The NOVA Obelisk swinging through 15° to vertical.
Obelisk Raised!
by Peter Tyson
September 12, 1999
From the moment yesterday morning when
I stepped into Fletcher Granite, the quarry in Chelmsford, Massachusetts that
was graciously hosting NOVA's attempt to raise an obelisk, I was on a mission,
and not a very kind one at that.
It wasn't something I did intentionally, or even consciously. But as soon as my boots crunched on the gravel path leading into the quarry, I began
searching for some chink in the armor, some flaw in the design, some forgotten,
seemingly trivial detail that Rick Brown and his exacting team had missed in
their preparations for hauling the obelisk the last 15° to upright.
Partly it had to do with the fact that the first half of this operation - getting the
obelisk to 75° - had gone so swimmingly that I
began to have adrenalin withdrawal by the end of the day. (Though it ultimately came up
short, the obelisk-raising attempt in Egypt last march did have its moments of
blood-pumping excitement.)
I didn't want to
suffer that again, nor, I knew, did Julia Cort, who is making a film for NOVA
about this attempt. But mostly my suspicions arose from having watched, in person
and on film, two previous attempts to erect an obelisk in Egypt come up short,
and knowing that those crews had put as much mental and physical effort into
their respective undertakings as this one had.
So, first I had to find out what Brown and Company had in mind for the raising.
Predictably, it proved as clean and elegant in design as a Henry Moore sculpture: Four
teams of 28 rope-pullers apiece would pull on four ropes stretching out more or
less in parallel from the tip of the obelisk to a point about 100 feet away in
the opposite direction to its lean. Meantime, on the other side of the obelisk,
Jim Kricker and Al Anderson would carefully ease off on the braking ropes
running back to the big braking timbers, while Joel McCarty - who heads up the
Timber Framers Guild when he's not raising obelisks—would keep his eye on
two other ropes tied off tautly on either side.
The pullers go at the ropes
during one of several test runs.
Predictably, too, Brown's crew had carefully trained the pullers, who hailed
from both Fletcher Granite and the Massachusetts College of Art. "If you want
to play in my sandbox, you have to convince me you can take instruction!"
belted out McCarty as he led training sessions soon after my arrival on how to
"pull with your fingertips."
But the team's conscientiousness only fueled my desire to turn up something
not thought of. I began probing:
"Joel," I said, sidling up to McCarty, "are you afraid the pullers might just
yank the obelisk right over?"
"Hell yes!" he said, grinning through his gray-flecked beard, and then began
reeling off figures. It will take 4,800 pounds of pull to get the obelisk
moving, he said, but that number will drop off rapidly once the stone is
underway. When it gets to an angle of 83°, the obelisk's center of gravity
will pass over the point where the rock's butt end rests on the edge of the
turning groove, and the force on the braking ropes will increase exponentially,
since it will then equal the mass of the obelisk times its velocity squared.
Thus, for every doubling of the obelisk's rotation speed, the force on the
braking ropes will increase four times. "If the gentlemen at the braking
ropes are sleeping," he said, "the obelisk will accelerate at the falling-body
rate of 32 feet per second per second." McCarty went on and on, staring me
down in a perfectly kind way and smiling.
Okay, I thought, so they've worked out the figures if all goes to plan, but
what if one group of pullers pulls harder than the others? I asked Rick
Brown.
"If you'll look closely, you'll see we braided the four ropes near the tip of
the obelisk," he said, pointing. He didn't need to explain: any out-of-sync
pulling would have no effect on the obelisk.
Could it tip to one side or the other?
With the 100-plus rope gang behind them, Jim
Kricker (standing) and Wyly Brown check for movement in the obelisk.
Not likely, Brown said. Each of the two ropes out the side had perhaps 1,000
pounds of tension in them, and both also had swigging lines, which crew members
could pull on to increase tension if the obelisk started to favor one side or
the other.
I was getting concerned; my mission was endangered. Then Wyly Brown told me
he'd heard the critical angle was 86.5°, not 83°. Aha, I gloated
secretly, now I've got something to work with. I announced the discrepancy to
one of the timber framers.
"Oh, it's 86 and a half now?" he said, laughing. "Ed must have rejigged the
numbers."
Not willing to give in so easily, I approached Ed Levin, the
mathematician-turned-timber framer who was in charge of working out the
engineering numbers.
"Oh, I recalculated it to account for the butt end resting in the turning
groove rather than right on the pedestal stone," he said, smiling like all the
others. "Eighty-six-and-a-half degrees is indeed the point where the obelisk
will become self-righting and"—he brought one hand down on the other - "will
want to go kerplunk." Confidence in his calculations oozed from him like
sweat.
Growing desperate, I walked up to Grigg Mullen, the barrel-chested engineer.
"Grigg, couldn't something go horribly wrong?" I asked, hoping my jocular tone
might jar something loose.
"Well, it could spin out of control," he said. He put a meaty hand on my
shoulder. "Remember when you were in camp, and you played that game where you
tried to raise a bottle off the ground with a wire, and it started spinning out
of control?"
No.
"Could happen here," he continued, and grinned. He couldn't have looked more
unconcerned.
The NOVA Obelisk swinging through 15° to vertical.
The pullers go at the ropes
during one of several test runs.
With the 100-plus rope gang behind them, Jim
Kricker (standing) and Wyly Brown check for movement in the obelisk.