LOCOMOTIVES – BUILD THAT LASTED 50 YEARS
Stuart tells the story of a locomotive build that proves that with enough patience, even the most complex and repeatedly put-aside project can eventually come to fruition...
The model featured in the story that follows is a 3½-inch gauge Princess Royal 4-6-2. The original was the William Stanierdesigned Pacific that was built in 1933 to run from London to Glasgow non-stop without having to doublehead to handle the steep climbs of Shap and Beattock banks.
The basic model was produced to drawings made in around 1933 by H. P. Jackson but with modifications to comply with modern practices and scale appearance. The only castings used were for the wheels, pony and bogie frames and some frame stretchers made from patterns that I supplied. The only bought items are the injector, hand-rail stanchions and nameplates. Everything else on the locomotive was scratch-made from the relevant raw material.
The original design for the boiler incorporated a wide firebox and was tapered. This had to be modified considerably to meet modern practices, in the end requiring almost a complete redraw.
The model, like the real locomotive has four cylinders with the outside pair operated by Walschaerts’ motion. Unlike the real loco, however, the model is fitted with slide valves with the inside cylinders’ valve gear working from rocker beams. Only one of the 13 built operated this way.
The model is fitted with hydrostatic lubrication, based on a sketch by G. Hawkins that was published in Model Engineer in May 1973, the oil reservoir being housed under the cab floor with a cone-type control valve and needle restrictor. An oil supply has been fitted to each of the model’s main axle bearings using scale sand boxes as the reservoirs.
The cylinder drain cocks are steam operated via a cone valve in the cab. They are based on a design for Okadee cylinder drain cocks
published in Model Engineer in November 1968 by Mr. J. N. Ranford.
The brakes fitted to the engine are steam operated via a cone valve in the cab, the design loosely based on the one described by the well-known model engineer LBSC for his Doris locomotive. The brakes on the tender, unlike the original model, are operated by a bevel gearbox from a handle on the front wall of the tender.
I also fitted an injector again supplied with steam via a needle valve from the main manifold and water from a slide valve , this operated by a lever originally used for the water scoop pick up located on the front tender bulkhead.
For interest my workshop at the time the loco was built was a 10ft by 8ft wooden shed, equipped with a Toolroom Southbend lathe of 1948 vintage, a Tauco drill stand, a bench-mounted Amolco vertical milling machine, a Dwalt hobby bandsaw and a Clarke 1-inch vertical linisher as well as being stocked with all the usual hand tools.
The Story
The long story of this project begins back in the 1960s when I was a young man in my late teens and still living with my parents in Southport. I had helped my father, a well-known model engineer in that area and founder member of Southport Model Engineering Club, for many years in his workshop, so when I broached the subject of building a loco of my own he came up with the original blue prints for H P Jackson’s ¾-inch scale LMS Pacific ‘The Princess Royal’ and suggested I have a go at it.
Today I can see that this project was far too ambitious for an outright beginner but at an age when nothing daunts your belief in your own ability I accepted the challenge. My father had built an example of this engine back in the 1930s although I never saw it, the story goes that it was sold to enable him to buy his first family car.
We searched his workshop in the vain hope of finding any items that might have been left over from his original build but the only components recovered were the castings for the bogie and pony truck frames as well as the rear stretcher that carries the pivot pin for the bogie truck – nothing else had survived.
We found some steel that would be suitable for making the main frames and I duly set to work under the watchful eye of my father, eventually completing them. I then turned my attention to the remaining frame stretchers, horn blocks and axle boxes.
Although castings for these items would have been available at that time I was still serving an apprenticeship at
BAC and there was certainly no money available for such extravagances, especially since by now I was saving every penny towards marriage and the purchase of my own house. However Meshams in Preston would cast the parts for me in bronze if I supplied the patterns, this I did and they supplied the castings.
A full-time job coupled with what had become full-time education as well meant little else was achieved and in 1969 I got married and moved into my own home some distance away. As a result the Princess became just a dream that might never happen.
During the next 30 years the frames and castings that I had made were hidden away in the loft and almost forgotten. I built up a small garden workshop that was more akin to DIY than model engineering. Some model-making projects were achieved but thinking back probably those my son was interested in.
As with most young families, work, family and the making of a home plus some voluntary work took most of my time. Work became more intense, I was away from home up to one hundred hours a week, sometimes never getting home at all, on one occasion for five months. The main use for my workshop remained DIY, there was neither the time nor the spare capital to convert it into a true model engineer’s workshop.
In 1988 one of these constraints changed – after a short illness my father died and with the other members of the family having little or no interest in the hobby I was able to transfer most of his equipment into my workshop. It took several years but I finally had a workshop capable of serious engineering. I hope my father would have been proud that the place he spent so much of his spare time in had been recreated so that his enjoyment and pleasure was able to be passed down to me.
His influence was to go much further than that. I can still remember him saying that he would like to build
a model steam-driven tug – he carved a wooden hull using the bread-andbutter method but never completed it. So in the latter years of my career I built the tug he never did, ‘St. Cruiser’ being made from copper and brass using the original works drawings. This model was finally completed in the autumn of 2020 as my lockdown project and featured in the October issue of EIM.
In 1998 things took an unexpected turn, I was ready for a career change when a major redundancy package was announced and with my wife’s encouragement that became my career change and in the year 2000 I retired. I finally had the time and at least some of the equipment to pursue my passion in earnest. My thoughts turned once again to the Princess.
“The Princess Royal was
one of the most complex locomotives ever built and as a beginner it was, in my opinion not suitable as a first project...”
Restart – and stop
I retrieved the drawings and frames still languishing in the loft and studied them closely. Firstly, as an aerospace engineer I knew very little about steam and the engineering that capitalised on its remarkable properties. Also in 1933 engineering drawings were little more than assembly pictures with a few key dimensions, relying heavily on the skills and knowledge of the manufacturers to build the end product. The Princess Royal was one of the most complex locomotives ever built and as a beginner it was, in my opinion not suitable as a first project.
Yet again I had to postpone the building of the locomotive started so many years before. My two concerns needed to be resolved before tackling such a major undertaking. I decided the best way to achieve this was to build a beginners’ loco and because my father was no longer there for support and advice I joined the club that he was a founder member of, Southport ME, and the support and advice over the years from members I have found invaluable.
At the same time I decided to build a Martin Evans ‘Rob Roy’, for a number of reasons, firstly it was designed for the less experienced with the drawings being far more recent. Secondly a book on its construction was also available and being a relatively small loco the cost was not so high.
This process of learning took five years but the knowledge gained from the club and from building this little loco proved to be so worthwhile. Finally in 2006, some 40 years after my father’s first suggestion and having completed Rob Roy successfully, I could start construction of The Princess Royal in earnest.
As far as I could ascertain at that time none of the castings for this loco
were available so the first ones to source were the wheels. The ones for the tender, pony and bogie trucks were fairly standard so they were obtained locally and for the main drivers standard castings produced by Blackgates Engineering were close enough not to make any difference.
The building of the running chassis followed standard procedure and since the engine is four cylinder I opted to make the crank axle by the press fit and pin method and it worked extremely well.
I now turned my attention to the cylinders, two outside and a twin cylinder unit inside. Although I had made Rob Roy’s cylinders from castings I was never completely happy with locating suitable datums from which to machine from. The castings also contained blow holes and had to be sleeved anyway so I decided to manufacture mine from solid bronze bar, a decision that I will never regret. I had of course to redraw them accurately, decide on the datum faces within the bar and do a lot of ball end milling but the quality produced far exceeded manufacturing from castings and at a much lower price.
Castings cast aside
From now on everything on this loco was either machined from bar or fabricated and silver soldered and that posed some interesting challenges, but the satisfaction of working out how to do it and the end results were very satisfying. Examples of this method included the smokebox saddle which was fabricated from brass sheet and silver soldered, while the motion brackets were also redrawn and machined from steel.
The spring support brackets for the bogie were fabricated in steel and silver soldered, the smokebox door was fabricated from two sheets of copper and silver soldered, its support ring being machined from solid brass plate. The axle pump and eccentric straps are machined from solid, as were the crossheads, steam chests and cylinder end caps.
Items that had to be fabricated prior to machining included the radius link support brackets, the tender horns and axle boxes, the hand pump and dummy tender springs.
The construction of the basic chassis for both loco and tender followed basic principles but with the drawings being of 1933 vintage a large number of drawings or sketches had to be done at each stage. But towards the end of 2008 both chassis were complete and my thoughts turned to the boiler.