Lecture 4 - Loading and Hauling

Question 1

What are the 3 ways to increase productivity?

Answer 1

1) Increase cycles per hour
2) Decrease time per cycle
3) Increase max speed

Question 2

What is the formula for estimating equipment travel time

Answer 2

Variable time + fixed time = Cycle time
1) Variable time - depends on:
A) Vehicle weight & power
B) Conditions of the haul road
C) Grade and altitude

2) Fixed time depends on:
- Spot time
- Load time
- Maneuver time
- Dump time

Question 3

What is the total resistance formula?

Answer 3

Grade resistance + Rolling resistance = Total resistance

Question 4

What is rolling resistance? What is the formula?

Answer 4

It is primarily due to tire flexing and penetration of the travel surface
Rolling resistance = Rolling resistance factor (RRF) x Vehicle weight

Question 5

What is the rolling resistance factor?

Answer 5

lbs/ton= 40 + 30 x in.penetration
Kg/t = 20 + 6 x cm penetration

Question 6

True or false
Crawler tractors considered to have no rolling resistance

Answer 6

True

Question 7

What is grade resistance? What is the formula?

Answer 7

It represents the component of the vehicle weight which acts parallel to an inclined surface.
Grade resistance = Vehicle weight (lbs or kg) x Grade
Grade resistance = Vehicle weight (t or ton) x Grade resistance factor

Question 8

How is the grade resistance factor calculated?

Answer 8

lbs/ton = 20 x Grade (%)
kg/t = 10 x Grade (%)

Question 9

What is the effective grade formula?

Answer 9

Effective grade (%) = Grade (%) + ((RRF (lbs/ton))/20)
Effective grade (%) = Grade (%) + ((RRF (kg/t))/10)

Question 10

True or false
a 1% effective grade is considered to have total resistance equal to 1% of the vehicle weight

Answer 10

True

Question 11

What is derating factor? What is the formula? What is the formula for power available?

Answer 11

Used by manufacturers to express the percentage of reduction in rated vehicle power at various altitudes
Derating factor (%) = (Altitude (m) - 915)/102
Power available = 100 - derating factor

Question 12

What is rimpull?

Answer 12

The power available to move wheel vehicles and their load

Question 13

What is drawbar pull?

Answer 13

The power available to move crawler tractors and their load

Question 14

What is the formula for max usable pull?

Answer 14

Coefficient of traction × Weight on driving wheels

Question 15

Which one is better in each of the following? Dozer of bulldozer
1) In a rought terrain aith low trafficability
2) For paved roads?
3) On steeper side slopes
4) As an effective soil compactor?

Answer 15

1) Track
2) Wheels
3) Track
4) wheels (dozer)

Question 16

Describe each of the following Dozer blades
1) Tilting
2) Forward pitching
3) Angling

Answer 16

1) Useful for breaking up frozen or crusty soils
2) Reduces the penetration of the blade and causes the loosened material to roll in front of the blade
3) Helpful when sidehill cutting, ditching and moving material laterally

Question 17

What is the total dozer cycle time?

Answer 17

Fixed time + Variable cycle time
Fixed = Time to maneuver, change gears, start loading and dump
Variable = Time to doze and return in reverse gear

Question 18

Name the 3 dozing techniques to increase dozer production

Answer 18

1) Downhill
2) Slot
3) Blade-to-blade

Question 19

True or false

Blade-to-blade dozing results in a combined blade capacity
greater than two single blades. However, it is not efficient for short distances.

Answer 19

True

Question 20

What are loaders used for?

Answer 20

1) Excavating soft to medium-hard materials
2) Loading hoppers and haul units
3) Stockpiling material
4) Backfilling ditches
5) Moving concrete and other construction materials

Question 21

What cycle time for a loader includes?

Answer 21

• loading
• dumping
• Maneuvering reversals of direction
• Travelling a minimum distance (15 ft. or
  less for track loaders)

Question 22

What is the haul unit load time formula?

Answer 22

Haul unit capacity/equipment production at 100% efficiency
OR

Question 23

What type of thread is best for sharp rock pits areas?
What type of thread is best for earth and gravel?

Answer 23

1) Deep threads (L2 up to L7)
2) Shallow threads

Question 24

Blade load (LCM) formula

Answer 24

0.375 x H x W x L

Question 25

What are the main advantages and disadvantages of scraper?

Answer 25

Advantages:
1) Self-load condition
2) no temp breakdown (nob shutdowns)
3) Disposing the load in layers of uniform thickness

Disadvantages:
NOt as efficient for hauling & loading like other machines

Question 26

What is spot tine?

Answer 26

The time it takes for a unit to position itself in the cut and begin loading, including waiting for the pusher.

Question 27

What is the optimum loading time?

Answer 27

A positive correlation between the load time and scraper load which is non-linear in ascending-descending order.

Question 28

What is the back-track method? Why is it the slowest one?

Answer 28

Back-track is the most common loading method, it is the slowest because it permits all scrapers to load in the same area.

Question 29

What are the 3 push-loading methods? Explain the latter 2

Answer 29

1) Back-track: Slowest, most common.
2) Chain loading - suitable for a long narrow cut area
3) Shuttle loading: Requires two separate fill areas for efficient operations

Question 30

Job management. Explain ripping.

Answer 30

Most types of soil will load faster if they are ripped ahead of the scraper

Question 31

Job management. Explain prewetting the soil.

Answer 31

Easier to load when they are reasonably wet. Since it helps to achieve uniform moist conditions in the soil.

Question 32

Job management. Explain loading downgrade.

Answer 32

Results in faster loading time especially in the direction of the haul. Also, ascending conditions are more fuel efficient

Question 33

Job management. Explain Dumpting operations.

Answer 33

The materials must be dumped in thin lifts (the thickness of the layer of soil). It makes it easier to compact.

Question 34

Job management. Explain Supervision.

Answer 34

A spotter should always control fill operations and maintain the dumping pattern.