Video — Linear Actuator Selection Made Simple: Engineering Guide & Best Practices
Choosing the right linear actuator is not just a matter of picking a force rating and a stroke length. A reliable actuator installation is a complete mechanical and electrical system: load path, mounting geometry, speed, duty cycle, power supply, controls, environment, and the consequences of a stall or obstruction all matter.
This article is a practical selection overview for builders, engineers, fabricators, and product teams who want to narrow the problem before choosing hardware. For the complete reference with more diagrams and formulas, use the Linear Actuator Engineering Guide. Treat this page as the field checklist: it explains what to measure, what assumptions to document, and where actuator projects commonly go wrong.
A good actuator choice starts with the job the mechanism must perform in the real installation. The same actuator can behave very differently when it is pushing a vertical lift, rotating a hinged hatch, sliding a drawer, or synchronizing two sides of a platform. In many failures, the selected actuator was strong enough on paper, but the linkage created a poor leverage angle, the rod was forced to carry side load, the duty cycle was exceeded, or the control system allowed one side to get ahead of the other.
What’s Covered in the Guide
Use these jump links to move through the selection process in a practical order. If you are early in the design, start at the top. If you already have a layout, go directly to geometry, force, duty cycle, and control checks.
- 1. The actuator selection framework
- 2. Simple sizing workflow
- 3. Application comparison table
- 4. Example: hinged hatch sizing assumptions
- 5. Mounting and geometry checks
- 6. Control, feedback, and synchronization
- 7. Mistakes to avoid
- 8. Frequently asked questions
- 9. Final selection checklist
The Actuator Selection Framework
Before comparing actuator models, write down the design assumptions. This prevents the most common selection error: choosing from a catalog before defining the load case. At minimum, document the moving mass or force, direction of travel, required stroke, desired time to move, operating voltage, number of cycles per hour, ambient conditions, and whether the actuator will ever be back-driven, stalled, or side-loaded.
For a straight vertical lift, the actuator force must exceed the weight being lifted plus friction and any guide losses. For a horizontal slide, the actuator may need much less force than the object weight, but it must overcome friction, seal drag, rail alignment, acceleration, and impact loads. For a hinged panel, the actuator force depends heavily on hinge location, center of gravity, actuator mounting point, and actuator angle. A hinged application is rarely sized correctly by using panel weight alone.
The major tradeoff is force, speed, and duty cycle. Higher force designs often move slower because gearing increases mechanical advantage. Faster motion may draw more current and produce more heat. A system that cycles repeatedly may require a more conservative load rating than a system that moves once or twice per day. If your design depends on a very fast actuator operating near maximum load for frequent cycles, verify the thermal and mechanical assumptions early rather than after the first prototype.
Simple Sizing Workflow
For calculator-based checks, pair the full guide with FIRGELLI engineering calculators. The Actuator Speed Calculator is useful when you know stroke and target move time, while the Duty Cycle Calculator helps translate run time and rest time into a realistic operating pattern.
- Sketch the mechanism. Mark pivot points, load location, actuator mounting points, closed position, open position, and any hard stops. Do not skip the sketch even for simple projects.
- Identify the worst-case load position. For hinged lids and doors, the hardest point is often near closed, where the actuator has the least favorable angle. For slides, the worst case may be startup friction or a contaminated rail.
- Choose stroke from geometry. Stroke is not the same as visible travel. Confirm the distance between actuator mounting points at the retracted and extended positions.
- Calculate or estimate force with margin. Add allowance for friction, manufacturing tolerance, wind, user loading, ice, debris, or seal compression when those conditions apply.
- Check speed and duty cycle together. A motion that feels acceptable in a one-cycle test may overheat if repeated continuously.
- Select the control method after the mechanics are known. A rocker switch, remote, relay, feedback controller, and synchronized multi-actuator controller solve different problems.
| Selection item | Why it matters | Practical check |
|---|---|---|
| Force | The actuator must overcome load, friction, leverage losses, and occasional abnormal conditions. | Calculate force at the hardest position, then add an application-appropriate safety margin. |
| Stroke | Stroke controls actuator travel, but linkage geometry controls how that travel converts into motion. | Measure mounting distance at both end positions before ordering. |
| Speed | Higher force usually requires more gearing, and high-speed motion may increase current and impact loads. | Choose the slowest speed that still meets user expectations and process timing. |
| Duty cycle | Repeated motor operation produces heat and can shorten service life if rest periods are ignored. | Estimate cycles per hour, run time per cycle, and rest time between cycles. |
| Mounting | Misalignment and side load can bend rods, wear bushings, increase noise, and cause early failure. | Use pivoting mounts where appropriate and let external guides carry side loads. |
| Control | Switching, feedback, synchronization, end-of-travel behavior, and current limiting all affect reliability. | Decide whether the system needs simple extend/retract control or controlled positioning. |
Application Comparison Table
Different actuator jobs stress different parts of the design. Use this table to identify the selection factors that deserve the most attention for common applications.
| Application type | Primary selection risk | What to verify before selection | Common mistake |
|---|---|---|---|
| Hinged hatch, lid, or door | Poor leverage near the closed position | Hinge torque, center of gravity, actuator angle, bracket strength, and end-position clearance | Sizing from lid weight alone without checking moment arm geometry |
| Vertical lift | Load capacity, guide friction, and stall consequences | Total moving weight, rail alignment, safety factor, braking or holding requirement, and power supply capacity | Using the actuator shaft as the structural guide instead of adding proper rails |
| Horizontal slide or drawer | Friction, racking, and contamination | Slide rail quality, starting friction, debris exposure, and whether the load can jam | Assuming horizontal motion requires no meaningful force |
| Adjustable furniture or ergonomic equipment | Synchronization, noise, and duty cycle | Cycle frequency, user load variation, controller behavior, and pinch-point protection | Driving multiple actuators independently when the structure can bind |
| Outdoor automation | Water, dust, temperature, wind, and corrosion | Environmental rating, drainage, mounting orientation, cable protection, and seasonal load changes | Testing indoors and ignoring rain, ice, UV exposure, or wind loading |
| Robotics or repeated positioning | Feedback accuracy, backlash, and cycle life | Required repeatability, controller update method, duty cycle, and mechanical compliance | Choosing a non-feedback actuator when position control is required |
Example: Hinged Hatch Sizing Assumptions
Assume a hinged hatch weighs 80 lb and its center of gravity is 18 in from the hinge. The static moment at the hinge is approximately 80 × 18 = 1,440 lb-in. If the actuator attaches 8 in from the hinge and, at the worst position, its line of force is only 30 degrees from the hatch surface, the perpendicular lever arm is approximately 8 × sin(30°), or 4 in. A simplified force estimate is 1,440 ÷ 4 = 360 lb before friction, seal compression, wind, or safety margin.
This is an example assumption, not a universal rule. Moving the actuator bracket farther from the hinge, changing the bracket angle, reducing hatch weight, adding gas springs, or changing the open angle can dramatically reduce required actuator force. The key lesson is that bracket geometry can double or triple the required force even when the hatch weight stays the same.
When evaluating a hinged design, check both end positions and at least one intermediate position. Many mechanisms are not hardest at the exact end of travel. If you have a CAD model, measure the perpendicular distance from the hinge to the actuator force line. If you are working from a physical mockup, use cardboard, plywood, or temporary brackets to verify that the actuator can move through the arc without binding.
Linear Actuator Speed vs. Force Tradeoff CalculatorMounting and Geometry Checks
Linear actuators are designed to push and pull along their axis. They are not meant to replace guide rails, hinges, or structural bearings. If the moving component can twist, rack, sag, or load the actuator sideways, add external support. A bent rod or noisy actuator is often a symptom of a mounting problem rather than a force problem.
Check the closed and open mounting distances before selecting stroke. If the distance between mounting pins changes from 14 in closed to 22 in open, the required stroke is about 8 in, but you still need to account for actuator body length, bracket clearance, and end-of-travel tolerance. Avoid designing a linkage that reaches a perfectly straight over-center condition unless that lockout is intentional and mechanically controlled.
Keep brackets in double shear when possible, use proper clevis-style pivots where the angle changes during motion, and avoid rigid mounts that force the actuator to absorb misalignment. If the installation is exposed to vibration, include fastener retention. If it is outdoors, route wiring so water does not run directly into connectors or collect around the actuator.
Control, Feedback, and Synchronization
Choose the control strategy based on what the system must know. A simple switch is appropriate when the actuator only needs to extend and retract to its internal end limits. A feedback actuator is appropriate when the system must stop at repeatable intermediate positions or report position to a controller. Multi-actuator systems require extra care because two actuators with small speed differences can cause a platform to rack or bind.
If two or more actuators must move together, do not assume that wiring them in parallel will guarantee synchronized motion. Load differences, friction differences, and manufacturing tolerances can create position mismatch. For electrical planning across more than one actuator, the Parallel and Series Actuator Configuration Calculator is a useful starting point, but mechanical synchronization and feedback control may still be required depending on the structure.
Power supply sizing also matters. Voltage drop in long wires can reduce speed and available force. Undersized power supplies may trip, stall, or behave inconsistently under load. Where safety is important, consider current limiting, fusing, emergency stop behavior, obstruction detection, and what happens after a power loss.
Mistakes to Avoid
- Choosing force from object weight only. Hinged and angled applications require torque and geometry calculations.
- Ignoring side load. Use rails, slides, or hinges to guide the load; let the actuator provide linear force.
- Selecting stroke by eye. Measure pin-to-pin distances at both travel limits.
- Running continuously without checking duty cycle. Motor heat is a real design limit in repeated-cycle systems.
- Leaving no adjustment in brackets. Slots or multiple mounting holes can save a prototype when geometry needs refinement.
- Using independent controls for linked motion. Large platforms and dual-lift systems may need feedback or a synchronization controller.
- Forgetting the environment. Dust, water, temperature, vibration, and corrosion can change the correct actuator and mounting choice.
Frequently Asked Questions
How much safety factor should I use?
There is no single safety factor for every actuator installation. A lightly used indoor cabinet door may need less margin than an outdoor hatch exposed to wind, ice, and seal drag. As a practical engineering habit, calculate the worst-case force first, then add margin for uncertainty, friction, wear, and abnormal conditions. If failure could damage equipment or injure someone, the surrounding machine design should include appropriate mechanical safety measures beyond actuator selection.
Is a higher force actuator always better?
No. A higher force actuator may be slower, draw more current, cost more, or place larger loads into brackets and hinges. Select enough force for the real load case with margin, but do not use force rating as the only measure of quality.
How do I estimate actuator speed?
Start with the required stroke and the acceptable time to complete the movement. For example, an 8 in stroke completed in 20 seconds requires about 0.4 in/s average extension speed. If you need to compare units or convert between linear speed formats, use the Speed Converter.
When do I need position feedback?
Use feedback when the actuator must stop at repeatable intermediate positions, follow automated commands, report position, or coordinate with other actuators. Simple end-to-end motion usually does not require feedback, but synchronized lifting or robotics often does.
How should I think about actuator life?
Life depends on load, stroke, duty cycle, alignment, environment, and how aggressively the actuator is operated. If you are comparing operating patterns, the Actuator Life Cycle Estimator can help frame the discussion using your cycle assumptions.
Snap Ring Selection Calculator — Axial Load CapacityLinear Actuator Selection Checklist
- Define the motion: push, pull, lift, slide, rotate, tilt, or position.
- Measure the required travel and confirm actuator pin-to-pin length at both ends.
- Calculate the worst-case force using the actual geometry, not only the load weight.
- Check bracket strength, hinge strength, and whether any part of the mechanism can bind.
- Confirm that external guides carry side loads.
- Choose a speed that is fast enough for the user but not unnecessarily aggressive.
- Estimate run time, rest time, and cycles per hour.
- Choose the control method: switch, remote, relay, feedback, or synchronized controller.
- Size wiring and power supply for expected current and voltage drop.
- Review environmental exposure and cable routing before final installation.
Final Thought
Linear actuator selection is a systems problem. Force, stroke, speed, duty cycle, mounting, and control all interact. A careful sketch and a few geometry checks usually prevent more problems than simply choosing the largest actuator that fits.
If you are specifying an actuator for a product, prototype, or one-off build, start with the complete Linear Actuator Engineering Guide, then verify speed, duty cycle, and electrical assumptions with the relevant calculators before committing to brackets and hardware.
