Firestone Marsh Mellow® Isolators (Rubber Mounts)
Marsh Mellow® springs are used like the Airmount® isolator as vibration isolators. However, they do not require air inflation. While not as efficient as air springs, Marsh Mellow® springs are an effective passive isolator with superior characteristics to steel springs.
Marsh Mellow® is a trade name of the rubber and fabric spring developed by Firestone Industrial Products in the early 1970’s.
Rubber springs have long time been a subject of interest in the vehicular suspension and industrial application fields because of their reliability, corrosion resistance, low cost, and basic simplicity. The concept has been tried with varying degrees of success over the years.
The major obstacle to solid rubber mount springs has been that to obtain the load requirements for many applications, solid rubber mount springs were either physically too large, or became unstable laterally when they were made long enough to provide good isolation.
The concept of “stacking” rubber springs answered the latter problem, but introduced the need for complicated mechanical guide systems to control the lateral movement.
Marsh Mellow® Advantages
Constant Vibration Isolation with Changing Loads
The variable spring rate allows for a nearly constant natural frequency, with changing loads, and therefore constant vibration isolation potential.
High Load Carrying Capacity
Due to the Marsh Mellow® spring’s greater deflection capabilities and load carrying influences of the fabric reinforced plies, it can carry a greater load when compared to a rubber mount of the same modulus and dimensions.
Excellent Vibration Isolation
Low natural frequencies provide excellent isolation of forced frequencies in the range of 800 – 1200 cpm [13.33 – 20 Hz].
Lateral Vibration Isolation
The lateral spring rate of a Marsh Mellow® spring can be less than the vertical spring rate, resulting in a lower lateral natural frequency. The Marsh Mellows® provide better vibration isolation in all degrees of movement than a comparable solid rubber mount or steel coil spring.
Compact Overall Size
The ability to support greater loads and maintain a cylindrical shape, results in a smaller overall size of the Marsh Mellow® compared to a standard rubber mount with identical load capacity. This is important when considering an application with a small design envelope.
Corrosion Resistant for a Durable, Long Life
Due to its rubber and fabric reinforced construction, the Marsh Mellow® has been proven in the damp and corrosive environments of mines and mills where a standard coil spring will fail.
Eliminates Downtime and Potential Damage to Machinery
When a coil spring fails, it will often crack allowing fragments of the coil to damage equipment. This problem is eliminated with the rubber construction of the Marsh Mellow®. Additionally, the Marsh Mellow® exhibits exceptionally high overload characteristics and usually does not fail catastrophically offering some support even during failure.
Increased Stability at Higher Percentages of Compression
The fabric reinforced plies support the core rubber as the Marsh Mellow® is compressed. This provides lateral stability even at 30-40 % compression.
Effective Noise Reduction
Marsh Mellows® reduce structurally transmitted noise caused by vibration. Marsh Mellow® springs are quite, unlike steel springs which often suffer coil shatter and readily transmit high frequency structural noise.
The Marsh Mellows’® high load capability means fewer springs may be needed in an application, resulting in less overall cost.
The Marsh Mellow® has no moving parts. No maintenance or lubrication is required