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(Part 1)

 by David Stick

The Authors Bulleid Pacific Wadebridge cracking on with the ACE

 – next stop Padstow – on Chris Arundell’s Little Eden Railway in deepest Cornwall


An Introduction


Ownership of a live steam locomotive in any gauge or scale truly transforms ones model railway hobby. I don’t think there is anything to beat sitting in a deck chair with a beer in one hand watching a train with a well selected consist working its way around a garden railway on a sunny afternoon. The sight, sound and smell takes one back to the glory days of our youth when we sat on embankments across the country, bottle of Tizer and a Mars bar by our side, watching our favourite locomotives parade by. Sure, we can still get the occasional thrill from a rail tour on the main line or on one of the preserved lines but somehow it’s not quite the same. Many of us have found that is a way of getting that feeling back and owning a model railway can often do it. Even better though if it is a live steam railway!


Many modellers regard the construction and operation of live steam locomotives as something that is beyond their ability. These armchair enthusiasts are frequently to be seen watching gauge one locomotives at a running track or at an exhibition with a longing look on their faces. When approached and asked ‘why don’t you join us and build one’ they respond with ‘I could never do it because I’m not an engineer’. This is usually just an excuse because of a lack of confidence and here I’m hoping I’m going to be able to convince you that there is no mystery and that you can do it.


There is no requirement to be a professional engineer nor yet for any training or engineering qualification though naturally, some knowledge is an advantage. There are many people who both scratch build and operate steam locos very successfully with nothing more than rudimentary knowledge. They have usually done some reading in advance of starting out and then asked questions and entering into discussion with those who have the experience. Joining the Gauge 1 Model Railway Association should be your starting point for standard gauge and there are several alternatives for the narrow gauge folks.


The Aster A3 Kit. All kits come boxed in extremely tough containers. In these are smaller boxes in which are housed all parts wrapped and sealed. Also included are the instruction manual and book of isometric drawings, sealant, tools, etc


Ready Machined Kit


Of course, many don’t have the machine tool facilities to be able to make the parts necessary. A lathe is pretty well essential and a good one is not cheap to purchase and requires some practice and study to get the best results. However, these skills can be learned by the tyro fairly quickly and with great satisfaction as has been proved many, many times.


Another method available to the keen enthusiast with few facilities is through building a ready-machined kit of parts. A fine example of a kit manufacturer is the Aster Company who produces the ultimate in locomotive kits. Not cheap but an amazing product that makes up to a truly magnificent and very satisfying model. There is usually a whole range of models available, all in standard gauge and at a range of prices. The cheapest, such as the antique Liverpool & Manchester Railway ‘Lion’ or the LNWR ‘Precedent’ (Jumbo) are both very good value and beautiful little models providing ideal starter kits.


Even building a kit is thought by some to be too difficult to risk the investment involved. Well, I’m here to tell you that this is simply not true and I hope to show you why in this article. I would like to show how easy it is providing a few simple rules are applied and all who invest in these beautiful kits will gain knowledge about steam locomotives and end up with a magnificent model. To illustrate the method used I have included a number of photos taken during construction of several different locos showing some of the design features and the various stages in construction.


The Aster Berkshire Kit of Parts. Here is shown most of the contents of the very large Berkshire kit. This has been unpacked to display the extensive number of parts but this is not recommended for fear of losing parts. Only those parts to be built should be removed at any time during the build process.


The Company


The Aster Hobby Company began building model steam locomotives in 1975 as a result of a need for diversification. Since the mid 1950s they had been in the business of manufacturing mechanical cash registers. Advances in technology in the early 1970s resulted in a change to electronic registers making their mechanical engineering design and precision manufacturing facilities redundant.


The company decided to preserve their investment in mechanical engineering and made the bold move in to the hobby industry. The first locomotives chosen in 1974 were the Southern Railway ‘Schools’ Class 4-4-0 and the Japanese National Railway Class 8550 2-6-0 manufactured by ALCO in the USA. These first two locos were produced in production run sizes of 3000 and 2500, numbers never again repeated except for the ‘Frank S’ locomotive produced as an engine for use with LGB systems. Since the 1990s the production runs have rarely exceeded 500 and around 300 is most common.


The development of their designs has been evolutionary rather than revolutionary much the same as the full size variety. Good sound principles developed by the model engineering hobbies were adopted and have been the bedrock of Aster loco design ever since.


The early boilers were either Smithies or Pot-boilers and it wasn’t until 1978 when a locomotive type boiler was introduced with the JNR Type 62 loco followed in 1979 by the ‘B’ type boiler for the 141R. Centre flue boilers for gas firing arrived in the early 1980s and the C Type boiler for the LNER A4 followed in 1984. This hugely successful boiler, a prodigious steam raiser, has been the most commonly used since that time. It combines ease of manufacture with a robustness that has resulted in very few failures and then only due to serious mishandling.


Aster Bulleid Pacific Cylinders. As can be seen in this view the cylinder castings are machined to a very high standard and assemble perfectly. The appropriate drawing can be seen beneath them.


Superheater Temperatures


The design of the cylinders has followed the same pattern from the beginning the only significant difference being the change from sealing the pistons by the use of fibre packing to the use of Rulon rings. These are believed to be a form of PTFE and have proved to be a great success with extremely low wear rates. I have had a set in my GWR King for fifteen years and it has been run very frequently!


One area of conservatism persists in that Aster continue to use slide valves rather than piston valves. Since superheater temperatures are relatively low and oil systems are of the displacement type, this seems appropriate. Remembering with tongue in cheek that old adage ‘slide vales wear in whilst piston valves wear out’!  As far as I’m aware the only changes in the cylinder area have been those associated with retaining the appearance of correct valve gear where the prototype has inside admission piston valves. It has been necessary to insert a plate beneath the port face to reverse the flow of steam to the ports in some models.


A3 Conjugated Valve Gear. The inside cylinder valve is driven using a derived motion provided by inputs from both outside gear exactly as in the full size loco.


The valve gear closely follows that of the prototype and is as near scale as is practical. Bronze bushes are usually provide in bearings though the A3 and Bulleid ‘Pacific’ or Spam Can for example, have what appear to be Rulon/PTFE bearings in parts of their valve gear and connecting rod bearings.


Bulleid Valve Gear Cassette. No chain gear as in original here! This beautifully designed version of the Walschaerts’ gear is built as a sub assembly from parts largely laser cut and requiring very little work to complete. The assembly is built upside down and is shown as such in this view.


Bulleid Pacific Chassis. The valve gear has been installed in this view together with the cylinders and multi blast nozzle. The latter is a miniature version of the full size Lemaitre device fitted to the full size loco.


Bullied Pacific Front end. This close-up shows the Lemaitre blast nozzles and behind them the blower nozzles. The vertical mounting of this assembly is imperative to ensure good steaming. The blast from all of the exhaust nozzles must fill the chimney venturi to create the necessary vacuum in the smoke box to draw the fire. The little stainless steel frame seen is there to ensure this happens.


Almost all of the chassis designs use plate frames with either bolted or in some cases welded stretchers. All are fitted with springing either by coil springs or leaf springs with sliding axle-boxes. A few use a prototypical suspension with compensation by levers as used on the full size loco. The most complicated example of this that I have come across is that fitted to the latest version of the JNR C62.


Aster A3 Chassis. The chassis is partially complete in this view with the three cylinders fitted together with the axle pump, the eccentric for which is shown on the driving axle with the pump behind it fitted through the frame stretcher.  Note the slide valves in the steam chests of the outside cylinders and above the chassis on the drawing, the inside valve gear motion nearly ready for assembly into the chassis.


The C Type boiler. This view shows the C type boiler as used in the A3. The backhead includes a water gauge glass, regulator, blower (just below the pressure gauge) and backhead clack valve. Just in front of these is shown the black dummy backhead and on the top of the boiler the two safety valves.


Highly Detailed


When it comes to systems and fittings model engineering experience has been used to good effect and in some cases improved upon. A good example of this is in the currently used axle pumps now fitted to almost all locos. The repositioning of the clack boxes has made maintenance easier and no longer requires dismantling of the pump to gain access.


Backhead fittings have largely used the same design for many years and include a needle type regulator, a needle type blower valve, usually a water level glass and a backhead clack fed by the axle pump and/or water tank mounted hand pump. The footplate on the ‘Duchess’ now has a needle vale controlled oil supply from an oil reservoir mounted under feeding the cylinders via a long gallery pipe under the boiler. Like the earlier oil feed systems, normally positioned at the front end and not controlled, it is of the displacement type. The needle valve is used to pressurise the oil reservoir before starting to prime the long gallery with oil. The valve is then closed after which the system runs as a normal displacement oiler.


The fuel system for spirit (meths) is straight forward with the usual chicken feed type feeding a three tube wicked burner, nowadays provided with a fibre glass type wick material instead of asbestos. Gas burners were of the poker type for many years but the new JNR C62 has a ceramic grate type burner as well as an exchangeable grate for coal firing. In this model the tender is fitted with a ‘U’ shaped gas tank which itself is fitted with a steam heater not unlike the shape of the superheater. This should ensure that the locomotive can be run in even sub zero temperatures.


The level of detail added to locos has steadily increased over the years and the use of lost wax technology has resulted in superb highly detailed and scale dummy fittings. If there is a downside to these it is in their fitting to the boiler case and footplate. This is often achieved by bending tags to hold the part in place. These are often difficult to access and not easy to bend and a loose fitting can result. If this is the case the problem may be resolved by applying (where it can’t be seen) a little epoxy resin.



 part 1 > part 2 > part 3


Appreciation is expressed to Dave Stick for sharing this series along with other articles and photographs for posting to SouthernSteamTrains. com


Dave Stick spent all of his working life as an aeronautical engineer.  His hobby has always been model steam locomotive building.  He built his first Aster locomotive, a New York Central Hudson in 1984.  Having graduated from college and served an engineering apprenticeship, he was employed as a development engineer in the gas turbine industry. Dave later joined the Royal Air Force as an engineer officer and retired after 20 years service and immigrated to Canada. There he worked for Boeing Canada retiring for a second time from the post of system director.  Returning to his beloved home in Cornwall, England in 1999, Dave Stick has spent the past decade building and running his collection of Asters.


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