The same wire rope isolator behaves very differently depending on how it is mounted and what environment it lives in. This guide covers the five mounting configurations, which load axis each one uses, and how selection changes across naval, transport, airborne and industrial applications.
Load axes — the foundation of every mounting decision
Every wire rope isolator publishes three load directions, and they are not interchangeable:
| Axis | How the cable is loaded | Relative capacity | Character |
|---|---|---|---|
| Compression | Loops squeezed face-on between the bars | Highest (100%) | Stiffest, highest load, least deflection |
| 45° Roll | Loaded diagonally across the loops | ≈ 60–75% | Balanced three-axis response |
| Shear / Roll | Bars slide parallel, loops roll sideways | ≈ 30–50% | Softest, longest stroke, best isolation |
The most expensive mistake in isolator selection
Reading compression ratings for a wall-mounted isolator. Shear capacity is often less than half of compression — a selection that looks comfortable on paper is then overloaded by a factor of two in service. Always match the axis to the direction gravity actually acts.
Floor and base mounting — gravity in compression
The classic arrangement: isolators bolted between the equipment base and the deck or floor, carrying weight in compression. Used for cabinets, gensets, compressors, pumps, deck-mounted sensors and directors.
- Use three isolators minimum; four is standard and simplifies load sharing.
- Position mounts symmetrically about the centre of gravity wherever possible — otherwise apply a CG load factor.
- Horizontal shock is carried by the 45° roll and shear axes, which are softer, so horizontal transmitted g is usually lower than vertical.
- Watch the height budget — isolators add 20–250 mm to the stack depending on size.
Floor mounting with stabilizers — tall equipment
Tall, narrow equipment such as a 2 m electronics cabinet will rock about its base mounts under horizontal shock even when the vertical selection is perfect. The solution is stabilizers: additional isolators fitted at the back or top, carrying no static load but adding stiffness where the rocking motion is largest.
A typical arrangement is four base mounts plus two rear stabilizers at cabinet height. In this configuration the system stiffness in each direction sums the contributions of both sets:
k_fore-aft = N × Kv(45° roll) + N_stab × Kv(compression)
The overturning check then compares the moment generated by horizontal shock against the restraint capacity of the mount pattern. The selector handles this automatically when you choose the “Floor + Stabilizers” configuration.
Wall and bulkhead mounting — gravity in shear
Equipment hung on a vertical surface loads its isolators in shear/roll. Common for bulkhead-mounted electronics on ships and wall-mounted control panels.
- Rated capacity drops sharply — expect to need a larger model than a floor mount of the same mass.
- The softer shear axis gives excellent isolation but larger static sag; check that sag does not compromise connector alignment.
- Shock perpendicular to the wall is carried in compression, the stiffest axis, so transmitted g in that direction is higher.
Ceiling and suspended mounting
Overhead equipment loads the isolators in tension. Published compression data is normally used for sizing, but tension behaviour differs and factory confirmation is recommended for critical suspended installations. Always fit a secondary safety restraint on overhead assemblies.
45° mounting — balanced three-axis protection
Isolators are installed at 45° to the horizontal so gravity loads the 45° roll axis. This equalises stiffness across all three directions and is the preferred arrangement where shock can arrive from any direction — transport frames, air-freighted payloads and gimballed assemblies. Adonitech's 100 kg air-and-road transport frame uses eight AWRI48-70 mounts in this configuration.
Naval applications — deck and internal
Open deck
The most demanding wire rope isolator environment: BR 3021 shock at 50 g vertical, salt spray, UV, temperature extremes and ship roll of ±12°. Elastomeric mounts perish here within a couple of years; all-metal isolators are effectively the only option.
- Specify SS 316 lugs with SS 302/304 cable for marine duty — never galvanised wire or EN8 lugs in salt spray.
- Include ship roll and pitch load-shift in the calculation, not just the shock case.
- Budget generous sway space — a 50 g deck shock produces 50–70 mm of stroke on typical selections.
Internal compartments
Shock levels are lower (typically 20 g), the environment is sheltered, and equipment is usually taller — consoles and cabinets. Stabilizer arrangements are common. JSS 55555 vibration with damp-heat testing normally governs alongside the shock case.
Road and rail transport
Continuous broadband vibration rather than single severe events, punctuated by pothole and coupling shocks of 20–30 g. Governed by ASTM D4169 or ISTA procedures.
- Target a low natural frequency — road input concentrates between 5 and 50 Hz, so fn should sit below 8–10 Hz where practical.
- Fatigue matters more than peak strength: thousands of kilometres of cycling. Wire rope isolators have no fatigue-sensitive elastomer.
- 45° mounting is common because road shocks arrive vertically and longitudinally.
Air transport and airborne payloads
Jet and turboprop environments produce high-frequency random vibration; handling and landing produce the shocks. Payload fragility is typically the tightest of any application — camera and optical payloads may be limited to 10 g.
- Design to fragility, not to a deflection limit. Allowing the mount to move is what makes 70%+ isolation achievable.
- Mass matters: ACWRI compact models suit instrument-scale payloads without weight penalty.
- Confirm sway space inside the airframe or container envelope.
Stationary and industrial machinery
Gensets, compressors, HVAC plant, pumps, transformers and seismic installations. The disturbance is usually a known running speed, which makes selection straightforward: place fn well below the running frequency.
Worked example: a 1500 rpm generator excites at 25 Hz. Targeting fn = 8 Hz gives r = 3.1 and roughly 88% isolation of the transmitted force. IEC 60068-2 typically governs the qualification testing.
Material and build options
| Component | Options | When to use |
|---|---|---|
| Retainer bars / lugs | Stainless steel SS 316 | Marine, open deck, corrosive or outdoor |
| Aluminium alloy | Weight-critical, sheltered environments | |
| EN8 (zinc plated) | Indoor industrial, cost-sensitive | |
| Cable | SS 302 / SS 304 | Standard for all marine and defence work |
| Galvanised steel | Indoor industrial only — not for salt spray |
Adonitech's default naval build is SS 316 lugs with SS 302 cable, giving an operating range of −100 °C to +260 °C with no elastomer anywhere in the load path. The selector lets you choose the combination and includes it in the RFQ.
Installation notes that protect your selection
- Never over-torque. Follow the catalogue value for the thread size — crushing the retainer bar changes the stiffness you designed around.
- Keep isolators free. Any rigid cable, conduit or pipe bridging the isolated equipment to the structure short-circuits the isolation completely.
- Mount on a stiff base. A flexible mounting plate adds its own resonance below the isolator's.
- Preserve sway space equal to the calculated stroke plus margin, in every direction.
- Load symmetrically where possible, or apply a CG load factor to the calculation.
Frequently asked questions
Can I mix mounting orientations on one machine?
Yes — base mounts plus stabilizers is exactly that, and it is standard practice for tall cabinets. What matters is that the calculation sums the correct axis stiffness for each group, which the selector does automatically.
How much sway space do I need?
At least the calculated peak shock stroke, plus a margin of 25–50%. For a 50 g naval deck shock this often means 60–90 mm clear in every direction. Check it before the equipment layout is frozen.
Do wire rope isolators need maintenance?
No routine maintenance. There is nothing to lubricate, no fluid to top up and no elastomer to replace. A visual inspection for broken strands or permanent set during scheduled equipment servicing is sufficient.
Can the same isolator handle both vibration and shock?
Yes, and that is the point of the non-linear design — a soft small-deflection rate isolates vibration while the stiffening large-deflection rate absorbs shock without bottoming out. The selector checks both cases against the same model.
Select for your application
Open the AWRI selector, choose your application and mounting configuration, and it selects the axis, runs the calculations and produces the report. See also the selection guide and standards explained.