Today, we test airplane propellers, 12 years before
the Wright brothers flew. 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.
I've just found an
astonishing article in the 1891 Century
Magazine. The industrialist Hiram Maxim is writing about an
apparatus for testing aeroplane propellers. But
this was before there were any aeroplanes. Maxim
had made a fortune on the Maxim Gun -- the first
practical machine-gun which was changing the face
of war.
But here his interest is in flight. He begins with
a critical look at French attempts to build powered
balloons. He thinks they're a clumsy form of
flight. Look at birds, he says. A bird weighs 600
times more than the air it displaces. He shows that
a goose in flight never exerts more than a tenth of
a horsepower.
Heavier-than-air flight is surely the way to go.
Yet birds combine lift and propulsion in the wing,
and that's too subtle for us to mimic. Maxim knows
we'll have to separate the wing from the propeller.
So he's built a central tower with a 32-foot
rotating arm to measure the effectiveness of
propellers and wing surfaces.
A steam engine drives the arm. At the end of the
arm is a propeller with a streamlined engine pod
and a short section of a wing. That test
configuration circles the tower at speeds up to
sixty miles per hour, while an electric motor
inside the pod drives the propeller.
The apparatus offers means for measuring power
input to both the propeller and the rotating arm.
Maxim's instruments let him separate out lift,
thrust, and drag. He finds that, at sixty miles per
hour, the propeller might use sixteen horsepower to
lift the wing and another 35 horsepower to overcome
drag and its own inefficiency.
With such detailed preliminary work on flight, did
Maxim ever fly an aeroplane? Yes, he did. Three
years later he built a great steam-powered machine,
and one of his people got a few feet off the ground
in it. Then it crashed. Maxim had done superb work
on the power inventory of flight, but he hadn't
solved the crucial problem of controlling a moving
aeroplane.
Yet we could use this fine article, from long
before the Wright brothers, to build our own
propeller test facility. Yesterday, a friend
jokingly remarked to me that his visit to Kitty
Hawk, North Carolina, had been a disappointment.
He'd found himself looking at a research lab -- at
test notes, a wind tunnel, and serious experimental
and theoretical work. "Shucks," he said, "I thought
they just went out and flew the damn thing." Of
course they did not. Flight didn't work that way.
I usually go along with the idea that the Wright
Brothers were first to fly. Add enough qualifiers
and it's true. They achieved repeated,
heavier-than-air, controllable flight
with a takeoff and a safe landing.
But the Wright Brothers had carefully studied all
that went before them. Then they added to it. This
1891 article offers just an inkling as to how many
people like Maxim and how much work it really took
to get us safely into the air.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
