Wheel acceleration in relation to vertical LOAD and current speed

In summary: The formula to calculate the torque loss (?) due to wheel load would be:velocity = velocity + (torque / (2*I*R))
  • #1
raze29
2
0
Hello everybody!

I'm trying to write a car simulation but I'm having problems with precisely calculating the acceleration / velocity of the car's wheel. Currently the simulation works as if the Car was lifted in the air, so there is no load (vertical force) on the Wheel. What I have so far:
- the applied torque (engine torque multiplied with appropriate values)
- mass moment of inertia of the wheel

Now I would like to take into account the weight Load on the Wheel. How do I do this?
Currently the wheel spins up pretty fast even in 5th gear (well not at low RPM, but once the engine and axle are rotating together), but in reality I know it should be accelerating slower at high speeds - but it accelerates at the same speed as in 1st gear. I assume this is normal for no load on the wheel (though I might be wrong!).

Any help would be appreciated! :)

Also this is my first post and this is not a homework assignment.
 
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  • #2
The only significance of the vertical load on the wheel is that it permits a frictional force to develop between road and wheel. This applies a torque to the wheel, leading to a forward force on the wheel axle. This is what propels the car. If the frictional force is sufficient, the torque from the road balances the torque from the engine sufficiently that the wheel rolls instead of skidding.
Your observation re accn versus gear is correct. If the engine is working at constant power then the kinetic energy will increase at a constant rate, regardless of the gearing. A low gear just means the engine spins faster. In practice, engines work best within certain ranges of spin, hence the need for gears.
 
  • #3
Thank you, it was really helpful for understanding how things work!

However I would really like to know the exact formula to calculate the torque loss (?) due to wheel load, but can't find anywhere on the internet. So if we have:

- torque applied to the wheel axle
- moment of inertia of the wheel
- mass or vertical force of load on wheel
- road friction maybe

how do I change the formula which I currently have:

velocity = velocity + (torque / inertia)

Does the load somehow reduce the torque? Change the moment of inertia? Reduce acceleration? If so, how? (just to be accurate with the weight + weight distribution of the car, I don't really want random numbers)

Edit: velocity is in rad/s, torque is in N-m
 
Last edited:
  • #4
You say I've helped, but from your latest questions I'm not sure. You're still fixated on vertical load, though I already pointed out this is mostly of interest in ensuring there's no skidding. It does not act to reduce torque or slow the vehicle. What matters is inertia.

Let the mass of the vehicle (including wheels) be M, the moment of inertia of the wheels (all 4 combined) be I, torque (total for driving wheels) T, wheel radius R.
The linear acceleration A of vehicle = TR/(MR2+I)
For normal road cars, I is fairly insignificant, simplifying it to A = T/(MR). I guess I matters for dragsters.
I'm assuming road friction is adequate to prevent skidding, and I've ignored rolling resistance. Rolling resistance deducts a constant amount from the acceleration, so long as the velocity is nonzero.
 
  • #5


I would first like to commend you for taking the time to accurately simulate the acceleration of a car's wheel. This is a complex and important aspect of vehicle dynamics that is often overlooked.

To answer your question, the weight load on the wheel does indeed have an impact on its acceleration. This is because the weight load creates a normal force that acts perpendicular to the surface of the wheel. This normal force, in turn, creates a frictional force between the wheel and the ground, which affects the wheel's acceleration.

To accurately calculate the wheel's acceleration, you will need to consider the following factors:

1. Vertical load: This is the weight of the car and its contents that is acting on the wheel. This load will vary depending on the weight of the car and the distribution of weight within the car.

2. Frictional force: As mentioned before, the normal force created by the weight load will result in a frictional force between the wheel and the ground. This force will oppose the motion of the wheel and affect its acceleration.

3. Current speed: The speed of the car will also affect the wheel's acceleration. At higher speeds, the wheel will experience more drag and resistance, which will slow down its acceleration.

To incorporate these factors into your simulation, you will need to use equations that take into account the weight load, frictional force, and current speed. You can find these equations in textbooks or online resources on vehicle dynamics.

Additionally, it is important to consider other factors that may affect the wheel's acceleration, such as air resistance, tire pressure, and road conditions. These may also impact the accuracy of your simulation.

In conclusion, to accurately calculate the acceleration of a car's wheel, you will need to consider the weight load, frictional force, and current speed. By incorporating these factors into your simulation, you will be able to create a more realistic and accurate model. I hope this helps and good luck with your simulation!
 

What is wheel acceleration?

Wheel acceleration refers to the rate at which the rotational speed of a wheel changes over time. It is typically measured in revolutions per second squared (rps2) or meters per second squared (m/s2).

How does vertical load affect wheel acceleration?

Vertical load, or the downward force exerted on the wheel, can affect wheel acceleration by changing the amount of friction between the wheel and the surface it is moving on. More vertical load can result in greater friction, which can slow down wheel acceleration.

Does current speed impact wheel acceleration?

Yes, current speed can impact wheel acceleration. As the speed of the wheel increases, so does the amount of rotational force needed to maintain that speed. This can result in an increase in wheel acceleration.

What is the relationship between wheel acceleration and vertical load?

The relationship between wheel acceleration and vertical load is inverse. As vertical load increases, wheel acceleration decreases, and vice versa. This is due to the effect of friction on the wheel's rotational speed.

Can wheel acceleration be controlled?

Yes, wheel acceleration can be controlled through various factors such as the amount of vertical load, the type of surface the wheel is moving on, and the amount of rotational force applied. By adjusting these factors, the wheel's acceleration can be increased or decreased.

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