Recreating a 300-year-old steam engine
By Graeme Quayle
[This article was first published in The Shed magazine in February 2014]
A replica steam engine that made its first appearance at the Glenbrook Vintage Railway near Auckland in 2013 was much more than just another piece of interesting machinery. Built to mark 300 years since what was believed to be Thomas Newcomen’s first engine, made in 1712, it celebrates an invention that contributed significantly to the industrial revolution.
No Newcomen engine was ever installed in the Southern Hemisphere, until now. It had been superseded by improved designs when colonisation was happening.
This splendid 21st-century example, named Gloribelle, was built by a group of volunteers in Auckland. It’s the first outside the UK, the USA, and continental Europe and made its public debut at Glenbrook’s Steam and Vintage Country Festival.
The 19 or so enthusiasts who built the Newcomen were mostly members of the Auckland Steam Engine Society, including a core of six led by Ken Pointon, the former Steam Section leader at MOTAT.
Working from simple drawings
Ken Pointon and his son, André, designed the Kiwi Newcomen as no complete drawings or instructions were available. The team only had original construction drawings of a side elevation and an end elevation showing the framework. The rest was worked out, often from just a sketch of the general idea. A basic requirement was the need for the engine to be transportable for display at different venues; most of the originals were built as part of the engine house.
This engine’s name comes from the nickname of Ken’s wife, Gloria. Sadly, Gloria died after a six-year battle with cancer, just three weeks before the engine ran for the first time.
Team members were surprised at the steam festival that they managed to get the engine to run automatically from its own controls so quickly after completion. It spoke volumes for the Pointons’ design and expertise. Gloribelle had only run on trial three times previously, under manual control. However, a few aspects of the running require fine-tuning.
The engine’s base comprises a five-inch steel channel bolted together with a perimeter frame and several longitudinal and cross members. The mainframe members are specially-sawn macrocarpa, tenoned and scarfed together with through bolts and tusk tenons holding some joints. The bolts are fitted with square nuts, typical of the period. Hundreds of these nuts, from 10 mm to 20 mm threads, were made for the project.
The mainframe consists of two A-frame side members connected at their apex with a cross member and short lapping side members. Partway down the A-frames is another set of lapping side members and a further cross member. This pair of cross members have two steadying diagonal steel braces.
Fastened to the top cross member are two sommer load-carrying beams that extend the length of the engine. These beams have mounted on the top, the over-stroking plinths with four spring-steel leaf springs, equally spaced on either side of the pivot plinths. The main pivot bearings for the rocking beam are mounted on substantial pivot plinths.
Over-stroking springs are standard trailer leaf springs, modified for the purpose, and work well.
A table with the top half-barrel cistern water tank is at the boiler end. The sommer beams are supported at each end with four vertical columns from the base and diagonal side braces to steady them. The cylinder mounting beams extend from the lower cross member in the A-frame assembly to the boiler-end columns. A platform, extending from the rear cylinder beam to the edge of the frame assembly, is reached by a vertical ladder at the rear and has a wooden handrail. Cross members connect the top of the columns.
The boiler consists of a round steel pot drum fitted at the base with water walls and cross tubes to aid circulation. It’s suspended from the top frame and stayed to the bottom frame of the boiler support assembly. There is a rectangular opening at the back for steam heater elements. The fire door is at the front, between the water walls. Heat passes under the boiler drum, through the water walls, to the back, and out through the left side of the boiler frame to the chimney.
Heater elements were formed from steel tubes bent back and forth to fit inside the boiler, welded to the rectangular steel cover plate that bolts to the back of the boiler over the opening. These tubes exit the boiler drum and weld into two-column pipes connected to the steam inlet and discharge into the boiler.
Outer walls are recycled brick individual panels, removable for maintenance. A fire door fits into the brickwork at the front wall with a brick arch over the top. Two doors at the top and two removable panels at the bottom of the back wall give access to gauges and valves. An exhaust outlet is set into the left-side brick panel. The right side has a vertical channel for the plug rod.
Walls, encapsulated and held in place by the angle perimeter frame of the top panel and dome assemblies, are further secured by the corner vertical angles. Doors and removable panels have numerous rivets replicating the original style; hinges and handles were forged to look authentic.
The dome top, including the top plate and circular rows of bricks, is a separate unit able to be jacked up and removed for maintenance. Although not part of the boiler it does house pipes and the main steam valve. The dome is riveted up from steel petals and has several pipe fittings. The largest is the buoy pipe; then there are two main steam pipes formed into a U with the safety valve and filler pipe branching off. On top, two bronze high and low water level try cocks discharge into tundishes. The top assembly is bolted to the boiler frame, pipes connected by flexible hoses.
An exhaust from the fire passes under the boiler to the back where there is a removable panel for ash. It then passes through the left brick panel through a Z steel pipe to a smoke box clamped to an extension of the base. This has a cast refractory base just below the Z pipe outlet. A removable panel to allow cleaning is on the outside face of the smokebox. On top are five stainless steel square chimney sections, each just over 1.2 m long. There’s an appropriate cap on the chimney.
The boiler runs from its own fire or from heater elements. It runs at 2 psi pressure, as did the originals, and has numerous safety features including a safety valve (not fitted to early Newcomen engines), a sight glass (also not fitted), and is filled like the original by a trickle of water into a tundish set high enough so that the column of water is of greater pressure than the 2 psi. The water comes from the half-barrel cistern on top of the engine. The worst that could happen if the safety valve stuck is that water and steam would be forced out of the filler pipe.
The firebox is about 400 mm square and has cast iron fire bars above the ash pan. An arch of one layer of bricks sits behind the fire bars on the edge and other bricks lay flat in a pan that extends to the back of the boiler and water walls. The fire has proved to be quite adequate to run the engine.
Modern instruments hidden inside the two rear doors comprise water level sight glass, pressure gauge, temperature gauge, incoming steam-pressure gauge for when the boiler is heated from another source, and other non-return and stop valves.
The boiler has a filling pipe, steam connection pipe and drain pipe at the bottom left corner at the back, alongside the lift-off panel. The whole boiler assembly, which weighs about 3.5 tonnes, is fixed to the base with clamp plates so it can be removed as a unit.
The main steam control valve, of the bronze swinging type, is set in the top of the dome, automatically controlled by the plug rod-trip pins. A two-piece flexible connection fits between the boiler and cylinder base cover.
A steam pipe connection and eduction pipe are fitted to the cylinder base cover. The eduction pipe removes condensate from the cylinder and discharges it into a small water tank at the back of the boiler (the hot well). A non-return valve and a ball valve regulate the flow of condensate.
An overflow pipe connects the hot well to the main water tank. This pipe has an overflow outlet preventing water from getting too high in both tanks. The hot well tank is made of sawn timber, strengthened with steel clamp bolts, lined with a plastic sleeve, and has a bronze drain cock to empty it. The hot well has several pipes discharging into it from overflows, including the cistern top tank, safety valve, try cocks, cylinder top, and snifter valve.
The cylinder is a piece of nominal bore nine-inch cast iron pipe, bored out and polished for the piston. Atop the cylinder, a bronze casting has a copper drain pipe to keep the level of water over the piston roughly constant. This drains into the hot well. The water is topped up from the cistern via a classic bronze cock.
A two-piece steel split clamp holds the cylinder to the cylinder beams. At its base are two fittings. One is the snifter valve, fitted in a tundish to remove any air from the cylinder. This valve is water-covered, also from a classic bronze cock fed from the top cistern. The other fitting is a water injection valve, a bronze cock turned on to condense steam when the piston is at the top of its stroke, automatically controlled by the plug tree trip pins. It, too, is fed from the cistern.
The piston comprises a two-piece bronze casting with a leather cup washer connected to a steel bar. A chain hook is forged on the top end; this couples to a chain hooked to the top of the arch head at one end of the rocking beam.
A laminated wood assembly with a steel plate sandwiched between two halves makes up the rocking beam, along with four wooden arch pieces, two at each end, and smaller ones about halfway from the central pivot. These arch pieces are steel faced for the chains to run on and braced to the main pivot beam with steel diagonal braces. Forged cheek plates at the central pivot pin replicate the original style and the main pivot pin is carried in bearing blocks mounted to the pivot plinths on the sommer beams.
Two steel crossbars, one at each end, project out each side of the beam and strike the leaf springs, which cushion and stop the movement if the beam over-strokes. The arch head at the boiler end connects to the piston. The mid one, coming back towards the beam pivot, connects to the plug rod, which controls the engine. Another, half-way out on the other side of the beam, connects to the small water pump. The other end one connects to the main water pump.
The plug-rod controls opens and closes the valves to provide automatic running, and is made from two pieces of wood with a gap between them and a weight on the bottom end. It is guided through guide blocks on the edge of the boiler frame and includes holes through which trip bolts are positioned to trip the main steam valve and the water injection valve, as required. The timing of these events is critical to the engine’s smooth running.
A rectangular plywood main water tank, about 61 cm high, sits on the base frame. It’s strengthened with steel angles bolted through the plywood and is lined with a plastic liner. A hatch allows inspection of the water level and acts as a platform for the engine drivers to stand on. On the top is a hand water pump and the small water pump.
Alongside the small pump is a pipe with a tundish on top, so the engine driver can bleed water out of the outlet pipe from the small pump, through a bronze cock, if too much is being pumped to the top half-barrel cistern tank. Two large holes at the right-hand end of the main water tank provide the connection to the main water pump and to the water return. A pipe at the back connects the hot well and the main tank.
The hand water pump has been substantially modified compared to a typical example. The pump cylinder is now in the base casting and has a stainless steel sleeve. The base bolts to a steel flange fastened to the top of the water tank with a pipe projecting down into the water with a non-return valve at the bottom. The piston has a non-return valve and a leather cup to seal to the cylinder.
What was the original cylinder and discharge casting is bolted to the base casting and has an elbow facing up to connect to the water pipe that goes to the top cistern water tank. The casting on the top of the whole assembly, from which the handle pivots, is sealed to the rest of the assembly and has a gland packing for the piston rod to work through. So the pump is now a pressure pump, used to fill the top cistern tank before the engine is started.
The small water pump is made from a piece of steel pipe with flanges welded each end and lined with a stainless steel liner. Similar to the hand pump, it feeds water to the top cistern. This pump keeps the cistern full when the engine is running.
Meanwhile, the large water pump is mounted to a substantial steel base bolted to the base frame. The base assembly connects to the water tank via flanges and has a removable lid allowing access to a non-return flap valve. The cylinder is a steel pipe with flanges welded each end and also has a stainless steel liner. The piston has a non-return valve. This is a larger bore pump than the small one, so pumps substantially more water.
The top assembly is similar to the smaller pump, and the outlet is controlled through a butterfly valve for initial testing. Water is pumped vertically, then horizontally, to discharge into a spreader box in the top of a water-cooling tower. This tower is intended to be temporary until a suitable water wheel is made.
A cool tower
Plywood and timber were used for the cooling tower. This has a rectangular box base and the tower is a separate structure sitting in it. The water outlet is in one end of the base and water gravitates back into the engine’s main water tank.
An old wine barrel with added steel bands is used for the top half-barrel cistern water tank. The barrel is lined with fibreglass and finished with rubberised sealing paint. Water from the hand pump discharges into the barrel via a vertical pipe with a U ends lipped over the edge of the barrel. The inlet for the small water pump is through a fitting set into the barrel’s base. The overflow pipe is fitted to the side, near the top.
The safety valve is a special one with a large valve to cope with the volume of steam and is set to lift at around 2 psi. A trip cord is fitted. The valve discharges through a pipe with a condensate return pipe, which discharges into the hot well tank.
Engine controls are reached from the top of the main water tank. A square cross shaft is held in bearings mounted in vertical wood members extending from the top of the brickwork on the boiler up to the cylinder beams. Off this shaft are fittings for operating the steam valve. The shaft is weighted to rock either side of vertical so that, when moved by the plug rod, there is a point where the shaft moves past vertical and the weights cause it to quickly close the steam valve. Some lost motion in the controls allows this to happen.
Available for display
The water-injection valve, on another pivot shaft, also has over-centre weights to quickly trip it. The mechanism is reset via pegs in the plug rod. All this has to move freely for it to work. Ropes connected to these weights limit the movement and cushion the flopping of the weights. A yoke with hooks, part of the steam control mechanism, connects to the controls and can be lifted out of connection when starting and moved manually to allow steam into the cylinder. The water injection valve can also be worked manually to start the engine.
A top platform is reached via a vertical ladder and allows visual inspection of the water levels above the piston, as well as the snifter valve. It also provides a closer view of the stroking of the beam and the water level in the top cistern.
Boiler pipe work is mostly hidden behind the brick walls and is completely removable as mac unions couple various sections together. The modern steel pipe is threaded to allow standard fittings.
The Auckland Steam Engine Society owns Gloribelle and can be contacted at, firstname.lastname@example.org. The engine is available for display at suitable venues, thanks to the ability to completely dismantle it for transportation. What would Thomas Newcomen have made of that?