Calculator Inputs
Formula Used
This calculator models a two-dimensional pinned linkage. The actuator base pivot is fixed at (Bx, By). The rod-end pivot moves on a circle around the rotation center (Cx, Cy) with radius r.
Rod-end coordinates at any angle θ:
x(θ) = Cx + r cos(θ)
y(θ) = Cy + r sin(θ)
Installed actuator length at angle θ:
L(θ) = √[(Bx − x(θ))² + (By − y(θ))²]
Dynamic stroke across the full motion path:
Stroke Required = max[L(θ)] − min[L(θ)]
Recommended nominal stroke:
Recommended Stroke = Stroke Required × (1 + Safety Margin) + 2 × End Reserve
Required extension from a chosen retracted actuator:
Extension Needed = max[L(θ)] − Closed Length
How to Use This Calculator
- Enter the rotation center and the fixed base pivot coordinates in one consistent unit system.
- Enter the rod-end radius from the rotating center to the rod pin location.
- Provide the start and end motion angles for the lever, arm, or flap.
- Set the actuator closed length and the available catalog stroke you want to verify.
- Add a safety margin and end reserve if you need extra design allowance.
- Press Calculate Stroke to view the result above the form.
- Review the graph and table to confirm whether peak stroke occurs inside the travel path.
- Use the CSV or PDF buttons to save the design summary and motion data.
Example Data Table
Example setup uses: center (0, 0), base (-180, 50), radius 130, start angle -30 deg, end angle 85 deg, closed length 190 mm, and available stroke 150 mm.
| Angle (deg) | Actuator Length (mm) | Extension From Closed (mm) | Extension Utilization (%) |
|---|---|---|---|
| -30.00 | 314.372 | 124.372 | 82.91 |
| -1.25 | 314.440 | 124.440 | 82.96 |
| 27.50 | 295.482 | 105.482 | 70.32 |
| 56.25 | 258.827 | 68.827 | 45.88 |
| 85.00 | 207.192 | 17.192 | 11.46 |
Example dynamic stroke: 109.624 mm. Example recommended nominal stroke: 130.586 mm.
FAQs
1. What does actuator stroke length mean?
It is the total linear travel the actuator must provide between the shortest and longest required installed lengths during motion.
2. Why can stroke be larger than the start-to-end change?
Some linkage layouts reach a hidden internal peak length between the entered end angles. The calculator samples the full travel to catch that case.
3. What is closed length in this calculator?
Closed length is the retracted pin-to-pin actuator length. It is used to check whether the actuator can physically fit at the shortest motion position.
4. What does available stroke margin show?
It compares the selected actuator stroke against the calculated extension demand. Positive margin means the actuator still has spare travel capacity.
5. Why should I add reserve at each end?
End reserve helps avoid running the actuator into hard stops, manufacturing tolerances, and field misalignment near both extremes of travel.
6. Can I use inches instead of millimeters?
Yes. Use any consistent unit system. The unit label simply changes how results are displayed on the page, graph, and exports.
7. What geometry is assumed here?
The model assumes a planar linkage with a fixed actuator base pin and a moving rod-end pin attached to a rotating arm.
8. How many sampling points should I use?
For general design, 100 to 200 points works well. Use more points when the mechanism has rapid geometric changes or sharp nonlinear motion.