15x03 - Train Rails/Desalinated Water/Racing Wheelchairs/Parquetry

[bunniefuu]

Narrator: In the early days
of the railroad,

Train rails were made of either
cast iron or wrought iron.

Cast iron was too brittle
and would break easily.

Wrought iron was too soft
and would wear out too quickly.

So steel eventually became
and remained

The train-rail metal of choice.

The train wheel's rim
runs on the inside of the rail

To keep the train on the track.

This plant makes train rails
entirely out of recycled steel

From scrapyards, food cans,

And recycled pieces from
the rail-making process itself.

Electromagnets pick up the scrap

And dump it
in a charging bucket.

A truck hauls the bucket inside,

Where a crane drops the contents
into a furnace.

An intense electric current

Melts the scrap steel
at 3,000 degrees fahrenheit.

It then flows into
a large brick-lined ladle,

Where they add carbon,
manganese, and other elements

To make the steel more durable.

The alloy then runs down
a ceramic tube

That shields it
from exposure to oxygen,

Which would ruin the metal.

From there, the molten metal
flows into molds,

Which extrude it into continuous
rectangular blocks

Called blooms.

Acetylene torches cut each bloom
into 12-foot lengths.

A crane then transfers
the blooms to a furnace,

Which, over the next five
to seven hours,

Reheats them
to 2,300 degrees fahrenheit.

This softens the steel
for further shaping.

Then the reheated blooms enter
a machine called a rolling mill,

Which elongates each bloom, more
than quadrupling its length.

A shear then slices the longer,
thinner blooms into four pieces.

The pieces now go into
another furnace for reheating.

This preps them for the next set
of rolling mills,

Which will gradually form them
to the final rail shape.

Different railroads used to use
different-shaped rails,

Which required changing
the train's wheels

When passing from one railway
to another.

By the turn of the 20th century,

The t-shaped rail
became the industry standard

And remains so today.

For the final shaping,
each steel rail

Passes several times
through three consecutive mills.

This is what a mill's rollers
look like.

And here's the standard
"t" shape

To which they form the steel.

Next, a saw slices off about 12
inches to square off the ends.

The cut-off pieces go back
to the scrapyard.

The rails, meanwhile,
are laid out

Until they cool
to about 930 degrees fahrenheit.

Then an electromagnet
piles them in a holding box,

Where they sit for 10 hours

Until they cool off
to about 190 degrees fahrenheit.

When they come out of the box,

They run through
two sets of rollers.

The first set
flexes the rail vertically.

The second, horizontally.

This flexing process

Straightens out the rails,
which curve slightly

Due to all that heating,
shaping, and cooling.

Next, each rail
passes over a mirror,

Enabling inspectors to examine
the bottom, as well as the top.

Finally, a saw cuts the rails

To whatever size
the railway ordered --

Most often the standard length
of 82 feet.

The quality-control department
measures random samples

To make sure
all the dimensions are precise.

Every rail bears a number

Identifying the batch of steel
from which it came.

In the event of a problem,
that number

Lets them trace all the rails
made from the same batch.

It's a system that ensures
a safe, smooth ride.

Narrator: In regions where
fresh drinking water is limited,

Desalination plants
remove salt from seawater,

Converting it into freshwater
suitable for human consumption.

There are more than 13,000
desalination plants worldwide,

Producing 12 billion gallons
of water a day.

The desalination plant that
produced this drinkable water

Is located right next
to an electrical power plant

Which uses seawater
to cool down its condensers.

Post-cooling, the water travels
via underground pipes

To the desalination plant.

Before salt extraction,
the water is pretreated

In a multiphase
cleaning process.

First, the water flows
through screens

That filter out large debris.

From there, it flows into basins

For the first
pretreatment stage.

As large paddles
agitate the water,

The plant adds two chemicals --

Sodium hypochlorite,
a disinfectant,

And ferric chloride,
a coagulant.

The coagulant
binds together sand

And other tiny particles
of debris,

Forming heavier clumps
that sink to the bottom.

This removes a significant
portion of dirt from the water.

But it's still far
from being crystal clear.

The water now moves
into another set of basins

For the second pretreatment
phase -- sand filtering.

Inside each sand filter,

Regulated by various
pressure and flow gauges,

A steady stream of air

Continually moves sand
in a circular motion.

The seawater enters
at the bottom of each filter

And flows to the top.

As the sand moves downward
against the rising water,

The dirt particles
attach to the sand.

The seawater now looks clean

But still contains
microscopic particles.

So it enters the final
pretreatment phase.

This time, the filtering medium
is diatomaceous earth,

A powdered rock
that contains algae fossils.

Finer than sand, it filters out
those microscopic particles.

The seawater
is now perfectly clean

And ready for salt extraction.

They do that using membranes --

Cylinders containing layers
of plastic sheets

That have pores .001
the diameter of a human hair,

Small enough to trap
microscopic salt crystals.

The plant
pumps the clean saltwater

Under extremely high pressure
through long tubes,

Each of which contains
eight membranes.

By the time the water
passes through all the membranes

And reaches the center of the
tube, it's completely salt-free.

Plant personnel and a slew
of sophisticated instruments

Continually monitor every one of
the system's 10,000 membranes.

Meanwhile, the plant
sends the debris removed earlier

To large waste basins

For another round
of chemical treatment.

After the solids
settle to the bottom,

The dirty water goes back
to the front of the plant

To be cleaned and recycled.

Pressure rollers squeeze
the remaining water

Out of the solids.

Trucks then transport
the dry solids to a landfill.

The extracted salt, meanwhile,
goes to the power plant,

Which dilutes it,
then returns it to the sea

In a way that doesn't upset the
water's natural salinity level.

Processing saltwater
into freshwater

Strips away
the water's natural minerals.

Not replacing them
would create two problems.

First,
the water wouldn't taste right.

Second,
it would damage metal pipes

By aggressively trying
to replace the missing minerals.

Therefore, the plant adds
liquid lime and carbon dioxide

To the water.

These two elements adjust the ph
level and raise the alkalinity,

Restoring the minerals
and natural taste.

Narrator: World w*r ii veterans
disabled in combat

Were the first to race
in wheelchairs.

But those chairs were clunky,
steel models.

Fast-forward to today
and wheelchair racing

Is a serious sport
with aerodynamic chairs.

These chairs
have elongated mainframes

And three wheels
instead of four.

This modern racing chair
is tailored

To the athlete's physique,
specific disability,

And skill level.

They begin by taking detailed
measurements of the athlete

As she sits in a demo chair.

They measure the width
and height of her knees

To determine
the best seating position.

They check the balance point

To decide how the rear-wheel
axle should be positioned,

And they measure her arms so
push rims can be sized for her.

They then produce
a digital drawing

Of the racing wheelchair,

Complete with any extras
requested by the athlete.

The fabricator selects
the appropriate aluminum tubing

And cuts it
to the desired length.

This one will be the main tube
for the racing chair's frame.

Rollers curve the tube slightly
at one end

So the framework
will accommodate the seat.

A press then flattens the tube
quite a bit.

This stiffens the metal

And will make the racing-chair
frame more aerodynamic.

This small tube, which they weld
to the main tube,

Will hold the racing chair's
steering fork.

He now tapes a steering
mechanism for the front wheel

Onto the framework

And confirms that its placement
is exact before welding.

This device will keep
the front wheel on autopilot,

Freeing the racer's hands
to push the rear wheels.

The welder now positions
the other end of the main tube

Perpendicular to the wheel axle.

He inches the tube
towards the center of the axle

Until it's right on the mark.

He welds the axle
to the main tube,

Giving the framework
a "t" profile.

Temporary wheels lift the axle

So he can install
the seat frame.

Then, a hydraulic machine
bends an aluminum tube

Into a "u" shape to make
the racing chair's seat frame.

He positions the seat frame
on the rear axle

And does a few more welds.

Finally, he installs fenders
on the wheels.

The main framework of this
racing wheelchair is complete.

But to make it look flashy,
they spray-paint it red.

This is a powder coating.

It's a thermoplastic paint

That's tougher
than the conventional kind.

Next, this machine rolls
the push rims,

Which the athlete uses
to propel the wheelchair.

They weld on pegs for attaching
the rims to the wheels,

Then glue a rubber sleeve
onto each rim.

They wrap it in tape to clamp
the two as the glue dries.

The tape stays on

Until the chair is delivered
to the customer.

They install the rear wheels
at an angle

To make the racing chair
more stable when cornering.

They add padding
for the athlete's knees,

Then assemble the nylon seat
to the chair.

Next comes the front-wheel
steering fork and handle.

They complete the assembly
with a spring-loaded cylinder.

That's part of
the steering autopilot system.

After testing the steering fork,
they install the front wheel,

Which is smaller
than the rear two.

Once it's been equipped
with brakes,

This custom racing chair

Is ready to take on
the competition.

An elite athlete will buy
a new racing chair every year.

Some choose rear wheels
made of lightweight carbon fiber

Because any advantage
is welcome in the push to win.

Narrator:
Parquetry was invented

In France in the 1600s
as an alternative

To high-maintenance
marble flooring.

It's made
from small pieces of wood

Bonded together
in a geometric pattern.

The most common motif
is squares.

But it also comes
in other patterns,

Such as herringbone,
lozenges, and triangles.

Parquetry can be made
of laminate or plywood.

However,
the best-quality flooring

Is made from genuine wood, such
as oak, maple, or yellow birch.

The factory first cuts the wood
into planks,

Measuring 2 to 5 inches wide
by about a yard long.

A drum saw then cuts each plank

Into 6 blocks
about 6 inches long

While an inspector
discards any misshapen ones.

The blocks then move
through a planer

That shaves a fine layer
off both sides.

This reduces the blocks to a
thickness of just under an inch

And smoothes the top
and bottom surfaces.

Next,
the blocks run through a saw

With 10 blades
that slice them into strips

Measuring .3 inches wide
by 6.2 inches long.

Quality controllers
remove any strips

With inconsistent thickness,

Which are usually the ones cut
from the block's extremities.

The good strips continue on
to another area,

Where they undergo
a more thorough

Quality-control inspection.

A worker checks
the tops and bottoms,

Then lines them up
on a conveyor belt good-side up.

She also discards
any substandard strips

That may have slipped past
the first inspection.

The conveyor belt
then flips the strips over.

This positions the strips
underside facing upward.

Saws then cut two parallel
grooves through them.

These grooves are set .9 inches
in from the edge...

...And are just deep enough
to hold a thin aluminum wire

That'll connect strips together
to form tiles.

The next machine
dispenses the parallel wires.

A wheel pushes the wires deep
inside their respective grooves.

After every seven strips,

The machine cuts the wires
and starts new ones.

The 7-length strips
form a 6-inch-square tile.

An end-matching machine
now squares each tile

So that the four corners
are precisely 90 degrees.

Then it carves tongues
on two of the tile's edges

And grooves into the other two.

Four tile feeders then drop
tiles into an assembly machine

That inserts the tongues
into the grooves.

The machine then applies
hot glue

Which bonds the four tiles
into one larger tile

Measuring 12x12 inches.

The tiles are now ready
for varnishing.

Feeders drop them onto
the automated varnishing line.

The tile surface gets a sanding.

Rollers then apply
an even coat of varnish.

From there, the tiles
immediately pass under

Ultraviolet light.

This dries the varnish
within a second.

Then the process
repeats three more times

For a total of four coats
of varnish.

Workers then stack them in 10s,

At the same time
doing a final inspection

And discarding any tile that
has a less-than-perfect finish.

On the packaging line,

Each stack gets a label
and clear plastic wrapping.

An oven shrinks the plastic
tightly around the tiles.

Those four coats of varnish made
this parquetry superdurable,

And because it's real wood,

When the many years of wear
do begin to show,

You can simply refinish the
floor to its original splendor.