Anish Kapoor’s vision for the Cloud Gate sculpture in Chicago’s Millennium Park is that it resembles liquid mercury, smoothly reflecting the surrounding city. Achieving this wholeness is a labor of love.
“What I wanted to do in Millennium Park was to include the Chicago skyline … so people could see the clouds floating in it and these very tall buildings reflected in the work. And then, since it is in the form of a door, the participant, the viewer, will be able to enter this very deep room, which in a sense does the same thing with the reflection of a person, as the appearance of the work does with the reflection of the surrounding city. — World famous British artist. Anish Kapoor, Cloud Gate sculptor
Looking at the calm surface of this monumental stainless steel sculpture, it is difficult to guess how much metal and courage hides under its surface. Cloud Gate hides the stories of over 100 metal fabricators, cutters, welders, trimmers, engineers, technicians, metalworkers, installers and managers – over the entire five years.
Many work long hours, work in workshops in the middle of the night, camp on a construction site and work in 110-degree temperatures in full Tyvek® suits and half-masks. Some work against gravity, hanging from harnesses, holding tools, and working on slippery slopes. Everything goes a little (and far beyond) to make the impossible possible.
Enhancing 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 Performance Structures Inc. (PSI), Oakland, California, and MTH. Villa Park, Illinois. At its 120th anniversary, MTH is one of the oldest structural steel and glass contractors in the Chicago area.
The requirements for the implementation of the project will depend on the artistic performance, ingenuity, mechanical skills and manufacturing know-how of both companies. They are custom made and even built equipment for the project.
Some of the project’s problems stem from its strangely curved shape – a dot or upside-down navel – and some from its sheer size. The sculptures were built by two different companies in different locations thousands of miles apart, creating problems with transportation and work styles. Many processes that must be performed in the field are difficult to perform on the shop floor, let alone in the field. The great difficulty arises simply because such a structure has never been created before. So, no link, no plan, no roadmap.
Ethan Silva of PSI has extensive experience in hull building, first on ships and later in other art projects, and is qualified to perform unique hull building tasks. Anish Kapoor asked a Physics and Art graduate to provide a small model.
“So I made a 2m x 3m sample, a really smooth curved polished piece, and he said ‘Oh you did it, you’re the only one who did it’ because he’s been looking for two years to find someone to do it. ” Silva said.
The original plan was for PSI to fabricate and build the sculpture in its entirety and then ship the entire piece south of the Pacific, through the Panama Canal, north along the Atlantic Ocean and along the St. Lawrence Seaway to a port on Lake Michigan. , according to Edward Ulir, chief executive 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. Thus, the curved panels had to be secured for transport and trucked to Chicago, where MTH assembled the substructure and superstructure, and connected the panels to the superstructure.
Finishing and polishing the Cloud Gate welds to give them a seamless look was one of the most difficult aspects of installation and assembly on site. The 12-step process is completed by the application of a brightening blush, similar to jewelry polish.
“Basically, we worked on this project for about three years making these parts,” Silva said. “This is hard work. It takes a lot of time to figure out how to do it and work out the details; you know, just to bring to perfection. The way we use computer technology and good old metalworking is a combination of forging and aerospace technology. .”
According to him, it is difficult to make something so large and heavy with high precision. The largest slabs averaged 7 feet wide and 11 feet long and weighed 1,500 pounds.
“Doing all the CAD work and creating the actual shop drawings for the job is a big project in itself,” says Silva. “We use computer technology to measure the plates and accurately evaluate their shape and curvature so that they fit together correctly.
“We did a computer simulation and then split it up,” Silva said. “I used my experience in shell building and I had some ideas on how to segment the shapes so that the seam lines would work so we could get the best quality results.”
Some plates are square, some are pie-shaped. The closer they are to the sharp transition, the more they are pie-shaped and the larger the radius of the radial transition. In the upper part they are flatter and larger.
The plasma cuts 1/4 to 3/8-inch thick 316L stainless steel, Silva says, which is strong enough on its own. “The real challenge is to give the huge slabs a fairly precise curvature. This is done by very precise shaping and fabrication of the frame of the rib system for each slab. In this way, we can accurately determine the shape of each slab.”
The boards are rolled on 3D rollers that PSI has designed and manufactured specifically for rolling these boards (see fig. 1). “It’s kind of like a cousin of the British rollers. We roll them using the same technology as the wings,” said Silva. Bend each panel by moving it back and forth on the rollers, adjusting the pressure on the rollers until the panels are within 0.01″ of the desired size. According to him, the required high precision makes it difficult to form sheets smoothly.
The welder then welds the flux-cored wire to the structure of the internal ribbed system. “In my opinion, flux-cored wire is a really great way to create stainless steel structural welds,” explains Silva. “This gives you high quality welds with a focus on manufacturing and great looks.”
All board surfaces are hand sanded and milled on a machine to cut them to the thousandth of an inch to fit together (see fig. 2). Verify dimensions with accurate measuring and laser scanning equipment. Finally, the plate is polished to a mirror finish and covered with a protective film.
About a third of the panels, together with the base and internal structure, were assembled in a test assembly before the panels were shipped from Auckland (see figures 3 and 4). Planned the planking procedure and seam welded several small boards to join them together. “So when we put it together in Chicago, we knew it would fit,” Silva said.
Temperature, time and vibration of the trolley can cause rolled sheet to loosen. The ribbed grating is designed not only to increase the rigidity of the board, but also to maintain the shape of the board during transportation.
Therefore, when the reinforcing mesh is inside, the plate is heat-treated and cooled to relieve material stress. To further prevent damage in transit, cradles are made for each dish and then loaded into containers, approximately four at a time.
The containers were then loaded with semi-finished products, about four at a time, and sent to Chicago with the PSI crews for installation with the MTH crews. One of them is a logistician who coordinates the transportation, and the other is a supervisor in the technical area. He works daily with MTH staff and helps develop new technologies as needed. “Of course, he was a very important part of the process,” Silva said.
According to MTH President Lyle Hill, MTH Industries was originally tasked with anchoring the ethereal sculpture to the ground and installing the superstructure, then welding sheets to it with final sanding and polishing. balance between art and practicality, theory and reality, required time and scheduled time.
Lou Czerny, MTH vice president of engineering and project manager, said he was interested in the project’s uniqueness. “To the best of our knowledge, things are happening on this particular project that have never been done before or never considered before,” Cerny said.
But working on a first-of-its-kind work requires flexible on-site ingenuity to deal with unforeseen problems and answer questions that arise along the way:
How do you attach 128 car-sized stainless steel panels to a permanent superstructure while wearing kid gloves? How to weld a giant bow-shaped bean without relying on it? How can I penetrate a weld without being able to weld from the inside? How to achieve the perfect mirror finish of stainless steel welds in the field? What happens if lightning strikes him?
Czerny said the first indication that this would be an exceptionally complex project was when construction and installation of the 30,000-pound equipment began. Steel structure supporting the sculpture.
Although the high-zinc structural steel provided by PSI to assemble the base of the substructure was relatively easy to fabricate, the platform for the substructure was half above the restaurant and half above the car park, each at a different height.
“So the base is sort of cantilevered and wobbly,” Czerny said. “Where we put a lot of this steel, including at the beginning of the slab itself, we actually had to force the crane into a 5-foot hole.”
Czerny said they used a very sophisticated anchoring system, including a mechanical pre-tensioning system similar to that used in coal mining and some chemical anchors. Once the base of the steel structure is anchored in concrete, a superstructure must be built to which the shell will be attached.
“We started installing the truss system using two large fabricated 304 stainless steel O-rings—one at the north end of the structure and one at the south end,” Czerny says (see Figure 3). The rings are fastened with intersecting tubular trusses. The ring core subframe is sectioned and bolted in place using GMAW, bar welding and welded stiffeners.
“So there is a big superstructure that no one has ever seen; it is purely for the structural framework,” Czerny said.
Despite the best efforts in designing, engineering, fabricating and installing all the necessary components for the Auckland project, this sculpture is unprecedented and new paths are always accompanied by burrs and scratches. Similarly, matching one company’s manufacturing concept to another is not as easy as passing the baton. In addition, the physical distance between sites resulted in delivery delays, which made it logical to produce some local production.
“While the assembly and welding procedures were planned in Auckland ahead of time, the actual site conditions required everyone to be creative,” Silva said. “And the union staff is really great.”
For the first few months, MTH’s daily routine was to determine what the day’s work entailed and how best to fabricate some of the subframe assembly components, as well as some struts, “shocks”, arms, pins, and pins. Er said pogo sticks were needed to create a temporary siding system.
“It’s a continuous on-the-fly design and production process to keep things moving and getting to the field quickly. We spend a lot of time sorting what we have, in some cases redesigning and redesigning, and then we make the parts we need.
“Literally on Tuesday we will have 10 things that we have to deliver to the place on Wednesday,” Hill said. “We have a lot of overtime work and a lot of work in the store done in the middle of the night.”
“About 75 percent of the sideboard suspension components are manufactured or modified in the field,” Czerny said. “A couple of times we literally made up for a 24-hour day. I was at the store until 2, 3 am, and at 5:30 I returned home to take a shower and go for the ingredients, still wet. .”
The MTN temporary suspension system for assembling the hull consists of springs, struts and cables. All joints between the plates are temporarily fastened with bolts. “So the whole structure is mechanically connected, suspended from the inside on 304 trusses,” Czerny said.
They start from the dome at the base of the omgala sculpture – “the navel of the navel”. The dome was suspended from the trusses using a temporary four-point suspension spring support system, consisting of hangers, cables and springs. Czerny said the spring provides “bounce” as more boards are added. The springs are then adjusted based on the weight added by each plate to balance the entire sculpture.
Each of the 168 boards has its own four-point spring suspension support system so it is individually supported in place. “The idea is not to over-evaluate any joints because those joints are put together to achieve a 0/0 break,” Cerny said. “If the board hits the board underneath it can lead to warping and other problems.”
As a testament to PSI’s accuracy, the build is very good with little play. “PSI did a fantastic job with the panels,” Czerny says. “I give them credit because, in the end, he really fits. The fit is really good and it’s great for me. We are talking literally about thousandths of an inch. .”
“When they finish assembly, a lot of people think they’re done,” Silva said, not only because the seams are tight, but because the fully assembled parts, with their highly polished mirror-finish plates, came into play, reflecting his surroundings. . But butt seams are visible, liquid mercury has no seams. In addition, the sculpture had to be fully welded to preserve its structural integrity for future generations, Silva said.
Completion of the Cloud Gate had to be delayed during the park’s grand opening in the fall of 2004, so omhalus became a living GTAW, and this went on for several months.
“You can see little brown spots all around the structure, which are TIG solder joints,” Czerny said. “We started restoring the tents in January.”
“The next major production challenge for this project was to weld a seam without losing shape accuracy due to welding shrinkage,” said Silva.
According to Czerny, plasma welding provides the necessary strength and rigidity with minimal risk to the sheet. A mixture of 98% argon and 2% helium is the best at reducing pollution and improving fusion.
Welders use keyhole plasma welding techniques using Thermal Arc® power sources and special tractor and torch assemblies designed and used by PSI.