Cylinder Rod-Side Force: The Two Directions Need Not Match

Define the illustrated geometry

SMC gives separate extending and retracting area expressions for the identified rod arrangement. Preserve that geometry rather than assuming equal directional areas. Primary reference: SMC directional-area expressions.

This guide considers a simple single-rod cylinder with bore diameter D and rod diameter d. Its full face is πD²/4; its annular face is π(D²−d²)/4. A different through-rod or specialized construction needs its own applicable geometry and force evidence.

Compare two hypothetical areas

With invented D = 20 mm and d = 10 mm, the full area is about 314.16 mm² and the annular area about 235.62 mm². At the same assumed 0.4 N/mm² effective pressure difference, the ideal contributions are about 125.66 N and 94.25 N. The annular area is 75% of the full area in this example.

Record the two areas and their force directions explicitly. The example assumes the stated pressure relationship and omits real chamber interactions and friction. These are geometric teaching values, not catalog thrust figures or measurements from HM equipment.

Keep both duty directions in the comparison

A task can require different external loads during extension and retraction. Compare each with the corresponding actual available-force basis instead of checking the larger area once and treating that as both directional conclusions.

Retain the actuator drawing and pressure assumptions with the offer. If the rod arrangement changes, earlier area calculations may no longer apply. This worksheet helps reveal directional asymmetry without selecting a cylinder, prescribing a load factor or implying that the two ideal values describe the complete dynamic performance of an installed assembly.

Customer Questions

Primary References

These references support the technical principles discussed in this guide. The worked examples and review questions are educational.

• Primary reference: SMC directional-area expressions