7 1/4-inch gauge ORENSTEIN & KOPPEL rack 0-4-0 and 0-6-0 adhesion variant.

Without a doubt, this was Ken’s most challenging and complex design.

In the late 1800’s, the renowned Benno Orenstein and Arthur Koppel’s design of industrial narrow-gauge locomotives signified a new era in localised transportation of bulk goods. By the early 1900’s O&K locomotives had established an international reputation and a key role in places so diverse as factories, refineries, mines, quarries, field and plantations.   

In total O&K delivered 13,264 locomotives to almost all countries around the world. They came in various sizes and horsepower’s with a choice of four, six and even eight and ten coupled designs. Added to this was a choice of either inside or outside frames – the latter being specified for very narrow gauges. An O&K hollow axle patent enabled provision for adjusted wheel gauge

In 1945 O&K stopped building steam locomotives.

A Reincarnation in 7 ¼-inch gauge:

Almost one hundred years later, it was Ken Swan who thought to reacquaint us with Koppel in all its technical innovation and eccentricity. It was a daunting project which only came to fruition through Ken’s dogged determination, persistent attention to detail and outstanding technical ability.

The challenge was made even more difficult through the absence of O&K’s technical drawings. It is assumed they were lost, or possibly destroyed after the war. Ken’s only recourse was to work up the entire design up from first principles based on whatever photographs he could source.

Ken’s eventual choice of prototype was works number 7000, a 30hp engine supplied to Chiron Ferres at Chambery in 1914 – importantly it combined rack and adhesion working; a dog clutch allowing the engine to be run independently of the chassis and Walshaert’s valve gear rather than O&K’s own patent system, all features Ken wanted to incorporate in 7 1/4-inch gauge.

The outcome after many years of research, design and construction is Ken’s highly acclaimed and technically fascinating rendition of Koppel circa 1914.

Without doubt an engineering masterpiece – equally at home on the level in adhesive mode as it is conquering an incline with rack engaged.

Kens original rack design featured in Engineering in Miniature volume 8 Feb 1987

Within a couple of years there followed a six-couple adhesion Koppel for those favouring more conventional layout. This also featured on the pages of Engineering in Miniature [volume 10  Jan 89].

The Story Continued:

In many ways, Ken’s legacy lives on in his various 7 1/4-inch locomotives and none more so than in the growing but selective band of Koppel builders.

In 2014 three such model engineers – Andy Clarke of Polly Model Engineering, Walter Ogden of Hereford SME and Brian Nicholls of TSMEE made the decision to work in collaboration to build three 6-couple adhesion Koppel’s.

That way each could work to their individual strengths producing three of each component and benefit from economies of a small-scale production run.

Whilst producing three boilers in one go or three sets of CNC frames and plate work would seem a herculean task for most of us, this combined approach has successfully resulted in three outstanding locomotives. All this despite having occasionally to work from some rather dubious “fag pack” [sic] sketches in Ken’s hand.

By a short head Walter was the first to completion although he has yet to get in a track run. Brian finished second in time for Doncaster 2019 and achieved a flawless and memorable run one sunny day in August 2020. Andy’s loco is close to completion.

For those who might be inspired to follow suit with what is a unique and now proven design, Polly Model Engineering has available some parts and drawings for the adhesion 0-6-0 design. Those interested in the rack version may be interested in Ken’s series written for Engineering in Miniature for which there is a full set of drawings.

Now here is how Brian tells it …..

The only real build challenge [according to Brian] ….

“….. were the steam pumps as the porting and machining had to be precise. But that was an addition to the basic engine build which went extremely well due to the commitment of the 3 of us and the accuracy of the components machined or otherwise by us.”

The engine steams extremely well. Alterations to some of the original designs proved to be beneficial in improving the performance.

and Brians advice to aspiring builders ….

“Seriously consider making use of modern engineering production methods – laser profiling, using CNC machined parts greatly reduced the build time (important to an older builder!) and improved accuracy”

and here’s how it was done ….

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If only Ken had lived long enough to see it completed there is no doubt he would have been well pleased.

.…. return to Ken’s Swansong page