Today, let's ride the Sforza Horse into the 20th
century. The University of Houston's College of
Engineering presents this series about the machines
that make our civilization run, and the people
whose ingenuity created them.
Some while ago I went to a
special exhibit of Leonardo da Vinci's sketches at
the Art Museum. I saw row upon row of drawings of a
heroic horse -- a great beast pawing the air from
every angle. This went beyond art. This was
obsession.
These were sketches for a monument, never built, to
Francesco Sforza. Sforza's son, Ludovico,
commissioned the statue. He meant to build up his
own political stock by making his father three
times larger than life.
But Leonardo got no further than the horse
Francesco was to ride -- a huge bronze horse, three
times life size. The sketches don't show us much of
Francesco. But that great snorting, pawing beast is
the stuff bad dreams are made of.
It was to have been hollow inside -- an
inch-and-a-half-thick shell. It would've weighed 65
tons and gone far beyond the foundry capabilities
of Leonardo's age. Worse yet, it would still
outreach foundry technique even today.
Leonardo made a clay model of the horse, and he
began amassing bronze. But Ludovico lost confidence
in the plan. He finally decided all that bronze
would serve his political fortunes better in other
ways. He had it melted down to make cannons for his
war with France. A few years later, French soldiers
wrecked Leonardo's clay model. They used it for
target practice.
Recently 150 art historians and engineers met to
see whether they might actually build that great
beast after all. What they found wasn't
encouraging. Even if all four legs were on the
ground, they couldn't possibly hold that much
weight.
For that matter, such a large mold could never
stand up to the hydrostatic pressure of the molten
metal. And a casting that large wouldn't cool
uniformly. Thermal stresses would crack it. So
Ludovico was perfectly right to doubt Leonardo's
plan. Like many of Leonardo's engineering works,
his Sforza Horse was doomed to live only in the
imagination.
Still, Japanese engineers have already built a
full-scale Sforza Horse, complete with rider. But
not of bronze! Theirs was made of plastic,
reinforced with fiberglass. Somehow that's not the
same. It just isn't the same.
An American foundry proposes to make a Sforza Horse
of bronze. They offer to cast a thin bronze skin in
ten pieces and assemble it over a stainless steel
skeleton.
So we probably shall see a Sforza Horse one day.
But I'd rather let that monster live where he came
from -- in the place where he has the greatest
effect. Better this horse should continue to live
-- inside the human head.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
