Wrightscale Wrens in the box

We look forward to seeing friends old and new at the AGM, Peterborough this Saturday 6th April. We'll be bringing along kits for signals, WD bogies, Pechot wagons and cranes. We'll also have examples of Wrightscale locomotives.
We are also delighted to say that we'll be showing off some newly finished Kerr Stuart 0-4-0 Wren  tank locomotives. A big thank you to everyone who has patiently encouraged us along the winding road! Various things, family and professional, have been hampering us but at last our little beauties have seen the light.

16mm Kerr Stuart Wren models made by Malcolm Wright. He has painted them in a livery standard for the prototype. Green pigment was resistant to the heat and weather. Red buffer beams were important for safety and black the best colour for parts exposed to coal and lubricant.

Malcolm's affection for the Wren goes back many years. It was the first design he created after being drawn into the world of 16mm, then as an enthusiastic amateur. As they say, first love never dies!
There were many moments of perplexity. What is the true Wren and what the pale imitation? There are many adaptaions that were made, over the years and two families which both proudly bore the badge. These were 'old' type and 'new'.  Needless to say, some 'old' types were being produced after the new were introduced ... but that just adds to the colour.
We just love the history and so, here, once again, is a little bit of history to explain why the locomotive was the way it was. The Engineering company, Kerr Stuart Ltd of Stoke on Trent, realised that a new market had grown up for small industrial and military locomotives which could be easily moved to temporary works. If and when they were no longer needed, they could be moved on.
Continental manufacturers such as Jung, Henschel and Decauville were already supplying the market. Decauville, for example, was supplying small locomotives to Australian sugar plantations, in the British backyard. Another significant market were the French and German armies which had realised the potential of 60cm (the Continental equivalent of 2' gauge) for military supply. This is a whole other story!

A closer view of the rear. Wrightscale Wren in 16mm scale

Kerr, Stuart already had an 0-4-0 Buya class locomotive design which was adapted for 2' gauge. The design was streamlined for easier manufacture. It included advanced features for the time. Typical of these were the round connecting and coupling rods with marine style big ends. The narrow gauge forced other adaptations. The firebox had to be waisted to fit between the frames which in turn were increased in height above the axes. It had a very low centre of gravity - both a good and bad thing on rough contractor's track. A low centre of gravity has obvious advantages but when the boiler and cylinders are so close to the rail, damage inevitably ensues. Soon, a steel firebox was fitted as standard though a copper inner firebox could be supplied on request. As the locomotive was so light, the rear wheels tended to 'dig in' when it started, causing excessive wear to the back two wheels. Soon steel tyres were fitted as standard.
In 1915, the 'new' type Wren was introduced. This was now fitted with Hackworth valve gear, rather than the Stephenson's link. This made a number of modifications possible. The reversing shaft was moved to a place above the axle and the boiler barrel was raised. The cylinders were inclined which allowed greater clearance between them and the track; proper cylinder drain cocks were fitted. The frame was strengthened by a substantial angle riveted along its top length. I should like to think that we could tell old and new apart because of all these technical improvements but probably what everyone notices first is that, in spite of the reinforced frames, 'new' is lighter and more airy in appearance.

Light and airy, the Wrightscale 16mm Wren

Given all these improvements it is surprising to note that 'old' type models continued to be requested. Presumably the boss of these concerns had not directly experienced draining a cylinder straight through the front cover.Steam and water get everywhere to the detriment of human and machine. One thing was not improved. The cab remained so light as to be almost ethereal, and not much protection from the weather. The ingenious drivers lashed up home-made cabs from wood and corrugated iron.
The Wren was a standard contractor's cab for many years. 58 examples of the old type were made and 104 of the new type before Kerr, Stuart closed its doors in 1930. The majority were 2' gauge with some metric. Two locomotives with enclosed gear were made for a steam tramway in Brazil, to 915 mm gauge. Further 'new' types were made by the Hunslet Engine Co of Leeds between 1930 and 1941 and the story is not over yet. Statfold Barn has taken over the design and there are two on the stocks there.
We hope you understand why Malcolm loves this model so much. He has, in fact, produced more 16mm models  than Kerr, Stuart did 2' gauge. He will have one or two on the stand ready to chuff away to their new homes.