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 […]
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 […]
Dave Wardale defined Equivalent Evaporation as follows: 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. [Letter from Dave Wardale to Chris Newman, 5th April 2001.] Equivalent Evaporation might be more simply […]
Boiler efficiency can be defined as the amount of energy delivered from the boiler in the form of steam divided by the amount of energy delivered to the firebox in the form of fuel/chemical energy. Boiler efficiency depends on the design of the boiler and firebox, the type of fuel, and the draughting system. In […]
Drawbar efficiency can be seen as the sum of the efficiencies of a locomotive’s various components. Wardale provides examples of these in his book “The Red Devil and Other Tales from the Age of Steam” where (in Table 78, page 457) he quotes figures for standard and (proposed) modified Chinese Class QJ locomotives, and where […]
Cylinder efficiency is calculated by dividing the work done by the steam in the cylinder by the heat drop in the cylinder. In Line 84 of FDC 1.3, Wardale calculates the isentropic cylinder efficiency of the 5AT at maximum drawbar power output to be 81%. He gets this figure by dividing the actual specific work […]
The word “indicated” comes from the use of “Indicator Diagrams” that before the electronic era were mechanically plotted to indicate the variation in steam pressure inside a cylinder against the piston position as it sweeps through the piston over the length of its stroke. Separate diagrams for both ends of the cylinder were usually being […]