Power-to-Weight Ratio The Power-to-Weight ratio of a car is a measure of its ability to accelerate. A steam locomotive’s ability to accelerate is governed by its the ratio of its “power : total train weight” ratio and by its adhesive weight and adhesion coefficient (ignoring resistance factors). The Power-to-Weight ratio of a steam locomotives is […]
How to construct a Reuleaux Diagram Whilst the exact movements of a locomotive’s valves are indeterminate because of the angularity effects of both connecting rods and eccentric rods, a close approximation of its valve events can be found through constructing a Reuleaux diagram in which the angularities are ignored. Porta used these as a first […]
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 Gear components of the […]
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, and is then […]
Kordina The concept of the Kordina named after its inventor Zsigmond Kordina (see below), is described on page 153 of Wardale’s book “The Red Devil and Other Tales from the Age of Steam”, its function being to: “expand the release steam to low pressure and high velocity at the point where the exhaust flows from the […]
Audio-visuals on the 5AT and Modern Steam Audio Recordings of Modern Steam 15 audio tracks recorded in South Africa in the early 1980s by David Wardale and Nick Bartlett are available on this website. They include several recordings of The Red Devil, including one during which it develops an equivalent drawbar power of around 2,460 […]
Adhesion and Adhesive Weight Adhesion is the frictional resistance that prevents a locomotive’s driving wheels from slipping on the rail. Available adhesion depends on the conditions of both the rail and the wheel. With a clean dry wheel running on a clean dry rail the “frictional coefficient” between them may be as high as 0.35 […]
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 […]
Specific Steam Consumption Specific Steam Consumption is defined as the steam consumed by a locomotive’s cylinders per unit output of power. It is typically measured in kg/kWh or kg/KJ. A locomotive’s Specific Steam Consumption carries important implications as may be deduced from one of Porta’s favourite equations: Thus for any given boiler output, a locomotive’s […]
Equivalent Evaporation Equivalent evaporation = evaporation from and at 100°C. Evaporation figures thus expressed eliminate the effects of different feedwater and superheat temperatures, and are therefore a true measure of comparison between different boilers. [Extract from letter from Dave Wardale to Chris Newman, 5th April 2001.]
Locomotive Power and Indicator Diagrams Power is defined as “the rate of doing work”. Common units of power in the metric system are Watts (W), kilowatts (kW), Megawatts (MW) and Gigawatts (GW), where 1 Watt = 1 Joule per second = 1 Newton-metre per second. Alternative units of measurement are calories per second and kilo-calories per hour […]
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 the […]