01/23/2023

Rubber Bobbin Mounts

Introduction

This type of vibration isolator is one of the most commonly used mountings in industry today, they are versatile yet simple.  Consisting of a rubber cylinder which is bonded to male or female threaded discs.

A wide range of sizes and options

Our current range of standard bobbins cover the following sizes:

• M3 to M20 threads
• 1kg – 2,500kg static loads
• Normal rubber type: Natural Rubber (Polyisoprene)

Some product ranges are also available in alternative materials for when increased resistance to ozone, oils, solvents, chemicals etc is required.

• Nitrile,
• Neoprene (polychloroprene)
• EPDM
• Food grade rubbers

A range of metal options are also available on request, the standard is plated mild steel.

Using Bobbin Mounts

These mounts are used in compression, shear or a combination of the two. The latter combination can provide an optimum for stability and isolation efficiency.

Assuming a vertical downwards load, these show pure compression,
combined compression and shear, and pure shear options

WARNING: Bobbin mounts are the simplest of all AV mounts to fit in most situations.  However, they are not intended for use in tension.  Although in the short term this may seem secure, the product will fail prematurely.  By using simple brackets, as in the image below, suspended loads can be mounted from bobbins which are loaded in compression.

A simple bracket to convert a tensile load to a compressive one

Bobbin Mount Design

AVMR have three key bobbin types, which relate to the shape of the rubber body.

1. The most common type is the simple cylindrical bobbin, which has a constant diameter to the rubber element. These are generally a lower cost option.
2. The waisted bobbin has a narrower middle section to the rubber which will deflect more than a comparably sized cylindrical bobbin when under the same load. This has the benefit of reducing the systems natural frequency to a greater degree, and therefore potentially offering improved vibration absorption.

A waisted bobbin will deflect more than a cylindrical one.

3. The hollow bobbin makes the rubber work through shear rather than compression. This results in notably higher deflections for given loads, and therefore enables better vibration absorption than for equivalent cylindrical or waisted rubber bobbins.

The RLF bobbin, an example of AVMR’s hollow bobbin range

In addition to each type, the threads can be configured with male, female, or mixed threads:

Male/Female, Male/Male, and Female/Female thread configurations.

Materials:

Rubber:

The majority of items are available in a single natural rubber hardness for each model, but many are also available in a wide range of grades of natural rubber (polyisoprene) from 35 up to 90ShA hardness or in polychloroprene (Neoprene™) and other synthetic rubber-like materials.

Metal:

All metal parts are mild steel with either Zinc plated or Sherardized. Both finishes are Rohs Compliant. On request at time of order, nuts & lock washers are available for all items.

Typical Applications

This could be a very long list, as bobbins are so widely used.  However, they are regularly found on:

• Fans
• Motors
• Compressors
• Pumps
• electrical equipment
• mountings for water or oil coolers
• vibratory machines (Sieves, shaker tables, feeders etc.)
• drive couplings for construction vehicles e.g. rollers.
• Radiators