Calculate hydraulic cylinders

Hydraulic cylinders are linear motors. They are force-displacement devices that exert a constant force over a specific distance. This force is used to redirect or lift other components.

Although hydraulic cylinders also exist as “slaves,” they only play a minor role in this function in modern hydraulics. Examples of slave cylinders can be found in pallet trucks, hydraulic jacks, or hydraulic braking systems.

However, the majority of hydraulic cylinders are used as master cylinders for the described application of high forces over defined distances.

Our online calculators for calculating hydraulic cylinders:

1. » Calculate force on the differential cylinder at a specific pressure
2. » Calculate required pressure on the cylinder for specific forces
3. » Calculate return volume / oscillating volume
4. » Calculate extension and retraction speed on the differential cylinder
5. » Calculate forces and speeds on the cylinder
6. » Calculate cylinder with anti-cavitation
7. » Calculate cylinder with tensile load
8. » Cylinder calculation – Calculate differential cylinders

Parameters for calculating hydraulic cylinders

When calculating a hydraulic cylinder, it is best to work from the “outside in.” This means that the basic parameters must first be defined before working towards the exact design of the linear motor. The basic parameters of a hydraulic cylinder are:

• maximum executable force
• maximum extendable path length
• maximum extension speed

These parameters determine the basic suitability of this component. A hydraulic cylinder can offer many advantages, but if these parameters are not met, the device is useless for the intended purpose.

The installation location in the calculation of a hydraulic cylinder

The second stage of conditions relates to the installation location. Here, it must be determined within which framework the hydraulic cylinder is allowed to move:

• Weight of the linear motor
• Size of the linear motor

The weight of the linear motor is particularly important for vehicles. The lighter the hydraulic cylinder, the less energy is required for its transport. Furthermore, a lower weight reduces the static load on the vehicle frame. This, in turn, can be made lighter or from less expensive materials, which again saves weight and energy.

It is therefore sensible to define a linear motor as precisely as possible. A precisely calculated linear motor also allows conclusions to be drawn about the required hydraulic pump and its drive.

Here again, it is vehicles that benefit particularly from precise calculation. Smaller hydraulic pumps and drives are lighter and require less active cooling. The vehicle as a whole becomes cheaper and lighter.

Calculate hydraulic cylinders: Formula and procedure

The following variables are required for the exact calculation of a linear motor:

D = Piston diameter Ø in mm
d = Piston rod diameter Ø in mm
A = Piston area in cm2 (Calculated via D²/4 × π)
p = Pressure in bar
F = Force dN (? kg)
h = Stroke in mm (=distance)

The most fundamental of all parameters for hydraulic cylinders is its producible compressive force. Therefore, the formula for calculating the hydraulic cylinder is designed for force. It is:

Force = Pressure × Piston Area / F = p × A = dN

In hydraulic systems, however, the efficiency in hydromechanical systems must be taken into account. This is approximately assumed to be 0.85 – 0.95.

Three formulas for calculating the hydraulic cylinder

Compressive force: Fd = (p × D2 × 0.785 × ηhm) / 100 = dN
Pressure: p = (Fd × 100) / (0.785 × D2) = bar
Diameter: [(Fd × 100) / (0.785 × p)]^1/2

It therefore requires several passes until you have worked your way towards the desired performance parameters of the ideal linear motor. You then select the most suitable hydraulic cylinder from a standard parts catalog. Important: when selecting, you must always round up, i.e., choose the next larger cylinder, otherwise the hydraulic system cannot achieve its required performance.

TIP: If a standard hydraulic cylinder is too large, a telescopic cylinder can be a good alternative.