FIRGELLI engineering guide
A static force rating does not tell the full story when a load hits a stop, drops into the actuator, backdrives the screw or changes direction quickly. Dynamic events can damage brackets, gears, screws and controller electronics even when the steady load looks acceptable.
This guide explains how to think about shock loads and end-stop energy in actuator systems without pretending a catalogue force rating covers every event.
Key Engineering Takeaways
- Static load and dynamic load are different design cases.
- Hard stops can create high peak forces over a short time.
- Overhauling loads can backdrive some mechanisms or push energy back into the electrical system.
- Side load can damage rods, bushings, screws and bearings.
- Soft stops, controlled speed and external mechanical stops reduce actuator abuse.
- Use calculate dynamic actuator force, calculate actuator side load and bending moment and calculate motor and drive braking energy for first-pass checks.
Engineering Guide
1. Why static force is not enough
Static force is a steady load number. Shock load is a transient event. A hatch slamming, a conveyor gate catching product, a linkage reaching a hard stop, or a vehicle-mounted actuator bouncing over rough ground can all create peak loads higher than the nominal design load.
The actuator may survive one event and still lose life from repeated impacts. Brackets can loosen, clevis holes can oval, rods can bend and gear wear can accelerate.
Before choosing a larger actuator, check rod and mounting loads with check linear actuator rod stress and calculate actuator side load and bending moment.
2. End-stop energy
End stops should stop the mechanism, not punish the actuator. If the actuator drives into a hard mechanical stop every cycle, the motor current spikes and drivetrain parts absorb impact energy. Internal limit switches are meant to stop normal travel before that becomes a repeated abuse case.
A controlled system can reduce speed near the end of travel or stop based on feedback. A simple system can use bracket geometry and external stops so the actuator is not the only part absorbing load.
Where the moving mass is large, think in energy rather than force alone. A slow, heavy lid can still carry enough kinetic energy to damage a clevis, bend a bracket or stretch a mounting hole if it is stopped abruptly. Reducing speed near the end of travel is often more effective than simply choosing a larger actuator.
For vehicle or mobile equipment, review review vehicle actuator safety factors because vibration and shock change the margin required.
3. Regeneration and overhauling loads
When a load drives the actuator instead of the actuator driving the load, the motor can behave like a generator. The importance of this depends on actuator design, screw efficiency, gearbox, brake behavior, controller design and whether the load can backdrive the mechanism.
Do not assume every actuator can safely absorb lowering energy or hold an overhauling load. If the application can pull the rod faster than commanded, the design needs braking, self-locking behavior, control review or mechanical restraint.
Use prevent backdrive in linear actuators as the starting point for holding-load and backdrive checks.
4. Actuator example: dump bed or hatch stop
A dump bed actuator may be sized for the lifting force but still be damaged if the bed drops, hits the end stop or twists the rod through a poor bracket. The right design checks lifting force, compression force, side load, stop location, bracket stiffness and what happens if the load shifts during motion.
A good commissioning test watches the bracket while the actuator stops, not just the actuator rod. If the bracket moves, clicks, rocks or elongates the pin hole, the impact path is wrong. Fixing the bracket and stop geometry usually gives a more reliable result than increasing actuator force.
Where high force and rugged construction are needed, compare the application against compare Super Duty linear actuators but still verify the geometry.
Specification Checks
| Check | What it means | Engineering note |
|---|---|---|
| Static force | Steady push or pull load. | Does not include impacts or sudden stops. |
| Dynamic force | Load with acceleration, deceleration or impact. | Can exceed static load by a large margin. |
| Side load | Force not aligned with the rod. | Shortens life and can bend components. |
| End-stop energy | Energy absorbed when travel stops abruptly. | Should be controlled outside the actuator where possible. |
| Backdrive | Load forces actuator to move. | Requires braking, self-locking or control review. |
Field Checklist
- Static load and dynamic load separately estimated
- Worst acceleration or deceleration case
- Hard-stop location and energy path
- Side load at full extension
- Rod buckling or bending risk
- Controller behavior at end of travel
- Overhauling or backdriving load condition
- Braking or self-locking requirement
- Bracket stiffness and pin wear
- Inspection plan after impact exposure
Common Mistakes
| Mistake | Why it causes problems | Better practice |
|---|---|---|
| Sizing from static load only | Impact loads are missed. | Include acceleration, stop and shock cases. |
| Using the actuator as the guide | Side load enters the rod. | Use rails, hinges or guides to carry off-axis loads. |
| Driving into hard stops | Every cycle creates drivetrain abuse. | Use limit behavior, soft stop or external stops correctly. |
Frequently Asked Questions
What is a shock load on a linear actuator?
A shock load is a short-duration force spike caused by impact, sudden stopping, load shifting, vibration or a mechanism hitting a stop.
Can I use static force rating for a moving load?
Use it only as one check. Moving loads also need dynamic force, acceleration, deceleration, side load, bracket strength and end-stop behavior reviewed.
What happens if an actuator hits a hard stop?
Current rises and the drivetrain, brackets and stop structure absorb the remaining energy. Repeated hard-stop impacts can shorten actuator life.
Can a linear actuator regenerate power?
In some overhauling conditions, a motor can be driven by the load and generate electrical energy. Whether that matters depends on actuator and controller design.
How do I reduce actuator shock loads?
Reduce speed near stops, use external stops correctly, guide the load, avoid side loading, add damping where needed and prevent the load from dropping into the actuator.
Does a higher-force actuator solve shock loading?
Not by itself. A stronger actuator can create higher structural loads. The mechanism still needs controlled stops, stiff brackets and proper guidance.
Which FIRGELLI actuator should I consider for rugged loads?
Start with compare Super Duty linear actuators for rugged general-purpose applications, then verify force, stroke, speed, mounting geometry, duty cycle and environment.
