Loading the lesson
Loading the lesson
Search AllRounder.ai
Search the courses, subjects, tracks, games and features, or jump straight to a page.
Search the courses, subjects, tracks, games and features, or jump straight to a page.
Learn it your way
A short class with Sarah and her students. The other ways are under More.
Sign up free to listen. Transcripts are free to read.
Today, we'll start with how we convert vehicle weight into tons, which is essential for calculating rolling resistance. If the vehicle weighs, let's say, 50,000 kg, how do we convert that?
We divide by 1000, right? So it would be 50 tons?
Exactly! Good job! Converting to tons is necessary because the rolling resistance is generally expressed as kg per ton.
What’s the rolling resistance in our example?
For our haul route, it’s given as 28 kg per ton. So, what’s the total rolling resistance for 50 tons?
That would be 50 tons multiplied by 28 kg per ton, which equals 1400 kg.
Correct! That's a crucial step in understanding power needs.
Let's recap: Always start by converting weight to tons for rolling resistance calculations. Ready for the next part?
Now, let’s discuss penetration resistance. It depends on how deep the tires sink. For instance, if a tire sinks 6 cm into the ground, does anyone know how we can calculate that resistance?
Is it based on the depth times the resistance per ton?
Right! It’s 6 cm times 6 kg per ton per cm. Can anyone calculate that for 50 tons?
That would be 1800 kg!
Exactly! So the total resistance is rolling resistance plus penetration resistance. What’s our total?
That would be 1400 kg + 1800 kg, which equals 3200 kg total.
Great teamwork! Remember, the total resistance is vital for determining the necessary tractive effort.
Next, we need to consider grade resistance, which adds to the challenges when machines are climbing slopes. Can anyone tell me how this type of resistance works?
It increases the effort needed to pull the load, right? Especially on steep slopes.
Absolutely! The percentage of the slope dictates the additional force needed. For a 5% grade, what’s the requirement?
That would be 5% times 10 kg per ton. If our load is 50 tons, that’s 500 kg for grade resistance.
Exactly! Understanding how to calculate this is crucial for selecting the right haul route!
Finally, let’s discuss usable power. What is it, and how does it differ from the available power provided by manufacturers?
Usable power is the actual power available for work after considering resistance, while available power is what the manufacturer states.
Correct! And what factors affect the usable power?
Altitude and temperature can affect it since they determine how much power can be realized on site.
Excellent point! Understanding the differences ensures we select the right machinery for the conditions.
Now, let’s apply these principles to a problem. A tractor weighs 15 tons with a rolling resistance of 60 kg per ton on a 4% slope. How would we approach calculating the usable power?
First, we calculate the grade resistance, which is 4 times 10 kg per ton for that slope.
And then for rolling resistance, that gives us a total of 1500 kg when we add everything up.
Fantastic! After finding total resistance, what’s our next step?
We subtract that from the maximum rimpull to find usable power for towing the load!
Exactly! Applying our calculations to practical situations reinforces our understanding.
Converting vehicle weight from kilograms to tons is necessary for resistance calculations.
Calculated by multiplying gross weight by rolling resistance rate (kg per ton).
Dependent on the tire's depth in the surface and needs proper calculation.
The force opposing movement on an incline; calculated based on the gradient percentage.
Power available for actual work after accounting for resistance.
To measure weight in tons, divide by 1000, it's fun!
Imagine a tractor on a hill, pulling a heavy cart. It needs extra might to move up the slope, just like you need energy to climb a flight of stairs.
REM, remember Energy Movement: Usable power = Available power - Resistance.
Term
Rolling Resistance
Click to flip
Term
Grade Resistance
Click to flip
Term
Usable Power
Click to flip
The force opposing the motion of a vehicle due to the weight of the vehicle and the type of surface.
The resistance encountered when tires sink into a surface, calculated by depth and effort per unit.
The additional effort required for a machine to move up an incline due to gravitational forces.
The effective power available for performing work after accounting for resistance.
The power rating provided by the manufacturer under standard conditions.
This section discusses how to calculate the power requirements of machinery based on rolling resistance and grade resistance.
The section explains the conversion of vehicle weight to tons, calculation of rolling resistance, penetration resistance, grade resistance, and the overall power required for a machine to operate effectively on different terrains.
In this section, we dive into how to accurately estimate power requirements necessary for machinery by considering key factors such as rolling resistance, penetration resistance, and grade resistance.
We start with converting the gross weight of the machine from kilograms to tons, where a machine weighing 50,000 kg is equivalent to 50 tons. Rolling resistance is defined as 28 kg per ton, leading us to calculate the total rolling resistance for a particular haul route as 1400 kg.
Further, we discuss penetration resistance, determined by the depth to which tires sink into the surface. Given a penetration depth of 6 cm and the requirement of 6 kg per ton per centimeter, we calculate the total penetration resistance at 1800 kg. Adding both rolling and penetration resistance gives a total resistance of 3200 kg, representing the minimum tractive effort required.
Additionally, we look at grade resistance, which is vital when machinery operates on inclines. Grade resistance is influenced by the slope percentage, with 10 kg per ton required for every 1% increase in slope, underscoring the need for careful route selection that minimizes resistance and operating costs.
Lastly, the concept of usable power is introduced, which is based on available power from the manufacturer’s specifications adjusted for project conditions, highlighting the importance of weight on the driven wheels and traction effects on performance.