Survpedia
Search
ES EN
← Inventions
Generated with AI

Piston

Made of

Iron Steel Aluminum Brass

Brief description

A component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings.

Use / Function

  • Primary Use: To transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod (in an engine) OR to transfer force from the crankshaft to the fluid in the cylinder for the purpose of compressing or pumping the fluid (in a pump).

Operating principle

  • In an Engine: Expanding gas (combustion or steam) pushes against the piston head, forcing it down the cylinder. This linear motion is converted to rotary motion.
  • In a Pump: The piston is pulled/pushed, creating a vacuum (suction) or pressure (compression) to move a fluid.

How to create it

Simple Piston

  1. Head (Crown): The top surface that withstands the pressure/heat. Usually Cast Iron or Aluminum (lighter).
  2. Skirt: The side walls that guide the piston in the cylinder bore.
  3. Pin (Wrist Pin): A hollow steel shaft that connects the piston to the connecting rod.
  4. Rings: Cast Iron or Steel rings that fit into grooves on the piston. They spring outward to seal against the cylinder wall, preventing gas blow-by and scraping oil.

Materials needed

Variants and improvements

  • Trunk Piston: Standard design (like in a car engine).
  • Crosshead Piston: Used in large engines (ships/steam); the piston rod connects to a crosshead which slides in guides, taking the side thrust off the piston.
  • Plunger: A solid cylinder used in pumps; simpler to seal.

Limits and risks

  • Seizure: If the piston expands more than the cylinder (due to heat), it can get stuck (seize), destroying the engine. Clearance is critical.
  • Slap: If the clearance is too loose, the piston rocks and makes noise (piston slap).
  • Blow-by: Worn rings allow gas to leak past, reducing power and contaminating oil.