Ihab Saad – Tractors and dozers
AI: Summary ©
The speakers discuss the various types of tractors and dozers used for earth moving jobs, including excavation and construction. They emphasize the importance of proper use and efficiency for the job and the need for proper training and development for employees. The speakers also go on to explain the various types of motion for the dozer, including scraper, dozers, and Ripper, and go on to discuss the use of the scraper and the dozer, as well as the production rate of the scraper, the types of blades, and the types of motion for the blade. The speakers also discuss the use of the scraper and the dozer, as well as the use of a cushion and the use of a cushion for various types of motion.
AI: Summary ©
Music. Hello and welcome to another class in construction
equipment. And today we're going to be talking about tractors and
dozers. We're going to learn about what their properties are, what
are they primarily used for, and then we're going to learn about
how to calculate the production rate for these different pieces of
equipment. So first of all, what are tractors and dozers? A tractor
is a self propelled machine used to pull a load or attachment or
push a load with a front mounted blade. So it's a machine that has
a blade in front of it used primarily to push a load, and it
can either be track mounted like crawler tractors or on wheels,
each one of them has its specific uses. Tractors with front mounted
blades are referred to as dozers, like in bull bulldozers, for
example.
They are quite versatile machines. So what are they used for? They
can be used to perform many earth moving tasks, primarily earth
moving tests, including backfilling trenches after
excavation is done through the excavators that we learned about
in the previous lecture, we can backfill by pushing the soil back
in that trench through the dozer clearing and grabbing it can also
be used to clear the site. If we have some rocks or some trees or
debris, it can push the debris aside to clear the site, creating
stockpiles. If we want to stockpile the soil that has been
excavated in one area for a while until it's ready for backfilling
again, then the dozers can be used for that excavating, although
that's not the primary use for double dozers, but as we learned
last time, if they are available, they can be used for that purpose,
pushing loading scrapers, as we're going to learn in future lectures.
When we talk about scrapers, there are cells that some self
propelled, scrapers that have their own engines, and there are
some scrapers that need to be pushed, even sometimes when they
are self propelled with a very big bucket. Then in this case, they
need to be pushed to be able to start moving, ripping compacted
soils or soft soft truck. We're going to see that one of the
attachment that can be added to dozers are rippers that can loosen
the soil or break soft truck, shaping slopes through some of the
motion and tilting of the blades, as we're going to see again in
this lecture, you can shape slopes and finally, spreading material.
If you want to elevate the level of the site by adding topsoil, you
can spread that material using a dozer as well.
Now, the decision to use
tracks or wheels for the dozers depend on the use and the
availability. So crawler tractors must be transported to sites,
whereas wheel tractors can be give driven from one side to another.
Of course, you cannot drive the crawler tractors on public
highways. They're going to rip the asphalt or the concrete, so they
have to be transported on the flatbed.
The crawler tractors are operated at slow speeds, six to seven miles
per hour, and they possess low ground pressure and they have high
traction. So they're not designed to be operating at high speeds,
whereas the weed tractors are operated at high speeds, up to 30
miles per hour, but they exert more ground pressure and lower
traction. Imagine if you're using that heavy equipment on a muddy
soil. Then in this case, maybe a crawler tractor is going to be
better, because it's going to distribute the weight of the
tractor on the tracks, which is going to be a line load, whereas
in case of a wheel tractor, is going to be a point load,
concentrated load under the tires of that tractor.
Tractors are not cost effective if distance to move material is
greater than 100 yards. So if that's the condition of death, if
that's the case, we're going to look at some other piece of
equipment to do that, task,
site, working conditions and scope of work determines specific size
and type of tractors to use. This is some part of your job as a
project manager, either to improve the job conditions or the site
conditions, or to look for another piece of equipment to perform the
job. Larger tractors are more productive than smaller ones, but
cost more per hour to own, lease and operate. So we always gonna
have the trade off between higher production and higher cost, or
lower production and lower cost. So there's a trade off between the
cost and the production. In this case,
we're gonna now start talking about the different attachments,
different kinds of blades that can be attached to the dozers. And
here, for example, we can see a full grown person about six foot
tall, standing in front of a blade. As you can see, that blade
is almost about 20 foot wide and about seven feet tall. And this is
quite normal on, especially in mines and quarries and so on,
pushing heavy loads in front of it.
It.
Another type is special clearing blades, which are primarily used
for land creating land clearing. So it's gonna scrape the top soil
and remove any debris or any obstacles and then push it in
front of it.
As we mentioned at the beginning of this lecture, dozers can also
be used to push scrapers. So here we have a scraper with a big
bucket, and then we're going to push it through a dozer to assist
it in its motion.
And another example, here we have the Ripper as an attachment that's
going to be used to rip the soil, whether it's tough, hard clay or
soft truck.
And now we were going to learn about the different types of
motion for the blade. If this is the bulldozer, and in front of it,
there's the blade, the blade can move this way, which is called
pilting, which is a vertical movement of the break of the blade
in that vertical level or plane. It's useful in cutting ditches,
breaking up soils in tough crust, and permits concentration of the
tractor, driving power on the limited length of the blade, so
you can tilt the blade and a small part of it's going to be in
contact with the soil, and then with the heavy power of that dozer
is going to be pushing on that tiny portion of the soil, so it's
going to create a very high level of power at that small point of
contact
another so this is the first motion. Is called tilting. The
second type of motion is called pitching. Again, here's the dozer
and here's the blade in front of it. The pitching is rotating the
blade in that direction. That pivotal movement allows the
operator to value the to vary the angle of attack of the blade
cutting edge with the ground and the pivotal movement of the blade
top towards,
towards or away from the tractor. It increases or decreases the
blade penetration by varying that angle. So that's the second kind
of motion, which is called pitching.
The fact the third one is the angling. Whereas, again, here's
the dozer, here's the blade, it's going to rotate in this way. So if
you want to push the soil aside, and the dozer is moving forward,
you tilt, you angle the blade this way. So it's going to be pushing
the soil sideways to create a clear path in front of the dozer.
So the blade is not perpendicular to the direction of travel. It
causes push material to roll off the trailing end of the blades.
Now, some of the blades can perform all three motions. Some of
them cannot. They're going to be limited to maybe tilting only, or
tilting and pitching, or pitching and angling, or, as I said, all
three of them.
So looking at the types of blades, we have four major types of
blades, the straight blade, something like this, which is
primarily used for excavation work, normally heavy duty, and it
can be tilted. It can be tilted.
It's good for penetration of hard materials, and may be equipped to
pitch as well.
The second one is the angled blade. It can be operated straight
or angled up to 25 degrees left or right of normal.
The blade can be tilted, so it can be angled and it can be tilted,
but not pitched. It's designed for side casting material.
The third one is universal blade. As you can see, it has wings on
the sides
that are canted to forward about 25 degrees, and it's efficient for
moving big loads over long distances, and it's used for
working stockpiles. The fourth one is the cushion blade, and that's
quite flat, as you can see, and it's going to be used for pushing
scrapers. So that's going to be the point of contact between the
front of the dozer and the back of the scraper.
Now to measure the production rate of the scraper, we're going to use
the generic equation, which consists of two parts, two main
parts. The first part is the cycle time. What's How long is each
cycle, and the second one is the number of cycles per hour. How
many cycles can we perform per hour? And that's going to be
measured in loose cubic yards per hour, contrary to the other
equipment that we have used so far, where we used to measure in
bang cubic yards per hour, the soil is, in this case, has already
been loosened. That's why it's going to be measured in loose
cubic yards per hour. And this is going to be dependent on the size
and configuration of the blade based on the four types that we
just discussed, the size of the tractor, the engine, power of the
tractor, and how heavy can that load be to push in front of it.
This is the material needs to be moved. So again, depending on how
far do we need to push the material, type and condition of
material to be moved. Is it? Is it loose? Is it in big chunks?
Going to put the heavy load in the trunk of your car, which creates a
heavy load on the drivers, which are the rotating tires the rear
wheel of the car, and that's going to enable the car to move. So
things like that, we're going to learn about them in our next
lecture. And this is basically the end of this lecture. I'll see you
in the next lecture.
You.