Vibration Solutions develops anti vibration mounting for gensets

Vibration Solutions provides a technical guidance from AMC-MECANOCAUCHO on
the selection of anti vibration mounts for gensets. This article explains
the necessary calculations for correct selection, recommendations on optimum
position, and different positions where the mounts can be installed on a
genset.

1 Necessary technical
information for the selection of a correct anti vibration mount for a genset

Basic information required to make a single degree of freedom
calculation: Total weight of the genset; Position of centre of gravity; Position
of the mounts with respect to the centre of gravity; Disturbing frequency; and Engine
model.

Due to the simplification of the mathematical model, the results of these
calculations must be understood as guidance recommendation only. When high
reliability of calculations is required, it is advisable to perform a
calculation that takes into account all the degrees of freedom of the suspended
element. Additional elements required for these calculations include 3D drawing
of the suspended element; and moments of inertia in X, Y and Z.

This type of calculation provides natural frequencies of the system and
the eigenvectors.

Eigenvectors provide information about the vibration modes of the system,
allowing AMC-MECANOCAUCHO applications engineers to optimise the suspension and
recommend an anti vibration mount that will provide a
transmissibility curve where the natural frequencies are far from the
disturbing frequencies of the genset.

2 Recommendation on the optimum
position of anti vibration mounts for vibration isolation purposes

2.1 Possible positions of mounts within a genset:

2.1.1 Between genset and frame. At this point, depending on the size of
the genset, single or multiple pairs of mounts can be used under the engine or
alternator.

2.1.2 Beneath the frame.

2.1.3 Double mass isolation system.

2.2 Optimum positions for isolation and stability. The correct stability
is achieved with the correct positioning of mounts with respect to the centre
of gravity.

Mounts equally loaded and positioned at the height of the crankshaft
allow stable suspended elements and uncoupled vibration nodes.

When rigid mounts are installed between the genset and frame, noise
interferences are likely to occur, especially if the frame is light and the
metalwork is not reinforced. In order to avoid this problem, softer mounts are
advisable.

When stability is the main priority and noise created by the genset is
not an issue, mounts under the frame can be used. In such cases, when the
mounts are correctly calculated, good vibration isolation ratios can be
achieved.

The best isolation ratios are achieved using double mass isolation systems.
If they are not properly designed, the result can be less than satisfactory,
creating amplification or lack of stability. We strongly recommend multiple
degrees of freedom calculation at this point.

The technical department of AMC-MECANOCAUCHO can be of great assistance
in these calculations.

Installations such as the one below provide a good balance between
isolation and stability.

Nevertheless other constructions are possible
and our technical department will be ready to advise and provide technical
evidences and empirical results on similar cases.

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