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Shock mount
Shock mount
Shock mount
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Transit case showing internal shock mounting

A shock mount or isolation mount is a mechanical fastener that connects two parts elastically to provide shock and vibration isolation.

Isolation mounts allow equipment to be securely mounted to a foundation and/or frame and, at the same time, allow it to float independently from it.

Uses

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Explosive shock test of naval ship; equipment on board is isolated from shocks by shock mounts

Shock mounts are found in a wide variety of applications.

They can be used to isolate the foundation or substrate from the dynamics of the mounted equipment. This is vital on submarines where silence is critical to mission success. Yachts also use shock mounts to dampen mechanical noise (mainly transmitted throughout the structure) and increase comfort. This is usually done through elastic supports and transmission couplings.[1]

Other common examples are the motor and transmission mounts used in virtually every automobile manufactured today. Without isolation mounts, interior noise and comfort levels would be significantly different. Such shock and vibration-isolation mounts are often chosen by the nature of the dynamics produced by the equipment and the weight of the equipment.

Shock mounts can isolate sensitive equipment from undesirable dynamics of the foundation or substrate. Sensitive laboratory equipment most be isolated from shock from handling and ambient vibration. Military equipment and ships must be able to withstand nearby explosions.

Shock mounts are found in some disc drives and compact disc players, where the disc and rainy agreement are held by soft bushings that isolate them from outside vibration and other outside forces, such as torsion.[2] In this case, isolation mounts are often chosen by the sensitivity of the equipment to shock (fragility) and vibration (natural frequency) and the weight of the equipment.

For shock mounting to be effective, the input shock and vibration must be matched. A shock pulse is characterised by its peak acceleration, duration, and shape (half sine, triangular, trapezoidal, etc.). The shock response spectrum is a method for further evaluating mechanical shock.[3]

Shock mounts used to isolate entire buildings from earthquakes are called base isolators.

Base isolators under the Utah State Capitol building
One of two shock mounts holding the back of the Eames Lounge Chair Wood (LCW).
The black rubber is glued to the wood and the bolt only connects the metal to the rubber. Three similar shock mounts support the seat.

A similar idea, also known as a shock mount, is found in furniture design, introduced by Charles and Ray Eames. It provides some shock absorption and operates as a living hinge, allowing the seat back to pivot.

Shock mounts are also sometimes used in bicycle saddles,[4] handlebars and chassis.

Design

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Molded Rubber Shock Isolation Mount

Maxwell and Kelvin–Voigt models of viscoelasticity use springs and dashpots in series and parallel circuits respectively. Hydraulic and pneumatic components can be included, depending on the use.[5]

Laminated pads

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One common type of isolation mounts is laminated pads. Generally, these pads consist of a cork or polymeric foam core which has been laminated between two pieces of ribbed neoprene sheet.

Molded rubber isolation mounts

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Molded rubber isolation mounts are typically manufactured for specific applications. The best example of this is automotive engine and transmission mounts. Rubber bushings compress synthetic rubber rings on bolts to provide some isolation – operating temperature is sometimes a factor. Other shock mounts have mechanical springs or an elastomer (in tension or compression) engineered to isolate an item from specified mechanical shock and vibration. Some form of dashpot is usually used with a spring to provide viscous damping. Viscoelastic materials are common. Temperature is a factor in the dynamic response of rubber. Generally, a molded rubber mount is best suited for heavy loads producing higher frequency vibrations.

Coiled Cable Mount

Cable isolation mounts

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Cable mounts are based around a coil of wire rope fixed to an upper and lower mounting bar.[6][7] When properly matched to the load, these mounts provide isolation over a broad frequency range. They are typically applied to high performance applications, such as mounting sensitive instrumentation into off-road vehicles and shipboard.

Coil spring isolation mounts

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Typical Coil Spring Isolation Mount

Coil spring isolation mounts generally provide the greatest degree of movement and the best low frequency performance. They are particularly popular for mounting equipment in buildings such as air handlers, filtration units, air conditioning and refrigeration systems and large pipes. Their degree of movement makes them ideal for applications where high flexure and/or expansion and contraction are a consideration.

Microphone mounts

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Large element condenser microphone in shock mount

Shock mounts for microphones can provide basic protection from damage, but their prime use is to isolate microphones from mechanically transmitted noise. This can originate as floor vibrations transmitted through a floor stand, or handling noise on boom poles. All microphones behave to some extent as accelerometers, with the most sensitive axis being perpendicular to the diaphragm. Additionally, some microphones contain internal elements such as vacuum tubes and transformers which can be inherently microphonic. These are often cushioned by resilient internal methods, in addition to the employment of external isolation mounts.

Astatic crystal microphone in a 'ring and spring' mount

Early microphones used a 'ring and spring' mount, where a single rigid ring was mounted and carried the microphone between a number of coil springs, usually four or eight. When early microphones were heavy and omnidirectional, this was adequate. However the single plane of suspension allowed the microphone to twist very easily; once microphones started to become directional, this twisting caused fading of the signal. A more three-dimensional and less planar suspension would be required.

Large side-address studio microphone are generally strung in "cat's cradle" mounts, using fabric-wound rubber elastic elements to provide isolation. While the elastic elements can deteriorate and sag over time, the low price of the mount and ease of replacing the elastic elements mean they remain a mainstay despite introduction of elastomer-based designs less sensible to degradation over time.

The same occurs for end-fire microphones, most often employed for location work, however positioning consistency issues in mobile contexts means elastomer-based alternatives have made more inroads: they offer more displacement (positional flexibility) along the prime axis, but better restrict movement along other axis, and have less tendency to keep oscillating after movements, which provide for better control of the microphone's precise position.

See also

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Shock mount

View on Grokipedia
from Grokipedia
A shock mount is a mechanical device that elastically connects two components to isolate sensitive equipment from mechanical shock and , absorbing sudden impacts or oscillatory forces to prevent transmission. These mounts act as storage systems, characterized by their ability to handle peak accelerations (in g-forces) and short-duration pulses, such as half-sine waveforms lasting milliseconds. Unlike pure vibration isolators, which focus on reducing steady-state oscillatory transmission by lowering natural frequencies below excitation levels, shock mounts prioritize transient dissipation to protect against abrupt changes. Shock mounts are constructed from resilient materials like elastomers (e.g., or Sorbothane), coil springs, or pneumatic elements, often combined with to control and optimize performance across frequency ranges. Key design parameters include (typically below 10 Hz for effective isolation), deflection under load, and transmissibility ratios aiming for values less than 1 to minimize force transfer. In applications, they extend equipment lifespan by reducing wear from high-g events, such as 15g shocks in environments, and can be customized for specific payloads using adjustable or modular structures. Widely applied across industries, shock mounts safeguard microphones in audio recording by suppressing low-frequency rumble and handling noise, as seen in designs from manufacturers like Shure that use elastic suspensions to isolate signals from stand vibrations. In automotive and marine engineering, they serve as engine mounts to attenuate operational vibrations and impacts, supporting loads up to 25 tons in naval radar systems or switch cabinets. Aerospace and military sectors employ them for avionics and weapon systems to withstand environmental shocks, while industrial uses protect optical instruments and electronics from seismic or machinery disturbances.

Overview

Definition and Purpose

A shock mount is a mechanical device that serves as an elastic fastener connecting two components, designed to absorb and dissipate energy from shocks and vibrations. This elastic linkage allows the mount to isolate the connected parts, preventing the direct transfer of mechanical disturbances between them. By employing resilient materials, shock mounts create a flexible interface that contrasts with rigid attachments, enabling relative motion that mitigates impact forces. The primary purpose of a shock mount is to prevent the transmission of unwanted mechanical disturbances, such as handling noise or structural vibrations, from one component to another. This isolation protects sensitive equipment from potential damage caused by excessive vibrations or sudden shocks, thereby maintaining operational integrity and enhancing overall system performance. In essence, shock mounts act as a barrier that decouples the vibration source from the protected element, ensuring that disturbances are minimized rather than propagated. At its core, the principle of elastic connection in a shock mount involves using deformable elements to absorb and convert it into heat or other non-harmful forms, effectively decoupling the components without a fixed, rigid bond. This decoupling allows for controlled deflection under load, reducing the of transmitted vibrations and shocks. Key benefits include significant by vibrational , extended of through minimized and , and improved operational stability by preserving alignment and functionality under dynamic conditions.

Historical Development

The origins of shock mounts trace back to the early , when engineers sought effective for industrial machinery and emerging vehicles. Early designs primarily utilized spring-based systems, such as and coil springs, to mitigate shocks from uneven terrain and mechanical operations. For instance, in 1906, the Brush Runabout automobile introduced front coil springs mounted on a flexible axle, marking one of the first applications of such technology to dampen spring bounce and improve ride stability. Concurrently, advancements in rubber compounding during the and enabled the integration of rubber elements with springs, offering superior energy absorption and reducing transmitted vibrations in and mounts. By the , rubber-steel composite mounts were employed in vehicles to isolate vibrations from the . In the realm of , shock mounts emerged in the and to address handling noise and structural vibrations in . Western Electric's "ring-and-spring" designs, such as the Model 600A , suspended the sensitive element within a metal ring using coiled springs, effectively isolating it from external shocks and improving broadcast clarity. These innovations were pivotal for early radio and recording applications, where even minor handling could introduce unwanted rumble. Mid-20th-century advancements extended shock mount principles to consumer products, exemplified by ' 1956 Lounge Chair. The chair's cast aluminum base incorporated rubber shock mounts to absorb minor vibrations, enhancing user comfort and demonstrating the technology's versatility beyond industrial uses. Post-World War II, military demands accelerated progress, with shock mounts becoming essential for protecting sensitive electronics and equipment in against underwater explosions. The U.S. Navy's MIL-S-901 shock testing standard, developed from wartime experiences and formalized in the early , mandated robust isolation for shipboard systems, influencing subsequent civilian adaptations in transportation and machinery. From the onward, modern shock mounts incorporated advanced synthetic polymers for enhanced and durability, alongside wire cable systems for extreme conditions. Aeroflex's 1980 patent for isolators introduced looped cables clamped between bars, providing multi-axis shock absorption in and defense applications, and paving the way for high-performance civilian uses.

Applications

In Audio and Recording Equipment

In audio and recording equipment, shock mounts serve the primary role of suspending the capsule within elastic slings to isolate it from vibrational interference, effectively blocking handling noise and floor vibrations that could otherwise contaminate the . This mechanical decoupling prevents structure-borne noise from reaching the , allowing for cleaner capture of low-frequency content without the need for post-processing filters. The evolution of microphone-specific shock mount designs began in the mid-20th century with simple cat's cradle-style elastic band suspensions, as seen in early broadcast models from manufacturers like in the 1940s. These rudimentary systems have advanced to modern baskets, which offer improved resilience and more precise vibration absorption while maintaining compatibility with standard mounting hardware. Prominent examples include studio condenser microphones like the U87, which rely on dedicated shock mounts such as the EA 87 to ensure vibration-free operation and optimal recording quality. These mounts are frequently integrated with boom arms, enabling stable positioning during sessions while minimizing interference from stand adjustments or environmental rumble. A key advantage in audio applications is the reduction of low-frequency rumble below 20 Hz, which helps preserve the microphone's and supports extended low-end essential for professional recordings. However, common challenges arise from the degradation of elastic components over time, which can diminish isolation performance. Regular inspection and replacement of these bands are recommended to maintain efficacy.

In Mechanical and Industrial Systems

In mechanical and industrial systems, shock mounts serve as critical components for isolating heavy equipment such as engines, pumps, and generators from their foundations, thereby preventing structural fatigue and the transmission of operational vibrations and shocks. These mounts absorb dynamic forces generated during machinery operation, reducing the risk of damage to both the equipment and the supporting structure, which is essential in environments where continuous vibration could lead to material degradation over time. By decoupling the machinery from rigid bases, shock mounts minimize resonant amplification, ensuring stable performance in demanding industrial settings. Representative examples of shock mount applications include HVAC systems, where they isolate compressors and fans to curb propagation through ductwork and building frameworks, manufacturing tools such as lathes and milling machines that require steady operation to maintain precision, and laboratory instruments like centrifuges, which use mounts to protect sensitive rotors and electronics from micro-s that could compromise experimental accuracy. In these contexts, the mounts enable reliable functionality by filtering out disturbances that might otherwise cause misalignment or data errors. The industrial benefits of shock mounts are multifaceted, including extended equipment lifespan through diminished on components, reduced requirements by limiting the need for frequent repairs due to vibration-induced failures, and compliance with occupational regulations by attenuating audible and structural-borne sound levels. For instance, proper isolation can reduce downtime in high-vibration scenarios, directly contributing to and cost savings. In specific high-stakes scenarios, shock mounts are vital on offshore platforms, where they isolate drilling rigs and power generation units from wave-induced shocks and platform motions, and in gear, such as systems and communication equipment, to absorb or impact shocks while maintaining operational integrity. Selection of shock mounts in industrial systems hinges on factors like load capacity, which determines the mount's ability to support equipment weight without excessive deflection—typically ranging from tens to thousands of pounds depending on the application—and frequency range, ensuring effective across the machinery's operational spectrum, often targeting isolation below 10-20 Hz for optimal performance. Engineers evaluate these parameters using deflection calculations and plots to achieve transmissibility ratios under 0.2 in the isolation zone, thereby tailoring mounts to specific vibrational profiles.

In Transportation and Vehicles

In transportation and vehicles, shock mounts play a critical role in isolating dynamic components from road-induced vibrations, impacts, and operational forces, thereby reducing noise transmission to and preventing premature wear on structural elements. In automotive applications, these mounts are commonly used to secure , allowing for effective that minimizes cabin noise and enhances passenger comfort. For instance, active engine mounts incorporate hydraulic or electrorheological fluids to adaptively dampen vibrations across a wide range, reducing the need for additional balancing mechanisms in . Similarly, shock mounts in suspension systems, such as rubber bushings integrated into shock absorbers, absorb road irregularities and control oscillations, which helps maintain vehicle stability and extends the lifespan of suspension components by limiting fatigue. isolators further contribute by decoupling vibratory forces from the vehicle , preventing that could amplify noise and accelerate component degradation. In marine environments, shock mounts are essential for isolating systems in vessels like and from wave-induced slams and hydrodynamic forces, particularly in the 10-25 Hz frequency range associated with wave impacts. These mounts, often featuring high-deflection rubber elements, protect engines and generators from excessive shocks, ensuring reliable operation while reducing structure-borne noise that could compromise stealth in . For example, in , specialized isolators designed for mine blast and wave slam attenuate in this low-frequency band, safeguarding onboard and crew compartments from repeated impacts. In setups, exhaust shock mountings provide up to 80 mm of deflection to handle slamming forces, thereby minimizing wear on mounting hardware and improving overall vessel durability. Aerospace and off-road applications employ shock mounts to shield sensitive and cargo from extreme vibrations in high-g environments, such as those encountered in vehicles traversing rugged . In , these mounts secure equipment to absorb shocks during takeoff, , and , protecting avionics from accelerations that could disrupt functionality. For off-road and vehicles, cable-based mounts offer robust isolation in hostile conditions, maintaining performance under severe shocks and vibrations while complying with standards like for environmental resilience. Such systems can attenuate shocks to below 10g in demanding scenarios, significantly enhancing ride comfort, operator safety, and equipment longevity by preventing damage from impacts up to high military-grade levels.

In Architecture and Furniture

In architecture, shock mounts, often implemented as base isolators, play a critical role in protecting structures from seismic activity by decoupling the building's superstructure from its foundation. These systems typically employ flexible bearings or laminated pads, such as lead-rubber bearings composed of alternating layers of rubber and with a central lead core, which absorb horizontal ground movements during earthquakes while maintaining vertical stability. By allowing the structure to shift up to 300 mm relative to the ground, base isolators minimize the transmission of seismic energy, preventing and reducing forces on the building by factors of up to five times in retrofitted designs. This approach is particularly effective for medium-rise or in high-risk areas like , , and , where over 10,000 such installations have been documented. For seismic retrofits, shock mounts are integrated at the base of existing structures, such as a 1990s-era building in , where 25 elastomeric isolators and flat sliders were added beneath the foundation to enhance capacity without requiring evacuation. These interventions, often combined with framing or fiber-reinforced wraps on columns, ensure structural integrity and limit interstory drifts, thereby safeguarding occupants in multi-unit buildings by mitigating floor vibrations and potential collapses. In high-rise applications, large-scale laminated rubber bearings—ranging from 1 to 1 and supporting weights up to 1 —enable skyscrapers to withstand events like the with minimal damage. In furniture design, shock mounts emerged as innovative components for ergonomic vibration damping, exemplified by Charles Eames's 1961 patent for a side-flexing shock mount that secures chair elements while permitting controlled twisting and flexing to absorb user-induced movements. These rubber-and-metal assemblies, embedded in molded fiberglass shells of Eames chairs from the mid-20th century, provide resilience against daily stresses, enhancing comfort without compromising structural integrity. Historical innovations like these influenced broader furniture applications, where small-scale mounts reduce transmitted vibrations in tables and seating for improved . Household applications extend shock mount principles to everyday built environments, such as anti-vibration pads placed under washers and dryers to isolate appliance oscillations from floors. Constructed from materials like or , these pads absorb shocks and distribute energy, reducing noise transmission in homes and multi-unit dwellings by up to 94.7% in some configurations. This noise mitigation benefits shared living spaces by preventing vibrations from propagating through structures, while also extending equipment lifespan through stabilized operation. Scale varies significantly: massive pads support isolators for seismic events, contrasting with compact, consumer-grade mounts for appliances that address routine mechanical disturbances. Overall, these uses enhance occupant , comfort, and acoustic quality across static built environments.

Design Principles

Materials and Properties

Shock mounts primarily utilize elastomeric materials to provide the necessary compliance and energy dissipation for effective and shock isolation. Common materials include and synthetic rubbers such as (chloroprene rubber) and , which offer high resilience and adaptability to various loads. Polymers like general elastomers and foams contribute to lightweight damping, while metals such as are employed for structural elements like springs and cables to enhance load distribution. Composites, including cork-neoprene laminates, combine rigid and flexible components for improved stability under compression. The effectiveness of these materials stems from key physical properties tailored to isolation needs. Elasticity, quantified by , determines deflection under load; for instance, natural rubber exhibits values ranging from 120 to 1300 lb/in², allowing significant deformation without permanent set. is achieved through loss, where the loss coefficient for typically falls between 0.1 and 0.2 at elevated temperatures like 88°C, converting vibrational energy to heat. Fatigue resistance ensures longevity under cyclic loading, with natural rubber demonstrating superior tensile and tear strength compared to many synthetics. Temperature stability is critical, as maintains properties from -90°C to +250°C, while operates reliably from -45°C to +120°C, encompassing a broad range such as -40°C to 120°C for many applications. Material selection for shock mounts considers several factors to optimize . Load-bearing capacity relies on the material's static modulus and , enabling supports from low weights to several thousand pounds without excessive deflection. tuning avoids resonance by matching the mount's stiffness to the system's , targeting low frequencies like 6-9 Hz for effective isolation above operational vibrations. Environmental durability addresses exposure to UV radiation, chemicals, and ozone; for example, provides moderate oil resistance, while excels in ozone-prone settings. Over time, elastomers in shock mounts undergo degradation that can compromise isolation efficacy. Aging processes, including oxidation and loss of additives, lead to stiffening, with increasing and damping peaking near the temperature. This results in cracking or reduced compliance, often manifesting after 5-10 years of service depending on environmental exposure, necessitating periodic or replacement.

Vibration Isolation Mechanisms

Shock mounts primarily achieve vibration isolation through passive mechanisms that leverage the interplay of stiffness and damping to attenuate transmitted forces and accelerations. In these systems, stiffness is provided by elastic elements that allow deflection under load, thereby lowering the natural frequency of the isolated system below the dominant excitation frequencies. This deflection shifts the system's resonance away from operational frequencies, preventing amplification of vibrations. For instance, the natural frequency ωn=k/m\omega_n = \sqrt{k/m}
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