Linear Actuator Selection Guide: Complete Engineering Reference for Force, Stroke, Speed, and Control

This page is a permanent engineering reference for linear actuator selection, sizing, mounting, and control.

📄 Download the Full Engineering Guide & Checklist (PDF)

 

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Table of Contents

• 1. What a Linear Actuator Is
• 2. What a Linear Actuator Is Not
• 3. Types of Linear Actuators (Taxonomy)
• 4. The Fundamental Tradeoff: Force, Speed, and Duty Cycle
• 5. The 7 Selection Criteria (Practical Decision Framework)
• 6. Engineering Sizing Models (Real-World Calculations)
• 7. Mounting & Geometry (Why Most Actuators Fail)
• 8. Common Failure Modes (and How to Avoid Them)
• 9. Control, Feedback, and Synchronization
• 10. End-to-End Actuator Selection Flow
• 11. Frequently Asked Questions (FAQ)
• 12. Summary, Charts, and Reference Checklist

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1. What a Linear Actuator Is

A linear actuator is a mechanical device that converts energy into controlled straight-line motion. Unlike a rotary motor that produces continuous rotation, a linear actuator extends and retracts along a single axis to push, pull, lift, open, close, position, or clamp a load.

Most electric linear actuators are built from a motor and gear reduction driving a screw mechanism (lead screw or ball screw) that translates rotary motion into linear travel.

Most modern electric linear actuators consist of:

• An electric motor

• A gear reduction stage

• A lead screw or ball screw

• A translating rod or carriage

• A structural housing

• End-of-stroke limit switches (internal or external)

Why linear actuators are used

Linear actuators are chosen when an application requires:

• Predictable, repeatable motion

• Compact packaging

• Straight-line movement without linkages

• Simple electrical control

• High force at low speed

Where linear actuators are used: adjustable furniture (desks, beds), doors and hatches, RV and marine systems, robotics, industrial automation, positioning fixtures, and general motion control where predictable linear travel is required.

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2. What a Linear Actuator Is Not

Many devices move in a straight line, but they are not interchangeable. Understanding category boundaries prevents incorrect design assumptions.

Gas struts (gas springs)

Gas struts provide passive force assistance using compressed gas. They do not create motion on command, do not provide controlled stop/start behavior, and are not position-aware. They assist motion; they do not generate controlled motion.

Hydraulic cylinders

A hydraulic cylinder is typically only one part of a hydraulic system. It requires a pump, valves, fluid lines, and a reservoir/filtration system. Hydraulics excel at very high force and heavy continuous duty, but add system complexity and maintenance.

Pneumatic cylinders

Pneumatic cylinders rely on compressed air. They are often ideal for fast repetitive motion in industrial settings with existing air infrastructure, but typically require additional components for precise positioning and force control.

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3. Types of Linear Actuators (Taxonomy)

Actuators are categorized by how they generate force. The right type depends on the environment, required force, speed, duty cycle, and control requirements.

Type	Best For	Key Advantages	Key Tradeoffs
Electric (DC)	Furniture, hatches, automation, robotics, vehicles, general positioning	Simple power, clean, compact, controllable; feedback possible	Force-speed tradeoff; duty cycle is thermally limited
Electric (AC)	Industrial environments with AC power standards	Robust options; plant-friendly wiring standards	More complex safety/wiring; DC more common for compact systems
Hydraulic	Very high force; heavy equipment; high load continuous duty	High force density; smooth heavy-load performance	Requires hydraulic system; maintenance/leaks; larger footprint
Pneumatic	Fast repetitive industrial motion	Fast cycles; simple cylinders	Needs compressed air; less precise without extra components
Piezo / Voice Coil	Micro-positioning, optics, precision small travel	Very precise; fast response	Short stroke; higher cost; specialized electronics

Key takeaway: For most consumer, commercial, and compact industrial applications, DC electric linear actuators provide the best balance of simplicity, control, cost, and performance.

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4. The Fundamental Tradeoff: Force, Speed, and Duty Cycle

Force, speed, and duty cycle are linked. You cannot maximize all three at the same time. The actuator must operate within a mechanical and thermal performance envelope.

4.1 Force vs Speed (mechanical tradeoff)

Higher force typically requires greater gear reduction and/or a finer screw pitch. Both reduce output speed. Faster actuators generally produce less force, so there is always a Force vs Speed trade-off when selecting the ideal Actuator

4.2 Duty cycle exists because heat limits motor life

As load increases, motor current increases, which increases heat. Many compact actuators rely on passive heat dissipation through the housing. Duty cycle ratings prevent overheating and premature wear.

As actuator load increases:

• Motor current increases

• Electrical losses rise

• Heat builds in the motor, gears, and screw

Unlike industrial motors with active cooling, most compact electric actuators rely on passive heat dissipation through their housing.
Once internal temperatures exceed safe limits, damage or premature wear occurs.

Duty cycle ratings exist to prevent this.

4.3 What duty cycle means (practical definition)

Duty cycle is typically defined over a window (often 10 minutes). For example, 20% duty cycle means 2 minutes ON / 8 minutes OFF in that window. Actual allowable runtime depends on load, ambient temperature, and cooling conditions.

A duty cycle such as 20% does not mean:

• 20% of the day

• 20% of continuous operation

It means:

• In a defined time window (often 10 minutes),

• The actuator may run for 20% of that time,

• And must rest for the remaining 80% to cool.

For example:

• 2 minutes on

• 8 minutes off

Actual allowable runtime depends on:

• Load magnitude

• Ambient temperature

• Mounting orientation

• Frequency of starts and stops

4.4 Why undersizing causes failures

Operating near maximum force pushes current toward stall levels, rapidly generating heat and accelerating wear. A modest safety margin typically improves reliability, consistency, and lifespan.

Operating near maximum force:

• Pushes current toward stall levels

• Rapidly generates heat

• Reduces effective duty cycle

• Accelerates wear of gears, bearings, and seals

Common symptoms include:

• Slowing under load

• Inconsistent motion

• Thermal shutdown (if present)

• Shortened service life

An actuator that appears “strong enough” on paper often fails in practice when friction, misalignment, or real-world loading are ignored.

4.5 The Engineering Rule of Thumb

Figure 4E Actuator sizing guide illustrating the "Engineering Rule of Thumb." Highlights the optimal operating region—typically 50-80% of rated capacity—where efficiency is highest and wear is minimized, avoiding the "danger zone" near stall force.

For long life and reliable performance:

• Select an actuator so normal operation occurs well below maximum force

• Avoid sustained operation near stall

• Allow thermal headroom for environmental variation

A slightly oversized actuator runs cooler, quieter, and more consistently than one pushed to its limits.

This principle applies regardless of application — from furniture and hatches to automation and robotics.

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5. The 7 Selection Criteria (Practical Decision Framework)

Reliable selection evaluates these seven criteria together. Optimizing one while ignoring others typically leads to compromised performance or early failure.

5.1 Force

Force must include friction, starting loads, and geometry effects. Use a safety factor (often 1.5× to 2× for many real-world builds) to account for unknowns and worst-case conditions.

5.2 Stroke length

Stroke is actuator travel, not necessarily load travel. Hinges, linkages, and pulleys can change the relationship. Always confirm retracted/extended lengths fit your available space.

5.3 Speed

Speed often drops under load. Choose speed for usability and safety (too fast can feel unsafe; too slow can feel unresponsive).

5.4 Duty cycle

Duty cycle must match how often and how long the actuator runs. Higher loads and higher ambient temperatures reduce thermal margin.

5.5 Environment (IP rating, corrosion, temperature)

Match sealing and materials to dust, water, temperature extremes, and corrosive exposure. IP rating is necessary but not the entire story—orientation and corrosion resistance matter too.

5.6 Noise

Noise is influenced by screw type, gearing, alignment, and mounting stiffness. Poor alignment increases noise and wear.

5.7 Control & feedback

Simple extend/retract can use basic switching. Repeatable stops, positioning, or multi-actuator lifting benefits strongly from feedback (Hall/pot) and appropriate control systems.

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6. Engineering Sizing Models (Real-World Calculations)

Correct sizing depends on how the actuator interacts with the load. Choose the model that matches your mechanism. The core sizing scenarios encountered in real actuator applications.
Rather than abstract formulas, these models focus on worst-case forces, geometry, and practical safety margins.

6.1 Direct push/pull (axial load)

Required Force ≈ Load Resistance + Friction

This is the simplest case if the load is guided. Ensure the actuator is not acting as a guide rail.

6.2 Vertical lifting (gravity dominated)

Required Force ≈ Weight + Friction

Vertical builds fail most often due to side loads and racking. Use guide rails/columns so the actuator applies force only.

6.3 Hinged lids/hatches (moment-based)

Hinged systems require torque about the hinge. Required actuator force changes through the motion and is often highest near closed.

Hinge Torque Needed ≈ Weight × Distance to center of mass

The actuator must provide that torque through mounting geometry (angles and moment arms).

6.4 Force variation through motion

Many hatch failures occur because the actuator is sized for mid-stroke rather than worst-case near closed. Design for the peak requirement.

 

6.5 Pulley/cable systems (mechanical advantage)

If you multiply motion by N, you typically multiply required actuator force by approximately N (plus friction losses).

6.6 Starting loads (static friction)

Starting force is often higher than running force due to static friction and seal preload. Size for the worst-case start condition.

Figure 6F Comparison of Static (Start) vs. Dynamic (Run) Friction. Highlights that the "break-away" force required to initiate movement is typically higher than the force needed to maintain motion due to seal preload and static friction, necessitating a sizing buffer.

Starting force is often higher than running force due to:

• Static friction

• Seal preload

• System compliance

Sizing must always consider:

• Worst-case start condition

• Cold temperatures

• Initial misalignment

An actuator that only meets running force may stall at startup.

6.7 Why Safety Factors Are Not Optional

Figure 6G Visual explanation of Engineering Safety Factors. Shows the "Operating Margin"—the necessary buffer between the actuator's maximum rating and the actual load. Recommends a 1.5x to 2x safety factor to account for real-world variables like wear, cold temperatures, and manufacturing tolerances.

Real systems include:

• Manufacturing tolerances

• Wear over time

• Environmental variation

• User behavior

A properly sized actuator operates comfortably inside its capability envelope.

Designing at the limit assumes a perfect world.
Engineering assumes the opposite.

Section 6 takeaway

• Size based on load interaction, not just weight

• Identify worst-case force positions

• Guide loads — never side-load actuators

• Hinged systems require geometry analysis

• Pulley systems multiply force requirements

• Always include safety margin

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7. Mounting & Geometry (Why Most Actuators Fail)

Most field failures are caused by mounting errors, misalignment, and side loads—not by the actuator itself.

7.1 Golden rule: actuators are not guide rails

Linear actuators are designed for axial push/pull loads. Side loads cause binding, noise, seal wear, bent rods, and early failure.

Figure 7A. Visualizing the "Golden Rule" of linear actuator mounting: Actuators are not guide rails. This diagram illustrates that actuators are designed only for push/pull force. Using an actuator to support the weight of a load (side-loading) causes rod bending, seal failure, and permanent damage.

Linear actuators are designed to take load only along their axis (push/pull).
They are not designed to:

• Support lateral forces

• Prevent racking

• Act as linear rails or columns

Consequences of side-loading

• Bent extension rods

• Excessive seal wear

• Increased noise and vibration

• Premature gearbox and bearing failure

These failures often appear “random,” but they are mechanical in origin.

Most linear actuator failures are caused by mounting and geometry errors — not by the actuator itself.

7.2 Guide the load independently

Use rails/slides/columns/hinges to keep the load aligned. The actuator should apply force only.

The load must be guided independently using:

• Linear rails

• Drawer slides

• Guide columns

• Hinges or pivots designed to carry side loads

The actuator’s job is only to apply force, not to maintain alignment.

7.3 Use pivot mounts at both ends

Geometry changes through the stroke. Pivot mounts (clevis/rod ends) allow angular change without bending the actuator.

Figure 7C. Best practice for Linear Actuator Mounting. Shows how using pivot brackets (clevis mounts) on both ends allows the actuator to rotate through its arc of motion. This prevents destructive side-loading (binding) that occurs if an actuator is rigidly fixed while pushing a rotating load like a hatch.

As the actuator extends and retracts:

• Mounting angles change

• Small arcs form

• Rigid mounts introduce bending loads

Correct practice

• Use clevis mounts, rod ends, or pivot brackets

• Allow angular movement at both ends

• Ensure the actuator can self-align through its stroke

Rigid, non-pivoting mounts are a frequent cause of hidden side loads.

7.4 Structural stiffness matters

Flexible brackets and thin panels deflect under load, creating dynamic misalignment and side loading. Reinforce mounts and reduce unsupported spans.

7.5 Hinged Applications: Mounting Location Matters More Than Force Rating

Figure 7E. Visualizing Mechanical Advantage in Hinged Applications. Illustrates the trade-off between force and stroke. Mounting the actuator close to the hinge (short moment arm) requires significantly higher force. Moving the mounting point further away reduces the required force but increases the stroke length needed.

Small changes in:

• Mounting distance from the hinge

• Actuator angle

• Anchor point height

can:

• Cut required force dramatically

• Reduce side loads

• Improve smoothness near closed

Poor geometry often leads to oversized actuators being used to compensate — masking the real problem.

Section 7 takeaway

• Linear actuators must never be side-loaded

• Loads must be guided independently

• Pivot mounts are essential

• Geometry changes throughout the stroke

• Structural stiffness matters

• Common failure modes can ealisy happen

Correct mounting extends actuator life more than increasing force rating.

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8. Common Failure Modes (and How to Avoid Them)

Nearly all actuator failures trace back to selection, sizing, mounting, environment mismatch, or control strategy.

Common Failures occure because of:

• Actuator acting as a guide

• Rigid mounts with no pivot

• Off-axis loading

• Flexible brackets

• Poor hinge geometry

These mistakes account for the majority of warranty returns and field failures.

Figure 8 summarizes the most common real-world linear actuator failures.
Almost all of them trace back to selection, sizing, or mounting errors rather than manufacturing defects.

8.1 Undersized force

Symptoms: stalling, slow movement, overheating, intermittent operation. Prevention: size for worst-case + friction + safety factor.

What causes it

• Ignoring friction and geometry

• Designing for average instead of worst-case force

• No safety margin

What it looks like

• Actuator moves initially, then stalls

• Sluggish motion under load

• Excessive heat buildup

• Premature motor or gearbox wear

How to prevent it

• Size for worst-case conditions

• Apply realistic safety factors

• Avoid operating near stall torque

8.2 Side-loading / misalignment

Symptoms: noise, jerky motion, bent rod, seal wear. Prevention: guidance + pivot mounts + rigid structure.

What causes it

• Actuator used as a guide

• Rigid mounting without pivots

• Flexible structures that deflect under load

What it looks like

• Bent extension rod

• Loud or jerky motion

• Seal damage and accelerated wear

How to prevent it

• Guide the load independently

• Use pivot mounts at both ends

• Ensure structural stiffness

8.3 Exceeding duty cycle (thermal overload)

Symptoms: intermittent stopping, reduced performance, shortened lifespan. Prevention: respect duty cycle, reduce load, increase thermal margin.

What causes it

• Frequent cycling without cooldown

• High loads combined with short rest periods

• Elevated ambient temperature

What it looks like

• Actuator stops intermittently

• Reduced speed after repeated cycles

• Permanent loss of performance

How to prevent it

• Respect duty cycle ratings

• Reduce operating load

• Increase actuator size or cooling margin

8.4 Environmental ingress/corrosion

Symptoms: contamination, rust, seal failure. Prevention: correct IP rating, corrosion resistance, protective orientation.

What causes it

• Incorrect IP rating

• Direct water spray or immersion

• Corrosive environments (salt, chemicals)

What it looks like

• Rusted rods

• Internal contamination

• Seal degradation

How to prevent it

• Choose appropriate IP rating

• Consider corrosion-resistant materials

• Protect actuator orientation where possible

8.5 Poor control strategy

Symptoms: uneven lifting, racking, inconsistent stop points. Prevention: feedback + proper controller for precision/sync.

Figure 8.5.  Visualizes Synchronization Failure in multi-actuator systems. Symptoms include uneven lifting, mechanical racking, and inconsistent stop points. Prevention requires using feedback sensors (Hall Effect) and a dedicated sync controller rather than simple open-loop switches.

What causes it

• Parallel wiring without feedback

• Load imbalance

• Lack of synchronization control

What it looks like

• Racking or twisting

• One actuator leading

• Structural damage over time

How to prevent it

• Use feedback-based controllers

• Design for symmetric loading

• Monitor position rather than time

8.6 Power issues (voltage drop)

Symptoms: weak speed/force, instability, controller faults. Prevention: correct power supply and wire gauge, minimize voltage drop.

Figure 8.6. Illustrates Power Supply Issues. Symptoms include weak force, unstable speed, and controller resets. Prevention involves using the correct wire gauge (thickness) to minimize voltage drop over long cable runs and ensuring the power supply can handle peak current spikes.

What causes it

• Undersized wiring

• Voltage drop under load

• Inadequate power supply capacity

What it looks like

• Reduced speed

• Inconsistent operation

• Controller faults

How to prevent it

• Size wiring for current draw

• Use appropriate power supplies

• Minimize cable length where possible

Section 8 takeaway

Most linear actuator failures are preventable.

They result from:

• Undersizing

• Poor mounting

• Ignoring thermal limits

• Environmental mismatch

• Inadequate control

When actuators fail early, the root cause is usually installation issues and design — not the actuator.

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9. Control, Feedback, and Synchronization

Control architecture determines reliability for positioning, shared loads, and safety behavior. As actuator systems become more complex, control strategy matters as much as mechanical sizing

9.1 Open-loop control (basic extend/retract)

Polarity reversal (DPDT switch or controller) drives extend/retract. Suitable when only end positions matter and loads are predictable.

Figure 9.1.  Schematic for Basic Open-Loop Control. Shows how to wire a 2-wire DC actuator to a 6-pin DPDT (Double Pole Double Throw) switch. Reversing the polarity extends or retracts the unit; no complex electronics required.

How it works

• Polarity reversal controls direction

• Internal limit switches stop motion at end of stroke

• No position awareness beyond fully extended or retracted

When it’s appropriate

• Simple doors or hatches

• Occasional use

• No need for repeatable intermediate positions

Limitations

• No position feedback

• No load balancing

• Cannot compensate for drift or wear

Open-loop control assumes everything behaves perfectly every time — which is rarely true in real systems.

9.2 Timed control (pseudo-positioning)

Runs the actuator for a set time. Inaccurate when load/voltage varies; use only for low-risk applications where drift is acceptable.

Figure 9.2. Diagram to show timed control using a timer relays controller.

How it works

• Actuator runs for a set duration

• Assumes consistent speed and load

Where it fails

• Speed changes with load

• Voltage variation alters timing

• Wear accumulates over time

Timed control is sometimes used for low-cost systems, but it is inherently imprecise, but for some applications like opening and closing a cattle feeder, this level of Actuator timer control is more than adequate.

9.3 Feedback (Hall sensor or potentiometer)

Enables repeatable intermediate positions, position awareness, and error correction. Strongly recommended for precision or synchronization.

Figure 9.3. Technical illustration of Position Feedback. Shows how Hall Effect sensors or Potentiometers are integrated into the motor or gearbox. These sensors count rotations to tell the controller exactly where the actuator is, enabling memory presets and synchronization.

Common feedback methods

• Hall sensors (digital pulse output)

• Potentiometers (analog position signal)

What feedback enables

• Repeatable intermediate positions

• Accurate stopping points

• Compensation for load and speed variation

• Monitoring of actuator health

Feedback transforms an actuator from a “blind mover” into a position-aware system component.

9.4 Synchronization (multi-actuator lifting)

Parallel wiring rarely stays aligned under real loads. Feedback-based synchronization compares positions and continuously corrects differences to prevent racking.

Figure 9.4.  Schematic for Multi-Actuator Synchronization. Illustrates the "Master/Slave" or centralized control architecture (like the Firgelli FCB-1). The controller reads feedback pulses from 2-4 actuators simultaneously and adjusts power to keep them perfectly aligned, preventing mechanical racking.

How it works

• Controller monitors position feedback

• Motion is adjusted in real time

• Errors are corrected automatically

Benefits

• Consistent positioning

• Smooth acceleration and deceleration

• Reduced mechanical stress

• Improved longevity

Closed-loop control is essential for applications where precision or repeatability matters.

Section 9 takeaway

• Control complexity should match application risk

• Open-loop systems assume perfection

• Feedback enables precision and reliability

• Synchronization prevents racking and mechanical damage

• Safety requires redundancy

A well-controlled actuator system lasts longer, performs better, and fails more gracefully.

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10. End-to-End Actuator Selection Flow

Use this flow before purchasing or fabricating mounts. It prevents the most common “it worked on paper” failures.

1. Define the motion type: push/pull, lift, hinge, pulley/cable.
2. Confirm the load is guided: add rails/slides if required.
3. Compute worst-case force: include friction, start loads, and geometry.
4. Apply safety margin: typically 1.5×–2× for many real-world builds.
5. Confirm stroke: travel + packaging constraints (retracted/extended length).
6. Confirm speed at load: usability and safety.
7. Confirm duty cycle: thermal limits for expected use.
8. Match environment: IP rating and corrosion resistance.
9. Select control strategy: switch vs feedback vs synchronization.
10. Validate geometry: pivot mounts, stiffness, alignment through motion.

10.1 Application Classification

Figure 10.1. Application Classification for Electric Linear Actuators (Diagram illustrating motion types, load behavior, and risk levels to guide sizing and control strategy decisions

Start by identifying:

• Motion type: push/pull, lift, hinge, cable

• Load behavior: guided vs unguided

• Risk level: cosmetic vs safety-critical

This classification determines how conservative your sizing and control strategy must be.

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10.2 Mechanical Path Decision

Figure 10.2. distinguishes guided from unguided systems.

• If the load is not guided, add guidance before proceeding.

• If multiple actuators share a load, assume synchronization is required.

This step eliminates the most common mechanical failure modes early.

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10.3 Performance Envelope Check