Calculator Inputs
Formula Used
Ap = π × D² / 4
Ar = π × d² / 4
Aa = Ap − Ar
Fext,theoretical = (Ps × Ap) − (Pb × Aa)
Fret,theoretical = (Ps × Aa) − (Pb × Ap)
Feffective = max[(Ftheoretical × η) − Ffriction, 0]
W = F × L
Here, D is bore diameter, d is rod diameter, Ps is supply pressure, Pb is back pressure, η is mechanical efficiency, and L is stroke length. The calculator returns extension and retraction forces, work per stroke, total force for multiple cylinders, and safety-adjusted load estimates.
How to Use This Calculator
- Enter bore diameter and rod diameter using the correct unit selections.
- Enter stroke length to estimate work done during each extension or retraction cycle.
- Provide supply pressure and any opposing back pressure on the return side.
- Set a realistic mechanical efficiency percentage and friction allowance.
- Enter the number of cylinders if your design uses multiple actuators together.
- Choose a safety factor to estimate a conservative working load.
- Press Calculate Force to show results above the form.
- Use the CSV or PDF buttons to save the final summary.
Example Data Table
| Case | Bore | Rod | Supply Pressure | Extension Force Total (N) | Retraction Force Total (N) | Safe Extension Load (N) |
|---|---|---|---|---|---|---|
| Compact Automation | 32 MM | 12 MM | 5 BAR | 331.25 | 277.30 | 236.61 |
| General Purpose | 63 MM | 20 MM | 6 BAR | 1,556.78 | 1,368.91 | 1,037.85 |
| Heavy Load Pair | 100 MM | 32 MM | 7 BAR | 8,760.86 | 7,631.69 | 4,380.43 |
These examples help compare compact, general, and heavier actuator selections using the same force model as the calculator.
FAQs
1. Why is extension force usually higher than retraction force?
Extension force uses the full piston face. Retraction force acts on the annular side, where the rod reduces available area. Less area means lower force at the same pressure.
2. Should I include back pressure?
Yes, when exhaust restriction, cushioning, or downstream control devices create resistance. Back pressure lowers the net usable force and can noticeably affect retraction calculations.
3. What does mechanical efficiency represent?
It represents real losses from seals, misalignment, wear, and internal friction. A lower efficiency gives more conservative results and better reflects field conditions.
4. Why add a separate friction allowance?
A fixed friction allowance helps model seal drag or guide resistance that remains present even when pressure changes. It improves practical sizing decisions.
5. What safety factor should I use?
That depends on shock loading, duty cycle, uncertainty, and consequences of failure. Many designs use values above 1.25, while harsher conditions often need more margin.
6. Does stroke length change force?
Stroke length does not change static force directly. It changes work per stroke because work equals force multiplied by travel distance.
7. Can I size multiple cylinders together?
Yes. Enter the cylinder count to estimate total combined force and total work. This is useful for synchronized lifting or parallel actuator arrangements.
8. Are these results enough for final machine design?
They are excellent for preliminary sizing. Final design should also check buckling, speed, valve flow, mounting loads, cushioning, temperature, and structural stiffness.