The α (alpha) Coefficient of a locomotive is defined as In other words, it gives a measure of the average forces applied to the locomotive’s machinery as compared to the maximum forces that it is designed to withstand. It could therefore be said to be a measure of “mechanical efficiency”, being the amount of use […]
The principles of “Compound expansion” are briefly outlined in the Simple/Compound page of this website which also describes the advantages of compounding as follows: Use of compound expansion allows longer cut-offs to be used, thereby delivering more uniform wheel-rim tractive effort; The ability of compound engines to operate efficiently at longer cut-offs increases their α-coefficient and thus their […]
The multiple element Piston Rod Packings fitted to The Red Devil are described on page 176 of his book as follows: Fully floating five-element metallic piston rod packings replaced the single element Paxton-Mitchell type which did not guarantee steam tightness over long periods without attention. Some time previously Porta had sent me a drawing made […]
Page Under Development This page is still “under development”. Please contact the webmaster@advanced-steam.org if you would like to help by contributing text to this or any other page.’ As stated on the Exhausts page under the “Terms and Definitions” section of this website, Wardale defines the exhaust system as “thermodynamically the heart of a locomotive which […]
The process of reducing constraints to steam flow is usually referred to as “Internal Streamlining”. Internal streamlining produces two benefits: It raises the Front-End Limit resulting in increased steam flow through the cylinders which in turn increases the upper limit of power output for the engine. It has the effect of reducing flow resistance and […]
This page covers briefly a number of topics related to the enhancement of valve events to improve a locomotive’s performance. These come under the following headings: Valve events Valve travel Porta’s view on lead Fixed lead Variable lead Ring-controlled events A separate page covering valves and valve gear can be found in the Technical Terms […]
There have been many and varied practices adopted by drivers and/or imposed by railway authorities, for “drifting” of locomotives – i.e. running at speed without power such as when descending a bank. On page 101 of his book “The Red Devil and Other Tales from the Age of Steam“, Wardale emphasise the complexity of the […]
Various other pages of this website are devoted to specific aspects of piston valve design including: An explanation of terminology relating to valves and valve gear; A discussion of the principles of tribology and lubrication with particular emphasis on piston valves; A discussion on the enhancement of valve events to improve steamflows and reduce losses; […]
The Oxford Dictionary defines tribology as the branch of science and technology concerned with surfaces in relative motion, as in bearings. It is therefore inseparably associated with the subject of lubrication. Ing. L.D. Porta was the first engineer to apply the science of tribology to the design of steam locomotives, seeing it as an essential […]
Page Under Development This page is still “under development”. Please contact Chris Newman at webmaster@5at.co.uk if you would like to help by contributing text to this or any other page.
It may seem counterintuitive that locomotives with smaller driving wheels should achieve higher efficiency than those with larger driving wheels, but it is a fact that high engine rotation rates offer a number of technalogical benefits. It may also seem counterintuitive that long strokes (such as used on GWR 2-cylinder locos) also offer advantages […]
Lack of steam tightness is usually imagined to be associated with steam leaking from pipe joints and piston rod glands resulting in the familiar leaks that can be seen as a white plume of steam eminating from wherever the leak is occurring. Steam leakage of this sort is indeed wasteful and deletarious to a locomotive’s […]