MINING EARTH MOVING MACHINERY/ BASIC WORKS

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 Hello everyone

 today we're going to start writting about the fundamentals of earthworking

we've been write about how much equipment costs and we've been writing about  how to describe the soil in terms of its type and how to read the geotechnical report

what we need to read about now is the fundamentals the basics of earth moving how do we take our  our flywheel

horsepower coming off of the engine converted into useful work and what do we want to do with that

useful work anyway and so we're going to spend some time this  this bolog going through

I don't know why it did that see it drives me crazy i'm gonna spend some time going through

 today's presentation and then there'll be another bolog that follows up that goes through some of the mathematics that come up towards

the end of determining how vehicle what amount of work a vehicle can do

so we're continuing on in our bolog and the first that we're going to talk about is

fundamentals of earth moving earth moving is moving materials from location a to location b

and  you might want to know why you want to do that but usually it's because the site that you're going to construct

on whether it's a highway or a building site or what have you is probably not at the elevation that the designer needs it to be at.

it's certainly not flat there's areas that have to be reduced in height

those are cuts and there are areas that need to be brought up to an elevation those are

called fills and so we have a cut and fill operations

or other earth moving where we're taking the existing soil that is  that is present at the time

that the site is being developed and moving it around we may also

be bringing in soil that has certain engineering properties and we'll write about that in a bolog,

later on when we write about compaction when we want to bring in the soil because our local soils are not strong

enough or stiff enough to support the structure that we want without it having to move

around so sometimes we build a building pad you know we've got a site that is that

is lower than we want it to be and we want to raise the building up and so we have to bring in phil to do that other times we want to

do a cut for example i want to put a beautiful building somewhere but there's

a hill in the way so i'm going to cut that hill down so that it's flat all of this is earth moving and it

it involves several operations it involves excavating picking up the

soil with a piece of equipment it may involve loading that soil into a haulage vehicle

either way we're going to haul it or move it we might push it with a bulldozer we may hold it in

a dump truck where we get to a fill operation we need to spread the

soil we need to compact the soil and then we need to grade the soil

all of those  operations are going to be done with machines i mean you could do it with shovels if you had infinite

time and money but since that's never the case  you're going to use the  the power we have been able to

generate from burning fossil fuels and and now some of these vehicles are becoming electric

to do the work that that we need done

we need to determine how productive this is going to be because we don't get to build the structure for whatever it cost

us. we have to put a bid in at the beginning of the project in order to do that we have to be able

to estimate our capacity without being on the job what is that going to depend on it

depends on two things what soil that we're moving that's why we talked about our geotechnical report

and how we're going to move it in other words what equipment we have available and in order to do that we need to read

the performance characteristics of those vehicles now we did talk about

physical characteristics of soil and how we have fine and coarse grained soils how we have

soils that are that  are going to  going to have different moisture

contents we talked about bulking the difference in density between the bank

loose and compacted and if you recall the bank is what's sitting there naturally loose means it's been dug up

dropped into a haulage vehicle or is being pushed along a grade by a dozer

either way it's going to increase its volume the mass won't change and then when we go to compact it we

will either be compacting it to be denser or less dense than the base was and so

we have to be very careful when we say cubic yards from this point forward we're going to have to indicate in what

compaction condition the material is because one bank cubic yard may be 1.3

loose cubic yards and maybe 1.1 or 0.9 compacted cubic yards so we're going to

start writing  about the characteristics of the equipment how to read the equipment

processing charts and how to determine how much work can get done so let's suppose that we come to a site

we have going to have certain operations that need to take place the first is clearing and

grubbing which refers to the removal of trees and vegetation and grass and anything else that happens

to be sitting on our area we're going to build of course some of these the trees if

they're lumber is valuable we're going to recover that uh pro if not we are going to move

materials around some of those times those materials are composted in times past and sometimes in other

places  they're burnt in sight in situ but they one way or the other .they have to be

removed and that's because organic material whether it's old organic material like peat

very recent organic material like the the trees you pushed over with a dozer

they're going to change with time and we don't want them in our building foundation or under our pavements

so we want to get rid of them we also want to get rid of the topsoil

topsoil is a black dirt lots of other things it contains some organic material it may be

it may be a silty soil it may be a sandy soil but it's going to be full

of organic material that's usually undesirable almost always

undesirable unless you're using it to to to grow something

often if you drive by a construction site you'll see a heap of topsoil that's because topsoil has a

as a value and we'll sell it to people and so you can include that in your bed you determine how much you recover and

how much it costs to put it up into a pile and then you can have that as part of your operation

or uh or you can treat it as a windfall profit either way you can you can end up getting rid of

that material so it's important to know what its quantity is in addition even if we're not even if

we're just flattening a relatively flat piece of soil we're going to have to excavate for

utilities water sewer power anything that we want

to be running underground the sewer is not a pleasant thing to have moved through an open channel

so we don't let anybody do that anymore similarly we don't want our wires to blow down

or we definitely want to be able to carry storm water away from the site when it rains so we're going to need

some some deep excavations and here in in wisconsin and in many parts

of the world we need a foundation that sits below the frost line the depth to which the

soil will freeze because soil will expand upon freezing and some soils will really expand upon

freezing if you give them a source of water below so we need to make sure that our footing

the or whatever else we're using for our foundation element is below that frost line

so i said we sometimes when the site is  is

being graded and cut and fill we may have a situation where the

excavated material is greater than

the amount of material that needs to be put back in compaction

and that's called a waste site we're going to have waste soil that needs to be put somewhere similarly sometimes we don't have enough

soil on the site and we need to borrow it from somewhere else and we call that a borrow site

we're also going to want to backfill utility trenches around the foundation and compact fill material we're going to

have to do that we're going to have to grade the site to meet contract requirements and we'll

have a drawing i think i have a good drawing that shows you what happens when you grade the site you have two contours you know a contour

map that shows you the local elevations one is what it looks like now and the second is

what it's going to look like when you start to build the building or when the building is turned over to the owner

that allows us to calculate how much soil has to be moved but we'll save that for another day we're

going to need to spread and compact soil in areas to be paved

and typically in a pavement structure we're going to be bringing in high quality

fills immediately below the pavement layer we're going to want 100 percent crushed um

rock  we will want it to be well graded and we want some fine material in it so that it becomes what engineers

call a trimmable compactable material in other words i can compact it it's not clear stone but i can also trim

it so if i get it too high i can come in with a blade and scrape it off without it disturbing too much and then

finally in those areas where i'm going to put landscaping or grass i might need some topsoil

and so i mean i will need to know what that quantity of topsoil is so that i don't sell it

and if i have to import more so that i include that in my bit

so let's take a look at some pictures here is some good old-fashioned clearing and grabbing

we've got uh an excavator up in the uh a ho

proper term up in the upper left-hand corner it looks like it's digging some stuff out on the right hand corner

on the upper right hand corner we have a tractor with a blade that's uh used for scraping up

soils and probably pushing over trees on the lower left you can see a bobcat a skid steer a

small small front end loader that has a cutting blade and that's been removing

the top soil and on the lower you can see we're converting large trees into small chunks of material so clearing and

grabbing a necessary operation because we don't want to see this uh to build on this

stockpile as in the lower left you can see the topsoil we're taking out it's not going to give us a very good foundation

on the other hand sometimes we just need a little narrow excavation here looks like we're putting in uh ductile iron

pipe which is almost always uh drinking water or the uh and so that drinking water is

being placed into a trench and you can see there is a hoe on the uh at the end of that trench

and it's getting ready to pick up that pipe you can use them as cranes as well as about that and inside the trench is a trench box

and so that trench is going to have to be not only dug out you'll have to know how many

hours of of uh excavator it takes per um per uh foot of

travel of the trench but you're also going to have to once the pipe's in place fill it back in you won't need as much

soil and in some cases you can't use the same soil because it isn't the proper soil for

betting the pipe and preventing it from breaking when it settles here's a

here's a step footing in a building and you can see the trench has been cut

so that um and the footing is just stepping up so that uh it's a sloped portion of the

structure and in this case we're going to place concrete in those uh forms for the footing we use the lower

piece of soil for the bottom form and that will give us our footing we're going to have to

back fill fill in that space once the footing and the wall are in place

here's a happy gentleman working in a happy trench that trench box prevents him from

worrying about having an accident because even if the soil was to slough off it's

unable to crush those large tubes that are acting as as columns to

prevent those two layers from coming together and i can't see is that mountain dew or  dry

but anyways and then here you can see here's the strip footing for a building on level

but the strip footing is down below the elevation uh finished elevation of

the slab which is likely what we're seeing there and so it has had to be dug out we're

going to place the footings and then those uh stubby walls with the protector or

stubby bars coming up with the protectors we'll get foundation walls on them but then that's all going to have to be

backfilled some of it inside and some of it outside of the building we need to be able to

tell ourselves that we're confident how much that's going to cost based on what equipment we try to do and

how much we're going to move per uh per unit time here we're placing some utilities this

is  this is not in uh in north america to remind you that we see a lot of places  that do

construction and in those areas of construction we have the opposite

this  gentleman uh here in the in near the center towards the bottom of the drawing is in

a very risky condition if that soil was to fail uh the wind would be knocked out of them

and no matter how hard they how quickly they dug they would not be able to remove him from the trench don't do that

so taking excess material away that's not needed for backfill

we have several operations up above in this photograph you can see there's a

hole it's picking up material and it's putting it into a

shaker that is shaking and separating the particles by size some of

them are going in one direction and some of them are are going in another and those 

though that type of sorting is done when we can when we can make money out of selling

one of the particle sizes here's the other way that's being done and the key to

look at this photograph is we're picking up soil with that hoe and we're putting it into a haulage truck but do you see that the

hole make sure it's sitting up at a higher elevation than the truck it's astonishing over time how much

faster that operation is if the truck bed and the tracks of the hole are at

the same elevation here's another one put some soil

into another college vehicle you can see that this is not an on-road haulage

vehicle it has a directional tires that's why those chevron semichevrons on

the tires are pointed in one direction and the soil is pretty loose and then you know do lots of other

things that if  you if you want you could use a bucket excavator or a bucket 

elevator rather and move  soil out by loading it and that has been being deposited

into a haulage vehicle and sometimes you have to do that when you can't get heavy equipment in place

backfilling happens almost every project even the smallest of projects this is a

this is a ride on bulldozer fully tracked a rubber track so perhaps

not not as great as we'd want it to be and the tracks are non-uni are non-directional because the chevrons

on them are semi-chevrons are straight and we have the blade canted to one side

and as it advances forward it pushes the spoil that we use for excavating that trench back into the hole and so

that's a piece of equipment it's going to have a certain productivity it's going to cost a certain amount of money and it's going

to be able to do a certain amount of work here's a backfill looks like a

residential house that seems to be that fiberglass escape window in the basement and you can see

the excavator is moving soil from a pile and dropping it and hopefully we're compacting it

and then here's a  another one we have a front end loader that's picking up soil and dropping it

into the into the trench what does it mean to compact material

and compacting material is pretty straightforward we take the soil and we press on it so that the particles

get closer together the net volume drops and the strength of the soil increases significantly

we'll have a  bolog i get this week that write about something called the proctor curve and the proctor maximum dry density is a

target that we use to determine the strength of the soil here this illustration is showing you a

 a roller it may be vibratory which means the rollers are going up and down

or it may be smooth but it's compacting soil this type of roller is used for for coarse-grained or fine-grained

non-cohesive soil like sand or gravel there uh we need to be careful because

the soil will push in all directions if you were to roll

that roller uh in that area they're looking at two-thirds of the height of that retaining wall on the other side

um you are then putting a very large force much larger than it was designed for

onto the wall and the footing so typically there we'll do hand operated light equipment a plate tamper

or maybe a walk behind plate roll or a walk behind a roller but if that larger vehicle gets in you

can cause that structure to fail you can also  imagine that's not a retaining wall

if that's the foundation wall for your building you may push that wall in during

compaction so you want to stay very far away at least two-thirds of the height away

from the soil for fear you surcharge it

this is an example of a poorly compacted material

if you dump a large amount of material into the excavation and then roll over

the top surface you will densify the top surface the effect of density typically we like to

see you know 12 15 18 inch lifts and that will be information

provided to you by the geotechnical engineer in this particular case if we drop in

four feet we can roll across it with a roller and we'll only densify that that soil at

the surface what will happen over time is the looser soil that is below

will compact you know with the action of rain uh with the action of loading and then we will get uh

settlement and some of you may have seen that in often residential driveways will come

up nicely and then they'll have a dip right when they hit the garage because they don't compact the soil very well in residential

construction there's a piece of uh of walk behind equipment's being used to

uh to compact uh soil bedding around or soil not the vetting this is the uh

side of a uh that's a what they call corrugated um

uh rubber or corrugated plastic pipe so that's a storm sewer and that piece of equipment

is a light piece of equipment it can work right up against the edge and you'll notice there's little feet

projecting from the drum it's not smooth like in the photographs that drum is in fact a sheep's foot

which will help us to knead the soil and as good at compacting cohesive soils

clays and of course there is the proverbial jumping jack of which is allows you to exert a force in the down direction usually gasoline

or a gasoline power that net are now four-stroke used to be two-stroke engines and that will

act to compact the soil as well you need to grade the site in addition

to compacting it and that grading operation includes several pieces one of which

is the use of a of a grade a grader

which is in the left hand side you can see it has a mortar board a blade in between the wheels and that

can be used for fine grading for smoothing out the soil

the upper right hand corner is a very large uh fill on a cut and fill operation and you can see

all the important parts that are going on there's a scraper that's the vehicle at the top

that's headed we're going right to left there's some dozers up in the upper right hand corner

there's a water truck down uh down the grade watering the

hull road there's another scraper you can see by that little gooseneck that curve we'll talk about

scrapers and then a grater and the back of that grater has a bunch of teeth

you can see it looks like a claw and that's a uh that can be used to rip the soil up loosen the soil or decompact it and in

the bottom right hand corner it's a gentleman using a gps uh surveying equipment to determine

what elevation they're at now and he's helping to control the fill operation

what happens today is we can get these vehicles to have their own gpr on them or gps

that tells them where they are and they know where the blade is relative to the gps and they can do all that fine

grading by themselves once we  once we've excavated the soil from the

places that uh we don't want them we go put it where we do and uh this is a this is an operation

that is  doing two things one is  it's spreading the soil and you can see the soil has been spread out

in layers there's then a sheep's foot compactor that's that vehicle in the middle with the projections you can see

the the texture that it leaves in the soil and when those feet those fingers push into the

soil it compacts them down but also to the side very effective it needs it like needing bread

very effective for compacting clay type soils then there's a smooth roller

that is uh that is doing the finished grading to make it smooth enough to work on that white and

gray vehicle is a mill and you can see beyond the

mill there is white or sort of a gray material and that's portland cement has been put onto the surface

and it's working the soil and the portland cement together it's called cement stabilization

it uh improves the capacity or improves the performance of the soil so um and this is a this is

a very interesting operation there's a lot of things going on in that one photograph

here's a highway uh operation where the uh the trucks come in and they dump material out and they dump it in

in a pile or several wind road piles and then a dozer is used to blade it flat

and a roller comes in and rolls it that's a very common operation

topsoil spread by dozers sometimes you can uh you can rig equipment and this is a

residential on this uh on the skid steer vehicle again this is a dozer with a uh

with a bucket uh it's a attract loader and uh here's a maze gets here again

with the bucket on it being used to place top soils a pretty straightforward operation in

order to understand how much work we can do we're going to need to see

how we turn flywheel horsepower into useful work and

it's going to depend very much on how our vehicle is designed

to transfer that power flywheel horsepower into motive power the power to move

and to push or pull and that's going to be very dependent on tract

versus wheeled vehicles a tracked vehicle does not have any rolling resistance so we're going to put that

aside for a second we'll show you how to handle track vehicles and the first piece of equipment we'll look at is

bulldozers or dozers and dozers are almost invariably tracked for uh for a very

good reason that's because they're the first people in there rolling resistance can be a

problem but rolling resistance refers to the fact that a tire

in soil is pushing in all directions and the part that pushes down means that

we penetrate into the ground and in order to roll

forward or in reverse we have to be perpetually climbing a hill that hill is the hill that's

created by our vehicle

that that is created by our vehicle having to

go uphill you can see here's a grade that this tire is actually

climbing and that's what we're going to we're rolling resistance we're going to uh differentiate from our grade

resistance but it's essentially the same thing the vehicle even on a flat surface is

attempting to climb similarly the uh there's uh friction in

the wheel bearings and that can make a difference and so we're going to look and see what we can

get and the rolling resistance is going to be expressed as the pounds of resistance per ton of

gross vehicle weight and  you've all experienced this if you have

 a four-wheel drive low geared pickup truck it can still get stuck in

the snow because it has to perpetually climb out of the snow and your rolling resistance

gets very high the gross vehicle weight again is the

weight of the vehicle without any load plus whatever load it's carrying so loaded vehicles are able to uh are able

to ha to have a higher gross vehicle weight therefore they have a higher rolling resistance

so our rolling resistance

is going to be r plus 30 pounds

per ton per inch of tire penetration for example if you are out on site and

you see that your tires are penetrating two inches into the material then you'll know that your that your

rolling resistance in pounds per ton is going to be 40 or 30 depending whether you're using

a radial or dual tire so probably 30 plus 30

mult pounds per ton multiplied by three inches of tire penetration

gives me 30 plus 90 is 120 pounds of rolling resistance per ton

sometimes and in every case when we're bidding it we don't have a clue because we're not

on the site yet so how much tire penetration are we going to get we're going to find out so we're going

to have to estimate it and you can see there's a table below here table 6.1

it's our representative rolling resistances for various types of surfaces if we're

operating on asphalt or concrete a rolling resistance is 40 pounds per ton

very very stiff hard non-penetrable surfaces if we're operating in loose gravel or

loose sand it could be 200 pounds a ton um some of you may have had the experience

of running on the beach and where the beach is dry and loose

most of your effort goes into pushing the particles away not pushing yourself forward as opposed to a smooth hard surface

of  sand where the water is it's only 50 pounds per ton and that's why it's harder for you to run

on loose sand and for that matter harder for vehicles to run on loose sand so we'll talk about some aspects of that

but this is what we're going to need to understand is our rolling resistance is a function of the tire

and how stiff the soil that we're pushing against this

and this  this can give us a a resistive force how much force

do we need to overcome and that resistance force is the rolling resistance multiplied by the gross

vehicle weight which is the weight of the vehicle plus the weight of the load

and this is critical because if you use a vehicle that is too powerful

for your site you get the work done but it might cost too much

if you use a vehicle that is underpowered it's either going to be operated

unsafely or it's not going to be able to keep up with your production requirements and that's going to cost you as well so

understanding these things is going to be important in meeting our requirements of management

then of course we have one we're a little bit more failure familiar with and that is the grade resistance

the grade resistance is the force of gravity that is pulling down the slope as you're moving up

it's also the force of gravity that's pushing you down the slope as you're moving down and so we refer to

that as a an assisting or a retarding grade an assisting grade

goes down and a and a retarding grade goes up they're usually

expressed in terms of a percentage which is the number of feet

that you would go up as you go forward for example if you have a five percent

slope that means every hundred feet you go up five a minus two percent slope for every 100

feet you roll forward you're going down two and so we can

we can convert this grade resistance using a little bit of

geometry into a pound per ton resistance or a

force resistance by assuming that we're going to get 20 pounds

per ton per percent slope in other words if we're going up a six percent slope and our

um our grain resistance would then be uh 20 pounds multiplied by that 20

percent slope which would be a 400 pound force opposing motion we're going down

that slope then it's 20 times 20 percent which gives us a 400 pound force pushing us

forward in addition to anything the vehicles do okay and grade resistance affects all

vehicles the rolling resistance is only for rubber tires the tracks don't flex the tracks don't

care if they penetrate but rubber tires do

we can convert that just like we did with our rolling resistance into a force

grade resistance multiplied by the gross vehicle weight and that will give us our resisting force if you have a vehicle that's too

powerful it costs too much if you have one that isn't powerful enough it also costs too much

sorry let's see we get this in here

so we have to become the total force the total resisting force

acting against forward or reverse movement is the sum of the grade resistance and

the rolling resistance for tracked equipment the rolling resistance is equal to zero

so the vehicle must be able to overcome the force of this

resistance in order to move and perform the desired task

if you use the wrong pieces then you can get into

trouble here you can see  a tractor which is a crack fully track tractor

and it's hauling stuff and it's going uphill and it is not happy

it's pulling a scraper by the way which we'll talk about but you can see here it's making it

but not as well as it could we're just about to encounter some additional grade

y

you can see that cat that caterpillar tractor did not like going up that slope

because it's under power

and he had to change gears again with a delay

and now he's wheeling away someone looking for their lost cat all right so you can see that's a little

bit of a problem

all right that's that is  what we wanted to cover

in terms of vehicles now how do we know where all these things are it's all well and good for  it's your  to

say make sure you have a power vehicle that's powerful enough but not too powerful and that's  that's an easy answer

because we can go to the manufacturer and we can say what's the capability of you know the kevco x 500 tractor

and it depends whether it's a wheel tractor or a tracked tractor but we're going to go through these two concepts drawbar pull

and rim pull and the easier one is drawbar pull so we'll do it first at the back of a dozer is a bar

to which you can attach a hook and you can tow things and that is the draw bar so we talk

about the draw bar is the ability of a cracked

piece of equipment to move itself and its load if the load is like we saw

uh with that vehicle trying to climb the hill a scraper or if the load was the vehicle rates are right at the beginning

which is pushing some soil those are the loads and that's the drawbar pull

the manufacturer will provide you with information on the performance of

the vehicle that gives you the available drawbar pull at various speeds and gears

under standard conditions which means at sea level and you can

use these charts to determine how much work a vehicle is going to be

capable of doing this is a drawbar pull chart for a

caterpillar d6r with steering clutch and brakes this 

curve is very useful we can compute

there is total resistive force which would be the grade resistance

and in this case only the great resistance and the weight that we're needing to

push once we have that total resistive force

we assume that we need a drawbar pull of that force in this case we need eight

pounds per thousand tons of gross vehicle weight so not not a very

large number we then mark that force on the vertical axis

draw a horizontal line until we intersect the maximum speed and it's

that those lines are the capabilities of the vehicle in first second and third gear you'll notice that

third gear gives you the highest speed the first gear gives you the largest

drawbar pull and that's why we gear our vehicles so that when we need a lot of power we can

transfer it to the to the engine in such a way

that it pushes hard in other words in other realms we can change the gearing so that

it doesn't push us hard but it's moving faster so if we if we look

in this case if the total uh resistive force is eight thousand pounds

draw a line until we hit the gear that we wanna also take the highest speed of course and we get four point uh about four

point executable four point six miles per hour and uh we'll use imperial units or a u.s

common system then it's also given in in kilograms so that you can use si

and this type of curve is available for all sorts of equipment this one in

particular as i said happens to be a d6 r caterpillar

tires are a little bit different rim pull

is the power available to move a wheeled piece of equipment and that is the pushing force

that is available to the tires on the operating surface it's a power

expressed in pounds of force that's available at the rims of the driving wheels

you need to again get manufacturers manufacturer's information and it's readily available particularly

if you're buying them you'll be surprised what they'll give you even hats that say caterpillar

and these charts can be used to determine the capacity so what do these look like

in these particular cases we are going to want to measure our

total resistance in terms of grade and rolling resistance

expressed as a percent or our maximum force

so right now we're going to use the maximum force method but we're going to also talk about very quickly

when we deal with wheeled vehicles how we convert everything into rolling resistance or an

equivalent total resistance rolling and grade resistance so how do we do it we compute our total

resistive force in this case 5000 pounds we know that we need

a resistive force of at least that large we go to five we move across until we

intersect one of the gears and then we drop a vertical to tell us what our speed is

and so we're going to end up with 5000 pounds of drawbar pull sorry 5 000 pounds of

rimple and we're going to be able to go about 21 miles an hour

and uh we're also going to be able to correct and then take a look

at another piece of information and that is the you can see there's a dotted line that

is marked e and another dotted line that's marked l those are the empty and loaded to the manufacturer's

capacity rating of the vehicles

if you don't have manufacturing information you can make some assumptions

we can use the assumption that the maximum speed that the vehicle is going to be able to perform at

is 375 multiplied by the horsepower uh at the flywheel leaves to the

flywheel horsepower multiplied by gear train efficiency and divided by our required rim pull in a

required effort to do work the gear train efficiency is a function

of gearing ratios and somewhere between 0.7 and 0.85 is where you're going to find but

there are very few pieces of equipment that you would need to you would need to do this for and we'll

provide you with i'll provide you with the curves as we go along there is a

there's an effect of altitude the higher up you go the less oxygen there is therefore for a

given a given throttle position and a given gearing you do less work we'll have a dra d a rating or d rating

factor a factor that says well you're 2 000 feet above sea level and so you need to reduce your

uh horse horse fat your flywheel horsepower by that uh amount and you will be able

to show you how to do that when we're talking about vehicles but that effective altitude is important to take into account

although um we typically um unless you're unless you're up thousands

of feet above sea level it's not too bad so let's take a look

here we have the manufacturer's equipment for a for various

types of bulldozers this is uh this is from the uh this is from

caterpillar again these are for uh for various engines we can take a look and you can see

let's go to what we were looking at a d6r the d6r series 3 at

up to up to 2500 feet above sea level you can use 100 of the

capacity up to uh continuing over

we don't start d rating the material or the vehicle rather until it's at 10 000 feet above sea

level so very frequently  we're not going to have that problem but we'll also want to look at the

at the engine and if we look here this table up in the upper right hand corner is a 545d

diesel engine made by caterpillar and it's telling you that uh you don't have to derate it unless

you're at 9804 feet

the last thing that we need to consider is how much work can we actually do um

we've all had this had this position we have a very high horsepower vehicle and it's penetrated into the snow so

it's going slower and put it into a lower gear and then it gets stuck because it can't climb up something and

then as the wheel turns the simplest way for the vehicle to

to do work is to turn the wheel without moving the vehicle

we're onto a patch of ice and the harder we spin the tires the more ice we

generate not a desirable condition and as a consequence

we are not able to get any work done and that's because our coefficient of traction will tell us

how much of the how much work we can actually do because if our coefficient of traction

multiplied by the weight of the vehicle is less than the force we're trying to exert

then we're not going anywhere the the tires or the tracks will slip on the surface and then we will have no

drawbar pull and so our maximum drawbar pull or maximum

rim pole that's available is going to be equal to the gross vehicle weight on a driving

wheel or a track multiplied by a coefficient

of traction c sub t and you can see again from the caterpillar handbook on

the right hand side there's a lot of things that are obvious

to us let's take a look at rubber tires on concrete we have a coefficient of traction of 0.9

it's very easy for us to to use almost all of the gross

vehicle weight of the vehicle to do work if we look at

dry sand it's only at two zero so it's packed snow at point

two zero but what is interesting is wet clay

where you're going to have some potential slippage of the tires you get a 0.45 so

the gravos vehicle weight is 80 000 pounds then 80 000 pounds multiplied by 0.4 is

32 000 pounds that's the maximum rimple you can get i don't care what the gearing is

and so you need to be aware of that tracks are different on concrete

tracks are not efficient tracks have little projections that come out of them called grousers

those grousers dig into the soil and they act as a lever they don't dig into the concrete so that's not good

however looking at that dry sand

rather at that wet sand we have an improvement in our ability look at uh look at the

difference between firm earth which would be uh you know soil that's been rolled over

a few times but really isn't compacted you getting 0.55 or 55 of the gross

vehicle weight is all the rubber tired vehicle can do but 90 just like rubber tires on

concrete of the gross vehicle weight of your tracked vehicle is what you can end up doing and so that is why we have some vehicles

that are wheeled and some vehicles that are tracked that look exactly the same because depending on where you're operating

you might want the other type of of driving of driving train or of drive

train okay as far as the weight

distribution for empty and loaded vehicles scrapers trucks haulers that

can all be found in the manufacturer's literature and the maximum amount of usable

attractive force is the gross vehicle weight on the driving wheels or the tracks

multiplied by the coefficient of excuse me in uh in some of these

cases all wheels will be driven but it's the uh it's the drive wheel the

one that is has the largest gross vehicle weight which in that articulated caterpillar

truck is articulated because the cab is  connected to the load with a

single single pin hinge  it's going to be the forward drive wheels

all right so we're going to have a little bit of a discussion there's also on the 

and a little bit of an assignment there's also a second discussion  available to you  on this same BOLOGS which walks through some of the mathematics and explains it in a slightly different way

all right next thing we're going to deal with is dozers and loaders

good luck