Roll resistance calculation

In summary, the conversation discusses the calculation of torque and power required to pass an obstacle with a given height on a rotating wheel. The energy and dimensions of the wheel are also taken into consideration. The formula F = m*g*sqrt(2rh-h^2)/(r-h) is used to calculate the force needed to overcome the obstacle, and T = F*(r-h) can be used to calculate the torque required.
  • #1
vladim1
7
0
Hi to all

Please help me to clarify this situation:

There is a rotated wheel on a plan surface. What torque/power will be necessary to spring an obstacle with a concrete height.

For ex. here are some data:

1.Wheel mass 10 kg
2.Wheel radius 0,3 m
3.Rotation speed 100 RPM
4.Obstacle height 0,01 m

Which formulas must I use to determine torque/power to get the wheel rotating at that speed without obstacle, and how much must be increased these parameters to pass obstacle without slowly speed.

Here is an image, hope it will help to understand what I mean.

Thanks
 

Attachments

  • wheel.jpg
    wheel.jpg
    4.7 KB · Views: 413
Engineering news on Phys.org
  • #2
Welcome to PF!

vladim1 said:
Hi to all

Please help me to clarify this situation:

There is a rotated wheel on a plan surface. What torque/power will be necessary to spring an obstacle with a concrete height.

For ex. here are some data:

1.Wheel mass 10 kg
2.Wheel radius 0,3 m
3.Rotation speed 100 RPM
4.Obstacle height 0,01 m

Which formulas must I use to determine torque/power to get the wheel rotating at that speed without obstacle, and how much must be increased these parameters to pass obstacle without slowly speed.

Here is an image, hope it will help to understand what I mean.

Thanks

Hi vladim1! Welcome to PF! :smile:

Isn't this just an energy problem?

As son as the roller hits the obstacle, it will start rotating about the obstacle instead of about its centre … you have to find what energy it needs to just reach "vertical". :wink:
 
  • #3
Ok, how you say then I must calculate energy whith formula E=mgh, to determine what power I need to pass an obstacle with "h" height.

But, how is explained that a wheel with bigger radius pass a same obstacle easier than one with smaller?

How much role play differences in dimentions, is there something with balance.
 
  • #4
vladim1 said:
But, how is explained that a wheel with bigger radius pass a same obstacle easier than one with smaller?

How much role play differences in dimentions, is there something with balance.

uh-uh, you tell me :wink:

for a wheel of density ρ, radius r, and speed v, what is its energy, and so what is the maximum height h of an obstacle that it will clear?

and how does that h depend, dimensionally, on ρ, r, and v, separately? :smile:
 
  • #5
Thinking we discuss about thing I don't need.

Me interest is to calculate rolling resistance (in N) for a surface which have obstacles of 1cm height (eg. after each 5cm). Also I observe that a heighter wheel go easier after road's deformations.
 
  • #6
I found a formula to calculate force needed to aply on axle (pushed wheel) to overcome obstacle:

F=m*g*sqrt(2rh-h^2)/(r-h)

where:

m= load
r= radius of wheel
h= obstacle height

Which formula must I use to calculate torque needed to overcome same obstacle, rotation start from rest wheel.

Can I use T=F*r ?

F - force calculated with above formula
r - wheel radius.
 
  • #7
T = F*(r-h)

To derive the formula that you found, simply take the sum of the moments about the tip of the obstacle.

sum of Moments: F*(r-h) - mg*sqrt[r^2 - (r-h)^2] = 0
 

1. What is roll resistance calculation?

Roll resistance calculation is a process used to determine the amount of force required to overcome the resistance of a rolling object on a surface. It takes into account several factors, such as the weight of the object, surface roughness, and coefficient of friction.

2. Why is roll resistance calculation important?

Roll resistance calculation is important because it helps engineers and designers optimize the performance and efficiency of rolling objects, such as vehicles or machines. It also allows for the prediction of energy consumption and potential wear and tear on the object and the surface it is rolling on.

3. What factors affect roll resistance?

Several factors can affect roll resistance, including the weight and shape of the object, the surface roughness and texture, the type of material the object is made of, and the speed of rolling. These factors can also change depending on the conditions, such as temperature or humidity.

4. How is roll resistance calculated?

Roll resistance is calculated by using the formula: Roll resistance = (Crr x W) + (Cdr x W x V), where Crr is the coefficient of rolling resistance, W is the weight of the object, Cdr is the coefficient of drag, and V is the velocity of the object. This formula takes into account both the rolling and aerodynamic resistance of the object.

5. How can roll resistance be reduced?

Roll resistance can be reduced by minimizing the weight of the object, using smoother and more aerodynamic shapes, choosing a smoother surface for rolling, and reducing the speed of rolling. Additionally, using materials with lower coefficients of friction and regularly maintaining and lubricating the object can also help reduce roll resistance.

Similar threads

  • Mechanical Engineering
Replies
1
Views
575
  • Mechanical Engineering
Replies
3
Views
3K
  • Mechanical Engineering
Replies
8
Views
3K
Replies
5
Views
3K
Replies
23
Views
5K
  • Mechanical Engineering
Replies
8
Views
3K
  • Mechanical Engineering
2
Replies
47
Views
5K
  • Mechanical Engineering
Replies
17
Views
3K
  • Mechanical Engineering
Replies
1
Views
1K
  • Mechanical Engineering
Replies
5
Views
2K
Back
Top