As noted below, the Fundamental Design Calculations for the 5AT locomotive are now complete. These calculations will provide the basis upon which the Detailed Design work can be commenced.

The Detail Design of the locomotive is likely to be the most difficult and demanding component of the whole 5AT project. The work will involve the engineering calculations and preparation of the detailed drawings of each and every large and small component of the locomotive. It is expected that this will involve the production of approximately 800 drawings, being the number of drawings needed for the manufacture of the Standard 5MT locomotive of similar size to the 5AT. However whereas the 5MT was designed by a group of perhaps 100 or 200 engineers and draftsmen who were skilled and experienced in the design and detailing of steam locomotives, there are today very few people remaining who have such skills and knowledge. More challenging still is the fact that engineering the 5AT will be a much more demanding task than the design work that was undertaken in previous eras. For one thing, with very few exceptions, new designs of the past were developments of existing designs from which a large amount of work could be "carried over", whereas the 5AT is a completely new design from the rail up. Secondly the standards of the design work that will be needed to achieve the performance and reliability levels predicted for the 5AT, and its acceptability to the railway and safety authorities, will be of a very high standard - of necessity higher than the standards of past generations.

To our advantage, we have computers and CAD/CAM software systems to aid the engineers in their task. Our intention is to ensure that a single 3D CAD system be used by all engineers and draftsmen engaged in the work (SolidWorks currently being the favoured tool for the job), and besides speeding up the drawing process, it will also be of enormous assistance in reducing the tedious tasks associated with checking for interferences and fit-up etc. It will also allow the automatic production of highly accurate shop drawings directly from arrangement drawings. Nevertheless, very high levels of dedication and perfection will be required from each person engaged in the work, and especially those charged with supervising and checking the work that is done if they are to ensure that the results of their labours are not just "good enough" for the job, but the best that is practically possible to achieve.

The current expectation (as expressed in the Business Plan) is that the detail design task, encompassing the production of calculations and engineering drawings, will take some 8.5 man-years. In fact, it may quite possibly a lot longer than this if sufficient time is to be given to the work involved in the calculations, tolerancing, laying-out and checking of each and every drawing - 8.5 man-years representing less than 3 man-days per drawing if the estimate of 800 drawings is correct. A more accurate estimate of the time required will be made once the detail design of a component part of the locomotive (currently in progress) is completed, since this will allow a more accurate estimate to be extrapolated for the time total required, based on either a "per drawing" or "per component" basis.

The question has still to be addressed as to exactly how the work might be organized and responsibility divided up so that the work is completed in a properly integrated manner and to a uniform standard of excellence, within a reasonable period of time. Expressions of interest are sought from anyone who has skills and/or experience that may be relevant to the task - particularly those with a mechanical engineering background, skills in the use of SolidWorks and a knowledge of steam locomotive technology and an interest in taking part in this exciting project, at commercial rates of pay. Please write to us at webmaster@5at.co.uk. and send us a CV following format of the attached proforma CV. (CVs that are sent to us will be treated in the strictest confidence.)  Expressions of interest will also be welcome from anyone (or any organization) with appropriate project management competence who might be able to assist in finalizing an organizational plan for the undertaking of this most challenging section of the work.

Note: Below is Wardale's ink drawing of the 5AT's light-weight connecting rod. Below left is a a 3D drawing of the rod prepared by David Smith using Wardale's dimensions. Next to it is a computer-generated FEA (finite element analysis) diagram of the small-end of the connecting rod kindly produced for us by specialist railway engineer Jamie Keyte, showing stress concentrations applying to a particular load situation. A full list of completed drawings is being compiled at the bottom of this page.

The fundamental design calculations (FDCs) are the starting point for any locomotive design, without which the engineering drawings cannot be made and the locomotive cannot be built. They are the foundation of the present scheme to build a high-performance steam locomotive.

In the past these calculations have been based on design "standards" or "rules", such as those of the Association of American Railroads (AAR). In the UK the "big four" railway companies had their own design rules, which were inherited by BR. Such rules are summarized in publications such as Steam Locomotive Design: Data and Formulae by Phillipson and The Locomotive Engineer's Pocket Book. They are a mixture of basic engineering principles and empiricism, the latter often resulting in "design ratios" which relate dimensions or parameters in one component to those in another (for example free gas area through the boiler tubes as a % of the grate area). In some areas of design, more especially for simple mechanical problems, these former design rules are still appropriate. However they are in general wholly inadequate for more sophisticated mechanical and thermodynamic design.

To obtain the performance level which the Class 5AT 4-6-0 will be capable of these former design methods cannot be used - to do so would result in performance being not markedly better than that already achieved with steam traction. Instead a more rigorous and refined engineering design methodology is required, making use of more sophisticated engineering data and calculations in such areas as stress analysis, heat transfer, fluid flow, etc. Chapelon's disciple, Ing. L. D. Porta, has adapted this principle to locomotive design, and the writer is one of the few people who have had access to the resultant methodology and become familiar with it, using it perhaps more extensively than any engineer except Porta himself, when putting it into practice in his work on steam locomotive development projects in South Africa and China.

Porta evolved a method whereby the calculations start from known or fixed parameters, e.g. desired levels of performance or limiting dimensions, temperatures or pressures, and work through the appropriate theory step-by-step until all the important dimensions defining the component or assembly concerned are arrived at. This step-by-step approach makes the calculation procedure extremely easy to follow.

An important feature of this technique is its holistic approach, each component being seen as part of a dynamic whole, being influenced by and influencing other parts of the locomotive.

As the procedure is in principle the same for all Stephensonian locomotives, it can be used for any design by simply changing the numerical values to suit. Thus, for example, a lightweight piston valve is designed by carrying out a stress analysis on each part of the valve to determine its section. The starting parameters might be the valve diameter, the maximum steam chest pressure, the release steam pressure, the maximum steam temperature, the distance between the inlet edges of the valve liner ports, the port widths, the valve steam and exhaust laps, the required lead, the type of coupling to the valve spindle and of the spindle to its crosshead, whether or not a valve tail rod and inlet and exhaust diffusers are to be fitted, the maximum cut-off and valve travel, the maximum rotational speed of the engine (allowing for overspeed when slipping if necessary), the materials and construction methods to be used, and the permissible stress levels in the various parts of the valve. Given these, all valve dimensions can be calculated to give the lightest possible valve (minimum weight being essential for optimum tribological conditions in service and for minimum loading on the valve gear), of the best thermodynamic design, and in which stress levels are always within those allowable. The work sheets will show the whole development of the calculations from these fixed parameters for the Class 5AT design, but by simply inserting the different starting parameters applicable to a different locomotive, the whole process can be repeated for any design. The calculation process is therefore "universal' in scope.

The following is a list of areas where such cardinal design calculations, based on fixed parameters such as the required power output, maximum operating speed, permissible axle load, permissible overall dimensions, etc., are required for the Class 5AT 4-6-0.

The calculations give references to all material used in their production, and are presented in tabular format according to Porta's method, i.e.: Item No., Description of item, including equations, etc. Unit Used, Numerical Value.

The calculation sheets are presented in Microsoft Word format. Deleting the numerical data for the Class 5AT will give sheets which can be completed for any other design.

The calculations have not been produced in program format. It is considered essential for the future of steam traction that the knowledge they represent is understood and learnt, and the way to do this is for them to be gone through and understood item by item. If presented as computer programs, in which data is inputted and answers simply come out, the intervening engineering will not be understood, and this is a sure way for the knowledge to become lost in due course. Computerization can, of course, be applied in the future, if desired.

The calculations are largely in SI units. These are superior to all other systems of units and the writer has always used them in his design work. We are looking forward and a break must be made with Imperial units: this is a good time to do so as far as steam locomotive engineering is concerned.

The calculations summarized above form the basis of the Class 5AT high-performance 4-6-0. They are the starting point of its design, without which the project cannot proceed or succeed. They will also be a starting point from which to spread the necessary wider knowledge of Porta's technology, and are an important means of assuring that Porta's knowledge does not become lost. They can be used as the basis for any other advanced Stephensonian locomotive project. Specific parts of the calculations can also be used in isolation where it is desired to improve just a part of an existing design, say the piston valves. As such the calculations themselves should be of considerable interest and value to the steam locomotive fraternity world-wide.

[Note: The following is reproduced from David Wardale's book "The Red Devil and Other Tales from the Age of Steam". It originally formed part of the test report on the South African Railways 26 Class locomotive no. 3450, the Red Devil, and describes the essence of how steam locomotive performance can be transformed from that associated with the locomotives of yesterday.]

Significant improvements to locomotive performance can be made by optimizing basic components whilst retaining the inherent simplicity and accessibility that is considered essential for reasonable locomotive availability even with the best prevailing standards of mechanical design and maintenance. The following factors are of particular importance: -

If the above are carried out, not to an 'acceptable' degree but to the maximum extent possible within the constraints of the available technology, steam locomotive performance will be in a different class from that hitherto known. This does not exclude other factors from being improved, but the above, which simply apply sound thermodynamic principles to the steam locomotive without any frills, are the key to enhanced performance.

The following drawings of the 5AT and its component parts make up the current drawing register:

Loco and Tender:

Motion:

Wheels:

Cylinders:

Last updated: 8th Apr 2008 - Part 2 rewritten in the past tense.
Previous Update: 2nd Feb 2008 - Updated Cylinder Block Drawing added
Previous Update: 31st Jan 2008 - Cylinder Block Drawing added
Previous Update: 11th Feb 2007 - Drawing list added
Previous Update: 19th Apr 2006 - connecting rod illustrations added.
Page created: 4th Feb 2004