Historical Hack: Henri Griffard’s Steam Injectors

August 19, 2026 by Tyler August 4 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 Griffard] 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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Building A Steam Loco These Days Is Nothing But Hacks

January 1, 2026 by Tyler August 35 Comments

The Pennsylvania Railroad (PRR)’s T1 class is famous for many reasons: being enormous, being a duplex, possibly having beaten Mallard’s speed record while no one was looking… and being in production in the 21st century. That last fact is down to the redoubtable work by the PRR T1 Steam Locomotive Trust, who continued their efforts to reproduce an example of these remarkable and lamentably unpreserved locomotives in the year 2025.

They say that 2025 was “the year of the frame” because the frame was finally put together. We might say that for the PRR Trust, this was the year of welding. Back when the Baldwin and Altoona works were turning out the originals, the frames for steam locomotives were cast, not welded. There might not be anywhere on Earth to get a 64′ long (19.5 m), 71,000 lbs steel casting made these days. Building it up with welded steel might not be perfectly accurate, but it’s the sort of hack that’s needed to keep the project moving.

The cylinders, too, would have been bored-out castings back the day. Getting the four (it’s a duplex, remember) assemblies cast as one piece didn’t prove practical, so T1 #5550 will have welded cylinders as well. Given modern welding, we expect no problem with holding steam pressure. The parts are mostly machined and will be welded-together next year.

The giant wheels of the locomotive have been cast, but need to be machined. It’s not impossible to believe that locomotive #5550 will be on its frame, on its wheels, in 2026. The boiler is already done and the injectors to get water into it have been reinvented, which can perhaps be considered another hack.

Right now, if donations continue to trickle in at the current rate– and prices don’t rise any faster than they have been– the Trust hopes to have the locomotive steaming in 2030. She’s now 59.8% complete. That’s up from 40% when we last checked in, back in 2022, which is great progress considering this is a volunteer-driven, crowd-funded effort.

If you don’t have the skills or geographical location to volunteer with this build, but we’ve piqued your love of steam, perhaps you could 3D print an engine to scratch the itch.

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This Tiny Steam Engine Takes A Watchmaker’s Skill To Build

September 9, 2024 by Dan Maloney 30 Comments

When your steam engine build requires multiple microscopes, including those of the scanning electron variety, you know you’re building something really, really tiny.

All of the usual tiny superlatives and comparisons apply to [Chronova Engineering]’s latest effort — fits on a pencil eraser, don’t sneeze while you’re working on it or you’ll never find it. If we were to put the footprint of this engine into SMD context, we’d say it’s around a 2010 or so. As one would expect, the design is minimalistic, with no room for traditional bearings or valves. The piston and connecting rod are one piece, meaning the cylinder must pivot, which provides a clever way of switching between intake and exhaust. Tiny crankshaft, tiny flywheel. Everything you’d associate with a steam engine is there, but just barely.

The tooling needed to accomplish this feat is pretty impressive too. [Chronova] are no strangers to precision work, but this is a step beyond. Almost everything was done on a watchmaker’s lathe with a milling attachment and a microscope assist. For the main body of the engine, a pantograph engraving machine was enlisted to scale a 3D printed template down tenfold. Drill bits in the 0.3 mm range didn’t fare too well against annealed tool steel, which is where the scanning electron microscope came into play. It revealed brittle fractures in the carbide tool, which prompted a dive down the rabbit hole of micro-machining and a switch to high-speed steel tooling.

It all worked in the end, enough so that the engine managed 42,000 RPM on a test with compressed air. We eagerly await the equally tiny boiler for a live steam test.

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Chugging Along: A Steam-Powered Sawmill Still Makes Its Mark

October 31, 2023 by Donald Papp 11 Comments

[Rural Heritage TV] has video of a private tour of a working, two-story, steam-powered sawmill at Lake Itasca, Minnesota. This is believed to be one of the only working steam-powered band-sawmills in the country with a shotgun (or reciprocating) feed carriage. The carriage moves back and forth with a log while a monstrous 44-foot long bandsaw cuts pieces off on every stroke. There’s even a log turning mechanism, because if there’s one thing that never changes, it’s that time is money.

There is great footage of the whole thing in action, and also a serious tour of just how much work was needed to keep such a tool running. For example, in its heyday a machine like this would be swapping bands out for maintenance and sharpening every few hours.

Viewers unfamiliar with such machinery may notice the lack of rims or guard rails on the bandsaw and other belts and pulleys. How do bands stay centered on spinning wheels without falling off? The crowned pulley was the steam era’s solution, providing a means for belts to self-center without any need for rims or other additions.

This tour of the sawmill is a nifty peek at a technology that, at one point, ruled the roost. Watch it in action in the video, just under the page break. If that leaves you hungry to know more, there’s a second video that goes into added detail about saw sharpening and more.

One last tip: if you’re hungry to know more about the history of the steam engine, The Perfectionists is absolutely a book you should read because it goes into fascinating detail about that, and more.

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A Steam Engine For Empty Beer Cans

October 27, 2022 by Al Williams 10 Comments

If Hero — the ancient Greek inventor — had been able to enjoy a beer after work, he might have pulled a trick like [BevCanTech] did: use it to create a simple steam engine. Of course, we aren’t sure why it has to be a beer can, but even with a soda can there is a fundamental problem: the can is open, assuming you’ve already enjoyed the beverage.

A pressure vessel with a big gaping hole in it isn’t much of a pressure vessel. The resealing process was actually quite simple. First, you bend back the tab to close up the opening as best you can. Next, you use cyanoacrylate glue and baking soda to seal up what’s left. We wondered if you could use epoxy, hot glue, or UV-curable resin. The top might get too hot for hot glue to last, but we aren’t sure.

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A streamlined black boiler with a headlight at the tip dwarfs the 5th wheel trailer and secondary trailer it is attached to.

Bringing A Steam Train Back From Extinction

October 11, 2022 by Navarre Bartz 75 Comments

There’s no denying that while railroads have switched to diesel and electric as their primary power sources, there’s a certain allure to the age of steam. With that in mind, a group of Pennsylvania train fans are bringing the alleged fastest steam train back from extinction.

It takes real dedication to build a 428-ton device from scratch, but these rail aficionados seem to have it in spades. Armed only with the original blueprints and a lot of passion, this team has already finished construction of the boiler and nose of the Class T1 replica which is no small feat. This puts the train at approximately 40% complete.

Some changes are planned for the locomotive including a change to fuel oil from coal and replacing the poppet valves prone to failure with camshaft-driven rotary valves. While not original hardware, these changes should make the train more reliable, and bring the world record for the fastest steam locomotive within reach. If the T1 replica can reach the 140 MPH storied of the originals, it will smash the current record of 126 MPH held by a British train, the A4 Mallard, which would be exciting indeed.

Speaking of Pennsylvania and steam, a trip to Scranton is a must for anyone interested in the age of rail.

A V2 Rocket Inspired Steam Turbine Skateboard Is Just Around The Corner

April 12, 2022 by Dave Rowntree 19 Comments

[Integza] never fails to amuse with his numerous (and sometimes really sketchy) attempts to create usable thrust, by pretty much all means possible and the latest video (embedded below) attempting to run a reaction turbine from decomposing hydrogen peroxide, doesn’t fail to disappoint. The inspiration came from the WWII V2 rocket, which used Sodium Permanganate to breakdown Hydrogen Peroxide. This produced high pressure steam, which spun a turbine, which in turn drove the turbopumps that delivered the needed huge quantity of alcohol and liquid oxygen into the combustion chamber.

After an initial test of this permanganate-peroxide reaction proved somewhat disappointing (and messy) he moved on to a more controllable approach — using a catalytic converter from a petrol scooter in place of the messy permanganate. This worked, so the next task was to build the turbine. Naturally, this was 3D printed, and the resulting design appeared to work pretty well with compressed air as the power source. After scaling up the design, and shifting to CNC-machined aluminium, it was starting to look a bit more serious. The final test shows the turbine being put through its paces, running from the new precious metal catalyst setup, but as can be seen from the video, there is work to be done.

There appears to be a fair amount of liquid peroxide passing through into the turbine, which is obviously not desirable. Perhaps the next changes should be the mount the catalyser vertically, to prevent the liquid from leaving so easily, as well as adding some baffling to control the flow of the liquid, in order to force it to recycle inside the reaction vessel? We can’t wait to see where this goes, hopefully the steam-turbine powered skateboard idea could actually be doable? Who knows? But we’re sure [Integza] will find a way!

With steam power, there’s more than one way to get usable rotational work, like using a reciprocating engine, which can be expanded to a whole machine shop, and whilst boiling water (or catalytically decomposing Hydrogen Peroxide) provides high pressure gas, how about just using boiling liquid nitrogen? Possibly not.

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