steam locomotive

9 Articles

Historical Hack: Henri Giffard’s Steam Injectors

August 19, 2026 by 16 Comments

Here’s a historical hack for you: you have a big, rolling pressurized kettle, also known as a steam locomotive. It needs water to make up for the steam constantly chuff-chuff-chuffing away, or bad things happen. How do you get water from an unpressurized tender into a high pressure boiler with no moving parts? What you need is a some way to inject steam with no moving parts — a steam injector, if you will. [Marc Flint] found that the steam injectors were the hardest part of a loco to understand, so he made a video for all of us once he’d figured it out.

The steam injector isn’t a new idea. [Henri Giffard] came up with it back in the 1850s to replace expensive and maintenance-hungry pumps. It’s rather ingenious and uses the fluid mechanics uncovered by another European bloke by the name of Bernoulli. First, the high-pressure steam from the boiler goes through a converging-diverging nozzle to drop its pressure and speed its flow up, just as you’d guess if you’ve seen Bernoulli’s laws. Even more vacuum-inducing is the presence of water: the steam, already cooled by its expansion, hits the water in the pipe open to the tender, and condenses into it, shrinking a couple of orders of magnitude, creating a vacuum that draws in no small quantity of feed water. That one we did not expect from Bernoulli, but it makes sense. So how to get from below atmospheric pressure to the 180-odd PSI or more in the boiler?

Well, the water is now moving at a good clip, between the Venturi effect and the momentum gained from absorbing that steam, so another converging nozzle is the trick. Bernoulli’s law, once more! A one-way valve lets the now-pressurized water into the boiler, with a gap in between to dump water while the pressure builds up. It’s a clever trick, and since the steam coming from the boiler makes it back inside along with at least some of its heat energy, it’s much more efficient in both coal and water than running a pump. It’s also a bit of a head scratcher how it works unless someone sits you down to explain it, so we’re glad [Marc] did.

Not many of us are likely to use this knowledge directly — unless we’re firing up a 90 year old boiler or building a new steam locomotive — but seeing how great engineers of years past made use of basic physical laws can serve both as education and inspiration.

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Examining A World’s Record From The Age Of Steam

March 2, 2026 by 19 Comments

There aren’t many speed records that remain unbroken for the greater part of a century, but one of them is that of the fastest steam locomotive. As with so many such things, there’s a bit of controversy and more than one contender, but the one in the record books is the A4 Pacific, Mallard. In 1938, this locomotive thundered down an incline on the London & North Eastern Railway’s mainline in the north of England at 126 MPH. But can that number be taken as reliable? The Institute of Mechanical Engineers has a video in which they investigate.

It’s a fascinating look at the science of railway speed measurement as it existed in 1938, the record itself, and the paper dynamometer roll which recorded it. We’ve placed the video below the break, and in it, we see an in-depth analysis of the noise and inconsistencies in the recording, and see them come to the conclusion that a safer figure to quote would be 124 MPH.

Our assessment is that, of course, the LNER wanted to squeeze every morsel of publicity from it in a game of one-upmanship with their arch-rivals in the London Midland and Scottish railway, so it’s likely that their use of a momentary figure makes sense in that light. Even the best-laid 1930s jointed track would have been bumpy compared to modern continuous rail, and we are guessing that the ancient clerestory dynamometer car would hardly be as smooth-riding as a modern express coach. The achievement of measuring at all with mechanical instruments in such an environment at those speeds would have been tricky, to say the least. It leaves us wondering whether 1930s electronics could have produced some kind of trackside measurement device, but perhaps the LNER trusted their mechanical instruments more. Perhaps the Pennsylvania Railroad should have followed its example.

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British Trains To (Maybe) Make Way For Steam Once More

July 6, 2024 by 72 Comments

There’s nothing more guaranteed to excite a grizzled old railway enthusiast than the sight of a steam locomotive. The original main-line rail propulsion technology still clings on in a few places, but for practical purposes, it disappeared a lifetime ago. It’s interesting then to hear of a brand new steam locomotive prototype being considered for revenue freight use on British metals. Is it yet another rebuild of a heritage design to be used for enthusiasts only? No, it’s an entirely new design with nothing in common with the locomotives of the past, as [Terrier55Stepney] tells us in the video below the break.

Gone is the huge boiler and reciprocating pistons of old, as indeed is the notion of boiling anything. Instead, this is a steam turbine, nothing like the 1920s and 30s experiments with conventional locomotives, nor even the Union Pacific’s oil-fired condensing turbo-electrics. The new idea here from the British company Steamology is to create steam directly from the combustion of hydrogen in a series of small modular steam generators, and the resulting prototype turbo-generator will replace the diesel engine in a redundant British Rail class 60 freight locomotive. It’s unclear whether it will incorporate a condenser, but since it has no need to retain the water for a boiler we’re not sure it would need one.

Prototype locomotives featuring new technologies have a long and inglorious history of not making the grade, so while this is definitely an exciting and interesting development we’re not guaranteed to see it in widespread use. But it could offer a way to ensure a low-carbon replacement for diesel heavy freight locomotives, and unexpectedly provide engine upgrades for existing classes. The fact it’s technically a steam locomotive is incidental.

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Staged Train Wrecks: An Idea That Ran Out Of Steam

September 2, 2020 by 35 Comments

Before there were demolition derbies, there were train totalings. That’s right, somebody had the idea to take a couple of worn-out train engines that were ready for the scrap heap, point them at each other, and drive them full steam ahead. And their boss said capital idea, let’s do it. This was the late 1890s.

Maybe it wasn’t the safest way to spend an evening, but a staged train wreck was surely an awesome spectacle to behold. Imagine being one of the brave engineers who had no choice but to get the train going as fast as possible and then jump out at the last second. A demolition derby seems like child’s play by comparison.

The largest and most widely-publicized wreck was put on by a man named William George Crush who was trying to find new ways to promote the Missouri-Kansas-Texas passenger railway. Once he got the okay, Crush found a large field surrounded by three hills that made for excellent viewing. He stood up a temporary town complete with a circus tent restaurant, a wooden jail cell, and 200 rent-a-constables.

On September 15th, 1896, forty thousand people gathered to watch two trains collide along a section of purpose-built track. They hit each other going 50 mph (80 km/h) and both engines exploded, sending hot iron projectiles every which way. Several people were injured, a few died, and a hired photographer lost an eye to shrapnel. Train totalings nevertheless continued until the Great Depression of the 1930s, when the practice was discarded as wasteful.

Thanks for the tip, [Martin]!

Considering The Originality Question

November 9, 2019 by 37 Comments

Many Hackaday readers have an interest in older technologies, and from antique motorcycles to tube radios to retrocomputers, you own, conserve and restore them. Sometimes you do so using new parts because the originals are either unavailable or downright awful, but as you do so are you really restoring the item or creating a composite fake without the soul of the original? It’s a question the railway film and documentary maker [Chris Eden-Green] considers with respect to steam locomotives, and as a topic for debate we think it has an interest to a much wider community concerned with older tech.

Along the way the film serves as a fascinating insight for the non railway cognoscenti into the overhaul schedule for a working steam locomotive, for which the mainline railways had huge workshops but which presents a much more significant challenge to a small preserved railway. We wrote a year or two ago about the world’s first preserved railway, the Welsh Tal-y-Llyn narrow gauge line, and as an example the surprise in the video below is just how little original metal was left in its two earliest locomotives after their rebuilding in the 1950s.

The film should provoke some thought and debate among rail enthusiasts, and no doubt among Hackaday readers too. We’re inclined to agree with his conclusion that the machines were made to run rather than gather dust in a museum, and there is no harm in a majorly-restored or even replica locomotive. After all, just as a retrocomputer is as much distinguished by the software it runs, riding a steam train is far more a case of sights and smells than it is of knowing exactly which metal makes up the locomotive.

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Retrotechtacular: How To Repair A Steam Locomotive

November 24, 2017 by 41 Comments

Steam locomotives, as a technological product of the 19th century, are not what you would imagine as fragile machines. The engineering involved is not inconsequential, there is little about them that is in any way flimsy. They need to be made in this way, because the huge energy transfer required to move a typical train would destroy lesser construction. It would however be foolish to imagine a locomotive as indestructible, placing that kind of constant strain on even the heaviest of engineering is likely to cause wear, or component failure.

A typical railway company in the steam age would therefore maintain a repair facility in which locomotives would be overhauled on a regular basis, and we are lucky enough to have a 1930s film of one for you today courtesy of the British London Midland and Scottish railway. In it we follow one locomotive from first inspection through complete dismantling, lifting of the frame from the wheels, detaching of the boiler, inspection of parts, replacement, and repair, to final reassembly.

We see steps in detail such as the set-up of a steam engine’s valve gear, and it is impressed upon us how much the factory runs on a tight time schedule. Each activity fits within its own time window, and like a modern car factory all the parts are brought to the locomotive at their allotted times. When the completed locomotive is ready to leave the factory it is taken to the paint shop to emerge almost as a new machine, ready for what seems like a short service life for a locomotive, a mere 130 thousand miles.

The video, which we’ve placed below the break, is a fascinating glimpse into the world of a steam locomotive servicing facility. Most Hackaday readers will never strip down a locomotive, but that does not stop many of them from having some interest in the process. Indeed, keen viewers may wish to compare this film with “A Study in Steel“, another film from the LMS railway showing the construction of a locomotive.

LMS Jubilee class number 5605, “Cyprus”, the featured locomotive in this film, was built in 1935, and eventually scrapped in 1964 as part of the phasing out of steam traction on British railways.

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Retrotechtacular: 6207, A Study In Steel

June 7, 2016 by 47 Comments

If you ever encounter railroad or railway enthusiasts, you may have heard the view that at some point in the past there was a golden age of rail transport that has somehow been lost. It’s something that’s up for debate as to when that age was or even whether with a selection of new super-high-speed trains snaking across our continents we’re in a golden age now, but it’s true to say that the rail business has had its fair share of decline in the last half-century.

It’s quite likely that when they talk of a golden age, they really mean a golden age of steam rail transport. At which point depending on where you live in the world it’s easier to put your finger on a decade. For UK residents a good candidate would be the 1930s; steam locomotive design had reached its peak, the rail network hadn’t been worn out by the demands of wartime, and private car ownership hadn’t eaten into their passenger numbers. The country was divided up into a set of regional rail monopolies, each of which had their own locomotive works and designers who were in fierce competition to show that their machines were the best and the fastest.

The LMS, the London Midland and Scottish railway company, served the northwestern segment of the country, North Wales, and the West of Scotland. Their high-speed express trains were in hot competition with those of the LNER, the London and North Eastern Railway, who served the eastern side of the country, to offer the fastest service from London to Scotland. It’s difficult to grasp through an 80-year lens, but this battle was one of national excitement, with the fastest locomotives becoming household names nationwide. The railway companies were justifiably proud of their engineering expertise, and so featured their locomotives as a key part of their marketing to the general public.

And so we come to the subject of today’s Retrotechtacular piece, a film below the break from 1935 following the construction of a high-speed express locomotive from start to finish in the LMS’s Crewe railway works. 6207 was one of a class of thirteen 4-6-2 Pacific locomotives designed by the company’s chief engineer [William Stanier], built between 1932 and 1935 and known as the Princess Royal class, all being named for princesses. In the film we see the various parts of the locomotive being cut, cast and forged from raw metal before being assembled in the Crewe plant. All the machinery is human controlled, and one of the surprises is sometimes the number of people involved in each task. The level of skill and experience in precision metalworking to be found in plants like Crewe was immense, and in some cases it is very difficult to find its equivalent in our own time.

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