DECOUPLING OF BOLTED FASTENERS USING SYLOMER + SUPPORTS CB, SCB, SCH AND TF

Decoupling bolted with mounts

Where bolted joints are used for the assembly of structures or equipment, an elastic decoupling of the different connected elements is required.

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.