Lecture 4 - Loading and Hauling Flashcards
What are the 3 ways to increase productivity?
1) Increase cycles per hour
2) Decrease time per cycle
3) Increase max speed
What is the formula for estimating equipment travel time
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
What is the total resistance formula?
Grade resistance + Rolling resistance = Total resistance
What is rolling resistance? What is the formula?
It is primarily due to tire flexing and penetration of the travel surface
Rolling resistance = Rolling resistance factor (RRF) x Vehicle weight
What is the rolling resistance factor?
lbs/ton= 40 + 30 x in.penetration
Kg/t = 20 + 6 x cm penetration
True or false
Crawler tractors considered to have no rolling resistance
True
What is grade resistance? What is the formula?
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
How is the grade resistance factor calculated?
lbs/ton = 20 x Grade (%)
kg/t = 10 x Grade (%)
What is the effective grade formula?
Effective grade (%) = Grade (%) + ((RRF (lbs/ton))/20)
Effective grade (%) = Grade (%) + ((RRF (kg/t))/10)
True or false
a 1% effective grade is considered to have total resistance equal to 1% of the vehicle weight
True
What is derating factor? What is the formula? What is the formula for power available?
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
What is rimpull?
The power available to move wheel vehicles and their load
What is drawbar pull?
The power available to move crawler tractors and their load
What is the formula for max usable pull?
Coefficient of traction × Weight on driving wheels
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?
1) Track
2) Wheels
3) Track
4) wheels (dozer)
Describe each of the following Dozer blades
1) Tilting
2) Forward pitching
3) Angling
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
What is the total dozer cycle time?
Fixed time + Variable cycle time
Fixed = Time to maneuver, change gears, start loading and dump
Variable = Time to doze and return in reverse gear
Name the 3 dozing techniques to increase dozer production
1) Downhill
2) Slot
3) Blade-to-blade
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.
True
What are loaders used for?
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
What cycle time for a loader includes?
- loading
- dumping
- Maneuvering reversals of direction
- Travelling a minimum distance (15 ft. or
less for track loaders)
What is the haul unit load time formula?
Haul unit capacity/equipment production at 100% efficiency
OR
What type of thread is best for sharp rock pits areas?
What type of thread is best for earth and gravel?
1) Deep threads (L2 up to L7)
2) Shallow threads
Blade load (LCM) formula
0.375 x H x W x L
What are the main advantages and disadvantages of scraper?
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
What is spot tine?
The time it takes for a unit to position itself in the cut and begin loading, including waiting for the pusher.
What is the optimum loading time?
A positive correlation between the load time and scraper load which is non-linear in ascending-descending order.
What is the back-track method? Why is it the slowest one?
Back-track is the most common loading method, it is the slowest because it permits all scrapers to load in the same area.
What are the 3 push-loading methods? Explain the latter 2
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
Job management. Explain ripping.
Most types of soil will load faster if they are ripped ahead of the scraper
Job management. Explain prewetting the soil.
Easier to load when they are reasonably wet. Since it helps to achieve uniform moist conditions in the soil.
Job management. Explain loading downgrade.
Results in faster loading time especially in the direction of the haul. Also, ascending conditions are more fuel efficient
Job management. Explain Dumpting operations.
The materials must be dumped in thin lifts (the thickness of the layer of soil). It makes it easier to compact.
Job management. Explain Supervision.
A spotter should always control fill operations and maintain the dumping pattern.
