Hydraulic Cylinder to Joint Torque Calculator
Enter your cylinder's bore, pressure and lever arm — or the load and its reach — and get the torque at the joint in Nm and lb-ft. Then see whether an electric rotary actuator can take the cylinder's place.
5,611 Nm is inside the RG600's 6,000 Nm rating, so a single unit covers this joint on torque.
Your cylinder pulls with only 69% of its push force, because the rod takes up part of the piston. The RG600 drives with the same torque in both directions, so the joint is equally strong lifting and lowering, opening and closing.
You need 9.0°/s. At 1,600:1 the RG600 turns up to 9.4°/s (1.6 rpm). The higher the ratio, the smaller the motor needed for the same torque.
That is the mechanical power the joint itself needs. Our 48V motors come in 1, 2 and 3 kW — send us the joint and we'll match the motor and ratio.
Your numbers carry across to the form. Evaluation unit A$4,950, credited in full against your first order of 10 or more. About 2 months lead time.
The maths behind the number
- Cylinder force = pressure × piston area. Pushing uses the full bore; pulling uses the bore minus the rod.
- Joint torque = cylinder force × lever arm, where the lever arm is the perpendicular distance from the pivot to the cylinder's centre line.
- From a load: torque = mass × 9.81 × horizontal distance from the pivot. 1 tonne held 1 metre out is about 9,800 Nm.
- Speed and ratio: degrees moved ÷ seconds taken. The RG600 comes in 800:1, 1,200:1 and 1,600:1 as standard (up to about 19, 12.5 and 9.4°/s), with custom ratios from 400:1 to 2,400:1. A higher ratio is slower but reaches the same torque with a smaller motor.
Cylinder torque FAQ
How do you convert hydraulic cylinder force to joint torque?
Multiply the cylinder force by the effective lever arm: the shortest distance from the pivot pin to the cylinder's centre line. Cylinder force is pressure times area — the full bore area when the cylinder pushes, and the bore area minus the rod area when it pulls. For example, an 80 mm bore at 180 bar pushes about 90,500 N; on a 250 mm lever arm that is about 22,600 Nm.
Why does the lever arm change as the joint moves?
As the joint rotates, the angle between the cylinder and the arm changes, so the perpendicular distance from the pivot to the cylinder's line of action changes too. That is why a cylinder-driven joint is strongest in one part of its stroke and weaker at the ends. Measure the lever arm at the worst-case position. A rotary actuator at the pivot delivers the same torque across its whole range of rotation.
Is a hydraulic cylinder as strong pulling as pushing?
No. Pushing, the oil acts on the whole piston. Pulling, it acts only on the ring around the rod, so the cylinder has less area and less force — often 50–70% of its push force, depending on the rod size. An electric rotary actuator like the RG600 drives with the same torque in both directions.
Should I use the relief pressure or the working pressure?
The relief pressure gives the most the cylinder can ever push, which is the safe upper bound. The pressure the joint actually works at under load is usually lower, and is the better number for sizing an electric replacement. If you only know the load, use the load-and-reach mode instead.
Can one RG600 replace my cylinder?
If the joint torque is within 6,000 Nm, one RG600 covers it on torque. Between 6,000 and 10,000 Nm it is above the rated torque but within the max, which suits occasional peaks. Beyond that, two or more units can share the joint. The RG600 is a slow, heavy joint: up to about 3.1 rpm on the standard 800:1 ratio, or about 6 rpm on a custom 400:1. It suits lifts, folds, tilts, legs and levelling rather than fast swing.
Replace the cylinder with an electric joint
The RG600 sits right at the pivot and drives it off your battery: rated to 6,000 Nm, 10,000 Nm max torque, with no pump, tank or hoses. See the RG600, or send us the joint and we'll size it for you.