Then assemble the parts back on the piston rod. Henszey's device consists of two pistons mounted on a single piston rod. There was thus no longer any need for a piston rod. Depending on how long the piston rod is, stresses can be calculated differently. Wear and corrosion resistant surfaces are desirable on the outer diameter of the piston rod. This accident was also caused by corroded threads in the piston rod and rod end. Rather than a piston rod, they used an iron chain. The smallest stage is often called the plunger or piston rod. The hammer would be welded to a piston rod contained in a cylinder. This means that a plunger cylinder in general has a relatively thick piston rod. That allows the piston rod assembly and the rod seals to be removed for service. The crosshead became part of the piston, and there was no longer any piston rod. The entire piston rod is chromium-plated to prevent fouling. A trunk engine locates the connecting rod "within" a large-diameter hollow piston rod. The piston rod connects the hydraulic actuator to the machine component doing the work.