Design calculation of gas spring cylinder

Posted by: harry | on February 8, 2025

7.5 Design calculation of gas spring cylinder

7.5.1 Calculation of cylinder inner diameter

The cylinder inner diameter of the gas spring should be decided according to GB/T 2348, and it is recommended to adopt the ratio of the cylinder inner diameter D₁ to the piston rod diameter d as approximate D₁/d = 2, or refer to Annex C. It can also be agreed between supplier and vendor.

7.5.2 Calculation of thickness of cylinder

The thickness of cylinder δ₁ is calculated according to formula (21), and is generally not less than 1 mm. The ratio of the cylinder outer diameter D₂ to the inner diameter D₁ is not less than 1.1. The allowable stress of the cylinder material is shown in Table D.2.

………………(21)

In the formula, P_max is the maximum internal pressure in the gas spring operating state, where P_max is calculated according to formula (22):

………………(22)

7.5.3 Verification of cylinder strength

The strength of the cylinder can be verified as described in Annex F.

7.6 The relationship between the design stroke S, guide length H and cylinder gas chamber length L₃ of the compression gas spring

When designing gas spring, the guide length should be calculated to ensure stability of the movement and a certain anti-deviated load capacity. See Figure 15 for details.

Figure 15 Schematic diagram of design stroke S, guide length H and cylinder gas chamber length L₃ of the compression gas spring

The design stroke S, guide length H and cylinder gas chamber length L₃ should meet the requirements of Table 2.

	Table 2	Unit: mm
Design stroke S	Guide length H	Gas chamber length L₃
S ≤ 150	H ≥ 15	L₃≥ S
150 < S≤ 200	H ≥ 20
200 < S≤ 250	H ≥ 25
250 < S ≤ 300	H ≥ 30
300 < S ≤ 350	H ≥ 35
350 < S ≤ 400	H ≥ 40
S > 400	H ≥ 45