Anish Kapoor’s vision for the Cloud Gate sculpture in Chicago’s Millennium Park is that it resembles liquid mercury, seamlessly reflecting the surrounding city.Achieving this seamlessness is a labor of love.
“What I wanted to do in Millennium Park was to make something that would fit into the Chicago skyline…so people would see the clouds floating in it and those very tall buildings reflected in the work. Then, Because of its form in the door, the participant, the audience, will be able to enter this very deep room, in a way it does the same thing to the reflection of a person as the exterior of the work does to the reflection of the surrounding city things.” – world-renowned British artist Anish Kapoor, Cloud Gate sculptor
Looking at the calm surface of this monumental stainless steel sculpture, it’s hard to guess how much metal and courage lies beneath its surface.Cloud Gate hides the stories of more than 100 metal fabricators, cutters, welders, trimmers, engineers, technicians, ironworkers, installers, and managers—all over five years.
Many were working overtime, doing workshop work in the middle of the night, camping on site, and toiling in 110-degree temperatures in full Tyvek® suits and half-mask respirators.Some work in positions against gravity, dangling from seat belts while holding tools and working on slippery slopes.Everything goes a little (and far beyond) in order to make the impossible possible.
Reinforcing sculptor Anish Kapoor’s concept of ethereal floating clouds into a 110-ton, 66-foot-long, 33-foot-tall stainless steel sculpture was the task of manufacturer company Performance Structures Inc. (PSI), Oakland, CA, and MTH, Villa Park, IL .On its 120th anniversary, MTH is one of the oldest architectural metal and glass structural design contractors in the Chicago area.
The requirements for realizing the project will tap into the artistic execution, ingenuity, mechanical skills and manufacturing know-how of both companies.They custom and even built equipment for the project.
Some of the project’s challenges come from its oddly curved shape – a dot or an inverted belly button – and some from its sheer size.The sculptures were built by two different companies at different locations thousands of miles apart, creating problems with transportation and work styles.Many processes that must be done in the field are difficult to do in a shop environment, let alone in the field.Much difficulty arises simply because such a structure has never been created before.So, no reference, no blueprint, no roadmap.
Ethan Silva of PSI has extensive experience in shell construction, initially on ships and later in other art projects, qualified for unique shell construction tasks.Anish Kapoor asked physics and art graduates to provide a small model.
“So I made a 2 x 3 meter sample, a really smooth curved polished piece, and he said, ‘Oh, you did it, you’re the only one who did it,’ because he’d been looking for two years for the Find someone to do it,” Silva said.
The original plan was for PSI to fully fabricate and construct the sculpture, and then ship the entire piece south of the Pacific Ocean, through the Panama Canal, north along the Atlantic Ocean, and along the St. Lawrence Seaway to a port on Lake Michigan, according to Edward Uhlir, executive director of Millennium Park Inc. According to the statement, a specially designed conveyor system will transport it to Millennium Park.Time constraints and practicality forced these plans to change.Therefore, the curved panels had to be braced for transport and trucked to Chicago, where MTH would assemble the substructure and superstructure, and connect the panels to the superstructure.
Finishing and polishing the Cloud Gate’s welds for a seamless look was one of the most difficult aspects of the field installation and assembly task.The 12-step process ends with a brightening rouge similar to jeweler’s polish.
“So we basically worked on that project for about three years, making these parts,” Silva said.”It’s a tough job. A lot of that time is spent figuring out how to do it and working out the details; you know, just perfecting it. The way we use computer technology and good old-fashioned metalworking is forging and aerospace technology combination.”
It’s difficult to make something so large and heavy with precision, he said.The largest plates averaged 7 feet wide by 11 feet long and weighed 1,500 pounds.
“Doing all the CAD work and creating the actual shop drawings for the work is actually a big project in itself,” says Silva.”We use computer technology to measure the plates and accurately assess their shape and curvature so they fit together correctly.
“We did computer modeling and then split it up,” Silva said.”I used my experience with shell construction, and I had some ideas on how to segment the shapes to get the seamlines to work so we could get the best quality results.”
Some plates are square, some are pie-shaped.The closer they are to a steep transition, the more pie-shaped they are, and the larger the radial transition.At the top, they are flatter and larger.
Plasma cuts 1/4- to 3/8-inch-thick 316L stainless steel, which is strong enough on its own, Silva says.”The real challenge is to get the huge slabs to a sufficiently precise curvature. This is done by forming and fabricating the rib system frame for each slab very precisely. This way we can precisely define the shape of each slab.”
The boards are rolled on 3D rollers that PSI has designed and manufactured specifically for rolling these boards (see Figure 1).”It’s kind of a cousin to the British rollers. We roll them using a technique similar to how fenders are made,” Silva said.Bend each panel by moving it back and forth on rollers, adjusting the pressure on the rollers until the panels are within 0.01 inches of the desired size.The high precision required makes it difficult to form sheets smoothly, he said.
The welder then seams the flux cored to the inner rib system structure.“In my opinion, flux cored is really a great way to create structural welds in stainless steel,” explains Silva.”It gives you high-quality welds with a strong focus on production and looks great.”
The entire surfaces of the boards are hand-ground and machine-milled to trim them to the desired thousandth of an inch accuracy so that they all fit together (see Figure 2).Check dimensions with precision measuring and laser scanning equipment.Finally, the plate is polished to a mirror finish and covered with a protective film.
About one-third of the panels, along with the base and internal structure, were erected in the trial assembly before the panels were shipped from Auckland (see Figures 3 and 4).Planned the siding procedure and did some seam welding on some small boards to join them together.”So when we put it together in Chicago, we knew it was going to fit,” Silva said.
Temperature, time and truck vibration can cause the rolled sheet to loosen.The ribbed grating is not only designed to increase the stiffness of the board, but also to maintain the shape of the board during transport.
Therefore, with the reinforcement mesh on the inside, the plate is heat treated and cooled to relieve material stress.To further prevent damage in transit, cradles are made for each plate, which are then loaded onto containers, about four at a time.
The containers were then loaded into semi-finished products, about four at a time, and sent to Chicago with PSI crews for installation with MTH crews.One is the logistics person who coordinates the transportation, and the other is the supervisor in the technical area.He works with MTH staff on a daily basis and helps develop new technologies as needed.”He was of course a very critical part of the process,” Silva said.
Lyle Hill, president of MTH, said MTH Industries was initially tasked with securing the ethereal sculpture to the ground and installing the superstructure, then welding the sheets to it and giving the final sanding and polishing, courtesy of PSI Technical guidance. The completion of the sculpture means a balance between art and practicality; theory and reality; required time and scheduled time.
Lou Cerny, MTH’s vice president of engineering and project manager, said what interests him about the project is its uniqueness.”As far as we know, there are things going on on this particular project that have never been done before, or have never really been considered before,” Cerny said.
But working on a first-of-its-kind job requires flexible on-site ingenuity to meet unforeseen challenges and answer questions that arise as work progresses:
How do you fit 128 car-sized stainless steel panels to a permanent superstructure while handling them with kid gloves?How do you weld a giant arc-shaped bean without relying on it?How to penetrate a weld without being able to weld from the inside?How to achieve a perfect mirror finish for stainless steel welds in a field environment?What will happen if lightning strikes it?
The first sign that this would be an exceptionally difficult project, Cerny said, was when construction and installation began on the 30,000-pound equipment.The steel structure that supports the sculpture.
While the zinc-rich structural steel provided by PSI to assemble the substructure base was relatively simple to manufacture, the substructure site was located half over the restaurant and half over the car park, each at a different height.
“So the substructure is kind of cantilevered and rickety,” Cerny said.“Where we put a lot of this steel, including at the beginning of the plate work itself, we actually had to get the crane to drive into a 5-foot hole.”
Cerny said they used a highly sophisticated anchoring system, including a mechanical preload system, similar to the type of stuff used in coal mining, and some chemical anchors.Once the substructure of the steel structure is fixed in the concrete, it is necessary to build a superstructure to which the shell will be attached.
“We started installing the truss system using two large fabricated 304 stainless steel O-rings—one on the north end of the structure and one on the south end,” says Cerny (see Figure 3).The rings are held together by criss-crossing tube trusses.The ring-core subframe is constructed in sections and bolted in situ using GMAW and bar weld and welded stiffeners.
“So there’s a large superstructure that no one has ever seen; it’s strictly for structural framing,” Cerny said.
Despite best efforts to design, fabricate, fabricate and install all the required components for the Auckland project, this sculpture is unprecedented and breaking new paths always comes with burrs and scratches.Likewise, combining one company’s manufacturing concept with another’s is not as simple as passing the baton.Additionally, the physical distance between sites caused delivery delays, which made some on-site manufacturing logical.
“While the assembly and welding procedures were planned in advance in Oakland, the actual site conditions required adaptive ingenuity from everyone,” Silva said.”And the union staff are really great.”
During the first few months, MTH’s daily routine was to determine what the day’s work entailed and how best to manufacture some of the components for erecting the subframe, as well as some struts, “shock absorbers,” arms, pegs, and pins. The pogo sticks needed to create a temporary siding system, Er said.
“It’s an ongoing process of designing and manufacturing on the fly to keep things moving and get them to the site quickly. We spend a lot of time sorting through what we have, redesigning and redesigning in some cases, And then manufacture the required parts.
“Literally, we’re going to have 10 things on Tuesday that we have to deliver on-site on Wednesday,” Hill said.”There’s a lot of overtime and a lot of store work done in the middle of the night.”
“About 75 percent of the board suspension components are fabricated or modified in the field,” Cerny said.”A couple of times, we literally made up a 24-hour day. I’d be in the store until 2, 3am, and I’d go home to take a shower, pick up at 5:30am, and still get wet.”
The temporary suspension system MTH for assembling the housing consists of springs, struts and cables.All joints between the plates are temporarily bolted together.”So the whole structure is mechanically connected, suspended from the inside, with 304 trusses,” Cerny said.
They start with the dome at the base of the omhalus sculpture – “the navel of the belly button”.The dome was suspended from the trusses using a temporary four-point suspension spring support system consisting of hangers, cables and springs.Cerny said the spring provides a “give and take” as more boards are added.The springs are then readjusted based on the weight added by each plate to help balance the entire sculpture.
Each of the 168 boards has its own four-point suspension spring support system so it is supported individually when in place.”The idea is not to overemphasize any of the joints because those joints are put together to achieve a 0/0 gap,” Cerny said.”If a board hits the board below it, it can cause buckling and other problems.”
As a testament to the accuracy of PSI’s work, the assembly is very good with few gaps.“PSI has done a fantastic job of making the panels,” says Cerny.”I give them all the credit because in the end, it really fit. The fitout is really nice, which is great for me. We’re talking, literally thousandths of an inch. The plate is placed on There is a closed edge together.”
“When they finish the assembly, a lot of people think it’s done,” Silva said, not only because the seams are tight, but because the fully assembled parts, and the highly polished mirror-finish plates, have come into play to reflect its surroundings.But butt seams are visible, liquid mercury has no seams.In addition, the sculpture still had to be fully seam welded to maintain its structural integrity for future generations, Silva said.
The completion of Cloud Gate had to be put on hold during the park’s grand opening in the fall of 2004, so omhalus was a live GTAW, and that went on for a few months.
“You can see small brown spots, which are TIG solder joints around the entire structure,” Cerny said.”We started rebuilding the tents in January.”
“The next major manufacturing challenge for this project was to weld the seam without losing shape accuracy due to welding shrinkage deformation,” Silva said.
Plasma welding provides the required strength and stiffness with minimal risk to the sheet, Cerny said.A 98% argon/2% helium mixture works best in reducing fouling and enhancing fusion.
Welders employ keyhole plasma welding techniques using Thermal Arc® power sources and special tractor and torch assemblies developed and used by PSI.