BIZOMAT MAKEOS · Pneumatics
Hinged Flap Cylinder Check (Force Through the Swing, Stroke, Cylinder Size)
For a hinged flap, lid or door raised by a pneumatic cylinder, what force does the cylinder need through the swing, what stroke, and is my cylinder big enough?
Check of a cylinder raising a hinged flap: the moment of the flap weight about the hinge at each angle through the swing, the cylinder length and its moment arm about the hinge from the base and rod-end pivot positions, the cylinder force needed at each angle and its largest value, the stroke needed, then the extend force, load ratio and smallest bore for that force at the supply pressure (as the pneumatic cylinder force tool), against your load ratio limit and the cylinder stroke.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Flap mass | kg | Mass of the flap or lid. |
| Hinge to flap centre of gravity | mm | Distance from the hinge to the flap’s centre of gravity, measured along the flap. |
| Swing (from horizontal) | ° | Angle the flap swings through, from closed (horizontal). |
| Cylinder pivots (hinge at 0, 0; flap along +X when closed) | ||
| Hinge to rod-end pivot along the flap | mm | Distance from the hinge to the cylinder rod-end pivot, along the flap. |
| Base pivot X | mm | Horizontal position of the cylinder base pivot from the hinge. |
| Base pivot Y | mm | Vertical position of the base pivot (negative below the hinge). |
| Cylinder | ||
| Bore | mm | Cylinder bore. |
| Rod diameter | mm | Rod diameter. |
| Supply pressure (gauge) | bar | Supply pressure. |
| Efficiency (seal friction) | % | Share of the theoretical force left after seal friction. |
| Largest load ratio | % | Largest share of the theoretical force the load may use (lower for smooth, fast motion). |
| Cylinder stroke | mm | Stroke of the cylinder you have. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Flap mass
- What it is
- The full mass of the moving flap, lid or door, including handles, glazing and anything fixed to it that the cylinder must lift.
- Units and format
- Enter a number in kg: kilograms. The form accepts 0.000001 kg to 100000 kg. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 50 kg as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The cylinder force needed at every angle rises in direct proportion to the mass.
- Get it right
- Weigh the flap or take the mass from the CAD model; remember linings, seals and fittings added later.
What this means: Hinge to flap centre of gravity
- What it is
- How far the flap’s centre of gravity sits from the hinge axis, measured along the flap. With the flap closed this is the lever arm of its weight about the hinge.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 400 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The weight moment, and so the force needed, rises in direct proportion to this distance.
- Get it right
- For a uniform flat flap the centre of gravity is at half its length from the hinge; heavy fittings near the free edge move it outwards.
What this means: Swing (from horizontal)
- What it is
- The angle the flap turns through from closed (lying horizontal along +X) to fully open. The tool checks the cylinder at many angles across this swing.
- Units and format
- Enter a number in °: degrees of angle. The form accepts 1° to 180°. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 90° as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger swing usually needs more stroke and can move the cylinder line close to the hinge, where the force climbs.
- Get it right
- Measure from horizontal, not from vertical: a flap that opens to upright swings through 90°.
Cylinder pivots (hinge at 0, 0; flap along +X when closed)
What this means: Hinge to rod-end pivot along the flap
- What it is
- Distance from the hinge axis to the cylinder’s rod-end pivot, measured along the flap. It sets where the cylinder pushes on the flap.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 150 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Moving the rod-end pivot further from the hinge lengthens the moment arm, lowering the force but needing more stroke.
- Get it right
- Measure to the centre of the rod-end pin, not to the edge of the bracket.
What this means: Base pivot X
- What it is
- Horizontal position of the cylinder’s fixed base pivot, measured from the hinge axis along the closed flap direction. Positive is towards the flap’s free edge.
- Units and format
- Enter a number in mm: millimetres. The form accepts -100000 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 100 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the pin centre of the base mounting; the hinge is the origin of the coordinates.
What this means: Base pivot Y
- What it is
- Vertical position of the cylinder’s fixed base pivot relative to the hinge axis. A base pivot below the hinge is a negative value.
- Units and format
- Enter a number in mm: millimetres. The form accepts -100000 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with -300 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Keep the sign right: a base mount under the hinge is negative. If the cylinder line passes through the hinge the tool stops with a message.
Cylinder
What this means: Bore
- What it is
- The inside diameter of the cylinder barrel, which the piston fills. The full piston area pushes when the cylinder extends to open the flap.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 63 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The extend force grows with the square of the bore, so the load ratio falls quickly as the bore increases.
- Get it right
- Use the nominal bore from the cylinder catalogue, not the barrel outside diameter.
What this means: Rod diameter
- What it is
- The diameter of the piston rod. Here it is only checked to be smaller than the bore, because the flap is lifted on the extend stroke where the full piston area acts.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Take it from the catalogue for the chosen bore; it does not change the extend force in this tool.
What this means: Supply pressure (gauge)
- What it is
- The air pressure reaching the cylinder while it opens the flap, read on a gauge above atmospheric pressure, after the regulator and any valve losses.
- Units and format
- Enter a number in bar: bar (1 bar = 100 kPa). The form accepts 0.000001 bar to 50 bar. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 6 bar as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The theoretical force rises in direct proportion to the pressure, so the load ratio falls as pressure rises.
- Get it right
- Use gauge pressure at the cylinder, not the compressor setting; long hoses and small valves lower it.
What this means: Efficiency (seal friction)
- What it is
- The share of the theoretical piston force left after seal and guide friction. It is used for the extend force the tool reports.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 10% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 90% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Take it from the cylinder maker’s data; it reduces the reported extend force but the load ratio check uses the theoretical force.
What this means: Largest load ratio
- What it is
- Your limit on how much of the cylinder’s theoretical force the flap may need at the worst angle. The rest is reserve for speed, friction and pressure dips.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 10% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 80% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A lower limit asks for a larger smallest bore.
- Get it right
- Type the percentage itself; pick it from the cylinder maker’s sizing advice or your own design rules.
What this means: Cylinder stroke
- What it is
- The stroke of the cylinder you intend to use: how far the rod travels from fully retracted to fully extended. It is compared with the change in pivot-to-pivot length over the swing.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 160 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the catalogue stroke, not the overall installed length of the cylinder.
Method and formulas
- Weight moment about the hinge = m g r_g cos θ; rod end at (r_c cos θ, r_c sin θ).
- Cylinder line from the base pivot to the rod end; moment arm = perpendicular distance from the hinge; force needed = moment ÷ arm, the largest over the swing.
- Extend force = p A η; load ratio = force needed ÷ p A; smallest bore = √(4F ÷ (π p × ratio)) (as the pneumatic cylinder force tool).
- Example: up to 1,377.5 N needed at 25°; stroke 156.84 mm; load ratio 73.648%.
Limitations
- Slow lift; acceleration and cushioning loads are extra.
- Flap centre of gravity on the line from the hinge through the rod end.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size a cylinder to lift a machine guard or hopper lid
- Choose cylinder pivot positions
- Check a flap cylinder after adding weight
Who it is for
- Machine designers
- Automation engineers
- Maintenance engineers
What you get
- Force needed through the swing
- Cylinder lengths and stroke
- Cylinder force, load ratio and smallest bore
Interpreting the result
- Moving the rod end further from the hinge cuts the force but lengthens the stroke in proportion.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3032–3041, 153–163. Topic reference; no source tables or recommended settings are reproduced.
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Open the Hinged Flap Cylinder Check (Force Through the Swing, Stroke, Cylinder Size) calculator