A closer look at the National Gas Engine No. 2 and No. 3

The National Gas Engine Company operated from Ashton-under-Lyne in Lancashire and earned its place in late-Victorian engineering by turning out slow-revving, single-cylinder horizontal engines for town gas, producer gas, and the new natural gas supplies reaching industrial towns. Through the 1890s and into the early twentieth century the firm served small workshops, country estates, print works, light manufacturing, and rural water-pumping stations across Britain and the wider Commonwealth. The No. 2 and No. 3 models sat at the heart of its product line, representing two scales of an essentially common design.

These two machines share most working principles, yet they were never intended for the same duties. The No. 2 was a compact auxiliary for modest loads, while the No. 3 was built as a heavier, more substantial prime mover for continuous running. Comparing their construction, governing, and day-to-day running characteristics brings the company's design philosophy into focus.

Origins and manufacturing background

The National Gas Engine Company emerged in a period when British engineers were racing to make internal combustion a credible alternative to steam in modest installations. Cast iron frames, single horizontal cylinders, water cooling, and slow running speeds were the conventions of the day. Within those conventions the No. 2 and No. 3 occupied adjacent places in the catalogue, separated by output and weight rather than by any change of underlying concept.

The No. 2 was sized for customers with light mechanical needs, including printers, laundries, and small corn mills where floor space was at a premium. Production stretched across several minor revisions, but its general arrangement stayed recognisable throughout. The No. 3 was the next step upward, with larger castings, a heavier flywheel, and a more robust crankshaft to take heavier loads. Engineers who maintained them often described the No. 3 simply as the smaller engine grown up, and that summary stuck to the family throughout its working life.

Engine architecture and mechanical layout

Both engines rest on a long, low bedplate that also supports the crankshaft bearings. The cylinder is mounted horizontally at one end, the flywheel at the other, and the trunk piston operates in a single-acting cycle with firing on every working stroke. The No. 2 carries a moderate bore and stroke, while the No. 3 extends both dimensions to extract more torque at lower revolutions per minute.

Cooling relies on a water jacket surrounding the cylinder in each case, and the No. 3 uses a noticeably larger jacket to dissipate the additional heat of combustion. Most installations were served either by an adjacent cooling tank or by tower-fed circulation, which made flow rate an important commissioning check. Ignition was by hot tube or low-tension electric system, with timing adjusted through a linkage driven off the flywheel.

The most visible difference at a glance is the flywheel itself. The No. 2 carries a lighter rim, which kept the overall weight low enough for upper-floor installation in premises without reinforced ground floors. The No. 3 is built around a heavier flywheel with a broader rim, better suited to ground-floor engine houses and capable of stronger rotational regulation. Lubrication is broadly shared, with oil reservoirs in the main bearings and a drip-feed system topped up during routine visits.

Governing and speed control

Hit-and-miss governing was the standard arrangement for engines of this era, and both National models use the same centrifugal governor linked to a gas admission valve. When the flywheel reaches its set speed the valve is held shut, and the engine coasts on stored energy until speed drops below the threshold and a fresh charge is admitted. The familiar surge-and-coast rhythm is a defining characteristic of the family.

The No. 2 typically runs around 180 to 200 revolutions per minute, governed to hold that figure across reasonable load swings. Its lighter flywheel stores relatively little energy, so the surge is clearly visible in any belt-driven equipment. The No. 3 runs somewhat slower, around 150 to 170 rpm, and its larger flywheel evens out the firing rhythm noticeably. Operators who moved between the two often commented that the No. 3 seemed quieter at the belt even though it was no slower when carrying load.

Both engines can be tuned at the governor for particular response characteristics. Common adjustments include varying the spring tension to favour close speed holding or to speed up load pickup. The No. 3 also benefits from a larger crankcase volume, which damps pressure fluctuations and makes the engine a calmer match for sensitive loads such as printing presses or small generators.

Power output and working characteristics

Rated output places the No. 2 in the two-to-three horsepower band, comfortably serving a single belt driving several small machines. The No. 3 sits well above it, usually rated at between four and six horsepower depending on gas quality and the load profile. Its low-speed torque makes it particularly well suited to pumps, mills, and small compressors that would otherwise stall a smaller engine.

Both engines run effectively on producer gas generated on site from timber, coke, or charcoal, and this versatility mattered in remote settings far from a town gas main. Isolated Australian operations at places like Ballarat, Bendigo, and the Western Australian goldfields relied on this flexibility, and a number of surviving engines in those districts trace their working lives to producer gas plants that supplied local workshops and pumping stations. Specific fuel consumption reflects the typical efficiency of single-cylinder gas engines of this era and compares well with small steam plants of equivalent date.

Routine maintenance is broadly similar for both models. Cleaning the water jacket, inspecting the ignition components, draining condensed moisture, and topping up the bearing oil account for most of the regular service work. The No. 3 simply takes longer to overhaul, mainly because of the heavier cylinder head and the additional labour of lifting it for decarbonisation.

Preservation in Australia and beyond

Working survivors of both models can be found in private collections, rally fields, and museum stores across the United Kingdom, Australasia, and North America. Australian collectors have long valued these engines because of their connection to the mining and pastoral industries, where gas engines once powered water pumps, workshop machinery, and small generating sets on remote stations. Several examples survived in service for many years after their original commercial role had ended, which is part of why good restoration candidates still turn up in regional sheds.

Modern preservation work in Australia operates within state-level heritage frameworks. New South Wales and Victorian heritage legislation, for instance, provides clear pathways for retaining significant industrial machinery in situ, particularly at former mining and pastoral heritage sites. Volunteer groups and local councils in regional Victoria, including towns such as Castlemaine and Daylesford, have taken a leading role in stabilising and interpreting engine houses containing early National Gas Engine installations. Original parts are scarce, and most projects depend on donor engines, machined replacements, or carefully chosen modern substitutes where strict originality is not essential.

Documentation is often the first obstacle a restorer faces. Original drawings, serial records, and works plate photographs sit in a mix of club libraries, private archives, and online collections, and pulling them together can take time. A useful first stop for researchers and restorers is the stationary engine index, where listings, cross-references, and image galleries for engine families are gathered together. Cross-checking period advertisements and owner's manuals against that material usually narrows down a specific machine's year of build.

Running, display and collecting communities

At rallies and open days both engines start readily on natural gas, methane, propane, or bottled LPG with only minor ignition adjustments, and a well-restored example will run cleanly for hours. Visitors often comment on the audible difference in firing rhythm between the two models. The No. 3 carries more visual presence thanks to its larger flywheel and longer stroke, while the No. 2 reads as more compact and is easier to handle in a workshop restoration. Both engines draw steady crowds at events such as the Goulburn Vintage Machinery Rally and at smaller gatherings held by regional heritage groups.

Educational use of paired engines has grown steadily. Institutions such as Sydney's Powerhouse Museum, along with several regional workshops, have used the No. 2 and No. 3 side by side to show how a single engineering concept scales across output classes without losing its essential character. Demonstration runs on a shared line shaft remain a powerful way to compare the two designs under load, and they are particularly useful when working with younger visitors who may not have seen a gas engine run before.

Long-term care rests on shared knowledge. Owners exchange governor settings, ignition timing notes, and cooling recommendations through clubs and online forums, building a body of practical expertise that rarely appears in print. A sensible approach for any new project is to photograph all fittings before disassembly, record the works plate in full, and reach out to others who have rebuilt a similar machine. Even relatively rare variants tend to be known to at least a handful of dedicated enthusiasts.

If you own either a No. 2 or a No. 3, or if you have come across an example that may be of interest to researchers and restorers, sharing what you know helps preserve a record of machines that have largely faded from everyday memory. Notes on works plates, original location, and current condition are all valuable, and photographs are always welcome. Please use the contact page to add your engine to the growing archive and connect with others working on these enduring British designs.