How do retractable roofs in convertible stadiums work?

Retractable roofs are the latest trend in sports stadium design. Marshall highlights multiple examples of convertible stadiums in the United States and explains how they work in this episode.

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Episode Transcript

Speaker 1 (00:00):
Welcome to Brainstuff from dot com where smart happens. Hi.
I'm Marshall Brain with today's question, how do the retractable
roofs on stadium's work? Ballparks are just as trendy as

(00:21):
clothes and hairstyles. In the nineteen sixties and the nineteen seventies,
many cities built donut shape multi purpose stadiums. It was
also the era of the domed stadium. We were in
awe at the immensity of the Astrodome in Houston and
the Kingdome in Seattle. Today, a new trend in stadiums
has led to the demolition of the Kingdome and the

(00:44):
likely demise of the Astrodome. The latest trend in sports
stadiums is the retractable roof stadium. These new convertible stadiums
allow athletic fields to be covered during inclement weather, but
can be open to allow the sun to shine in
on fair weather days. This new type of stadium has
all been killed off the idea of artificial turf stadiums,

(01:07):
which cause a greater number of injuries than natural turf.
Retractable roofs are an idea whose time has come, But
just how do they work? It? Turns out there's no
single answer to that question, because no two retractable roof
stadiums are exactly alike. Let's look at a few of
these convertible stadiums and see what's going on. First, there's

(01:28):
the sky Dome in Toronto. It's the home of the
Blue Jays of Major League Baseball, and it was opened
in nine nine to begin the era of retractable roof stadiums.
While other stadiums had previously been built with removable tops,
for example Montreal's Olympics Stadium, the sky Dome was the
first to have a fully retractable roof. The roof consists

(01:52):
of four steel panels, and it moves along rails at
a rate of seventy one ft or twenty one meters
per minute, takes about twenty minutes to open or close.
When closing the roof, seventy two motors are used to
move the two panels backward and forward over a fixed
panel like a telescope, and a fourth panel rotates a

(02:13):
hundred eighty degrees to completely close the roof. Then there's
the Bank One Ballpark in Phoenix. It's home of the
Diamondbacks of Major League Baseball. Bank One ballpark or the
Bob opened in in the searing heat of the Arizona Desert,
it was almost a necessity to have a ballpark that
could be opened during moderate days and closed and air

(02:35):
conditioned on hot summer days. Bank One's roof uses a
system similar to a drawbridge. A pair of two hundred
horsepower motors drive the roof panels to open and close
in just four minutes, using four miles of cable strung
through a complicated police system. They're Safeco Field in Seattle.

(02:56):
In baseball's mariners said goodbye to the key Dome and
moved to Safeco. Safecoas roof is divided into three independent
panels made of a thin gypsum and glass fiberboard. A
waterproof skin covers the panels. The three panels are staggered
so that the roof can slide completely away from the

(03:17):
field of play. The panels roll on motorized steel wheels
that move over steel rails. The wheels are powered by
ninety six ten horsepower d C motors. Power is provided
by long cables that are reeled in and out as
the roof slides open and shut. Opening and closing the
roof is done at a rate of thirty ft or

(03:39):
nine point one meters per minute and takes ten to
fifteen minutes. There's Minute Made Park in Houston, opened in
two thousand is Enron Field, and then after the Enron scandal,
it was temporarily known as the Astroids Field before Minute
Made bought the naming rights. Minute Made Park is the
home of Baseball's Astros. The newest of the retractable roof stadiums,

(04:04):
it consists of three panels with staggered heights that slide
completely off the top of the playing field. Even the
glass walls on one side of the stadium retract to
allow baseballs to be hit completely out of the stadium.
Sixty electric motors with seven point five horsepower drive a
hundred and forty thirty six inch steel wheels that slide

(04:28):
over tracks on the east and west sides of the stadium.
Opening and closing takes between twelve and twenty minutes. And
then there's Reliance Stadium in Houston. Reliant, opened in two
thousand three, is the home of the Texans, the National
Football League expansion team. Reliance nine fifty six by three
hundred eighty five foot roof divides into two panels that

(04:51):
open in the middle of the stadium over the fifty
yard line. The panels are made out of a transparent
teflon coated fiberglass. Five tri chord trusses support each panel
and span between super trusses. The panels will slide over
rails built on top of the super trusses at a
rate of about thirty five ft per minute. Retractable roofs

(05:15):
are really marvels of modern architecture. They're designed to move
panels that weigh millions of pounds in just a few minutes.
By doing so, they give fans a new experience at
baseball and at football games. Given their popularity, it's likely
we'll see many more of these convertible stadiums built in
the next decade, until they're replaced by the next stadium trend.

(05:41):
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