06x18 - Chainsaws, Pumps and Trains.

[bunniefuu]

[Dallas, off-screen] This is the
Science of Stupid, Engineering.

[Dallas, off-screen] Engineering stands
as a colossus,

straddling ignorance and
uncertainty.

It's both the apex of man's
accomplishments

and the bedrock upon which they are all
built,

or at least that's the theory.

This is the show where we look at what
happens

when the wheels fall off complex
mechanics,

then we examine what went wrong and
why,

with the help of such staples of
engineering

as expl*sive demolitions,

ladders and

water jet propulsion.

-[man] Oh [beep].
-[woman] Oh my God.

[Dallas, off-screen] So,
buckle up, because this is the

Science of Stupid, Engineering .

In this show we'll be looking
at post and lintel,

airfoils and trains,

but first...

This.

Whenever you set foot in your car

you are standing on the shoulders of
engineering giants.

The scientific developments that led to
you being able to just drive off go back

over 1,000 years.

Al-Jazari first described the crankshaft
way back in 1206, and even combustion

engines have been around a lot longer
than you might reasonably expect.

[Dallas, off-screen] Robert Street
patented

the first internal combustion
engine

to use liquid fuel back in 1794.

He'd be spinning in his grave.

This guy's injecting his engine with
nitrous oxide,

which is a bit like using hot

pepper sauce in your cooking.

It's exciting, but only a good idea if
you actually know what you're doing.

[Dallas, off-screen] Yes, engines need
to be treated a bit better than that.

At its essence a combustion engine is a
machine designed to turn chemical energy

into kinetic energy, and it does
that in a rather ingenious way.

By taking a fuel and air mix into a
cylinder,

and then compressing it using a piston.

A spark then ignites this mixture, which
causes a small-scale expl*si*n that

drives the piston down.

This is the combustion that
gives the engine its name.

The piston rod drives the crankshaft,

which translates linear motion into
rotational

motion to power the car.

Engines are designed so that thousands
of these

small-scale explosions take place every
minute,

but combustion can happen anywhere that
fuel, oxygen and a heat source meet,

so if the material strength of a single
component is overcome the results

can be, well, dramatic.

[Dallas, off-screen] This racing truck
has been tuned

so that it's working at the very edge of
its capabilities.

[man] Holy cow!

[Dallas, off-screen] Or maybe
just a little bit beyond them.

The expansion of gases is usually
contained by the piston cylinders,

but here the material strength of one of
the components is overcome,

making it much easier to have
a close look at the engine.

[man] Ready?

[man] OK, go.

[Dallas, off-screen] This car was in a
flood,

so before you start it you'll want to
check

that it has been properly drained.

[man] Okay, go.

[Dallas, off-screen] The movement of the
pistons here

puts the water that has seeped

into the engine under pressure.

Oh, that's what they mean
by a 'flooded engine'.

A smaller go-cart engine this time, but
it relies on the same engineering,

with all the same dangers.

[screams]

[man] Holy ****!

[Dallas, off-screen] Some part of this
combustion engine

has suffered a material failure,

allowing the fuel to ignite outside the
engine.

[man] Oh my God!

[Dallas, off-screen] And with plenty of
oxygen from the air it'll keep

on burning until the fuel runs out.

[man] I just caught my engine on fire.

[man] That is insane!

[Dallas, off-screen] Yeah, here's a tip
that's nothing to do with engineering,

if you do ever need to put out a flaming
go-cart hitting it with a stick

is of limited use.

This truck is fitted with a jet engine,
which still uses a chemical reaction to

get kinetic energy, but
in a much more dramatic way.

See what I mean, dramatic.

That looks bad from here.

I bet it's even
worse from behind.

Yep, that's worse.

There are some bits of engineering that
didn't just make life a little easier,

but actually managed
to change the world.

Trains are one of them.

Before the railways every town
used to run on its own time.

Trains not only made far away towns much
more accessible,

but also introduced the notion

of standardized time.

But it's hard to remember
how revolutionary they were,

especially if you're a commuter
beset by bizarre delays,

and like any huge vehicles,
trains are potentially deadly,

so never, ever play
near the tracks.

The engineering behind today's trains

makes them four times more efficient
than trucks,

and the largest is capable of pulling
more than 10,000 tons,

so how do they work?

[Dallas, off-screen] The locomotive
provides

enough tractor force to accelerate

the large mass of carriages
and cargo that it pulls.

Once moving a train has
a huge amount of momentum,

which means it takes a
long time for it to stop.

That's all thanks to
Newton's laws of motion.

And of course, trains are constrained to
tracks,

which means they can't move out of the
way of obstacles,

but they do benefit from extremely low
rolling resistance.

[Dallas] The very first steam train ran
in Merthyr Tydfil in Wales in 1804,

carrying ten tons of iron and 70 men at
a whopping five miles an hour.

Nowadays the fastest trains on a
national rail system

can run at over 200 miles an hour.

[Dallas, off-screen]
But even at lower speeds...

[man] Look, watch this ****!

[man] Oh, here we go.

[man] Wow!

[man] That's wild, bro!

[Dallas, off-screen] Trains
still have a lot of momentum.

[man] Damn!

[Dallas, off-screen] Luckily the driver
bailed before the train arrived,

because the average freight
train traveling at 55 miles

an hour takes 18 football
fields to stop.

That's more than a mile.

[man] Still dragging it bro.

[Dallas, off-screen] And of
course, the thing with trains is

they can't swerve.

Trains use tracks to benefit from low
rolling resistance, but they're

also constrained by them.

Another good reason
to stay away.

So, here's one nugget of engineering
wisdom, don't park on train tracks,

because if Newton taught us anything

it's that large masses don't like to
stop quickly,

and you will come off worse.

A bouncing truck and a lot of dust, but
what engineering fail is to blame?

[Dallas, off-screen] We asked you what
engineering fail happened here.

It's all down to friction.

When the crane lifts the container, it
should have released from the truck,

but one of the twist locks isn't fully
undone

and the friction between it and
the seven-ton

truck lifts and twists
the truck into the air

until friction is overcome by gravity,

giving that suspension
a quick workout.

[Dallas] Yep, it's time
for the tool station.

That part of the show where we guide you
through the safe

and proper use of a tool, and today we
are talking about chainsaws,

which should only ever be used by
qualified

professionals who follow all the
necessary safety precautions.

Because while we may have found better
ways to prepare wood on the

industrial scale, on the domestic level
experiments to find a better alternative

haven't been going so well.

[man] Woah.

[Dallas] See what I mean.

The largest working chainsaw, called
'Big Gus',

is just under 23 feet long and six feet
high,

which you'd probably think is far too
large

to be practical, and you'd be right.

A chainsaw's narrow teeth have a small
area,

creates high pressure when pushed
into

wood using applied force.

This allows the teeth to overcome the
material strength of the small amount

of wood in front of it.

But since the chain is continuously
being

driven in one direction it is
consistently

receiving a reaction force from

the wood that risks pulling the saw out
of the operator's hands.

When a professional tree surgeon fells a
tree,

they need to control where that
tree is going

to fall, and by cutting a notch

and narrowing the base of support you
can encourage

a tree to topple safely in your chosen
direction without injuring anyone.

[woman] Here it goes...

...and it's going
the wrong way.

[woman] Oh my gosh!

[Dallas, off-screen]
But it doesn't always work.

[woman] That was not good at all.

[Dallas, off-screen] Despite cutting a
notch to encourage the tree to

fall away from the house.

[woman] Here it goes...

...and it's going the wrong way.

[woman] Oh my gosh!

[Dallas, off-screen] The distribution of
weight from the upper branches means it

leans the other direction.

This isn't an exact science.

[woman] That was not good at all.

[Dallas, off-screen] Okay, always
remember that chainsaws are dangerous.

[man] You're kind of
scaring me with that saw.

[man] Careful, Steve.

[man] [beep].

[Dallas, off-screen] As is
not thinking things through.

What Steve has forgotten is that the
chainsaw is constantly receiving

a reaction force from
wood it's cutting.

It's okay if you're braced for this, but
as the wood moves in relation to you.

[man] Careful, Steve.

[man] [beep].

[Dallas, off-screen] You
could easily overbalance.

[man] You scared me man.

[Steve] Sorry!

[Dallas] You have a whole new set of
problems when it comes

to cutting leaning trees.

A leaning tree is in flexion, with part
of its trunk compressed

and part under tension.

A top tip is to always start
with a relieving cut into

the part under compression.

[man] If I die...

...someone come back and...

...kick Zooba in the nuts.

[Dallas, off-screen] Last words for the
ages,

but this guy isn't going to die,
even

though he has forgotten a relieving cut
on the compressed part of

that leaning tree,

which is a mistake.

[man2] Are you all right?

[man] Yeah!

[Dallas, off-screen] Despite being
flexed,

the trees own strength can
withstand

the compressive and tensile stresses
from its own

lean and the weight of the
other tree.

It's a marvel of nature

that he completely ruins,
which just goes to show

how careful you need to
be when using a chainsaw.

As with many bits of engineering we
regularly rely on,

the origins of the pump

are shrouded in the mists of time.

We know that Archimedes' screw has been
in use for over 2,000 years

and is still used today
to move fluids around in

water treatment plants
across the globe,

but pumps are useful
for so much more.

Like extracting oil.

The deepest oil well in history
pumped from a vertical depth

of over seven and
a half miles down.

Or putting out fires.

Impressive as fire hoses undoubtedly
are, the most powerful water pumps pump

at a rate of 60,000 liters a second,
that could fill an Olympic swimming pool

in under 42 seconds.

Much like the SodaStream, it's all about
the careful management of pressure.

[Dallas, off-screen] Truly one of the
marvels of modern engineering.

We all know that pumps a mechanical
device

is used to move fluids from place
to place,

but did you know that, amongst others,

you can get reciprocating and rotary
types.

Reciprocating pumps use pressure

with a piston-like back and forth action
to pull fluid

from a reservoir, such as air from the
atmosphere or oil from underground,

and then expel it in
a given direction.

Whereas some rotary pumps
use centrifugal force from

a spinning wheel to move fluid
from the inlet to the outlet.

In both cases pressure can be amplified

by either increasing the power to the
pump or

decreasing the width
of the outflow pipe.

Well that's me
suitably pumped up.

Let's see some
engineering in action.

A waterlogged hole in a muddy bit of
Russia,

the perfect place to test a
motorized pump,

or drill or something.

Water is being directed into the
cylinder,

building up pressure, but in
this case,

it was all a bit too much.

Petrol is typically pulled from below
ground reservoirs

by an above ground suction pump,

before it makes its way through
the dispenser and into your car.

It is idiot proof.

As long as you remember to remove that
hose before you drive off.

Don't worry the attendant walked away
and lived to pump another day.

This cow is operating
a reciprocating pump.

The back and forth action of the handle
drives the piston,

which pulls water up from underground.

And if she can get a handle of this then
I'm pretty sure you can too.

[Dallas] If the sign of success for any
feat of engineering is longevity,

then there are few things that can rival
the humble post and lintel.

[Dallas, off-screen] Stonehenge was
built

around 5,000 years ago and is still
standing today.

It's a classic example of post and
lintel in both senses of the word,

where horizontal beams are
held up by vertical posts.

The biggest stones weigh
an average of 25 tons.

It's a very solid way
to build a structure,

unless you
decide to do that.

The post and lintel, or trabeated
system, wasn't just popular in late

Neolithic Britain, but as a fundamental
principle

in everything from Ancient Greek

architecture to traditional Japanese
buildings,

and it is still the most popular

engineering solution to holding up roofs
and doorways today.

[Dallas, off-screen] The
downwards force of the load is

transmitted via the lintel
to the post on either side.

This puts the posts under compression,

while applying a bending force to the
lintel that

puts the bottom of it under tension.

With sufficient material strength the
structure is good at transmitting

and withstanding
downwards oriented forces.

So, it is all about compression,
tension and material strength.

[Dallas, off-screen] The
engineering sounds solid.

In other words, columns are a
great way to hold up a roof,

as long as you leave
those columns alone.

By knocking out the bricks of this post

it no longer has the strength to
withstand the

compression from the roof,
meaning this guy

is no longer employed
as an archaeologist.

The posts here are rock solid, but there
are two parts to the trabeated system,

and you do need both.

That lintel is under load, and it's
supporting its own weight,

the weight of that rubble

and him, so cutting through
it is a terrible idea.

When you begin to keep your eyes open

for posts and lintels, as I'm sure you
will,

you'll start to see
them everywhere.

Like this high bar.

The rigid beam is experiencing a bending
force and transmits force to the posts,

so needs to be solid.

Okay, that one's a bit rusty, but in
general trabeated systems are very good,

especially at withstanding
downwards oriented forces, see.

When people look back in 100 years or,
so I think they'll probably pinpoint

two technological advances
that define our age.

Mobile Internet
and cheap flights.

I had an extremely
cheap flight recently.

I couldn't work out why it was such a
bargain until I got to the airport.

[Dallas, off-screen] And they made me
pay extra for my baggage, huh.

Airplanes, like pretty much allaircraft,

make use of airfoils, like the shape of
these

helicopter blades, specifically
engineered

to generate aerodynamic force,

allowing tricks like that.

Heavier than air flight is surely one of
the greatest engineering feats of the


all thanks to the airfoil.

[Dallas, off-screen] Simply put,
airfoils are shapes that

generate aerodynamic
forces when moving through air.

Those aerodynamic forces
consist of upward directed lift

and backward directed drag.

The relative proportions of lit and drag
depend on the airfoil's angle of attack,

that is its angle relative
to the incoming airflow.

General speaking, as speed and angle of
attack increase lift increases,

causing this plane to take off.

Well that's airfoils.

So ingeniously effective that amazingly
there is still a debate about exactly

how they generate lift.

Is it Bernoulli's principle of fluid
pressure,

or Newton's third law of motion, or
both?

It seems nobody is quite sure.

What we do know though is
that they definitely do work.

This hang glider's wing provides lift

from that large updraft simply bytilting

it to increase the
angle of attack.

Now, how are you
gonna get down, hey?

Airfoils make
flying a lot easier.

Good news when you're attempting a
mountain landing, as they can be tricky,

although it's hard
to get it that wrong.

This looks a lot safer.

Yeah, well I did
say it was tricky.

[man] Whoops.

[Dallas, off-screen] He throws the
glider at a steep angle,

which means the lift force from its
wings sends it into a loop.

I wonder if he'll say whoops again.

[man] Whoops.

[Dallas, off-screen] Great.

[Dallas] The American academic,
Randy Pausch, once said,

'Engineering
isn't about perfect solutions.

It's about the best you can
do with limited resources,'

but as you can see,

sometimes the best you can
do isn't really good enough.

[music plays through credits]

[man] Careful, Steve. [beep].