Steam Engine/Terminology

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Steam engines, like many technical subjects, have their own terms and jargon. These terms are described and illustrated here.

Terms

(the following terms need to be defined and ideally illustrated)

• Cylinder - A cylindrical shaped chamber into which steam is introduced to push against a piston to generate power.
  • Cylinder Cap - A part used to seal one or both ends of a Cylinder.
  • Cylinder Liner or Sleeve - A liner on the inside of Cylinder. Designed to be replaceable since the Piston Rings wear against the liner to create a pressure seal.
  • Cylinder Chamber - The volume between the Cylinder Cap and the Piston Crown.
  • Bore - The inside diameter (ID) of the Cylinder Liner and the outside diameter (OD) of the Piston Ring.
• Piston - A cylindrical shaped element that fits inside of the Cylinder. Expanding steam presses against the piston to generate power.
  • Piston Crown or Face - The top of the piston (steam side).
  • Piston Tail - The bottom of the piston (drive site). Usually connects to a Piston Rod to drive a Crankshaft.
  • Piston Rod (Connecting Rod) - A rod or linkage that connects the Piston Tail to the Crankshaft.
  • Piston Ring - One or more rings set into the piston to form a seal between the piston and the Cylinder Liner. Seal is necessary to prevent Blow-by.
  • Piston Cycle - The motion of a Piston in the Cylinder from Top Dead Center to Mid-Point to Return.
• Crankshaft - One or more offset (eccentric) Cranks attached to a Drive Shaft that translate the linear motion of a piston into rotational motion.
  • 'Crank- An shaft offset set from the Drive Shaft connected to a Piston via a Piston Rod used to transfer motion from the piston to the Drive Shaft.
  • Throw - another term for Crank.
  • Eccentric - Another term for Crank.
  • Mains and Pins (re. crankshaft)
  • Flywheel - A heavy disk attached to the Drive Shaft to store rotational energy as momentum. Helps move the Piston past Top Dead Center (TDC).
  • Drive Shaft - Outputs the rotational motion created by one or more Cranks from the Crankshaft assembly.
  • Cam - An elliptical or circular shaped part of the crankshaft designed to translate the rotary motion of the drive shaft to linear motion needed to activate a Cam Activated Valve (etc).
• Valves - A device to control the admission of steam into Cylinder Chamber.
  • Bump Valve or Bash Valve - A valve activated by a Bump Pin. A variety of shapes are possible.
  • Ball Valve - A Bump Valve in the shape of a ball held against the Valve Seat by a Valve Spring.
  • Piston Valve
  • Poppet Valve
  • Solenoid Valve - A Valve opened and closed by a Solenoid.
  • Cam Activated Valve - A Valve opened and closed by a Rocker Arm.
  • Pressure Activated Valve - A Valve opened and closed by Compression Pressure Activation.
  • Rocker Valve - A Valve opened and closed by a Rocker Arm.
  • Piston Valve - A cylindrical shaped valve attached to the piston face that slides in an out of the cylinder cap.
• Valve Activators - Parts, devices, or forces that cause a Valve to open and close.
  • Bump Pin - A small pin usually attached to the Piston Crown that causes a Bump Valve to open just before, during, and just after TDC of the Piston cycle.
  • Rocker Arm - A small linkage that opens a Cam Activated Valve driven by a Cam Link Rod.
  • Cam Link Rod - A linkage that transfers motion from a Cam to a Cam Activated Valve.
  • Solenoid - An electromagnetic plunger that opens (or closes) when a current is applied across a coil.
  • Valve Spring - A spring designed to hold a bump or ball valve against the valve seat.
  • Compression Pressure Activation - Pressure during the compression phase of the Piston Cycle used to open a Pressure Activated Valve.
• Valve Case - A piece that surrounds the valve mechanism to hold steam in before it is release when the valve opens.
• Valve Seat - The place where the valve comes into contact with the cylinder or cylinder cap.
• Steam Inlet - The place where steam enters the engine or cylinder.
• Steam Outlet or Vent - The place where steam exits the engine or cylinder. Also called the exhaust vent.
• Steam Engine - A engine based on the expansion of steam to drive it.
  • Uniflow or Unaflow - An engine design where steam enters at one place and exits at another. Steam always flows in the same (uniform) direction.
  • Counterflow -
• Action - The movement of a piston in a steam engine.
  • Single Action - 'Steam pushes the piston from a single direction.
  • Double Action - Steam pushes the piston from alternating directions.
  • Continuous Action
• Exhaust Plenum - A guide that channels steam being exhausted from the cylinder in multiple place to a single exit point.
• Oil Sprayer - A hole or nozzle that sprays oil onto the piston and piston rings to maintain lubrication against the cylinder liner.
• Steam Generator - A device to generate steam, for example, a boiler.
• Water Drain - A hole in the cylinder stopped with a plug or valve to enable condensed water to be removed from the cylinder.
• Clearance
• Cutoff
• Blowout and Blow-by - Steam blowing past a seal intended to hold it.
• Honing - Polishing the inside of a cylinder liner to reduce friction by the piston rings.
• Horsepower (hp)
• DeSaxe Principle
• Cycles (various kinds)
• Starter - A means to start up a steam engine.
  • Starter Motor - An electric motor used to start a steam engine.
  • Starter Hand Crank - A hand crank, sometimes on the flywheel, used to start the steam engine.
• Forces
  • Compression - Force pushing on an object from two or more directions.
  • Torsion - Force causing a rotational stress on an object.
  • Tension - Force pulling on an object from two or more directions.
  • Shear - Two or more oblique forces pushing on an object.
• Spalling and Galling - Surface defects resulting from frictional wear.
• Sensors - Devices to measure some quantity or quality.
  • Water Level Sensor - A device to measure the level of water in a reservoir or tank.
  • Pressure Gauge - A device to measure steam (etc) pressure in a closed system.

Abbreviations

• AES - Automotive Engineering Society
• SACA - Steam Automotive Club of America
• HP - High Pressure
• hp - Horse Power
• LP - Low Pressure
• OD - Outside Diameter
• ID - Inside Diameter
• DIA - Diameter
• IC - Internal Combustion
• TDC - Top Dead Center
• RPM - Rotations per Minute