The Aerothrust propulsion system: An insanely great idea

It might look dumb, but this little engine catalyzed the American Air Boat industry, and its legacy might yet have several more significant chapters in general transportation. Pusher engine technology can create very efficient vehicles, capable of doing things better … maybe even for personal transport. Just not like this!

America was already home to five million horseless personal vehicles in 1900 – they were all all bicycles. The bicycle brought personal transport to the masses for the first time, catalyzing disruptive societal change. At modest speeds, it offered the most energy-efficient human-powered transport conceivable. But who wants to travel at modest speeds … or power their own transport? The Aerothrust was the answer.

The bicycle was quickly and widely adopted. America bought a million bicycles a year during the 1890s, with 400 bicycle manufacturers springing up as companies sought to diversify their businesses into this booming new market with its almost insatiable demand. Most of those new bicycle manufacturers came from industries with parallel skill sets, with horse-drawn carriage makers, locksmiths, gunsmiths, clockmakers, watchmakers and manufacturers of everything from sewing machines to farm machinery all joining in.

During the 1890s, New York was at one stage home to 29 bicycle manufacturers at the same time. Massachusetts had a peak of 21 concurrent bicycle makers and in 1896, Chicago was the epicenter of the American bicycle industry with 54 manufacturers operating simultaneously in Illinois.

This mercantile gold rush drove relentless improvement as makers sought to differentiate their products. Between 1890 and 1900, the ferocious marketplace competition drove the average bicycle price down two-thirds. The initially overweight bicycle offered a very practical demonstration of Newtonian physics to the masses – if “Force = Mass x Acceleration” then weight was the enemy of performance. Between 1890 and 1900, the average weight of a bicycle sold in America HALVED!

Bicycle manufacturers lobbied the government for better roads before the automotive industry existed, and in particular, the industry recognized there was a massive latent marketplace available if a power source could be added to the existing bicycle fleet. With the advent of the internal combustion engine and the dawn of flight, anything seemed possible and there were some remarkable concepts prototyped at a time when the automotive form factors we now know were still evolving.

Remarkable Rarities (RR Auction)

The first aerosledges and airboats appear to have been built at roughly the same time in different parts of the world. In Russia, Sergei Nezhdanovsky worked on the first aerosledges in 1903–05 and Igor Sikorski designed and tested an aerosledge in 1909/1910.

Sikorsky Historical Archives

The first airboat was built and developed by Alexander Graham Bell, inventor of the telephone and convener of the fabled Aerial Experiment Association (AEA) which drew together all of aviation’s pioneers (except the Wright Brothers) into a collaboration with epic results: the world’s biggest aircraft company, naval aviation, dirigibles and eventually, the democratization of flight.

Bell’s invention of the telephone guaranteed himself immortality and unfortunately obfuscated how he advanced understanding of many other scientific fields. On 7 March 1876, Bell was awarded one of the most valuable patents in history. This monumental achievement has blinded the world to his many, often herculean contributions to the greater good, and his creation of the Aerial Experiment Association saw him influence history almost as much as he did with the telephone. If he hadn’t discerned and applied a dozen other technologies that he channeled for the betterment of humankind, he’d also probably be called the “father of the airboat industry.”

Bell was a polymath applied scientist with a vivid imagination, whose significant accomplishments are too many and too diverse to list. It was his “greater good” mindset that should see him revered alongside Einstein as a role model scientist. Bell consciously decided not to file patents on some of his inventions, enabling free propagation of the enabling technologies he invented. Bell’s contribution to the world we now live in is immense and far beyond “inventing the telephone.” Bell lived in Nova Scotia and witnessed first hand how much of the world is impassable in polar regions for large parts of the year.

RRAuction

With flight underway by 1910, the cross-fertilization of ideas saw innovators across the world come up with the same idea – that of powering terrestrial conveyances with a propeller! Count Jules Albert de Dion and countless others explored the concept, but it was an American company that came up with the first viable commercial package – a self-contained single cylinder two-stroke engine and propeller – that could be attached to canoes, row-boats and sleds to drive them on water and ice. They had a version for bicycles too.

Priced at US$50 and weighing 50 lb (22.6 kg), the Aerothrust single cylinder engines were sold to the consumer as instant add-on power plants. Aerothrust was doing very well, selling far more engines to boating enthusiasts than expected. Just then, air boats became big news.

Scientific American

The Scientific American cover would have supercharged Aerothrust’s business. Wartime is when every technological advantage is prosecuted and the British Army’s deployment of propellor-driven boats would have completely legitimized Aerothrust’s business model. News stand magazine covers at that time served as miniature billboards for their contents, and they were the shorthand news of the day.

The exciting new military technology would have sold quite a few extra copies of Scientific American at the same time as dispelling any doubts about the legitimacy of pusher engine technology, but the booming newsstand of the day was also bullish about the prospects of adding a powerful aircraft engine to all manner of near-future machinery.

Aerothrust had already commercialized this ground-breaking military technology, and it had done so with a convenient, low-priced, $50 bolt-on package for the consumer. It also met a massive latent demand for motorizing the bicycle, but its immediate availability to power a canoe, sled or rowboat turned out to be the killer app.

It enabled a substantial boost for what had previously been done by hand, by foot and by exhausting human effort.

Aerothrust Advertising

The single cylinder engine seemingly gave way to the two-stroke twin as the most popular version, all enabled by a clever universal coupling that was claimed to mount the engine and propeller unit inside a minute on a canoe or boat. As ingenious as the outboard motor turned out to be, it didn’t work on ice, or swamps, or everglades and operating it anywhere in shallow water was tempting fate, quite possibly a long way from home. The airboat fixed that.

That advertising claim was probably a little over-reaching, but almost anyone could do it in a few minutes and the new capabilities on offer enabled far more wilderness trekking than had been possible before. Watch this quick clip of a 1914 airboat using the same Aerothrust 5HP twin motor and think of how many miles could be covered in a day using the airsled.

The clip illustrates the new possibilities the Aerothrust offered for the very first time – in 1914.

Now we’re guessing here, but we’re thinking that the single cylinder Aerothrust engine needed ideal conditions to create a strong breeze, so no-one fitted the heavy propeller guard for fear of mitigating the already anemic power. Why Aerothrust decided against showing a propeller guard on the bicycle, we have no idea, but within a short time frame, boys being boys, the twin cylinder engines were being attached to bicycles and secured more permanently … it seems like insanity now, but quite substantial pusher motors were being used to drive ever-bigger propellers.

Aerothrust’s advertising targeted bicycle riders and clearly did so without those propeller guards, though it only ever seemed to picture the bicycles with the innocuous single cylinder engine. Product liability laws didn’t get any teeth in the United States until the 1960s, and public safety standards were very different not long ago.

This exquisitely restored version captures exactly how the single cylinder version of the Aerothrust would have looked 100 years ago.

That’s a handsome if somewhat terrifying contraption, and the more you think about it, the more terrifying it becomes.

Suppose you’ve got up some momentum on such a steed, the fan is pushing hard and you come hurtling around a corner to be confronted by Farmer Brown’s cows. These days, you’d shut the throttle and get on the brakes. This bike doesn’t have any brakes, and adjusting the throttle speed (i.e 50 mph self-contained gale) requires tinkering with the fuel-air-mix at the motor, which is two feet behind you. Hence, there’s no immediately available throttle adjustment and no kill switch either, so you’re taking your own meat grinder to the picnic.

Every sporting pursuit has its crazies: people who delight in taking extreme risks, and there’s no doubt the people who rode these bikes came from the same sub-set of humanity. It’s the same group that turned toys such as the bicycle, skateboard and motorcycle into stunt props. This is slightly different, because it’s not just yourself you are putting at risk. Falling off a motorcycle is vastly different to crashing one of these things, because that torquey aircraft motor is attached to a lethal propeller and has no kill switch and can commit untold carnage from a minor mishap. The thought of a steampunk mobile buzzsaw on public roads might seem implausible but it obviously happened.

We’ve traced a half dozen of these bikes, so they were definitely a thing 100 years ago, but they do not seem to have made any impression on the media of the day so we have little understanding of how they were used and tolerated on public thoroughfares … and used and celebrated by the adrenalin junkies. Folks didn’t wear helmets at that time, so falling off an airthrust-powered bicycle could easily be fatal. Did they go riding together? Race one another?

Duane Peters

Aerothrust-enabled bicycles began appearing at auction only recently, and we’re bound to see more, as the Excelsior bicycle with Aerothrust motor in the imagery of this article sold for $88,000 and several others have followed, all fetching appreciable amounts at Mecum’s January Las Vegas auction. Hence, there’s obviously a community of people who know more about their origins and the tribe of berserkers who rode them, so if you’d like to share it, please start at the comments.

There is no information as to how many $50 bolt-on Aerothrust engines were sold or how many made it onto bicycles, but we’d estimate tens of thousands of the 3-HP and 5-HP twins were fitted to boats, canoes and sleds, and hundreds maybe thousands were fitted to bicycles. From all reports, the single-cylinder was such an anemic lump that it offered scant propulsion, so we’re lucky that even one has survived. Given the attrition rates of cars from 100 years ago, if we can find half a dozen extant bicycles fitted with Aerothrust engines in 2025, there must have been a lot more around back in the day.

So is it an insanely good idea like the premise we started this article with, or just plain bonkers?

The Aerosthrust is not a good idea on a bicycle, at least not one set up this way. Brakes, throttle control, a propeller guard and a kill switch might fix most of those issues, but we’ve come a long way in a short time, and Alexander Graham Bell was definitely onto something when he built his “Ugly Duckling” as it evolved into several entirely new forms of transport.

Over the course of a century, aero-boats and aero-sleds have evolved to better suit their local environments and they are now known by many different names in different parts of the world depending on what they used for. You may know them as a fan boat or swamp boat or aero sled, and their usage in the tourism industry is driving sustained growth.

The airsled that appears to have changed the course of the the Russian industry was the Tupolev A-3. It was extensively reported in the western media 30 years after its availability in Russia, mainly because a single fully-restored unit made it to the West, where it has been a prominent regular at collector car auctions for 20 years, initially fetching $187,000 in 2007, with a high of $220,000 in 2015.

The Tupolev A-3 was designed by the Tupolev Design Bureau, founded in 1922 by Andrei Tupolev (generally regarded as the father of Soviet aviation), which designed over 100 different civilian and military aircraft and produced more than 18,000 aircraft for Russia.

The A-3 was the result of the needs of the Soviet space program, which had to quickly reach returning cosmonauts in arctic conditions. The re-entry window for returning spacecraft can vary wildly, with maybe hundreds of miles of snow and ice between the rescuers and the returning cosmonauts. The A-3 is lightweight and compact, and was designed to fit inside a Russian Military Mi-6 transport helicopter, or be hung beneath it, fully-crewed, on cables for immediate deployment. It’s role was to quickly reach areas inaccessible to ground and air transport, so it would be deposited on the ground as close as possible to the spacecraft and get to do its thing.

Doing its thing was the sled’s forte, and having the good fortune to be designed by a genius, the Tupolev A-3 had capabilities that hadn’t been seen before and it quickly outgrew the Space Program and became indispensable in many roles across Russia as it could traverse previously unpassable terrain and previously unnavigable rivers at speed.

The smooth surface of the amphibian enabled it to pass through meter-high bushes and sparse forest. The A-3 was simultaneously a boat capable of operating with a 5-cm draft, a sled when there was less water, and as it uses ground effect to provide its own air cushion, it basically swims, bounces and slithers across any terrain, be it ice, water, frozen earth or acres of slushie. When it went into production in 1964, it had a 120 km/h (74.5 mph) maximum speed and could carry a 1200-kg (2,645.5-lb) payload. We’ve written about the innovations incorporated into the A-3 in detail in a separate article, but there are a few punchlines relevant to this story.

Not surprisingly, the A-3 was warmly received wherever it was witnessed and demand for the A-3 outstripped supply as it was variously pressed into service by the military in countless ways, with 800 units being produced and the A-3 eventually seeing a lot more non-military service across the Russian tundra’s seven time zones. There are reportedly still units in operation today, still servicing remote outposts with passenger and freight service, plus filling the everyday needs of arctic communities such as search and rescue and polar ambulance.

The A-3 became a very influential vehicle because it highlighted just how efficient an aerosled could be given a bit of thought – taking running costs into account, the cost-per-kilo of transportation on the A-3 was half that of traditional aerosled and 30% less than on boats. That’s an important statistic because the world’s trade goes almost exclusively by boat. There is an efficiency to be found here that deserves greater exploration. Carrying the same commercial load, the range of the A-3 was also more than double that of ski aerosleds.

With modern production and materials, there are now far cheaper and more up-to-date models from many manufacturers in use across Russia, and some of these modern vehicles now use four and six cylinder engines from Subaru and Toyota to achieve the desired horsepower without having to fit an expensive radial engine. Freight and passengers are now routinely moved by such watercraft, in a land with endless semi-frozen landscape.

At 6.6 million square miles, Russia is almost twice as big as Canada (3.8 million square miles), the United States (3.79 million square miles), China (3.7 million square miles) or Brazil (3.3 million square miles). Inside its 6.6 million square miles, Russia has 2.2 million square miles of land north of the Arctic Circle, with 2.5 million people living there, which is half of the global Arctic population.

Pusher motors make infinite sense in this environment. It’s not surprising that Russia has embraced the pusher prop boat, sled and hovercraft concept more than any other country. Some of the larger military applications have created warships of immense size.

Quite clearly, there are many applications for pusher engines that have not yet been explored, and there are many different ways to harness the forces of nature that are becoming ever more accessible. A decade ago, Thrustpac developed a backpack that used a miniature internal combustion engine to drive a powerful pusher fan, which could be used numerous ways … as it was mounted on the driver.

Thrustpac has videos demonstrating the unit being used in a variety of circumstances, including assisting a human riding a bicycle, paddling a kayak and a using a paddleboard. Beyond Aerothrust’s original 100-year-old markets of bicycles, boats and sleds, mounting the engine on the human offers propulsion assistance for skateboarders, skiers, snowboarders and paddleboarders, and … fill in the blanks. You could even turn your already hybrid (human-power and Electric) electric bike into a tribrid with a Thrustpac or electric equivalent.

The growing availability of high performance Electric Ducted Fans and batteries is opening up a new vista for the growing maker tribe, and the future suddenly looks bright for non-conventional ways to go places and have fun at the same time. The speed of the surfboard in the video below, with just the addition of a few EDFs, suggests the Aerothrust concept might be worth revisiting.

We found the above video at Foil.zone, and one of the comments in the forum really fired up the neurons – life jackets have been passive for hundreds of years. Why not equip them with a big battery and a propulsion system? Maybe even a GPS tracker and comms and lights could all run off a battery-powered smart lifejacket. Good idea!

Foil.zone also led us to Dreamscience Propulsion, which is developing thrusters specifically for the type of applications we are considering here. Dreamscience started out building very powerful electric thrusters for paragliders but has found applications in many other extreme sports, and they’re powerful enough to do the things the aerothrust promised, but failed to adequately harness given the technological hurdles of the day.

Dreamscience makes small but very powerful thrusters with an output wind speed of over 200 mph (322 km/h) plus it adds the previously unavailable use of “reverse thrust” to quickly reduce speed. The company site quite clearly states its relevance: “The thruster system allows the user, not only to get more air in an extreme sport, but also get more forward speed … the most impressive is uphill skiing and pulling up (stopping while skiing downhill) using reverse thrust to slow down!”

The Practical Engineer addressed the pusher backpack a different way, with a transforming backpack that pops out two electric ducted fans (EDFs) when he’s cycling. This video addresses how he did it, though if you don’t speak Dutch, try this article from Hackaday.

There are many paths to the same goal, and TechIngredients recently went through the exercise of building a 10,000=W add-on to an existing bicycle. The great thing about the video is the detail of each of the components used.

In closing, yes, it is a great idea and with the ongoing rapid development of electric motors and electric ducted fans, the future of personal transportation looks bright.