Example data table
These examples show realistic values for testing. Match the inputs to reproduce similar results.
| Case | Mode | Drive | Key inputs | What to expect |
|---|---|---|---|---|
| A | Rotary | Pneumatic | Break 650 N·m, Seat 720 N·m, Arm 0.08 m, Pmin 6 bar, SF 1.25 | Design torque near 1,035 N·m and a practical bore recommendation. |
| B | Linear | Hydraulic | Push 12 kN, Pull 10 kN, Stroke 200 mm, Pmin 5 MPa, SF 1.20 | Smaller bore due to higher pressure; check stroke volume. |
| C | Rotary | Electric | Control torque 500 N·m, Angle 90°, Time 12 s, Motor eff 0.8 | Power estimate from average torque and speed. |
Formulas used
- Controlling torque = max(Breakaway, Seating, Running)
- Design torque = Controlling torque × Safety factor × Service factor
- Controlling thrust = max(Push, Pull)
- Design thrust = Controlling thrust × Safety factor × Service factor
- ΔP = Pmin − Pback
- Force = Torque ÷ Arm length
- Area = Force ÷ (ΔP × Efficiency)
- Bore = √(4 × Area ÷ π)
How to use this calculator
- Select Rotary for torque-driven devices or Linear for thrust-driven devices.
- Choose the Drive type. Use pressure inputs for pneumatic or hydraulic sizing.
- Enter the worst-case load values and set safety and service factors.
- For rotary pressure drives, set a realistic effective arm length.
- Click Submit. Results appear above the form for quick review.
- Use Download CSV or Download PDF to document the calculation.
Technical article
1) Define the governing load case
Actuator sizing starts with the worst-case demand, not the normal operating value. For rotary devices, compare breakaway, running, and seating torque and let the maximum control the design. For linear devices, use the larger of push and pull thrust. This calculator applies a safety factor and a service factor to convert the governing load into a design load suitable for preliminary selection.
2) Convert pressure into useful force
Pneumatic and hydraulic actuators deliver force from pressure acting on piston area. The effective pressure is the available inlet pressure minus any back pressure at exhaust or return. Using a realistic efficiency (often 0.75–0.90) prevents overestimating output when linkages, seals, and friction are present.
3) Translate torque to cylinder force
For rotary applications with a lever or scotch-yoke approximation, torque is related to force by T = F × r, where r is the effective arm length at the critical position. A short arm increases required force rapidly, so confirm mounting geometry and the torque peak location.
4) Bore and consumption checks
Once force is known, the calculator computes piston area and an equivalent bore, then suggests a nearby standard bore. For linear pneumatic sizing, it also estimates air per cycle using an approximate normal-liter conversion. Use this result to validate compressor capacity, line sizing, and expected cycle frequency.
5) Use exports for traceable documentation
Construction commissioning and handover often require a repeatable calculation record. After you submit inputs, export CSV for quick spreadsheet review or PDF for submittals. Keep notes about assumptions like effective arm length, minimum pressure at the actuator, and environmental service conditions.
FAQs
1) Which torque should I enter for rotary sizing?
Enter breakaway, running, and seating torque when available. The calculator selects the maximum as the controlling torque, then applies safety and service factors to create a design torque for preliminary selection.
2) What is “effective arm length” and how do I choose it?
It is the assumed radius where actuator force produces the required torque. Use the shortest effective radius at the critical position, based on linkage drawings or manufacturer geometry, to avoid undersizing.
3) Why does back pressure matter for pneumatic and hydraulic drives?
Back pressure reduces usable differential pressure across the piston. The calculator uses ΔP = Pmin − Pback, so even small back pressure can increase required area and bore.
4) What efficiency value is reasonable?
For preliminary work, 0.80–0.90 is common for clean, well-aligned mechanisms, while dusty environments or complex linkages may be closer to 0.70–0.80. Use project experience and confirm with vendor curves.
5) Does the electric option size motor torque accurately?
It estimates average power from design load and travel speed, then divides by motor efficiency. Final electric actuator selection should also verify peak torque, starting current, duty cycle, and any stall or overload limits.
6) Why does the tool recommend a “standard bore”?
Cylinders and rotary linkages are typically purchased in standard sizes. The calculator rounds up to the nearest common bore to provide a practical starting point for vendor selection and availability checks.
7) Can I use this output for final procurement?
Use it for preliminary sizing and documentation. Before procurement, validate torque or thrust profiles, temperature range, mounting geometry, required fail position, and manufacturer output curves at the true site pressure and voltage conditions.