Selecting hydraulic cylinders: force, stroke and the right dimensions

Force and direction of movement

First describe whether the task involves pushing, pulling or working in both directions. Double-acting cylinders can have different forces and oil volumes for extension and retraction. Catalogue figures are therefore always read for the relevant movement direction.

For multiple cylinders, the load at each point matters. The total load must not be assumed to be evenly distributed across all cylinders without considering load distribution.

Stroke and height

Stroke is the usable travel. Retracted height describes the space needed before movement, while extended height describes the space needed at the other end of travel. Saddles and other accessories can further change the installation height.

The manufacturer recommends allowing margins for force and stroke during selection. Specific sizing depends on the application, load support and manufacturer documents; a filter match is initially a technical shortlist.

Four diameters, four meanings

Outside diameter describes the cylinder’s external body. Piston rod diameter relates to the moving external component. Bore diameter refers to the internal cylinder geometry. For a hollow-ram cylinder, the clear centre hole for the rod passing through it is an additional decisive dimension.

Not every design is round. For RLS, for example, the drawing specifies outside dimensions C1 and C2. The finder keeps these dimensions separate so that a rectangular or flattened envelope is not incorrectly treated as a round diameter.

Important for your enquiry

• What force direction and load per point apply?
• What stroke and minimum and maximum heights are permitted?
• Are you looking for an outside dimension or a clear through-opening?

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