below.

Anti vibration mountings such as AMC-MECANOCAUCHO® Hydraulic mounts and hydraulic cone mounts have this damping feature.

The image below shows the section of the hydraulic mount and the speed of the liquid transfer from chamber to chamber in colors. The energy dissipation is done through the liquid transfer. These products can be tuned to meet the required stiffness and damping for each application. AMC-MECANOCAUCHO® applications engineers can calculate and select the optimum properties of the anti vibration mount for your application.

3. Natural frequencies of the system

Another point to analyze are the natural frequencies obtained. Depending on the excitation frequency that is produced in the application, the natural frequencies that are obtained during the calculation will indicate the level of expected vibration isolation.

The further away the natural frequencies are from the excitation frequency, the greater the isolation level will be.

If we take the highest natural frequency mode obtained and multiply it by √2 we will obtain the frequency at which we will start to have vibration isolation.

If a low natural frequency is needed, we will need to select softer solutions (lower stiffness ‘’k’’), maintaining the necessary load capacity.

Therefore, depending on the target frequency, one type of support will be more appropriate than the other.

• Rubber-metal and Sylomer® solutions:

With these solutions the lowest natural frequencies obtained are around 8-10Hz. For this it is recommended to use the softest rubber compounds (40-50Sh) and lower Sylomer® densities.

If the application needs to have lower frequencies than 8Hz, we will need surely the use of supports that allow larger displacements (Spring mounts).

• Vibrabsorber+Sylomer® Spring mounts



These supports allow a greater displacement than metal-rubber solutions, allowing to obtain lower natural frequencies of between 3-6Hz. Being solutions with low stiffness, their use is recommended for static applications. If stability is also needed, it is recommended to use anti-seismic spring solutions.

4. Position of the mounts

The position of the anti vibration mountings determines the vibration modes of the suspended element. An even load distribution of all the anti vibration mountings is advisable. One easy way of obtaining this is by installing the anti vibration mounts equidistant to the COG (center of gravity).

Anti vibration mounts at the COG level provide more stable solutions and avoid excessive movement of the suspended elements, particularly on machines with high eccentricity. Since this is not possible in most of the cases, anti vibration mounts at different height levels crossing the center of gravity can be of great help for stability and longevity purposes.




Nevertheless even if this feature cannot be achieved, AMC-MECANOCAUCHO® applications engineers will be able to study the limitations of the application and propose positions where the best vibration isolation and stability can be achieved. Contact form AMC-MECANOCAUCHO® Applications engineers.

5. Temperature

In cases where the surrounding temperature is high, the limitations of the elastic element must be considered. The dynamic forces can also produce internal heat within the mount due to the friction. For an application which exceeds 60ºC a correct selection on the rubber compound must be done. AMC-MECANOCAUCHO® applications engineers can calculate and test in the laboratory different anti vibration mounts in order to reproduce such conditions and verify if the resistance of the anti vibration mount is acceptable.

6. Structural limitations of frame

The issue of vehicle interior noise is becoming increasingly important as secondary characteristics such as vibration and sound levels are replacing primary ones such as reliability in vehicle purchasing decisions. Interior noise can come from many different sources, but a common one is booming noise. This phenomena can be generally described as a low frequency (less than 200 Hz) acoustic resonance that is driven by the structure. Structural inputs usually come from either the power train or structural response from road inputs.

In these cases, anti vibration mounts can mask the problem but they will not be able to resolve the problem as the origin of it is structural. A correctly selected anti vibration mount will be able to attenuate the vibration arriving to the vehicle cabin, reducing the boom effect. Rubber compound with low dynamic stiffening properties are especially interesting for these cases. For this purpose AMC-MECANOCAUCHO applications engineers will be able to help and give you advice.

7. Vibration measurements

The previous considerations have taken into account theoretical aspects of the cabin. Empirical results on vibration isolation on cabs can be only understood by making physical vibration measurements. Understanding this data and contrasting it against the theoretical calculations can allow us to progress and find better solutions for our customers.

AMC-MECANOCAUCHO® provides a full service of engineering and vibration measurements for all types of applications. Should you be interested on this topic do not hesitate to contact our applications engineers.

For cases in which we have a lack of information to perform a 6 DOF calculation, a more simplified selection of supports can be achieved.

For cases in which the input data described at the beginning of this article is not available, and you want to make a pre-selection of the supports, please be noted that AMC Mecanocaucho® has developed a new online calculation tool to assist with this selection. This calculation tool is called VIBRATION ISOLATOR PRO WEB.

As the input data is limited, it is recommended to use this tool to get a general idea of what type of support could be used in a certain application. It is always advisable to ask AMC-MECANOCAUCHO applications engineers and get their approval according to the pre-selection carried out.

The Vibration Isolator Pro has been developed to perform anti-vibration calculations in a simple and effective way using basic input data such as the equipment mass and number of mounts. It is accessible as a web version on Mecanocaucho.com and also via our mobile app ‘Vibration Isolator Pro’ which is available for Android and IOS environments.

From our homepage https://www.mecanocaucho.com/en/ you can navigate to the Vibration Isolator Pro Web application. This selection tool will require the input of basic information about the application, while the resultant output will be the most suitable choice of anti-vibration supports from the AMC product range.

In case you have any questions or need clarifications, do not hesitate to contact the AMC MECANOCAUCHO® technical team.

INTRODUCTION

As the drive for greener technology is increasing so is the use of Lithium-ion batteries as the main energy storage device, applications such as modern electric vehicles are becoming more common, in these installations important shocks and vibrations exist.

As the lithium-ion battery market grows, so must our understanding of the effect of mechanical vibrations and shocks on the electrical performance and mechanical properties of such batteries. Recent studies investigated the effect of vibrations on the degradation and fatigue of battery cell materials as well as the effect of vibrations on the battery pack structure. The results of these studies show that mechanical degradation produced by vibration decreases the longevity of Lithium batteries.

Another important requirement which must be considered are the forces which are transferred to the battery pack during shock conditions. It is crucial that excessive forces do not reach the battery cells and result in cracks occurring.

STANDARDS FOR BATTERY INSTALLATIONS

Due to this fact and in order avoid the premature wear of these vital and expensive components. Battery manufacturers are requiring end users to comply with several norms where limits are set for vibration speed, acceleration and displacement.

Examples of these norms are R100r2 ,UN38.3, IEC 62133, IEC 62619 or UL 1642 to mention some.

The R100r2 is specifically for vehicles that have an electric drivetrain. This norm requires a sign off test in which a vibration sweep from 7Hz to 50Hz is carried out every 15minutes. This cycle is repeated 12 times totalling 3 hours.

The norm UN 38.3 relates more to the safety during transportation of the Lithium batteries. The vibration is a sinusoidal waveform with a logarithmic sweep between 7 to 200Hz and back to 7 Hz in 15 minutes, the wavelength used is 0.8mm (peak to peak amplitude 1.6mm). This cycle is repeated during 12 times during a total of 3 hours, three mutually perpendicular mounting positions of the cell must be analysed. This norm also requires a test for shocks where a half-sine shock of peak acceleration of 15 g during 6 milliseconds is applied. For larger cells 50g’s during 11 milliseconds is applied. Each battery cell must be subjected to three shocks in the positive direction followed by three shocks in the negative direction of the three mutually perpendicular mounting positions, for a total of 18 shocks.

AMC Solution

Taking in account the multiple axis of shock and vibration required, AMC-MECANOCAUCHO engineers developed a mount that can work in multiple directions having an integrated end stroke snubber for extreme load displacement containment.

Below is an image of the CB mounts from AMC-MECANOCAUCHO®

The below image shows the typical installation of a lithium battery pack.

Detail picture in section of the CB mount installed.

In order to make the selection of the correct CB mount, the total load, COG and position of mounts has to be taken in consideration.A 6 degree of freedom vibration calculation can allow us to know the natural frequencies of the system and have a prediction of the isolation level that will be key to know if the above norms can be passed.

AMC-MECANOCAUCHO application engineers can perform such calculations and help engineering offices to select the correct solution.

Articles of reference:

Effect of dynamic loads and vibrations on lithium-ion batteries - Xia Hua, Alan Thomas, 2021 (sagepub.com)

Effects of vibrations and shocks on lithium-ion cells - ScienceDirect

INTRODUCTION

The elevator area in the loading zone is one of the most problematic areas of a supermarket in terms of noise transmission. If it is not elastically disengaged correctly, the impact of the load is transmitted to the entire structure to which the elevator is attached and to the hydraulic systems as well. This can have a negative impact on the entire supermarket environment. Noise is a pollutant that can cause damage and undesirable effects of an auditory nature. A similar situation occurs with structural vibrations, which can cause damage, injury or discomfort-related effects due to whole-body vibration exposure. In recent years, it has been documented that musculoskeletal injuries, specifically lower and middle back pain, in the elevator operating area are closely related.

That is why AMC MECANOCAUCHO® sees the need to offer different solutions with vibration specialists for this type of application. A good solution is to use Sylomer to elastically decouple the supermarket elevator. Since these machines have different parts that are in contact with the surrounding structure, solutions for each of them are shown below.

SOLUTION FOR THE BASE

The best and simplest solution for the base plate of the elevator is its suspension on Sylomer.

To know the appropriate density, it is necessary to know the weight to be supported and the dimensions of the base plate.

In addition, it is crucial to avoid acoustic bridges. For this, one of the options is to place CB supports, secured with a central bolt, as shown in the images below.

	A.Torque regulator bushing B.Bolt or threaded rod C.Base D.Sylomer® pad E.Top metal plate F.Support CB G.Washer CB H.Nut

GUIDE SOLUTION

On the other hand, another of the elements that can transmit vibrations can be the guides. To elastically decouple the guides, Sylomer can also be used. AMC MECANOCAUCHO® recommends not compressing the Sylomer more than 1 mm for these cases.

Regarding the execution at the time of isolating, there are different options. The two main options recommended by AMC MECANOCAUCHO® are:

OPTION 1

In this option, plates are used on both sides of the supporting wall for fixing the guide. Due to this, it is not necessary to use large metal sheets, since putting medium or small sized ones right where the fixing points are is enough. The only drawback is the need to have access to the opposite side of the wall in order to make the joint. In addition, the number of connection points is usually less in this type of configuration. In the following image you can see an example of how this assembly is carried out schematically.

Option 1

In the images shown below you can see a real example of elastic fixing using this option.

WALL ON THE SIDE OF THE ELEVATOR

Sylomer

WALL ON THE OPPOSITE SIDE OF THE ELEVATOR

OPTION 2

In this second option, metallic plates are used only on one of the sides of the support wall when fixing the guide. Due to this, it is necessary to use large metal sheets, since the number of fixing points is greater, to prevent any risk of failure of any of the points anchored in the wall. Furthermore, in addition to the large sheet, it is necessary to use another layer of Sylomer and small metal plates to prevent acoustic bridges between the bolts and the wall.

Option2

In the image shown below you can see a real example of elastic fixing using this option.

PLATFORM OF THE ELEVATOR DOOR

Finally, it is necessary to elastically suspend the floor of the elevator door. To do this another layer of Sylomer is used underneath as shown in the images below.

These types of joints are secured with bolts or threaded rods which are made of materials that transmit vibrations and acoustic bridges are generated, an example is shown in the image on the right through which all vibration continues to be transmitted.

Consequently, any material introduced between the different components to be joined becomes ineffective and does not fulfil the objective of vibration isolation.

In all bolted joints the bolt is in contact with:

• The bottom base or structure to which you want to attach another element.
• The element that you want to attach to the base.

A. Path of the acoustic bridge B. Base C. Sylomer® pad D. Bolt E. Supporting point for union

To ensure that the insulating material fulfils its function, AMC MECANOCAUCHO® has the following isolator options:

• - Sylomer + CB
• - Sylomer + SCB
• - Sylomer + SCH
• - Sylomer + TF

With these solutions it is possible to make the bolted joint without the bolt or the threaded rod coming into contact with the element to be joined to the base structure of the joint.

In the image below an example is shown using Sylomer and a SCB support in the joint.

A. Nut B. Bolt or threaded rod C. Base D. Sylomer® pad E. Element to join F. Support SCB G. Washer

SYLOMER + CB

The first solution would be using Sylomer + CB. A single CB mount is used for this connection (typically they would be installed in pairs) since its function is not to support the expected loads of the system. The only function of the CB is to decouple the screw from the element to be joined. The load bearing is taken care of by the Sylomer layer.

In addition, the AMC MECANOCAUCHO® design includes a metal bushing that sits between the CB bracket and the base. The function of this bushing is to limit the tightening torque that is given to the bolted joint. Thanks to this, overloading the Sylomer is avoided very easily, simplifying and speeding up assembly.

In the image below you can see the elements that compose it.

A. Torque regulator bushing B. Bolt or threaded rod C. Base D. Sylomer® pad E. Element to join F. Support CB G. Washer CB H. Nut

SYLOMER + SCB

This solution comprises of Sylomer + SCB mounts. One SCB mount is used for this joint, its function is not to support the expected loads of the system. The only function of the SCB is to decouple the screw from the element to be joined. The load bearing is taken care of by the Sylomer layer.

In addition, the AMC MECANOCAUCHO® design includes a metal bushing that sits between the SCB bracket and the base. The function of this bushing is to limit the tightening torque that is given to the bolted joint. Thanks to this, overloading the Sylomer is avoided very easily, simplifying and speeding up assembly.

In the image below you can see the elements that compose it.

A. Torque regulator bushing B. Bolt or threaded rod C. Base D. Sylomer® pad E. Element to join F. Support SCB G. Washer SCB H. Nut

SYLOMER + SCH

This solution comprises of Sylomer + SCH. It is used without the rubber washer since its function is not to support the anticipated loads of the system. The only function of the SCH is to decouple the screw from the element to be joined. The load bearing is taken care of by the Sylomer layer.

In addition, the AMC MECANOCAUCHO® design includes a metal bushing that sits between the SCH bracket and the base. The function of this bushing is to limit the tightening torque that is given to the bolted joint. Thanks to this, overloading the Sylomer is avoided very easily, simplifying and speeding up assembly. In this case, a greater thickness of Sylomer is required than in the other cases due to the length of the support.

In the image below you can see the elements that compose it.

A. Torque regulator bushing B. Bolt or threaded rod C. Base D. 2 Sylomer® pads E. Element to join F. Support SCH G. Washer SCH H. Nut

SYLOMER + TF

This solution comprises of Sylomer + TF. A single TF mount is used for this connection (typically they would be installed in pairs) since its function is not to support the expected loads of the system. The only function of the TF is to decouple the screw from the element to be joined. The load bearing is taken care of by the Sylomer layer.

In addition, the AMC MECANOCAUCHO® design includes a metal bushing that sits between the TF bracket and the base. The function of this bushing is to limit the tightening torque that is given to the bolted joint. Thanks to this, overloading the Sylomer is avoided very easily, simplifying and speeding up assembly. In the image below you can see the elements that compose it.

A. Torque regulator bushing B. Bolt or threaded rod C. Base D. Sylomer® pad E. Element to join F. Support TF G. Washer TF H. Nut

EXAMPLE OF THE DESIGN PROCESS OF THE JOINT

In the following text, an example of the design progress of the joint is detailed. To design the joint, the thicknesses of the different materials to be used must be defined:

• 1. Sylomer (calculation)
• 2. Metal plate (9.5mm)
• 3. Height of the spacer between the support and the base (calculation)
• 4. SCB 38 Inner Sleeve Height (19mm)

Point 2 was defined by the client, and point 4 is the standard measurement for this type of support, so no calculation is required.

It would only be necessary to calculate the thickness of the Sylomer and the spacer bushing that regulates the tightening torque. This would be done by AMC MECANOCAUCHO®. In the picture below can be seen the different elements of this assembly.

A. Torque regulator bushing B. Bolt or threaded rod C. Base D. Sylomer® pad E. Element to join F. Support SCB G. Washer SCB H. Nut

A) CALCULATION OF THE THICKNESS OF THE SYLOMER:

The first step would be the calculation of the thickness of the Sylomer. For the calculation, it is necessary to define the following:

• - Horizontal length and width of the sylomer layer
• - Desired natural frequency
• - If there are, number of holes and their diameter

With this data and using calculation software within AMC, the calculation of the image below is achieved. Here we obtain the ideal thickness and its desired static deflection taking into account the previously defined parameters.

B) CALCULATION OF THE THICKNESS OF THE SPACING BUSHING:

The other step would be calculating the thickness of the spacing bushing that limits the maximum tightening torque that can be applied.

In the following image dimensions G and H can be seen. The description of each variable and the calculations that have been done are:

H = total thickness of the piece to be joined and the Sylomer without deflection.

H = 25 + 9.5 = 33mm

G = distance between the upper support point of the SCB and the end of the standard metallic bushing of the SCB.

A (mm) 33,5 B (mm) 19 C (mm) 10,5 D (mm) 20,5 F (mm) 20,5

G = 19 – 9.5 = 9.5mm

J = static deformation of the Sylomer.

K = deformation due to tightening torque (default 2mm).

RESULT:

h = H – G – J – K = 20.7mm

Finally, in the images below can be seen the result of this example before and after applying the tightening torque. It is recommended that the stiffness of the selected supports is lower than that of the sylomer used so that the deformation of the tightening torque is suffered by the support and not the sylomer, thus preventing the sylomer from suffering excessive deformations.

Assembly without the tightening torque and without static load

Assembly with the torque

As additional information, the following pictures show real examples of joints installed by clients.

1: PLACE THE MOUNTS IN THEIR POSITIONS

Place the anti vibration mounts on the base frame in their position, according to the orientation recommended by the technical department of AMC.

Be sure to pay attention to the orientation of the mounts when placing them, since not all anti vibration mounts have the same properties in all horizontal directions.

The bolts of the baseplate can be introduced but AMC recommends not to tighten them yet, since small adjustments might be necessary later for alignment.

Fastening the mounts misaligned can considerably increase the stress on the rubber, making it stiffer and potentially reducing its durability.The Hydraulic Mounts are conceived to be installed in vertical position. If they are installed angled, the weight of the suspended equipment would create static radial loads, which might make the internal piston to directly rest on the internal wall of the hydraulic chamber, dramatically increasing its stiffness and therefore reducing the vibration isolation.

2: PLACE AND FASTEN THE HEIGHT ADJUSTERS

Insert the lower threaded part in the mount.

Tighten the lower hexagonal nut to the tightening torque defined for each height adjuster depending on its thread size:

Hold the stud bolt from milled area to prevent it from rotating while the tightening torque defined for each of the height adjusters is applied to the nut.

3: PLACE AND FASTEN THE HEIGHT ADJUSTERS

Place the leveling nut of the Hi-Sec height adjuster (do not tighten it) and place the suspended equipment on the height adjusters, so its brackets rest directly on the leveling nuts. Try to keep the alignment between the anti vibration mount and the fixation brackets.

The slotted holes help to accommodate the position of the Anti Vibration Mounts to keep the alignment.

Let the suspended system rest for a minimum of 48 hours, allowing it to settle on the mounts. Rubber mounts may experience a creeping deflection of up to 25% during this first phase.

4: ADJUST THE HEIGHT OF THE HEIGHT ADJUSTERS

Once the system has stabilized, make the final adjustments by turning the lower nut. By doing this, the height of the suspended system is adjusted considering the creeping deflection of the mounts.

Hold the stud bolt from the milled area to prevent it from rotating while the suspended system is raised.

Do not exceed the maximum height allowed for each type of height adjusters. See table below for reference:

5: PLACE AND FASTEN THE HEIGHT ADJUSTERS

Tighten the top fixation nut of the Hi-Sec height adjusters to secure the system.

Hold the stud bolt from the milled area to prevent it from rotating while the tightening torque defined for each of the height adjusters is applied to the nut. See table below for reference:

Do not exceed the maximum height allowed for each type of height adjusters.

6: WHEN TO REPLACE THE HEIGHT ADJUSTERS WITH SHIMS

In case of dynamic applications or when there is a longitudinal thrust force on the mounts (for example, the thrust created by the propeller of a vessel), AMC recommends not raising the height adjusters more than 3mm.

To obtain the desired height in these cases, AMC recommends to use shims under the anti vibration mount, up to a maximum thickness of 5mm. The shims are available in three different sizes depending on the mount model being used.

Do not hesitate to contact our application engineers for more information on the installation of Hi-Sec height adjusters.

INTRODUCTION

Lifts in buildings can be a potential source of noise and vibration production, they can be one of the most problematic areas for building occupants. This noise and vibration generated is transmitted to the entire surrounding structure where the elevator is operating. This can lead to a significant disturbance to the occupants and ruin the enjoyment of the building, in particular the sleeping conditions. In fact, noisy lifts are one of the most important sources of complaints in customer´s hotel reviews.

There are often challenges to identify the transmission path (airborne vs. structure borne) and how the transmission paths can be mitigated to reduce the noise and vibration. Issues relating to the reliability and safety of the elevator operation can introduce difficulties and conflicts with implementing vibration isolators.

That is why AMC MECANOCAUCHO® sees the need to offer different solutions with vibration specialists for this type of application. Since these machines have different parts that are in contact with the surrounding structure, solutions for each of them are shown below.

Depending on the type of elevator, this engine frame can go in a machine room, attached to the lift shaft or at the top of the shaft of the lift installation. For a calculation of the correct anti-vibration mount selection, it would be important to know if it is an elevator with electric traction or if it is a hydraulic elevator (where it could have a small installation, for example, inside the shaft).

Before proceeding with a calculation, it is important to have a technical datasheet of the lift. For the motor mount, for example, we could consider its insulation using Sylomer® material. To recommend the correct Sylomer® material, it would be necessary to know the loads of the motor-pulleys, cabin, counterweight, cables, etc. and the contact surfaces or surface area of the engine mount where Sylomer® strips would be installed.

To know the appropriate density, it is necessary to know the weight to be supported and the dimensions of the base plate.

In addition, it is crucial to avoid acoustic bridges. For this, one of the options is to place CB supports, secured with a central bolt, as shown in the images below.

In principle, the purpose of these guides is to guide the elevator without the intermediate fixings having the function of supporting the mass of the guides, and therefore normally the reactions at the fixing points are usually not too high.

The typical solution that it can be adopt in this type of application is the installation of TF type supports at the fixing points of the guides to the wall. Below are shown several photographs of similar installations with these TF type supports. In order to propose the most suitable TF type support for the application, it is necessary to know the operative and maximum axial and radial reactions at each fixing point, and the number of total installation points.

As this type of mount is installed in pairs, for each installation point we would need 2x supports (1x pairs of mounts) and it would be very important to respect the T dimension of the frame. The number of supports needed will be determined by the loads. The assembly would be carried out with the supports in a horizontal position (perpendicular to the guide) and the Rx reaction would be given axially to the support.

LINK

In relation to the counterweight, it would be necessary to see how the installation of the guides is carried out and, if necessary, also isolate them.

It is important to insulate the base where the structure of the guides would rest in order not to transmit vibrations through the base.

The best and simplest solution for the base plate of a lift or elevator is its suspension on Sylomer®.

In addition, it is crucial to avoid acoustic bridges. If the bolts are directly fixed to the floor, vibration can be transmitted through them. For this, one of the options is to place CB supports, secured with a central bolt, as shown in the images below.

A.Torque regulator bushing B.Bolt or threaded rod C.Base D.Sylomer® pad E.Top metal plate F.Support CB G.Washer CB H.Nut

Another option is to fix the plate to the ground using SCB type mounts. Below there is an installation example of SCB+Sylomer® system:

A.Torque regulator bushing B.Bolt or threaded rod C.Base D.Sylomer® pad E.Top metal plate F.Support SCB G.Washer SCB H.Nut

In the below link you can find more information of how to install an elastic decoupling of the different connected elements with bolted joints:

LINK

Do not hesitate to contact our application engineers for more information on the installation of anti-vibration mounts for lifts and elevators.