But When I joined the industry, they said “The LUG pattern has got more traction than Thread Pattern, that’s why we use it in offroad applications”. OK… But why?
Hmmm… its like that.
Think it is time for an explanation – an excuse for not knowing???
Wikipedia.org Explanation Below.
Traction - refers to the friction between a drive member and the surface it moves upon, where the friction is used to provide motion.
And it depends upon the following factors
· Material properties of each surface.
· Macroscopic and microscopic shape or "roughness".
· Force of contact.
· Area of contact.
· Contaminants at the material boundary including lubricants and adhesives.
-------------------------------------------------------------------------------
Considering my whole vehicle as a single system the only external forces are the wind resistance, rolling friction and force from the ground (- can I call it the Traction force?).
Which force pushes my vehicle forward – neither rolling friction nor wind resistance – So Traction??
Traction – Is that a friction force? – what friction?
- If it is friction force, how can it be dependent on area?
So ‘MY EXPLANATION’ BELOW – AGAIN – ITS AN EXPLANATION.
Traction force – Comes into play when the patch of tire in contact with the ground (instantaneous velocity = 0) tries to push the ground by virtue of a torque or force acting on it.
I will ‘try’ to explain the factors which wikipedia.org has taken into account.
1. Friction aids traction
When the torque from the engine through the drive line tries to accelerate the axle of the vehicle OR the braking torque acting on the tire trying to decelerate the vehicle – the tire surface in contact with the ground try to achieve a relative velocity with respect to the ground. The friction force that resists this torque is one component of traction as shown in the figure 1 and its magnitude equals the torque on tyre divided by the radius of the tyre – provided the value of force is less than µM1 g – where µ is the co-efficient of Static friction, M1 g is the effective weight on the tyre.
2. Property of tyre material.
If the material of the tyre is soft and has got greater resilience it will have better traction. This can be explained like this – When torque is applied on the tyre the ground resists its relative motion. This will compress the rubber in that part and as it rotates and come in contact with the ground it releases the energy that it absorbed – the value of which depends on the resilience of the tyre material being used. This is shown in figure 2.
The blue arrow shows compression in region and red arrow shows the expansion in the region due to torque and force from the ground.
3. Surface on which it is rolling
If the surface is loose sand then the traction is low, because it cannot provide the force by resisting the slippage of tyre – which results in slipping of the ground.
This explains the lack of traction in loose sand, smooth icy surface.
Now consider the figure 3 below – the surface is a bit exaggerated.
But I would like to use it for explaining the difference between LUG pattern and THREAD pattern
The surface (shown in green) is pretty hard that it resists the rotation of the tyre and by providing a push as shown as red arrow.
Also the LUG pattern allows the tyre to deflect more taking more energy which will contribute to the force as explained in “property of tyre material” above.
No comments:
Post a Comment