Engineering Challenges of Building Hudson Yards Over Live Rail Tracks

[00:00:01][Music] Manhattan Island, New York. 26 square miles of some of the most valuable land in the world. Demand for space is high. But surrounded by water, spreading out is not an option. The only way is up if you can find somewhere to build.

[00:00:27]It's extremely difficult to get a large plot in Manhattan because everything's been spoken for for over 100 years. So basically, when you do find a large plot, chances are it's because it's a railroad yard. These vast expanses may be free of building, but they're strewn with tracks. Any construction seems impossible. But now on the west side of Manhattan, ambitious engineers are taking that challenge on.

[00:00:57][Music] Hudson Yards, America's largest real estate development, is being built directly on top of a working [Music] railard. The engineering on this site is [Music] incredible. But it's not one individual piece, right? There's a whole series of these things added together.

[00:01:23]I mean, not just you're designing a building, but then you're designing a complete specialty underlying structure to be able to support that. And unless you look out at the Western Railards and see the trains there, you have no idea what's underneath us. Changing the skyline is not just one new skyscraper, but six with more towers to come. Jeff Butler is the senior project manager on site. Each of these buildings is an amazing building. We have over a million square ft of retail space. We have almost 5 million ft of residential space, 10 million ft of commercial space. It has no comparison in scale. There have been some great developments in New York, but I'm very excited that this is the biggest and [Music] best. Built almost entirely over a giant base platform above a working railard, Hudson Yards covers a 28 acre site on the west side of Manhattan.

[00:02:29]Multiple mega structures are being constructed simultaneously, including the third tallest tower in New York, an arts venue that can appear from nowhere, and a brand new park constructed from [Music] scratch. When Hudson Yards is complete, we'll have 125,000 people here working, living, and playing every day. It's an entire city within a city.

[00:02:57]But this ambitious $25 billion project poses immense engineering challenges.

[00:03:03]How do you build New York's highest external observation deck? We're about,50 ft up. So the combination of engineering and understanding the construction sequence was really complicated. In a city blighted by power cuts, how do engineers keep Hudson Yards running 24/7?

[00:03:24]The firms at Hudson Yards absolutely cannot live with the threat of power outages, but it's the specific site that poses the biggest problem of [Music] all. Jay Cross has masterminded the project from the start. The actual plot of land is highly valuable because there's just only so much of it. There's rivers all around us. But the Westside Yards was always like the hole in the donut because it was all train tracks spanning seven city blocks. The Westside Yard was used solely as railway sidings for Penn Station. The audacious plan to construct on top of the tracks while the trains continue to run. The engineering challenges were significant, not least of which we have to build over an operating railard. That logistically is a challenge unlike any other.

[00:04:20]How is it possible to build directly over 30 active train tracks? Part of the answer is to be found 715 mi west of Manhattan.

[00:04:39]Architect Marty Sandberg is in Chicago discovering how ambitious engineering helped a newspaper company overcome the confines of this cramped city. In the 1920s, the Chicago Daily News was one of the bestselling papers in the city, and as a result, they had outgrown their current building and were on the search for a new home. Unfortunately, there was just simply no open land left at that time.

[00:05:06]The problem was the same as that faced by the Hudson Yards team, the railways. At the beginning of the 20th century, Chicago was the busiest railroad hub in North America with more lines radiating out than any other city. The downside to being such a rail hub was at the time Chicago was literally choked off by rail yards on every side of the city. You had yards like this on the north side, the west side, the south side. There was really just physically nowhere else to grow it, even as the city wanted to. But the Daily News decided to attempt an extraordinary engineering [Music] feat. So, this is the Daily News building. I'm a sucker for a gorgeous old limestone building. And this is a great example of it.

[00:06:06]In a city hemmed in by train lines, how did they manage to find the space to build this? It was down to a new law known as air rights. The Daily News had bought from the rail company the right to build in the air above their tracks.

[00:06:22]Essentially, the trains were only so high and they weren't really getting any higher. So, they recognized that they were wasting a whole lot of space up above. and they saw this as a pile of money just waiting to be had.

[00:06:35]Pouncing on this opportunity were architects John A. Holer and John Wellborn Root Jr. Incredibly, they built the 26story tower block directly on top of active tracks. So, when we look at the building now, you can't tell there's still a mess of train lines running back and forth underneath. Everyone coming in there dayto-day would never have any idea that they're still sitting over an active rail line.

[00:06:58]This is what the engineers at Hudson Yards need to achieve. So, how was it done here? This is our sandbox of Chicago right here. All we need are areas where we can sink a couple of key foundations in between the trains. So, we start by seeking out a couple of areas where we can sink these deep foundations down, trying to aim for the bedrock if possible. From there, we go ahead and drill our foundations down nice and steady. And all of a sudden, ground level is no longer down here.

[00:07:30]We're up here at 20 ft above. The building could then be constructed on top of this platform with the weight being supported directly by the pillars.

[00:07:39]And we've just turned a train yard into some of the most valuable and useful land in Chicago. The city's happy. The railroad is happy. The person walking down the street is no longer standing next to a train. It really turned into a great solution for everybody.

[00:07:55]Polar Bird and Root's incredible achievement led to an explosion in air rights. Railroad plots once shunned by developers were now worth millions.

[00:08:06]It's a complicated solution that really is a simple idea. You get a couple of genius minds figuring out how to actually make it happen. And now a good part of Chicago is built exactly this way.

[00:08:27]In New York City, the Hudson Yard development is thought to be the biggest air rights deal ever. A billion dollars paid for fresh air above Manhattan's Western Railard. Tracks covering 28 acres must somehow be straddled to build multiple skyscrapers.

[00:08:46]a superized steel sculpture, an assortment of public buildings, and 14 acres of open space. And throughout construction, the trains below have to keep running. We work basically at the mercy of rail traffic. So, think of it as they own the basement and you own everything above the basement. And so, of the 30 tracks, we were only allowed to close four tracks at a time for the purposes of construction. What we had to then do is weave all of the foundations for the buildings between the tracks to go down to rock.

[00:09:24]The foundations for this massive 28 acre site draw on techniques used in Chicago over 90 years ago. The first step is to drill 45 m deep holes into the bedrock which is up to 75 m below the ground.

[00:09:39]then insert the superized steel and concrete support columns known as quesons. 300 quesons support the entire development. Carefully located between train tracks, they take the weight of the steel frames for the tower blocks as well as the giant 40,000 square meter base platform that surrounds the buildings. This concrete and steel platform creates a new ground level above the tracks.

[00:10:09]The platform doesn't support anything except the open space where we're standing right now. So where the platform is underneath the buildings, the buildings go right down between the tracks. They go all the way to rock. So the trick is in the foundations. That's where all the load transfer goes. The platform just fills in the space in between.

[00:10:30]But while boxing in the active railard creates acres of new usable space, the incoming trains below are now confined underground, creating a fresh challenge. When the trains come and bring commuters in, they drop them off in Penn Station and they park here for the day. We've engines running and just all the train activity is creating heat below us. It can get up to 150° F, which is very hot. The team had to find a way to keep the rail yards cool. So, they came up with an awesome solution. Below you right now are about five jet engines. Uh they're about 40 ft long, maybe 5 ft in diameter. They're actually lined up right like this, and they exhaust through that shaft.

[00:11:17][Music] Twin ventilation shafts at the plaza connect to 15 giant fans within the thickest section of the platform. Principal engineer Eli Gotautle has special access to the restricted area inside the platform itself. It's pretty exciting to be in here and to be able to see this. This is something that nobody ever gets to see and to experience when we go down here, right? to to actually see down into here and be within the structure and to see the fan systems that are operating on either side.

[00:11:54]The fans are installed at the plaza directly above the trains. Welcome to the central fan plant underneath the the yards. This is one of three fan plants that are actually down here. These fans are really part of the lungs of the facility that actually allow it to breathe.

[00:12:12]The criteria on the railard is we weren't able to allow the temperature in the railard to rise more than 10° above the ambient temperature. So if it's 70° outside, it can't be more more than 80° inside the railard. So these fans allow us to exhaust any of the heat generated by the trains out and pull in new fresh cooler air to maintain a tenable client for everybody who's down there. These fans can fully exhaust the entire facility in 7 minutes of all the air that's here and completely replenish it.

[00:12:46]But for Hudson Yards engineers, more impossible problems could jeopardize the project.

[00:12:52]You're just running out of space to actually be able to install anything.

[00:12:56]And the challenges are set to rise to an even higher level. They came up with this protrusion, so we weren't quite sure how to construct it.

[00:13:06][Music] For many, every buildable inch of Manhattan Island is spoken for. But the trailblazing Hudson Yards project is challenging this belief. America's largest private real estate development is attempting the impossible.

[00:13:29]building directly on top of 30 train tracks to create a 28 acre New York neighborhood from scratch. Most of the buildings are over an active rail yard. So, there's some amazing engineering going on just to build our buildings. And when the development's done at Hudson Yards, it'll be very amazing to work on a project like this that has so many pieces to it. each one of which is incredibly challenging and amazing.

[00:14:01]And then to fit them all together, I mean, the project is just [Music] astounding. Multiple skyscrapers will provide 18 million square ft of commercial and residential space, including a school and over 200 room hotel and a retractable art center, all perched on 300 quesons squeezed between a network of train tracks.

[00:14:27]But in one critical section, this isn't possible. Where the tracks converge in an area called the throat. Engineer Eli Gotautle is one of the team charged with solving the problem. As you look through this, you're actually looking east down into the fourtrack narrows where the trains come into the Hudson Yards. From here, you can actually see that there's going through a lot of switching. And this switching allows them to fan out from the four tracks that they come in at to the 30 storage tracks. And you can imagine that if the tracks are spaced far apart, there's space in between them to be able to build a queson and a column coming up. But as the tracks converge in together, you can just imagine that you're just running out of space in between the two of them to actually be able to install anything. This area of the development is earmarked to have a tower block and a shopping mall built on top of it. If engineers can't span the 45 m wide gap and support the buildings above, Hudson Yards will be left with a massive hole in its plans. This is really a key problem on the site. All of that underneath us really narrows down the number of possibilities of what we could do to be able to support everything above.

[00:15:41]Can the solution to this impossible challenge be found in the past?

[00:15:54]When it came to spanning, many of history's bridges appeared to have cracked the problem. Until you added a load in 1297, Scotland's Sterling Bridge stood proud. Until the battling English and Scots met in the middle. In 1444 in romantic Venice, the Rialto Bridge was the perfect spot to view a wedding.

[00:16:20]Until a swelling crowd, but a dampener on the big day. To span their gaps, bridge engineers needed something stronger. Almost there now. Wow, it's a long way down. Physicist Andrew Steele is getting a close-up look at the Worcester Railway Bridge.

[00:16:48]Wow.

[00:16:51]What a beautiful view. Can a gamechanging innovation from the British railway boom be the missing piece of the puzzle for the team at Hudson Yards? In the early 20th century, the UK railway system was undergoing a huge period of expansion. Not only were there more tracks, but there were also more trains.

[00:17:08]And these trains were much faster. And as they were getting faster, they were also getting heavier. And that meant that bridges on the railway network were being put under increasingly large strains. Like the team in New York, engineers needed to find something strong and reliable to bridge the gap. James Warren was a merchant with no formal training in engineering. In 1848, he registered a patent that would revolutionize bridge design. The Warren Truss. This is Warren's design. This repeating pattern entirely made of equilateral triangles. So triangles which the same length along each side.

[00:17:53]Now triangles like that have the advantage that they're incredibly strong. The railway track is above my head right now. What that means is that as a train passes over the top of us, then its weight is distributed through all these different struts and every single one of them can share that load.

[00:18:10]That means that all these individual beams are either in tension, so being pulled, or compression, so being squashed. There are trains rumbling over my head right now. This bridge is still very much in use.

[00:18:23][Music] Previously, many bridge engineers had used vertical struts. So, how much stronger was the triangle so they can both take one brick? Two model bridges are being tested to breaking point. So, in this simple design, all that load is mainly going through honestly just this vertical strut here. Whereas on the Warren TR over here, all of that load with this triangular pattern of struts is being spread throughout the whole bridge.

[00:18:54]We're going to go for brick number three. Right, brick number four. Bit nervous about this one to be honest. The question is, can it take a [Music] fifth? But a sixth. I think this is going to be it. Surely this time.

[00:19:15]Oh, total structural failure there. You can see there's lollipop sticks everywhere. But the Warren Truss, it's still supporting that load pretty strongly because no individual lollipop stick is taking that much weight. And so incredibly, it can hold all of that mass. The Warren Truss really was an incredible engineering innovation. And of course, it's not just bridges.

[00:19:37]Wherever a weight needs to be borne and spread over a structure, you'll see these equilateral triangles holding them up. This incredibly time-t tested design Engineers are superersizing this 170-year-old creation to support part of a sevenstory shopping mall and skyscraper where piled foundations are impossible. Sandwiched between the retail space above and the converging rail tracks below lie a series of 4 m high Warren trusses. So we're inside the platform underneath retail over all the switching of Long Island Railroad. We're standing basically within a bridge structure right where we're standing on the bottom of the bridge and there's the top of the bridge above us. And these trusses are those main elements of the bridge that are spanning across. In total, 14 giant trusses are used to span the crucial 45 m gap.

[00:20:44]By being able to use this truss structure and build a nice stiff bridge deck that's actually really efficient for being able to support the buildings above. It's a pretty incredible piece of engineering when you think about what these trusses need to do and how much they need to be able to carry. The historic Warren Trust design plays a vital part in this huge modern development. There's a lot of engineering that we stand on the shoulders of those who came before us.

[00:21:14]And so there's a lot of incredible engineering that comes out of especially the 19th century that has a thread that travels through uh what we're doing to today.

[00:21:30]The tower supported by the truss is not only the highest on the project, but once it's complete will be the second tallest office building in New [Music] York. Engineer Jay Cross has special access to its most incredible feature on the 100th floor, a 10-minute ride away in the temporary lift.

[00:21:58]The view changes so dramatically as you get higher and higher. It's amazing.

[00:22:03]And it's the view from the top that inspired another phenomenal piece of [Music] engineering. At first, we designed the building without an observation deck and we realized how high we're going to be.

[00:22:25]So we challenged the architects to say come up with the idea of an observation deck. We of course thought they were going to come up with something that was inside the tower. Instead they came up with this protrusion which was pretty darn dramatic. This is the highest man-made outdoor observation area in the Western Hemisphere. Almost a third of a kilometer up. It offers a brand new bird's eyee view of the city below.

[00:22:57]But constructing a platform in the air calls for more impossible engineering.

[00:23:03]At first we weren't quite sure how to construct it. We thought maybe it would be like bridge where you just kind of build piece and you inch your way out from the building. Uh but the problem was we felt that we would have to have a lot of supporting scaffolding to do that.

[00:23:18][Music] So, our steel fabricator came up with the idea of making 14 pieces that would come up pre-assembled, and you would just bolt them on as you go out. Built out from the building section by giant section, some weighing up to 45 tons, the result is a 700 m sky deck.

[00:23:46]But the final piece of the puzzle will be an immense triangle made of reinforced [Music] glass. We felt that in addition to walking towards the peak, which I think will be exciting enough, we thought why not make it a little bit more exciting and create a glass floor. Right now there's nothing there.

[00:24:06]There's no glass. We're just looking down 1,000 ft. And um it's pretty exciting. Don't you think? It felt a lot more comfortable when the orange netting was across here. Now that it's down to like two or three wires, there's no need to get too close.

[00:24:21]Four 550 kg triangular sections of glass will complete the sky deck. 2 and 1/4 in thick, it will allow visitors to take in the vertigo inducing views from this mind-blowing vantage point.

[00:24:38]I'll walk on it. I'm sure I'll be goated onto it, but I'll be nervous about it.

[00:24:43][Music] But this impossible project is attempting more audacious engineering, throwing up further challenges.

[00:24:57]We're moving the equivalent of about 600 elephants stacked up on top of each other wearing eight roller skates. Can their innovative construction be taken to another level? It's very difficult to figure out that solution from an engineering standpoint.

[00:25:16]New York's biggest ever impossible engineering challenge. Hudson Yards is a 1.6 million square meter real estate project constructed over a fully functioning rail [Music] yard perched on a specially constructed base platform above the tracks. This is a multi-tower mini city. Multiple skyscrapers, a superersized mall, 14 acres of public land, all coming to life simultaneously. But perhaps the most inventive engineering on site is a unique arts venue known as the shed. Engineer Eli Gotautle is overseeing its build. The shed is built up of two parts. One is what we've always thought of as the fixed building, which is the building that we're standing in right now. And then it has the sleeve that slides over the fixed building, so that when it's not in use, it's actually retracted. But then when they have larger events and they need the space, they'll be able to roll the shed out to enclose the plaza and turn it into this larger venue that we can see here in front of us. There's really no other places like this.

[00:26:34]The team are using a special inflated plastic to keep the shell as lightweight as possible. So the power required to move it is kept to a minimum. The drive system on the roof generates just 180 horsepower. So we're up on the roof of the fixed building of the shed. You can see here here are the main teeth from the drive mechanism that the actual shed motors will then roll against and drive the assembly back and forth.

[00:27:03]We're moving the equivalent of about 600 elephants stacked up on top of each other. Uh, in this case wearing eight roller skates. The roller skates are in fact eight pairs of 2 m high wheels running along heavyduty rails. And in [Music] 2016, this retractable building was put through its paces for the first time.

[00:27:30]To see the shed move was actually fantastic, but it was also really surprising because it is so quiet that in fact a whole number of people actually kind of missed it because it happened and they sort of didn't hear it or realized that it was going on in that moment and all of a sudden, hey, wait a second, it was back there. Now it's here. How did that happen? So smoothly, so effortlessly.

[00:27:52]The vast 28 acre Hudson Yards is a series of separate construction projects. With many being built over an active railard, the challenges are undoubtedly huge. But although the corner is clear of the main tracks, it poses an equally taxing problem. A massive tower has to be perched directly on top of a $2.4 billion Manhattan transport hub.

[00:28:21]55 Hudson Yards is an office building and it's just outside of the platform area that's over the rail yards. It is however over a large subway station.

[00:28:33]Just 3 years old, the 34th Street Hudson Yard station is one of the city's newest. With 1 and a2 million commuters coming into Manhattan every day, it's a key selling point for the development. But it presented the engineers with a weighty challenge.

[00:28:51]We've limited opportunities to put weight on the subway station and limited footprint to put weight outside the subway station. So, we're looking for ways of putting as big a building as we can with the limited options we have at the foundations.

[00:29:08]Lack of space for new foundations meant 40% of the tower block's weight had to be carried by the foundations of the subway station itself.

[00:29:19]Overloading was a real danger. The tower had to shed some weight without shrinking in size. Our building is 51 stories of office space and that's a lot of building to put on limited foundations.

[00:29:33]So the engineers needed to find solutions to lighten up the building as much as possible. It may sound easy to make a building light, but it's very difficult to figure out that solution from an engineering standpoint.

[00:29:47]It seems impossible, but can engineers of the past shed any light on lightweight materials?

[00:30:00][Music] It's beautiful.

[00:30:04]Kipique State Park in Virginia. Engineer Megan Hart is off to discover how a material used to solve a wartime problem could help the team in New York.

[00:30:17]During World War I and World War II, there was a massive manufacturing effort and that took a lot of raw materials.

[00:30:24]The main one was steel. Steel production went into overdrive to supply the military. This led to a shortage. But the US Navy needed to build a fleet of supply ships.

[00:30:38]So, how did they manage it? These ships didn't need to be made out of steel.

[00:30:42]They would never see active combat. What they needed was another material.

[00:30:51]These are the inspired solution made out of an innovative version of a surprising material.

[00:30:59]These are concrete boats. Can you believe that? And they actually float.

[00:31:04]Not only do they float, but they carried supplies during the war efforts. You think concrete, you think massive and heavy and super dense, but density makes it very difficult to be buoyant. This concrete is different. The man behind it is Steven J. Hay. He was working in the Kansas City building trade in the early 1900s when he had a Eureka moment.

[00:31:35]He noticed that shell stones left too close to the kiln during the firing process would bloat up when they overheated. The heat caused air bubbles to form in a honeycomb like structure inside the stones, making them lightweight. So hay added them to cement and water to create his revolutionary new concrete. An invention that could help out Hudson Yard's engineers.

[00:32:02]So Steven Jhade instead of using traditional aggregate which is heavy it's just rock he used an expanded shale uh and that expanded shell is much less dense. This lightweight aggregate would not only flow but also weigh a whole lot less.

[00:32:22]During World War II, 24 of these 100 m long concrete ships were made. The unexpected solution to the Navy's problem at sea.

[00:32:33]Wow, that's amazing. You can see that the shell is still intact. Steven Ji came up with a perfect material to build these boats.

[00:32:47][Music] In New York, engineers draw on Haye's discovery to solve a skyscraper's serious weight issue. 55 Hudson Yards is a whopping 240 m high, and its sizable mass bears down on a major transport hub. To avoid overloading, the team had to save weight on the inside.

[00:33:20]We're on the 47th floor of 55 Hudson Yards and lightweight concrete helped us achieve a light building to uh go over the limited foundation we had around the subway station. So if we look above and below us, slab above, slab below, every floor on this building is made out of lightweight concrete. And we saved about 20 to 30% in weight overall. It made a huge difference. If we save 20% in weight, we can make the building 20% higher. So 20% more buildings quite a bit. The concrete floors are also lightweight because they're only 9 in thick. But spanning the tower's vast open plan areas is problematic for such a thin floor. The team's solution is a pioneering technique known as post-tensioning.

[00:34:09]Historically, post-tension technology in New York City specifically hasn't been used regularly. And this is the first building where it was used regularly in the slabs. So over our head we can see white painted areas that say PT zone.

[00:34:24]That's where we're using post-tension concrete. Simply put, it's a high strength cable that's pulled through the concrete that helps limit deflection. A network of steel cables are threaded through liquid concrete.

[00:34:39]Hydraulic jacks apply massive tension to pull them tor.

[00:34:44]Anchored in place, the compressive force of the concrete is increased from 7,000 to 8,500 PSI, reducing deflection, allowing a thinner, lighter slab. With our high strength lightweight concrete and using the post-tension slabs, it makes for the most robust system we can for a thin slab. It was a perfect solution to lighten up the building and allow us to build as much as we could over the subway station.

[00:35:13][Music] But the engineers of this brand new neighborhood face another hurdle. They must defy New York's notoriously unpredictable weather. When we lose power here in Manhattan, it's eerie.

[00:35:28]We're used to seeing the city alive.

[00:35:31]Keeping Hudson Yards up and running calls for impossible engineering.

[00:35:40]the New York skyline is set to change [Music] forever. Thanks to the city's biggest ever development, Hudson Yards is built on a giant base platform over an active rail yard. But incredibly, all of this is just the first half of the $25 billion project. What you're looking at here is the western yards. That's we call phase 2. So we'll do another 5.7 million ft of development over here. With phase 1 almost complete, a second even bigger steel and concrete platform will be built above the tracks on the other side of the 11th Avenue vioaduct. Eight colossal buildings will be created. This city within a city will double in size.

[00:36:34]We have six giant buildings around us and we have a lot more coming in very short order. We're bringing more office space to New York City than there is in downtown San Diego. To be a success, Manhattan's newest business quarter must stay online 365 days a year. But maintaining a steady power supply in New York is a huge challenge.

[00:36:59]Hurricane Sandy caused the latest and most devastating in a long history of power cuts affecting the city.

[00:37:08]When we lose power here in Manhattan, it's eerie, right? It's a large city.

[00:37:12]We're used to seeing it lit up and we're used to seeing the city alive 24 hours a day. Frank Norcross is in charge of Hudson Yard's energy supply team. He needs to find a way to protect the new development from power cuts.

[00:37:30]The customers that will call Hudson Yards home can absolutely not afford to lose power at any moment. They run 24 hours a day, 7 days a week, and they need reliable provision of electrical service. It's a huge problem when we lose power because vital systems, the things that we maintain to keep safety and security in in a large city are under threat when we lose power. In the face of a hurricane, how do you keep the power supply running? The team need to turn to the past to stop history repeating itself.

[00:38:15]When it comes to creating power, factories have led the way. First, elbow grease drove machines until the industrial revolution brought steam. Now, one enormous engine could power everything. But with their eggs in one basket, if anything went arry, everything ground to a [Music] halt. Physicist Andrew Steele is at the Anson Engine Museum in the north of England in search of an historic innovation that would blow steam power away.

[00:38:58]It was Nicholas Otto, a German salesman with a passion for engineering, who came up with an invention that transforms the 19th century. This is what Otto came up with.

[00:39:13]It's called an atmospheric gas engine, and it's got a number of advantages over the steam engines that existed at the time. Firstly, you don't need a huge supply of water to run this thing.

[00:39:22]Secondly, you don't need a team of people. You can do it with just one person. And thirdly, you can have a load of these small engines scattered around the factory to operate individual machines rather than having one massive steam engine to drive all the equipment in the whole [Music] place. More powerful for its size than its steam engine counterparts.

[00:39:43]So that's a bit of physical labor. It's not like starting a car.

[00:39:48]This new breed was fueled by natural gas. Oh wow. There we go.

[00:39:57]The way this atmospheric gas engine works is it's got a massive piston inside this cylinder. So then when that piston starts moving upwards, it draws in a mixture of gas and air. And when it gets to a certain point somewhere around here, that pilot light, a little bit of that flame gets pulled into the cylinder, causes an explosion, and that throws the piston up through the cylinder. Essentially a power station in miniature, Otto's single acting cylinder was hugely successful. But it was his newly improved gas powered model that could provide the solution for Hudson Yards engineers. This is the next iteration of Otto's design, and it's truly revolutionary. It uses something called the four stroke cycle. Unlike his previous engine, this makes four strokes of the piston for each ignition.

[00:40:50]First, the piston moves downwards sucking air and gas into the chamber. Secondly, as the piston rises, the air and gas is compressed. Thirdly, it's ignited and the piston forced down. And on the fourth stroke, the exhaust gases are pushed out. The result is an incredibly efficient, reliable, and quiet engine.

[00:41:15][Music] The principle behind this engine, the four- stroke cycle, is also known as the auto cycle after the man who invented it. Engines like this were quickly deployed in factories. But they also rapidly found much more widespread use, particularly in the emerging automobile industry. This is a truly revolutionary principle of engineering. It's absolutely everywhere in the modern world.

[00:41:51]Whereas Otto's innovation found its fame in light industry, engineers at Hudson Yards are using this game-changing design to provide an immense power backup system. In 2015, four of the biggest four-stroke gas engines in the world arrived on site in Manhattan.

[00:42:14]40tonon 20cylinder 4,600 horsepower beasts.

[00:42:24]What we're looking at here is very comparable to what you'd find in the front end of any souped up hot rod. It's an internal combustion engine that operates on a four stroke cycle. It just happens to be about 30 ft long and 10 ft tall. This is really the beating heart of the energy infrastructure here at Hudson Yards. If New York's electricity fails and the city is plunged into darkness, the natural gas supply will kick in and these monumental machines will take over the job of running the Hudson Yards power plant.

[00:42:57]This plant protects Hudson Yards from power outages because it has the ability to operate in micro grid mode. What that means very simply is if there were an issue out on the utility grid, we could simply disconnect from the grid, then start restoring power that we source from our plant here. So the residents of Hudson Yards, the businesses that call Hudson Yards home would be able to stay here and keep working come what may. When called upon, these monster engines will produce over 13 megawatt of power.

[00:43:34]It is exciting to hear one of these engines fire up. It is the same sort of teenage boy excitement that you would find, you know, turning over any engine multiplied several fold because of the size of these engines.

[00:44:03]This engine has a heartbeat. This engine breathes. This engine creates energy.

[00:44:09]And you get a very visceral sense of that when the plant is [Music] running. The Hudson Yards project represents impossible engineering on a staggering scale.

[00:44:32]A brand new 28 acre neighborhood built over a working railard. Everybody knows the Manhattan skyline of New York. So when you change it, that's actually some ways the most exciting thing. How all of a sudden there's this monumental cathedral in the [Music] middle. Every stage of this trailblazing enterprise poses extraordinary challenges.

[00:45:00]The engineering on this site is such an example of incredible teamwork and incredible vision from so many people to be able to bring this to fruition, but inspired by the work of the pioneers of the past. Upscaling and breaking the mold themselves, the engineers are succeeding in making the impossible possible.

[00:45:27]Coming onto the construction site, you get to appreciate it every day, but still every single day it's a wow moment. I love this project.

[00:45:40][Music]