# A Tank tracks treads friction coefficient

1. Apr 28, 2016

### roineust

What kind and value is the friction coefficient of tank tracks on the move, when force is applied forward in the direction of the tracks movement?
Is the friction coefficient in that case, closer to kinetic/sliding coefficient or to a rolling resistance coefficient?
What about the sideways friction coefficient of rolling vehicles ? Do the same values of resistance apply in both the direction of movement as well as sideways force? Do the sideways resistance of a moving vehicle and the rolling resistance in the direction of moving have the same value or is the sideways resistance, closer to kinetic/sliding resistance? How big is the difference between the friction coefficient of wheeled vehicle in direction of movement and the sideways coefficient of that vehicle? What is the difference in value of this sideways friction coefficient between tank tracks and car wheels?

Here is the same question articulated differently:
Say we have 2 vehicles: A 4 rubber wheel car and a tank with 2 rubber track treads. Both weight is 1000kg, both motor and gear are held in 'neutral', both of these vehicles are moving on the same asphalt road.
From a table i have here, i see that a typical rolling resistance of rubber on asphalt is 0.05.
This means that in order to make the car move forward, i need to push it forward at a force equal to about 50kg. What about the tank? What would be the force needed to apply forward on the 1000kg tank, in order to make it move?
Now sideways: if that 1000kg car is moving at 0.1 m/s on an asphalt road, what is the force needed to move it sideways? Now at 10 m/s would the sideways friction coefficient be the same? is it calculated according to kinetic/sliding coefficient or according to other type of coefficient? Is there influence on kinetic/sliding coefficient, when pushing a car moving forward sideways, as a result of the fact that it is moving forward at the same time? If there is such an influence on kinetic/sliding coefficient value, what is the scale of it? How does it change when dealing with tank treads, instead of car wheels?

Last edited: Apr 28, 2016
2. Apr 28, 2016

### A.T.

Depends on if the tracks slide or not.

Rolling resistance is a separate issue. A tank has a high rolling resistance coefficient, compared to a wheeled vehicle.

3. Apr 28, 2016

### roineust

A.T,
i am not sure what you mean by "if the tracks slide or not" - but as mentioned, the question is asked under the condition that the motor and gear are in neutral, so they make no resistance at all.

How much higher in general scale of order is the rolling coefficient of a tank, compared to a vehicle of the same weight? Say a 4 wheel 1000kg car has a 0.05 rolling coefficient? What would be that of a 1000kg tank having the same types of material as road (asphalt) and track treads (rubber)?

4. Apr 28, 2016

### A.T.

There is static friction and kinetic friction.

Try a web search.

5. Apr 28, 2016

### roineust

i was relating to kinetic and rolling friction all through the entire question and not to static friction at all.
i got here, after looking for these values or approximations of them, in many web queries - but couldn't find the answer.

6. Apr 28, 2016

### CWatters

If the tracks aren't skidding/slipping then the friction between the track and the ground is static friction and it acts forwards.

In short..
If the tyres/tracks are rolling without skidding/sliding then it's static friction.
If the tyres are skidding/sliding it's kinetic friction.
Rolling resistance is something else. Typically that depends on how hard/soft the tyres are because on soft tyres the rubber has to flex more as the wheel rotates. That flexing of the tyre takes energy which heats up the tyre and is the main cause of rolling resistance.

There is no reason to assume these are the same. Consider an ice skate. The coefficient of friction is very dependant on direction.

You can't always consider them in isolation. For example if you approach a bend too fast and close to the limit of adhesion you may find you are forced to choose between braking and steering. You can always do both.

I imagine it's higher for the tracked vehicle but I have no numbers to support that.

In general tracked vehicles have higher rolling resistance than correctly inflated tyres. So a greater force will be required.

It's quite difficult to model friction. In some problems friction is independent of the contact area. That's because the greater the contact area the lower the pressure per unit area.

I'm sure whole books have been written on the subject of wheels vs tracks. Not really my field.

7. Apr 28, 2016

### roineust

Thanks CW,
In an attempt to try and simplify things, i'm searching the web for generalized scale of order values, for side-wind side ways sliding effect on the average car on the move. But can't find such generalized numbers yet.

8. Apr 28, 2016

### roineust

Here are 2 articles that might have an answer, but since i'm not a scientist, i can't interpret what is written there:

https://deepblue.lib.umich.edu/bitstream/handle/2027.42/65022/MacAdam 1990 VSD Aerodynamic Crosswind paper.pdf?sequence=1