We talk about a lot of big structures on this
channel. But, it takes a lot of big tools to build the roads, dams, sewage lift stations, and every
other part of the constructed environment. To me, there’s almost nothing more fun than watching
something get built, and that’s made all the better when you know what all those machines
do. So, in this episode, we’re going to try something a little bit different. I’m Grady, and
this is Practical Engineering. Let’s get started! [musical transition] A big part of construction is just shifting around
soil and rock. If you’ve ever had to dig a hole, you know how limited human effort is in
moving earth. Almost no major job site is complete without at least one excavator because
they’re just so versatile. Depending on size, the heavy steel bucket of an excavator
can match an entire day’s digging of one guy or girl with a single scoop.
But excavators get used for more than just digging. They are a lifter,
pusher, crane, and hammer all in one. A skid steer is second only to an excavator
when it comes to versatility. These little machines are often equipped with a bucket, but
you can attach almost any type of tool as well. While there are often purpose built
machines that can do the same job, none of them can convert from loader to mower
to forklift to drill rig quite so quickly, and in tight confined spaces, a
skid steer is the perfect tool. A loader is one in many machines
meant to carry soil and rock across a distance. They’re often articulated in
the center for tighter turns and use a large bucket on the front for lifting and dumping. They’re meant to carry materials over short
distances, like the length of a construction site. Longer hauls use a dump truck. These trucks
feature a large open-topped tub meant to withstand repeated loading with various heavy materials. A
typical dump truck features a hydraulic cylinder that can lift the bed, tilting it at a steep
angle and allowing material to dump out of the back.. Since dump trucks carry heavy loads, lots
of them have auxiliary axles that can be lowered to distribute the weight over more tires and keep
the truck in compliance with roadway and bridge weight limits. Articulated haulers are dump
trucks used in off-road and difficult terrain. If you want to move a lot of soil
around a large construction site, another option is a scraper. Rather than
loading from the ground into a dump truck, these machines do it all in one. A huge
blade scrapes directly from the ground into a hopper. It’s carried directly to where it’s
needed and unloaded with a hydraulic ejector, and these are often used on large
embankments like for highways and dams. Another Swiss army knife of the construction yard is the backhoe that is kind of a
combination excavator and loader. Great for small sites where it doesn’t
make sense to have two pieces of equipment. And don’t forget the bulldozer that specializes in
moving material at ground level. They can’t move material over large distances, but they can spread
out literal tons with their tank-like tracks. The last stop on the digging train is the
trencher. There are a huge variety of styles and sizes, but ultimately they all specialize
in digging long holes for pipes and utilities. Many use a tooth chain like a
giant chainsaw for the Earth! By the way, there are about a hundred
different colloquial names for almost every piece of large equipment.
Different sites, suppliers, regions, and countries use different words for the same
machine; it’s part of the fun. One easy tip to sound like a pro is just to add the drive
style to the front of the name. It’s not a loader, it’s a wheel loader, or a tracked
excavator and so on. Now let’s hit the road. Roadwork is something we’ve all seen, and
while it can be a bit frustrating if you’re stuck in a traffic jam from it, roads might be
the largest engineered structures on earth. Our modern lives depend on them, and it takes
some pretty cool tools to get them built. A grader is technically an earthwork tool, but it’s used mostly on roadways. The extra
long wheelbase makes it well suited for precisely leveling surfaces and evening
out bumps, leaving a nice even grade. Once all that soil is in the right place,
it needs to be solidified so it doesn’t settle over time. A roller compactor
is the main tool for this job. There are a few varieties of these depending on the
material being compacted. Smooth drums are used for most soils and asphalt. Sheep’s foot and
padded drums have protrusions that work best on clay and silt. Pneumatic tire rollers are
best to knead and seal the surface. And a lot of roller compactors have a vibration
feature to shake the soil into place. An asphalt paver is the machine where
the road meets the road. Hot asphalt is loaded into the machine, which
spreads it into an even layer onto the subgrade using a screed. Many
paving machines have a wand that follows a stringline as a reference to the
exact elevation required for the roadway. If we’re talking about making a road out
of concrete, then the tool for the job is a slip former. It’s usually more efficient and
produces better quality of work when paving, curbs, and highway barriers are installed
continuously rather than building forms and casting them in batches. Careful control
of the mix makes it possible for a slip form machine to create long concrete
structures without any formwork at all. If we just added another layer of pavement to
the road every time it started to wear out, pretty soon, we’d have walls! Roads are
designed to be extraordinarily tough, so removing the top layer isn’t easy. That’s
a job for an asphalt mill or planer. These specialized tools grind and remove the
surface with a large rotating drum. The material is routed up a conveyor system and
can be loaded into a following dump truck. It’s actually fairly common to see multiple
vehicles following one another in roadwork like this. An interesting example is
the so-called paving train. On one end, we have a dump truck full of asphalt fresh from
the plant. This is loaded into the asphalt paver, which continuously lays a layer of asphalt that
is then compacted by one or more rollers. Workers on the ground also continuously monitor the
process to ensure a nice even road surface. Not everything at a construction site
is a machine with wheels or tracks. A lot of equipment gets hauled in on a trailer,
or is a trailer itself. A light tower lets you work outside of daylight hours, illuminating the
site so you can work at night or underground. An air compressor enables the use of lots
of tools on a job site, like jackhammers, sandblasters, and painting rigs. If you need
electric power instead of compressed air, diesel generators offer access to power
when grid service isn’t available. So far, the actual material we’ve seen is in bulk
like earth or asphalt. Often in construction, the materials we need to lift or move
are objects like girders or concrete pipes. For that you need a crane or
similar material-handling equipment. This is a pipe layer. The name is a bit confusing
since the workers that operate them are also often called pipe layers. And it's no surprise
what kind of jobs they do. They specialize in handling large sections of pipe and precisely
lowering them and placing them into trenches. A telescopic handler, or a telehandler
or teleporter is like an all-terrain forklift. The boom can have attachments
like a bucket, pallet forks, or a winch, and it telescopes to make it easy to deliver
materials and equipment exactly where you need it. If you happen to be the load that needs
elevating, then you’ll need a boom lift or its cousin, the scissor lift. The operator
of these controls the platform while standing on it, allowing for very positioning
of people that’s much more precise, and usually safer, than a ladder. Another
relative of the boom lift is a bucket truck which has a boom lift in the back, used a
lot of electric and utility work on poles. Stepping up in size, we have
road-rated all-terrain cranes. If you’ve passed a giant crane driving
down the highway, it was one of these, since most other types of cranes have to be
hauled to a site in pieces and assembled. As the name implies, all-terrain
cranes don’t require perfectly level, paved surfaces to get to work. However,
if your job site is particularly rough, you need a rough-terrain crane. The giant
rubber tires on these mean you’ll need to have them transported, but once rolling, they can
go where highway-rated vehicles might struggle. If the crane you’re looking at is mounted
on tracks, you’ve got a crawler crane. These heavy-duty cranes, while slower and bulkier than
all-terrain cranes and also requiring modular transport to job sites, can carry immense loads
and extend to even greater heights than any of the cranes we’ve seen so far. Most crawler cranes can
be configured according to the job with different lengths of booms, amounts of counterweight,
and extensions called jibs. A particularly fun configuration is for demolition where a crawler
crane might be fitted with a wrecking ball. Most can move from place to place, but not
all. Tower cranes use large counterbalanced horizontal booms with an integrated operator cab
on top of a large, well… tower. Like most of the cranes we’ve seen so far, these come in a wide
range of sizes but can be absolutely enormous, almost a construction project themselves
requiring other cranes for assembly. One way to build bridges uses a specialized
crane called a launching gantry. You may have heard the term gantry before for a
bridgelike overhead crane. These are in all kinds of industries. A launching
gantry uses the existing structure of the bridge as a base and often lifts
whole pre-built sections of the bridge. Turning from the sky and looking underground, let’s talk about a few
foundation-specific machines. The biggest and heaviest structures are supported
on bedrock or some deeper geological layer. Even if the usable soil is just clay for hundreds
of feet, sinking deep subterranean columns or piles below a heavy structure can keep it
from settling too much over time. One way to install a pile is to dig a very deep hole, place
a reinforcing steel cage in the hole, then fill the whole thing with concrete. This is the exact
job that a pile drill rig is designed to do. These large-scale drills are pretty closely related to
the machines used for oil and gas exploration. Another way to install piles is
to drive them into the earth, the job of a pile driver. Just like the name
implies, they repeatedly strike wooden, steel, or concrete piles to sink
them to the required depth. Speaking of concrete, there’s a whole
subset of construction machines that are specifically designed to handle, transport,
and place this important material. You’ve probably seen a mixer truck before, and I’ll
forgive you for calling them cement trucks, even though cement is just one of
the ingredients of a concrete mix. The truck can be loaded with dry materials
and water, and the mixing occurs en route to the job site, since concrete generally has
a limited time before it begins to cure. Concrete is often placed directly from the truck
using a chute, but that’s not always the easiest way. Concrete pumps are used to pump concrete to
job site locations that are hard to access with a truck, often with a huge overhead boom. Since
concrete is more than twice as dense as water, these pumps operate at extremely high pressures,
sometimes over 100 times atmospheric pressure! Finishing concrete is mostly a hand-tool job, but
there are some machines for big jobs, like ride-on trowels, that speed up the job of floating
a slab smooth once it has started to set up. Big jobs with lots of concrete might just
mix it onsite with a mobile batching plant. This is helpful if you need to produce vast
volumes of concrete over a long period in a way that would be too inconvenient or maybe
even impossible for mixer trucks to handle. Sometimes concrete needs to be placed on a sloped
or vertical surface to stabilize a rock face, shore up a tunnel, or even just install a pool!
The catch-all term for the various varieties of sprayed concrete is shotcrete (although some
pool installers might disagree). Shotcrete machines use compressed air to apply concrete to
all kinds of surfaces in the construction world. When projects require the installation of new
or additional utility lines in areas that are already built up, the traditional method of
digging trenches isn’t feasible. This kind of job calls for a directional drilling machine.
While these are technically boring tools, they are anything but uninteresting.
I actually have a dedicated video just to talk about how they work, and
specifically how they steer that bit below the ground. Go check that out
after this if you want to learn more. Hopefully there have been a few machines in the
list so far that are new to you, but if not, I have a few more specialized machines you
might be lucky enough to spot on a site: Fans of the channel might recognize a soil nail
rig, a specialized machine that drills out more or less horizontal shafts in an earthen slope and
then adds soil nails to greatly enhance stability. Jobs that require grout often use mobile batch
plants, called grout plants. You can even inject ground into the ground at high pressures using a
hydraulic pump to fill voids and stabilize soils. A wick drain machine installs prefabricated
vertical drains into the soil at regular intervals to speed up drainage of water
in clay soils which helps speed up the inevitable settling of the soil so
construction can get started faster. One option for repairing existing pipelines in
place without trenching is cured-in-place pipe lining. Inverting a liner impregnated with
epoxy-resin into an existing pipeline using air pressure essentially puts a brand
new pipe inside an old or damaged line. One of the least boring machines that
you’d be really lucky to see above ground is a tunnel boring machine. These behemoths use a
complicated face of various cutting tools followed by a material removal and shoring installation
apparatus to efficiently bore full scale tunnels! Obviously I can’t be exhaustive here. The
construction industry is just full of machines. There is such a variety in the type and scale of
projects that manufacturers are always coming up with new and improved equipment that can get a
particular job done better. And lots of industries outside of construction use heavy machinery,
including mines, oil and gas, and railroads. Let me know what you think I missed or if you
want a similar list within a different industry. But I think this is a good starting point
for any burgeoning construction spotter, and I hope it’s exhaustive enough that if
you see something that didn’t make the list, you can puzzle out its purpose on your
own. That part of the satisfaction of construction spotting anyway, so get out there
and see what kinds of machines you can find. I am obviously fascinated by the machines
that both build and make up our constructed environment, from the oldest to the most
modern. I think it’s interesting that a lot of the differences we see in vehicles
comes down to how efficient they are at doing a very specific task. For example, my
friend Brian from the Real Engineering channel just released a video all about maglev trains, and
he explains why there is only one commercial high speed maglev line in the world, even though
the technology seems ready to revolutionize train travel. I had no idea how travel time
factors into the economics of these projects. Maybe you’ve noticed what I have over the past
few years: my old favorite TV networks are just running reality shows, and the best video content
that I actually enjoy watching is being made my independent creators. There’s just something
different about a small team who is passionate about their topic instead of being told what to
do by some studio executive looking at ratings numbers. You can catch the Real Engineering video
on maglev trains on YouTube when it comes out eventually, but if you want to watch it right now
(with no ads), you’ll have to head over to Nebula. You’ve heard me talk about Nebula before. It’s the
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