Locking vs free gas springs: three typical applications compared
Free (compression) gas springs only push; locking types hold at any position. Comparing lift-up doors, height-adjustable legs and medical bed backrests, with a selection order and installation notes.
Short answer: choose a free (compression) gas spring when the load only needs to be "lifted and held"; choose a locking type when a person must move the load to any position and lock it there. One criterion decides: does the load position need to be changed and fixed by hand, frequently?
The structural difference drives the behaviour
A free gas spring is a nitrogen-charged cylinder that only outputs pushing force; the end of stroke is the working position. A locking type adds a release mechanism - before the release lever is pulled, the rod carries tension and compression loads and stays put at any point.
Three typical scenarios
| Application | Type | Why |
|---|---|---|
| Service doors and lids | Free | Gas pressure holds the door once opened; the open position is the natural end |
| Height-adjustable legs and columns | Locking | Set height must stay rigid under working loads - gas holding force alone cannot resist them |
| Medical bed backrests and recliner backs | Locking | Angle is set by the patient or carer; the release lever must sit within reach |
Selection order and notes
First ask whether the load position changes by hand - if not, free type; if yes, locking. Then calculate the required force (F1) from the pivot geometry and check stroke and installed length. Force calculation and the rod-down mounting rule are covered in Gas spring mounting direction: three common mistakes.
Two notes: the locking force depends on release-lever placement, so state the release direction when ordering; and specific force/stroke combinations follow the original manufacturer data. The HAHN range (e.g. G 02-06) covers both structures; Juanmu provides per-scenario sizing support.
