Background

 

Almost 10 years ago, I made a model of a lime kiln as a ‘scenic accessory’ on my North Leigh layout. For some reason, I never wrote a blog post about its construction but did write a short article for ‘Railway Modeller’, published in November 2015.

 

I have, however, described how my model was based on the kiln at Fawler that originally had a siding from the Oxford Worcester & Wolverhampton Railway. Fawler is close to the real North Leigh, on which my pre-grouping layout is based

 

My starting point for the kiln was the ‘Wills’ ref.8838 kit of a cattle creep, which provided suitable arches set into walls of stone blocks. To make my model, I placed the two arches from the kit side by side and set them into a hillside, behind my railway, as part of the back-scene.

 

Model Lime Kiln on my North Leigh layout

 

West Drayton Coke Ovens

 

Now, I have realised that kilns (or ovens) for a different purpose but of a generally similar design played a significant role in the early development of railways. Because of Parliamentary Acts that required locomotive engines to ‘consume their own smoke’, the early engines burned coke as a ‘smokeless’ fuel. It wasn’t until the adoption of the brick-arch in the firebox, around 1860, that coal could be used as a fuel, without emitting large amounts of soot from the chimney.

 

MacDermot, in his ‘History of the GWR’*, states that the principal railway companies made their own coke and, for this purpose, the Great Western established coke ovens at West Drayton.  Whishaw, writing in 1842, reported that “the coke-ovens are situate at West Drayton, about half a mile to the east of the station ; and are very similar to those of the north of England and Scotland, being without a lofty chimney, which adds so greatly to the cost. They are conveniently placed on the level of the railway, which saves much labour in filling the wagons.”

 

*NB MacDermot Vol.1 is now available as a PDF Download from the ‘Internet Archive’ https://archive.org/details/historyofgreatwe0001etma

 

I found a little more information in an article by the Greater London Industrial Archaeology Society , which states that there were fourteen coke ovens, built in 1839-40, which produced 440 cwt of coke per day, using coal brought along the Grand Junction Canal from Brentford. Initially, a daily coke train ran from West Drayton to Paddington. Once the GWR main line reached Bristol, however, forty coke ovens were built there, so that by 1850 the West Drayton coke ovens were discontinued. The site is clearly marked on the 25 inch OS map, which can be viewed on the National Library of Scotland website , although the ovens must have been out of use by the time the map was made. I show an extract below:

 

West Drayton coke ovens – OS 25” second edition

 

Operation of Coke Ovens

 

I found it difficult to determine how the site actually appeared when operational but found illustrations of various sites in the North of England, which are said to have been similar. The coke was produced in a ‘coke battery’ comprising rows of ovens into which coal was loaded. The coking process involved heating coking coal to around 1000-1100ºC in the absence of oxygen, to drive off the volatile compounds. The process took from 12-36 hours in the coke ovens. The coal charge did not fill the oven. Space was left above the charge in which the gas liberated from the coal was burned. At first, no attempt was made to recover any of the gas, tar or other by-products, which were driven off from the coal when it was heated. In later designs, the gas was led through openings in the upper part of the walls into flues where it could be burned out of contact with coal and add its heat to the charge through the oven wall.

 

There are two paintings by Wheldon, dated 1845, which show coke ovens associated with a colliery in North-East England. They include two views, apparently from opposite sides of a row of coke ovens in process of being fired. I have extracted the sections that show the coke ovens.

 

 

Two Extracts from oil paintings by W.Wheldon of a NE Colliery and Coke Kilns

 

In these paintings, there appear to be two rows of ‘beehive’-shaped ovens, with access doors arranged in a line alongside a railway track. There is a raised platform at the top for charging the ovens, or kilns, with coal. The second painting appears to show a person pushing a wagon along a track above the kilns, presumably carrying coal to be fed into the tops of the kilns.

 

The first painting also depicts a ‘Hackworth’ type of locomotive in the foreground

 

Taken together, I feel that these illustrations provide a fair idea of what once existed on the West Drayton site. The map suggests that there was probably a single row of 14 kilns, with the discharge doors adjacent to the railway, while coal was supplied to the kilns from a wharf on the Grand Union Canal.

 

Designing a Model

 

Although I couldn’t find much detailed information about coke ovens in Britain, I found plenty about similar beehive kilns that were used in the early 19th century around Birmingham, Alabama. There is a chapter in Peele’s ‘Mining Engineers Handbook’ Published 1918 that contains diagrams and detailed description of the operation of ‘beehive’ kilns

 

Dimensioned Sketch from Peele’s ‘Mining Engineers Handbook’

 

There have even been HO-scale railway models distributed by ‘Walthers’ (US) but I didn’t find anything that is currently available

 

US models of Beehive Coke Ovens

 

Nevertheless, these resources provided me with plenty of guidance on how to design a plausible model.

 

From the map of West Drayton, the complete ‘battery’ of kilns extended for 675 feet – a little over 200 m – but the complete array seems to be divided into five individual groups, so I decided to start by modelling a single oven, which could be extended into ‘batteries’ depending on the space available.

 

Brickwork

 

Since the ovens were close to the clay pits and brick works that were scattered around the West Drayton area, it seems most likely that the ovens were constructed from bricks, rather than stone as in my previous model of the Fawler lime kiln.

 

Of course, I could have used pre-printed sheets of brick-effect card but I decided to experiment with creating my own brickwork, by means of 3D printing. I soon found it was easy enough to produce a wall of ‘stretcher bond’ by drawing a single brick and then using the ‘rectangular pattern’ tool in ‘Fusion 360’ to produce a regular array of bricks.

 

A photo of a surviving battery of ovens in the North East, said to be similar to those at West Drayton, showed that the facing was laid in ‘English Bond’ with alternating rows of ‘headers’ and ‘stretchers’.

 

Remains of the last working beehive coke ovens in the country.
Built in 1861 and worked until 1958

 

So, as often happens in railway modelling, when additional skills are needed, I had to give myself a crash course in the art of brick-laying. I found a very helpful YouTube video that got me started – thank you Rodian.

 

I started by creating a row of four ‘stretcher’ bricks, leaving suitable gaps for mortar. I then created a row of nine ‘header’ bricks, which needed to be carefully aligned so that the joints fell neatly between those in the row of ‘stretchers’. Once I had two rows, I could use the ‘rectangular pattern’ tool in ‘Fusion 360’ to repeat the initial pair of layers, to create a wall.

 

There is one twist, which I learned from my course on brick-laying, and that is the use of ‘queen closers’ to produce a straight end to the wall. I decided to create three sections of wall, one cut square at both ends, so that several panels could be joined together to make a longer wall, and two others with left and right ‘queen closures’, as shown below:

 

Steps in creating English Bond Brick Wall

 

The symmetrical ‘centre’ section can be extended as necessary to create longer walls:

 

Multiples of ‘centre’ wall section.

 

I created the mortar (or ‘muck’ as the professionals call it) by extruding a rectangle from the back of the wall to a suitable depth below the front face. I then used the ‘Combine’ tool in ‘Fusion 360’ to make each section of wall into a single body.

 

Creating the Doorway Arch

 

I made the door and its arched frame as a separate body, creating the pattern of the arch from a single brick, followed by use of the ‘pattern on path’ tool in ‘Fusion 360’. The ‘lessons learned’ from creating the brick wall proved very useful and I found this to be an easier task than I had expected. I added a second inner ring of bricks as a door frame and then extruded a flat panel from the back to create the door. I used the 'Combine' tool in ‘Fusion 360’ to bind together all the bricks and the door into a single body. As before I show the series of steps in a group of screen-shots from ‘Fusion 360’:

 

Steps in creating the arched door

 

One useful aspect of working in the ‘virtual’ world is that solid bodies can slide through one another, so I could set the door into the brick wall without having to cut an aperture in the wall.

 

Creating the Dome

 

Having solved that first construction exercise, I turned my attention to the domed top of the oven, which was also made from brick-work, as shown in another photo of the Gateshead ovens.

 

Top domes of the last working beehive coke ovens in the country.
Built in 1861 and worked until 1958

 

My approach to creating this structure in ‘Fusion 360’ was to start from a profile view of the dome. I then created notches in the slope of this profile to represent the gaps between the brick courses. I also create the aperture in the top, for products of combustion to escape and be burned off.

 

Once I had a domed top, with rings for brick courses, I sketched a narrow rectangle to extrude a gap between bricks in each course. I then used the ‘circular pattern’ tool in ‘Fusion 360’ to create a ring of bricks around the central axis of the dome. I repeated this process for each ring of bricks, varying the numbers in the patterns as appropriate for the longer courses, lower down on the dome. My procedure is illustrated below:

 

 

Steps in creating brickwork dome

 

 

Printing the Components

 

The front face, with the arched doorway and the domed top of the oven are the only parts needing specialised design. I assembled these around a simple box structure, to show the overall layout of a single oven, rendered in ‘Fusion 360’

 

My 3D-model of a ‘beehive’ coke oven

 

All that remained was to transfer the design files to my ‘Cura’ slicer software and then to my 3D printer. I had been a little apprehensive as to whether the mortar courses would be discernible in the prints but need not have worried. Surface indentations usually print more reliably than small raised features, such as rivet heads, which easily disappear if the limits of the FDM printer are exceeded

 

This is the dome, still on the printer bed, with no fettling having been applied. The time to print was 24 minutes.

 

My 3D-printed oven dome, still on Printer bed

 

The brick courses have also printed cleanly on the central panel of the front of the Coke Oven:

 

My 3D-printed arched door, still on Printer bed

 

Both these prints were made from Gcode files prepared by ‘Cura’ software when using its ‘Fine’ resolution setting. For detailed finishes, such as these bricks that are only a few millimetres long in 4mm scale, there is a significant advantage over the ‘Normal’ resolution, with a small penalty in terms of print time, using my Geeetech E180 printer.

 

Detail Comparison between prints made at ‘normal’ and ‘fine’ resolution settings

 

The following print times are those estimated by the ‘Cura’ software for :

 

• normal 1h 13m
• fine 1h 40m
• extra fine 3h 24m

 

I have not tested the ‘Extra Fine’ setting but, for this model, I felt the time penalty was excessive and that the ‘Fine’ resolution print is adequate.

 

I’ve enjoyed making something ‘different’ with my 3D printer.

 

Now I need to create an embankment, into which I can insert a row on ovens, once I have designed a layout 🙂

 

Mike