1.2 Output Force

As the spring is compressed, the shaft enters the body, reducing the internal volume and increasing the internal pressure. (This is known as BOYLES LAW.) When the shaft is at the end of its stroke the pressure in the spring is at its maximum.

---

BOYLES LAW

The ratio of the final pressure to the charge pressure is the Force Ratio.The output force of the shaft is equal to the internal pressure times the cross section area of the shaft minus any friction effects.

NOTE: The above formula can be used at any position of the stroke to determine the internal pressure and output force. However, this formula does not consider the effect of temperature change which will be discussed in section 1.4

---

Example

Assume a gas spring with a:

If the shaft is inserted the full stroke,

Therefore, the output force of the shaft at full stroke equals:

The force ratio for the gas spring in the example is

NOTE: This example does not take frictional effects into consideration.

---