The material acts as both spring and damper.

It deflects under load and dissipates energy internally as it flexes.

No separate damping element is needed.

That makes it the most economical isolation method.

Pumps, fans, compressors and general machinery use them widely.

For steady vibration at moderate amplitude they are usually the right answer.

By load per mount and by the frequency being isolated - both are required.

The mount's natural frequency must sit well below the disturbing frequency.

A substantial margin is normally specified.

A mount resonating at the disturbing frequency amplifies vibration.

That is worse than no isolation at all.

Manufacturers publish selection data against both figures.

Too stiff and it achieves nothing; too soft and the machine moves excessively.

An over-stiff mount barely deflects and transmits vibration through.

An over-soft mount lets the machine rock and wander.

That stresses connected pipework and cabling.

Flexible connections are used where movement is expected.

Both errors are common and both are avoidable with the published data.

Because machines are rarely symmetrical.

Mounts under the heavy end carry more.

Identical mounts at every corner leave the machine sitting unevenly.

It also isolates differently at each point.

Calculating load at each mount is what makes the installation work.

Dividing the total by four is the shortcut that causes the problem.

The material - elastomers harden, creep and degrade.

Ultraviolet light and ozone attack them over time.

Oils and solvents attack them directly.

Sustained load causes creep and loss of height.

Isolation deteriorates gradually rather than suddenly.

Mounts have a finite service life and are replaced rather than repaired.

Where the environment is aggressive or replacement is impractical.

Oils, solvents, ozone and extreme temperatures all attack elastomers.

Shock and large deflections suit wire rope better.

So does equipment that must not be serviced for decades.

Wire rope costs more and is bulkier.

For ordinary indoor machinery, elastomer mounts remain the sensible default.

Setting a machine true on an uneven floor without packing.

A threaded stud allows height adjustment at each mount.

That corrects both floor variation and machine base tolerance.

Packing under a mount changes how it isolates.

Levelling adjusts height without affecting the isolating element.

Locking the adjustment prevents it drifting under vibration.