So say you have a pneumatic cylinder (ram) with a certain length and wall thickness. The ram is pressurized to the same pressure each time (1000psi)
Force is equal to pressure x area. So as the length (stroke) of the cylinder increases, so does the area and thus the force, right? Does this mean that as a ram gets longer, the wall thickness must also get thicker to prevent it from cracking/exploding?
The increased area of the cylinder walls would increase the net force those walls experience if we are considering the same pressure in each scenario (force on the piston should therefore be the same as it doesn't change diameter in your example).
There are a couple other factors to consider though. For example, although the force will be greater, the way materials resist forces is actually more analogous to pressure (i.e. Stress and strain). You're increasing the total force, but force per unit area is the same. This means that the stress in the material is also approximately the same, and it is the stress that causes failure in material.
For a pressurized cylinder, the wall thickness is generally proportional to the pressure and the radius of the vessel. This means that for a general cylinder, you shouldn't require a change in wall thickness if it is only the length of the cylinder changes. With a large change in size this may vary, as at some point the weight of additional material vs thickness could become a factor causing localized buckling of the walls.
You can find a lot of good information on the scaling of wall thickness for pressure vessels on this page. Many mechanical design textbooks also cover this topic in detail.
