Troy Pinkerton in tower crane

The San Diego skyline rumbles toward heaven, ponderous monoliths surmounted by the spindly tower cranes that serve as both heralds and midwives. Market Street, between Harbor and Fifth Avenue, braces itself for the much-anticipated influx of retiring baby boomers, whole blocks leveling and sinking before sending up piled masses of luxury condominiums, some complete with space for restaurants and retail. Five projects are either advertised or under construction between State and Third alone: City Walk on the north side between State and Union, Renaissance to the north between Front and First, Horizons just across the street to the south, Marina Place just west of Horizons, and finally, 235 on Market, a relatively modest (one-third of a block) structure going up between Second and Third.

And what about those bolts? If they went...

Of these, Horizons is the nearest completion. The signs that enticed passersby to consider relocating to the complex’s twin towers -—“211 Luxurious Condominiums and Townhome Residences. 1-2 bedroom plus den, 1036-2918 square feet”— are down now. Down also are the two tower cranes that stood alongside them for over a year — one raised just higher than the other to avoid boom collisions as they traced their expansive arcs in the sky.

Tower crane at Horizons, downtown. My fingers started to ache from exertion.

Before the cranes came down, I wanted to be up in one of them, connected to the ground not by the enormous solidity of the building but by the slender skeleton of steel that clung to its side. I wanted to sit in the tiny, glassed-in box tucked under the crux of boom and shaft and look — now down, now out, my gaze following the perpendicular that seems to stretch out past the point of credulity. (The diagonal between the two sections of the crane stood empty; there was no brace where I imagined a brace should be.) I wanted to see structural chunks rise against the backdrop of the Gaslamp, the convention center, the Coronado Bridge.

I kept climbing, section after section, the weight of the crane increasing in 4500-pound increments.

But before I could sit in the box, I had to ascend to the box. As I approached the site, my eyes turned tourist-style toward the heights, I made what started as an observation and then grew into a full-blown realization, the sort that made my feet feel just a little bit heavier — there was no elevator to the box. There was only a ladder, running up the interior of the crane s four-sided frame. I was going to have to climb.

Inside one of Roel Construction’s onsite trailers, I was given a hard hat and a harness that would connect me to the cable that runs alongside the ladder. If I fell, a clamp would lock around the cable, leaving me dangling but safe. A lady at a desk smiled and rocked from side to side, warning me about the crane’s tendency to sway in the wind. My feet felt heavier still.

The crane I was to visit stood 280 feet high; 180 feet of my ascent was taken care of by the elevator that ran up the outside of the unfinished building. Then, on the 18th floor, a rudimentary walkway — plywood floor and round metal railings — provide access to the crane tower. I walked across, stepped inside the frame-within-a-frame that surrounded, the ladder, latched onto the cable, and looked straight up at the remaining hundred feet. The metal floor at the tower sections base eased the strain of looking down. Though the world dropped off in every direction, the view directly under me would never encompass more than a hundred feet. I reminded myself that crane operator Troy Pinkerton did what I was about to do every day without incident (but, then again, he had the advantage of doing it every day, making a habit of it) and started climbing.

As my body traveled up — slowly, half-time, letting one hand catch up with the other instead of reaching over it for the next rung, my grip too tight on the narrow steel cylinders so that my fingers started to ache from exertion, my camera bag catching on the frame, jerking me back as I lifted myself up — my thoughts traveled down. What exactly was holding this thing up? Surely the column was too narrow to provide sufficient foundation to support the jutting boom and whatever weight hung suspended from its hook?

Down at street level, a white wooden fence surrounded a yawning hole in the concrete; the crane tower plunged into the hole. Two parking levels down, the tower disappeared into a block of concrete encompassed on all sides by the garage floor. The top of the concrete had crumbled away, revealing thick lengths of rebar. The four posts of the tower were bolted into extensions of the crane, about five feet in length, encased within the concrete. Below these lay a heavy rebar mat, just like the one poking through at the top of the block. (During a later, solid-ground interview, Pinkerton told me that almost 200 yards of concrete went into the footing and that it was “tied into the footing of the whole base” of the building.)

Shelby Chabot, who works for the crane’s owners, Lewis Cranes, told me, “Tower cranes today can free stand between two and three hundred feet as a height under hook from the top of the foundation.” While this crane came in under the maximum, two collar-and-strut assemblies had been attached to the tower. “There’s a structural steel collar mounted to the tower of the crane, and then there are three strut assemblies that go from the collar to the building— two of them tying off at one shoe on the building and the other angling off in the other direction and tying off on the other shoe.” The shoes are then bolted into the concrete floor of the building.

The tower was constructed of multiple, roughly 13-foot sections held together by fat steel bolts, and as I got about halfway up — comfortable enough now to marvel at the view, taking in the Children’s Park (a glorious wading pool fronted by a No Wading sign, concrete-rimmed domes of grass crying out for a round of King of the Hill), the Children’s Museum, the Hyatt, the Marriott, and most of all, the bay—my mind continued its inverse meanderings. My altitude and vista were vast, my thoughts focused on the minute: those lacings couldn’t be more than 3"x3", and Pinkerton told me, “If one of those gets bent, the whole thing’s shot” And what about those bolts? If they went...

Shelby again: “Typically, the tension on the bolts is quite high. It can be anywhere from 3000 to 4500 foot-pounds of torque. We use a hydraulic bolt-stretching device. Essentially, you thread the nut onto the bolt first — the nut is always at the top, the bolt head always on the bottom. Then you thread the stretching device down onto the bolt itself, so that it’s truly stretching the bolt, rather than torquing the nut It stretches the bolt to a certain tension, which is determined on a gauge on the machine, and the bolt is hand-threaded to fit snugly against the locknut. The tension is released on the bolt, which essentially lets the bolt go back to its normal dimension, and that creates a torque value in the bolt. It’s not physically possible for ironworkers to torque to that level — these new devices can torque anywhere from 3000 to 10,000 foot-pounds.” There would be no slippage, but what about breakage?

My thoughts telescoped to the level of the electron, its bond to the electron of an adjacent atom, the attraction that bound the atoms in the bolt despite exterior forces like the bolt-stretching device, not to mention the wind and the weight of the boom. (This is the strength of steel: that it can bend [and stretch] and not lose its elastic faculty. The bonds, though strained, will draw the atoms back together, and the whole will try to return to its original shape. A lesser material would bend—or break.) As Larry Thompson, associate professor of mechanical engineering at SDSU, explained, “There are defects that are present inside the crystal structure of the atoms.” As force is exerted, “Those defects start moving around, and the net result is that the atoms shift in position permanently.

“Steel is a combination of iron plus carbon. Something like the fender of your car is going to contain simply iron plus carbon plus a small amount of residual elements —impurities. They’re in there simply because it’s not worth it economically to try to get them out of the mix. When you want to make a high-strength steel [such as the steel for your bolts], you start alloying specifically for the purpose of changing the way the structure evolves inside the steel. For example, a chromoly steel [steel alloyed with chromium and molybdenum]. Inside the steel, these elements form very strong carbides with the carbon that’s present. A carbide is a ceramic. So now you have this hard, brittle ceramic material inside the steel, and its presence tends to strengthen the steel. On a basic level, the motion of those defects is interfered with by the presence of the carbides.” Shelby told me that several areas on the crane used high-strength steels, “but particularly the bolts.”

I kept climbing, section after section, the weight of the crane increasing in 4500-pound increments. By this point, it was almost fun, not much different from standing atop a skyscraper, held back from the edge by a thin steel railing. Soon, I arrived at the platform just below the box, and after a moment’s hesitation before freeing myself from the cable, I was up and inside with Pinkerton.

Troy Pinkerton sat in a padded armchair situated on a swiveling, tilting base. At his hands were two levers, rather like video-game joysticks, which controlled the boom’s motion from side to side, the hook trolley’s motion along the boom, and the hook’s motion up and down. The hook ran on a three-speed gearbox: first gear, 22,045 pounds maximum at 108 feet per minute; second gear, 9920 pounds maximum at 289 feet per minute; third gear, 3970 pounds maximum at 587 feet per minute. The cabin’s front was almost entirely glass; one section was open to the outside. Another glass panel lay at Pinkerton’s feet, so that if he leaned forward, he could look straight down the crane tower.

Beneath his cowboy hat and behind his aviator sunglasses, Pinkerton managed to seem both relaxed and attentive to. his work, making picks and delivering loads as we talked. “I’ve been working downtown 12 or 13 years now. I’ve worked on about six buildings — the Hyatt, Great American.” Before gaining his lofty status, he worked in rigging, binding loads and hooking them onto the crane. “You learn the crane down there — how it moves.” From there, he moved into ground-based hydrocranes and then into tower cranes. Now, he served as the connection between the equipment and supplies on the ground and the workmen dotting the top of the building, 80 feet below. He hauled “everything to do with concrete, all the rebar, lumber, glass for the side of the building, all kinds of material.”

“These cranes are pretty nice rigs,” he told me. “They handle nice. It’s kind of like a car. [Just like little cars], the smaller the crane, the whippier it is — the quicker around.” These cranes are midsized — the boom extends 158 feet, “and they can go to 300 feet. The hard thing is learning to catch the load — part of the challenge of it is to get it there smooth for these guys. You’ve got so much line to play with; you can really get [the load] going. If you get your load block swinging, you’ve got to bring the boom over to catch it. It’s a timing thing, like a big plumb bob. You go past it and then let the block come in, swing back into your load and bring your boom back over”

Even after you master the crane’s movements, there is the wind to contend with. “The wind blows these cranes pretty good — it catches all the lacing in the boom, and it’ll blow this thing pretty fast, as fast as you want it to swing. That’s part of the trick to tower cranes is learning how the crane coasts. Instead of keeping it swinging, you coast into your load, and if you know where the wind’s coming from, you can just coast to the next pick. It’ll coast pretty good — like going downhill in a car. It’s amazing how this much weight just pulls around with the wind. The owner of the cranes wants us to shut the crane down [if the wind gets to] 30 miles per hour, so we don’t wreck the swing motors. Also, at 30, it really gets pretty much out of control. But the highest it gets around here is 20,25.”

He delivered what looked like a chest of tools to a blue-helmeted electrician who eased it to its precise destination via an eight-foot guide rope dangling from the bottom of the load. I was impressed with Pinkerton’s precision; the electrician didn’t have to do much maneuvering.

We stepped out of the cabin onto the back side of the boom, which housed the motor, the cable winch, and the counterweights — six 7000-pound concrete „ blocks hanging side by side. Here, strung over the tower top and descending to both sides of the boom, I found my missing diagonal: narrow pendant bars, held together by pins, strengthening the boom to the point where it can make a 22,000-pound pick. We were free there — metal rails stood at waist height and a steel mesh floor supported us, but no solid surface blocked our view in any direction. Troy returned to the box and circled the crane, giving me a panoramic view of downtown, Point Loma, Coronado. The winch whirred into life; the boom shivered slightly. They ought to sell tickets, I thought. “I like the country,” said Pinkerton, “but it ain’t bad coming down here, working, and then going home.”