Some time ago, when I made a model of Aeolus , I was very puzzled by the arrangement of the valve gear, which included a shaft running across the front of the smokebox. After further investigation, I discovered that this shaft was actually part of the regulator mechanism, which Gooch applied to some of the first engines built (or re-built) at Swindon, although it was soon abandoned. I never found out much more about it until recently, when a fellow Broad Gauge Society member pointed out that a digital copy of Gooch’s Sketch Book is now available online

In those pages, I could see various drawings of the components of this type of regulator mechanism on the cylinders of engines to which it was fitted, such as the ‘First Lot Goods’, which started with ‘Premier’, the first engine to emerge from the new Swindon works, in 1846. The same mechanism appeared on the ‘Prince’-class passenger engines, which appeared shortly afterwards, but then it was abandoned and engines reverted to being fitted with a central regulator in the smokebox, controlled by a lever high on the backplate of the firebox. Once again, we are fortunate to have one of E.T.Lane’s beautiful drawings, dated 3rd July 1849, of ‘Queen’ (from the ‘Prince’-class):

‘Queen’ drawn by E.T.Lane 1849

The regulator mechanism with its cross shaft can be seen in front of the smokebox in this drawing. It seems odd to me to fit two separate regulators – one to each cylinder – as these seem unlikely to provide even distribution of steam at all settings. Perhaps the point is that these same engines were also the first to be fitted with Gooch ‘link motion’. No doubt, drivers were being encouraged to use the new ‘expansion control’ to adjust the power output from their engines, rather than the wasteful ‘throttling’ process. If that was the thinking at the time, then the regulator was being relegated to a mere ‘on-off’ switch, with all the fine adjustment being made by ‘notching up’ the expansion gear.

I have annotated one of Gooch’s sketches to show how a regulator valve was fitted on top of each cylinder casting, immediately in front of the slide valve chest. A gland, passing through the front of the smokebox contained the operating rod for the regulator valve. Unfortunately, I have not yet found a drawing of the valve itself, so have to assume a simple sliding flap across the live-steam input pipe

Sketches of Regulator and Valve Components from Gooch’s Sketch Book

I decided to make a 3D model to see how everything might have been assembled together and, fortunately, the drawings in Gooch’s sketchbook include side and end elevations, as well as a plan view. My mode of working was to create each part separately, by extruding from the most appropriate drawing and then to move the pieces around until views from all directions looked correct. Some parts of the drawings puzzled me until, for example, I realised that they showed webs to strengthen the sides of the valve chest. The following views show how my modelling progressed.

Creating 3D models of cylinder and valve chest

My next step was to determine how two of these cylinders fitted into the bottom of the smokebox and how the regulator operating system was laid out.

I noticed on the sketches that the exhaust duct from the cylinder was angled towards the front of the engine. When I placed two cylinders alongside each other at the correct spacing, I found that if I set the exhaust on the other cylinder at the same angle towards the rear, then the two ports feeding up into the blast pipe lay neatly adjacent to each other, as shown below:

My 3D models of Two Cylinders behind the Smokebox Front

Now I turned my attention to the mechanism in front of the smokebox.

There are detailed sketches of the various components in Gooch’s Sketch Book, from which I extruded all the individual parts.

Sketches of Regulator Components from Gooch’s Sketch Book

There is another page of sketches, which show the handle on the footplate and the rod that connects this handle to a lever on one end of the regulator shaft. Once I had built up a set of 3D-modelled parts, I could assemble them into the overall arrangement shown below:

My 3D models of the Operating Rods for the Gooch Regulator

I set this assembly up onto the front of the smokebox that I had previously created for my model of a Gooch Goods . In those engines, the cylinders were raised and angled at 7° for the motion to clear the front axle while driving the central axle.

I felt pleased to have sorted out this short-lived piece of locomotive history. It seems an odd step for Gooch to have taken, since this arrangement of shafts and levers on the front of the smokebox does not look to have been a very robust arrangement. It seems to be associated in some way with his introduction of the Link motion to drive the valves.

Now that I have designed the parts, I may try retro-fitting the visible items to my model of a Gooch Goods at some time.

My Model of a Gooch Standard Goods

Mike