Cylinder Clearance Volume The clearance volume of a cylinder (often presented as a percentage term) is that part or proportion of the cylinder volume that is not swept by the piston. It is therefore the volume (or proportion of total volume) taken up by the steam passages and cylinder-head cavities – i.e. the volume contained […]
Steam Chest The steam chest (or steamchest) is the “reservoir” for collection of steam as it passes between the superheater header and the inlet port to the cylinder. The advantage of a large steam chest (as is the advantage of any reservoir) is that fluctions in pressure as the steam passes from the steamchest into […]
Superheating of Steam Page Under Development This page is still “under development”. Please contact Chris Newman at webmaster@advanced-steam.org if you would like to help by contributing text to this or any other page.’ Background On page 160 of his book “The Red Devil and Other Tales from the Age of Steam” Wardale confirms that: “The […]
Primary and Secondary Combustion Air and Combustion Gases Combustion Air is the air drawn through the firebox by the draughting system which allows combustion to take place. Only the oxygen content of the air (approx 18%) is used in the combustion process, the remainder (mostly nitrogen) being inert and serving no function other than wasting […]
Dynamic Augment or Hammer Blow Hammer Blow or “Dynamic Augment” is a dynamic force imposed through the driving wheels and onto the railway track resulting from the rotation of out-of-balance weights that are attached to the driving wheels for the purpose of counteracting the horizontal inertia forces resulting from the “to-and-fro” motion of the reciprocating […]
Snifting, Drifting, Bypass and Herdner Valves Snifting, Bypass and Drifting Valves were commonly used as a means of preventing negative pressures occurring in the cylinders of a locomotive during “drifting” or free-wheeling. If a negative pressure does occur, it will immediately result in combustion gases and solid particulates being sucked down from the smokebox through […]
Valve Gear and Valve Events This page covers (very briefly) a number of topics related to valves. These come under the following headings: Valve types Valve ports Valve events Predicting valve events Valve travel Lap and Lead Lead Lap Purpose of steam lap Purpose of exhaust lap Attention is also drawn to separate pages as […]
Motion A locomotive’s “motion” consists of the reciprocating and rotating parts incorporated in its drive and in the operation of its valve gear as shown and described below: Drive components of the Motion: Pistons and rings; Piston rods; Cross-heads, Cross Head Arms, and Small Ends; Connecting Rod and Big Ends; Coupling Rods. Valve […]
Simple and Compound Expansion The term “Simple Expansion” refers to the single use of steam in powering a steam engine. “Compound Expansion” refers to the multiple uses of steam in powering a steam engine. In a “simple” engine, the steam enters the cylinder at high pressure, expands as it pushes the piston through its stroke, […]
Triangular Losses in Cylinders Page Under Development This page is still “under development”. Please contact Chris Newman at webmaster@advanced-steam.org if you would like to help by contributing text to this or any other page. The term “triangular losses” is used to describe the rounding of the corners of a locomotive’s indicator diagram caused by the […]
Wall Effects and Condensation NOTE Since the publication of this page in 2017, new information has become available in the form of correspondence from André Chapelon about the testing of his experimental 2-12-0 6-cylinder compound freight engine No. 160A1, which suggests that steam heating of its cylinders with live steam was effective in overcoming wall […]
Locomotive and Train Resistance A locomotive’s tractive force is required to overcome the resistance to motion of both locomotive and train. When the tractive force is greater than the resistance, then the train will accelerate in accordance with Newton’s law of motion: Force = Mass x Acceleration or Acceleration = Force ÷ Mass. If the tractive […]