Application data
The load ratio sets how much of the theoretical force is used (allowance for friction, acceleration and pressure drop).
Recommended set
| # | Product | Code | Qty | Note |
|---|
Comparison for all bore sizes
| Bore Ø (mm) | Rod Ø (mm) | Theoretical force (N) | Load utilization | Buckling | Status |
|---|
Force is calculated on the effective area of the selected stroke (rod area is deducted on the pull stroke). Results are estimates. Cylinder and valve data come from the Pemaks catalog; for critical applications catalog and engineering approval are required.
Print / PDF
When you print, usage data (calculated values and the information you entered) is sent to Sistemay; your e-mail is not used for contact unless you give consent. Choose “Save as PDF” in the print dialog.How is it calculated?
First the load force is found: the weight of the vertically lifted mass (m·g) plus any external force (pushing, friction, clamping). For horizontal motion leave the mass at 0 and enter the required force (for example μ·m·g) as the external force. The cylinder is selected so that it uses only the chosen load ratio of its theoretical force, leaving allowance for friction, acceleration and pressure losses.
The bore is the smallest size in the Pemaks ISO 15552 range (DMC series Ø32–Ø100; ISO series for Ø125; PMB series Ø160–Ø320) that meets this condition and the rod buckling check. The valve is the smallest Pemaks valve that covers the peak flow needed to fill the cylinder.
Force: F = p · A (p in bar, A in mm², F in N: F = p·A/10)
Required force: F_req = F_load / load ratio
Buckling (Euler): F_cr = π² · E · I / (K · L)², I = π·d⁴/64, allowable = F_cr / 4
Peak flow: Q = A · v · (p + 1.013) / 1.013 (free air, L/min)
Example
Lifting a 100 kg load vertically at 6 bar with a 300 mm stroke at 300 mm/s gives a load force of about 981 N and, at a 70% load ratio, a required force of about 1,401 N; the smallest suitable Pemaks cylinder is Ø63 (1,870 N at 6 bar).
Selection tips
- For fast or impact applications use a 50% load ratio; the cylinder is one size larger but lasts longer.
- On long strokes rod buckling can decide the bore; shorten the stroke or use an external guide where possible.
- Mount the valve close to the cylinder and choose tubing suitable for the valve port; long or thin tubing reduces flow.
- For heavy loads and vertical applications consider a rod lock or a 5/3 closed-center valve for safety.
Frequently asked questions
What is the load ratio and which should I choose?
It shows how much of the cylinder’s theoretical force is used for the work. 85% is typical for slow, steady loads, 70% for normal applications and 50% for fast or impact motion.
Why is the buckling check important?
On long-stroke cylinders the rod can bend under push load and overstress the cylinder. The tool checks this with Euler’s formula and suggests a larger bore if needed.
How is the valve flow selected?
The free-air flow needed to reach the cylinder speed is calculated and compared, with a safety factor of 1.5, with the flow values in the Pemaks valve brochures. For critical applications also consider tubing and fitting losses.
Where can I get the recommended products?
Send us the product codes in the result; we will reply with stock, price and delivery time.
What if there is a side load?
A plain cylinder rod must not carry side loads. Use an external guide or the guided / slide cylinder series; send us your application and we will choose the right series together.
Shall we finalize your selection together?
Send us the result and your dimensions; we will quote the cylinder, valve, fittings and tubing with stock and price.