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SHOXS has been protecting crews and extending maritime careers for over a decade with premium-quality suspension seating designed for high speed watercraft. The technical team leads the industry with experience delivering proven solutions for real world challenges, through a combination of sea trials, lab testing, science and engineering. We are consistently raising the bar with forward-thinking innovation, functional design, and most importantly, a focus on safety.

A(8) is a measure of the daily exposure to vibration. It is the weighted RMS acceleration value normalized to an 8-hour period with units of m/s^2. The UK Control of Vibration at Work Regulations and the EU Vibration Directive specify whole-body vibration exposure limit values (1.15 m/s^2) and action values (0.5 m/s^2) in terms of this metric.

Related terms:
vibration dose value, vibration directive, exposure limit value, action value.

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An accelerometer is a sensor used to measure acceleration. Accelerometers can measure acceleration along a single axis or in all three directions. Estimates of vibration and shock exposure are calculated from accelerometer measurements.

Related terms:
A(8), mechanical shock, vibration

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The exposure action value is a legislated threshold specified in the EU vibration directive and corresponding national documents. The action value is defined as 0.5 m/s^2 A(8), and if workers are exposed to reach exposures equal to or in excess of this threshold, then risk-reduction strategies are required.

Related terms:
exposure limit value, the EU vibration directive, A(8), vibration dose value.

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A suspension system with the capacity to dynamically adjust its position (length) in addition to other system parameters by means of an onboard control system.

Related terms:
Passive suspension, semi-active suspension

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The unit of measurement of acceleration.

Related terms:
accelerometer

A transient acceleration event characterized by its abruptness and severity. Impacts and collisions are examples of mechanical shocks. When experienced by a human, mechanical shocks are a source of whole body vibration.

Related terms:
vibration, whole-body vibration

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A suspension system whose response is determined wholly by external inputs such as the load it bears and the forces applied to its base. Passive suspension systems may include adjustments, but these will be operated manually and not dynamically modified by a control system.

Related terms:
active suspension, semi-active suspension

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A suspension system with the capacity to dynamically alter its damping characteristics by means of an onboard control system. Manually operated adjustments are not a form of semi-active suspension.

Related terms:
active suspension, passive suspension

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The percentage by which an impact is reduced. Numerically defined as 100%*(1 – Mitigation ratio), a seat with an average mitigation ratio of 0.7 will have a shock reduction percentage of 30%.

Related terms:
mitigation ratio

A measure of shock/vibration severity based on the response of an idealized single-degree-of-freedom (SDOF) model consisting of a mass-spring oscillator. For a given model’s natural frequency and damping ratio, the SRS is calculated by solving the second-order linear ODE.

Related terms:
Dynamic Response Index, vibration dose value, mitigation ratio

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On a high-speed boat, wave slams may occur so frequently that a suspension seat is unable to reach its full equilibrium position before the next impact event. In such circumstances, a seat may progressively stack (or pack) its way downwards, eventually incurring a bottom-out event that amplifies the impact.

Related terms:
bottoming-out, packing, shock amplification

A factor by which safety equipment extends a vehicle’s operating time before the exposure limit value is reached. On a boat in conditions that reach the exposure limit value in 1 hour, a suspension seat with an average mitigation ratio of 0.5 (in the VDV sense) can be expected to extend safe operating time to 16 hours.

Related terms:
exposure limit value, vibration dose value

An oscillatory mechanical motion characterized by its small amplitude. Motion may be periodic or random and aperiodic.

Related terms:
mechanical shock, whole body vibration

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The VDV is a measure of acceleration severity, closely related to A(8). Its definition involves a fourth power of the frequency weighted input signal (defined in ISO 2631) that strongly favours contributions from large-amplitude acceleration events. The underlying frequency response was derived from experiments on human perception of discomfort to vibration. Exposure limit values in the EU vibration directive are set in terms of the VDV and A(8).

Related terms:
A(8), action value, EU vibration directive, exposure limit value, time-to-limit

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The European Union’s legal directive imposing whole-body vibration exposure limits on workers within its jurisdiction. Exposure limits are specified in terms of the A(8) and vibration dose value.

Related terms:
A(8), action value, exposure limit value, vibration dose value

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An impact between a boat’s hull and a wave, typically severe in nature. Wave slam intensity is often described in peak-g, but pulse duration and rate of onset are also relevant characteristics.

Related terms:
Mechanical shock, g, pulse duration

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A mechanical shock or vibration transferred to the human body. The EU vibration directive specifies daily WBV exposure limits for workers within the European Union

Related terms:
mechanical shock, vibration

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