Will It Fit? Retracted Length, Clearance, and the Space Check Before You Order
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Here is the most avoidable return in the linear actuator business: the stroke is exactly right, the force is exactly right — and the actuator does not fit. It is too long when closed to sit in the space, or it collides with the frame halfway through its travel, or its cable snags on a hinge. The buyer measured the movement and forgot to measure the machine doing the moving.
This guide covers the space check that should happen before you order, not after the box arrives: three lengths, three clearance points, and a five-step method you can do with a tape measure and the load itself.
Why "Enough Stroke" Is Not Enough
A linear actuator has three lengths, and buyers usually check only one of them:
- Stroke: how far the rod travels, from fully retracted to fully extended. This is the number that moves the load.
- Retracted length: the actuator's full length when closed, measured between its two mounting points, including brackets and pivots. This is the length that must fit in the space when the job is at rest.
- Extended length: the actuator's full length when open. By definition, extended length equals retracted length plus stroke — but you still need to check it, because the open assembly occupies space too, and its rod end ends up somewhere different from where it started.
The classic failure is ordering by stroke alone. Take a hypothetical example, not any specific model: a 200 mm stroke actuator that is 300 mm long when closed does not fit a 250 mm cavity, however perfect the 200 mm of travel is. The stroke was right; the box was wrong.
Our stroke measurement guide covers how to work out the travel you need. This guide covers the other half of the order: whether the actuator that delivers that travel fits in the place it has to live.
The Three Clearance Points
Before ordering, check all three of these. Checking one and assuming the rest is how "it fit in the shop" becomes "it binds on the job."
1. Retracted length — the closed assembly
Measure the space available with the load in its closed or rest position, between the two points where the actuator will mount — and measure it along the actuator's actual line, not along the nearest convenient straight edge. Then compare it with the model's retracted length from its product page, including the brackets and pivot hardware you will actually use.
Watch for the details that make a catalog length longer in real life: a bracket eye that sticks out past the mounting face, a pivot bolt head, a cable exit that needs a bend radius, and the thickness of the frame member the bracket bolts to. Measure the assembly, not just the actuator body.
2. Swing clearance — the whole arc, not the two ends
An actuator does not stay in one line as it works. As a hinged load swings, the actuator rotates on its two pivots, and its body sweeps through an arc. Clearance that exists at rest and at full extension can disappear mid-travel, when the body is at its most angled position.
Check this by hand before you drill: hold the actuator in place, move the load slowly through its full range, and watch the body, the rod, and both brackets. Anything that touches, rubs, or comes within a hair of an edge, a corner, a hose, or another moving part at any point in the arc is a collision — not a close fit.
This is also why both ends must pivot, as our mounting guide explains. A pivot that cannot rotate forces the body into a different arc from the one you checked, and the clearance you verified no longer applies.
3. Cable, hinge, and hardware interference
Three small things cause outsized trouble:
- Cable slack. The cable must have enough slack for the full swing, without pulling tight at full extension and without drooping into a moving part at rest. A cable that pulls tight acts as a second, unintended limit — and then fails.
- Hinge and fastener interference. Bracket bolts, hinge pins, and pivot bolts all occupy space the actuator's swing may pass through. Check the bolt heads and nuts, not just the bracket plates.
- The load's own hardware. Handles, latches, gas struts, and stops mounted near the actuator's path can all become collision points mid-travel. Check them in the load's moving position, not just in its rest position.
The Five-Step Space Check
Do this in order, on the real load, before ordering:
Step 1: Mark the two mounting points. Decide where the body end and the rod end will attach, on rigid structure — not on thin panels. Mark both points with the load closed.
Step 2: Measure the closed distance. Measure between the two marks, along the actuator's line, with the load closed. This is the space the retracted actuator must fit into. Write it down, and note any bracket, bolt head, or frame thickness that eats into it.
Step 3: Measure the open distance. Move the load to fully open and measure between the same two marks again. The difference between the open and closed distances is the stroke the geometry actually requires — compare it with the stroke you worked out in our stroke measurement guide. If the two disagree, trust the geometry measurement and rework the selection.
Step 4: Check the model's lengths against both measurements. On the product page, confirm the model's retracted length fits the closed distance with clearance, and that its extended length (retracted length plus stroke) matches the open distance. If a model's retracted length is longer than your closed distance, it does not fit — regardless of stroke.
Step 5: Swing it by hand. With the load unpowered, move it slowly through its full range while watching the three clearance points above. Only when nothing touches, pulls tight, or binds at any point is the space check passed.
If any step fails, change the mounting points, change the model, or change the mechanism — in that order of cheapness. Do not order first and hope the failure goes away in shipping.
Three Scenarios Where This Check Saves the Order
Boat engine hatch. The closed compartment is the constraint, not the open lid. The actuator must fit, with clearance for the engine and hoses, when the lid is shut — and its body must swing clear of the engine as the lid opens. Measure closed first.
Lift platform or scissor mechanism. The actuator often sits inside the mechanism's own frame, where the closed length competes with cross-members and linkages. The swing of the linkage, not just the actuator, needs clearance.
Cabinet door or TV lift. The cabinet interior looks generous until the actuator, its brackets, its cable, and the moving panel all have to share it. Check the cable's path at full extension, when the panel is farthest from its rest position and the cable is at its tightest.
In all three, the same rule applies: the space check is a measurement on your project, not a dimension copied from someone else's build.
Common Space Mistakes
| Mistake | What happens | Fix |
|---|---|---|
| Ordering by stroke alone | Closed unit too long for the cavity | Check retracted length before ordering |
| Measuring body length, not assembly length | Brackets and bolt heads make the real unit longer than the catalog body | Measure mounting-point to mounting-point, with hardware |
| Checking clearance only at rest | Collision or cable snag mid-travel | Swing the load by hand through the full range |
| Measuring along the wrong line | The actuator's actual line is longer or angled differently | Measure along the line between the two mounting points |
| Forgetting the cable | Cable pulls tight, chafes, or snags | Give slack for the full swing and route clear of moving parts |
| Letting the actuator be the stop | Load slams the limit switch every cycle | Give the load its own mechanical stop; the built-in limit switch is protection, not a routine endpoint — see our limit switch guide |
| Assuming a dual setup fits like a single | Two actuators need mirrored clearance, not just doubled force | Check both units' swing and cable paths — see can you sync two linear actuators |
Pre-Order Checklist
Run through this list with the product page open, before you click buy:
- ☐ Closed mounting-point distance measured on my project, along the actuator's line
- ☐ Model's retracted length confirmed on its product page, and shorter than the closed distance with clearance
- ☐ Stroke required by the geometry confirmed, not just the lid's edge travel
- ☐ Model's extended length matches the open mounting-point distance
- ☐ Full swing checked by hand: body, rod, brackets, and cable clear at every point
- ☐ Cable slack sufficient at full extension, routed clear of hinges and moving parts
- ☐ Load has its own mechanical stop; limit switch is backup, not the daily stop
- ☐ Force checked for the worst position — see how much force you actually need
- ☐ Power sized for full-load current — see what power supply you need — and wire run checked for voltage drop — see long-wire voltage drop
- ☐ Mounting plan follows the pivot and alignment rules — see how to mount a linear actuator
If any box is unchecked, that is the next thing to measure — not a reason to order and find out.
FAQ
Is retracted length the same as installation length?
They are closely related but not interchangeable words. "Retracted length" is the actuator's closed length between mounting points; "installation length" is sometimes used for the same measurement, and sometimes for the closed distance on your project. Compare like with like: the model's closed mounting-point length against your project's closed mounting-point distance.
Can I mount the actuator at an angle to make it fit?
Angling the actuator changes its geometry, its effective force, and its swing path — it is not a free way to gain length. If an angle is needed, rework the force calculation for the new geometry and re-check the full swing. See our force calculation guide.
What if the perfect-stroke model is just slightly too long when closed?
Do not force it. Look for a model with the same stroke and a shorter retracted length, move a mounting point if the structure allows, or change the mechanism's geometry. A "slightly too long" actuator that is installed under strain becomes a bent rod or a torn bracket.
Does the cable really need its own clearance check?
Yes. Cable failures from pulling tight or chafing are common, quiet, and often misdiagnosed as actuator failures. Our troubleshooting checklist lists cable and connector checks before motor checks for exactly this reason.
I already ordered and it does not fit. What now?
Do not modify the actuator or force the installation. Re-measure the closed distance and the model's lengths, identify which of the three clearance points failed, and contact support with those two numbers — the fix is usually a different model or a moved mounting point, not a stronger actuator.
Where to Go Next
Space is the last sizing check before power and control: how to measure stroke length, how much force you actually need, how to mount a linear actuator, what power supply you need, and how to wire a linear actuator. For control hardware, see our linear actuator controllers and remote kits, and for the full decision path, our linear actuator selection guide.