Heavy Vehicle or Light Vehicle in Offroad?

Off-road Basic Technical Information

Dear off-road and nature enthusiast friends, we are together with another sharing of our Off-road Basic Technical Information article series. The information I will provide; These are concentrated, technical-based, lived experiences, and some of the details that will find a name in the off-road literature for the first time. With the hope that it will benefit the readers.

Our topic today is “Heavy Vehicle or Light Vehicle in Offroad?” :

Our question is actually whether a heavy vehicle or a light vehicle should be preferred on the axis of successful offroad driving, but the weight will be evaluated parallel to the size of the vehicle and shifted to the axis of large, vehicle or small vehicle.

I will try to evaluate the road holding point, which is the basic element of a successful offroad driving, without causing too much axis shift.

track ; mud, loose dry ground, snow, sand, rock.

The essence of the problem is not which vehicle we use more efficiently within the framework of picnics, camping and other outdoor activities, but which vehicle we get more efficiency from directly offroad.

For successful offroad driving, the answer to the question of whether it is a heavy vehicle or a light vehicle lies in the basic laws of physics.

The force that makes the vehicles move is the force that occurs between the wheel and the ground on which it walks. We call it traction. Wikipedia definition; (traction or traction force) is the force used to produce motion between a surface and a tangential surface through the use of dry friction.

There are many parameters that affect this force. Ground quality, rubber compound, tire pattern, tire width etc. are the most important of these.

Therefore, in order to make the evaluation under correct and equal conditions, all of the vehicles started to slide at 45 degrees inclination in the inclined plane test, that is, the static friction coefficient.

We will assume that µ = tan 45 = 1.

To simplify the situation, I will not distinguish between static and kinematic coefficients of friction.

There is an upper limit to the resulting traction force between the tire and the surface. The higher this limit is, the better the vehicle will handle, the lower it is, the worse it will handle.

Here, we call the value that creates this upper limit of the traction force “F_s, friction force”.

The frictional force is equal to the perpendicular force between the two surfaces times the coefficient of friction.

F_s = N x µ

Since we assume µ=1 in this equation, the friction force is a linear function of the normal force N. The result here is indisputable and very clear. In cases where frictional motion is provided, the higher the vehicle weight, the higher the handling. The higher the grip, the higher the offroad driving success .

So, is this situation as many times as 4×4 = 16?

This is offroad, nothing can be that precise of course.

Now let’s consider other situations that affect it.

Walking on the ground happens in two basic ways; the first by floating on the ground, the second by clinging to the ground.

Progress by floating on the ground; in sand, sometimes in snow, very rarely in mud.

Progress by holding on to the ground; It happens on loose dry ground, rock ground, sometimes snow, often when hard ground can be reached at the bottom of the mud.

If the vehicle is floating on the ground, if the vehicle weight increases, the vehicle will sink, that is, the differentials and / or the chassis will sit and the vehicle cannot continue on the road. Here the situation is balanced by using large and wide tires on heavy vehicles.

If it is advancing by holding onto the ground, the heavier the vehicle, the better the handling.

Other considerations for weighted or already heavy vehicles:

– Engine with enough power for the weight of the vehicle is required

– Fuel consumption of heavy vehicles is always higher.

– Axles, differentials, shafts, cross-country gearboxes and gearboxes are required to be robust enough to meet the weight of the vehicle.

– It should be noted that the mass moment of inertia of the heavy vehicle will be more difficult to overcome and the acceleration performance will be low. That’s why rally drivers, whom I describe as “dirt road gassers”, always prefer vehicles that are as light as possible and gain the greatest advantage in races by reaching the highest speed as soon as possible after their speed drops. This is only possible with a light vehicle. Since we evaluate offroad driving, not time-trial competitions, our preference should be heavy vehicles.

Please remember the video he took of all the vehicles attached to the back of the Lada Niva, of which there were about 10 men.

The information I give is for situations that are expected to happen in the majority. Situations that occur outside of this are also different situations that can arise under their own conditions within the framework of the physics rules I have defined. But the laws of physics are absolute and cannot be changed, at least within the framework of current knowledge.

As we said, 4×4=16 doesn’t happen all the time. Despite all the equipment, Niva can sometimes pass where other vehicles cannot pass. Sometimes, a heavy and bulky Toyota can pass by where the Niva floundered.

Yes, where the heavy vehicle cannot go, the niva may have walked away. It is a ground where it is not possible to cross the loose ground and find the hard ground without the vehicle sitting on the base. If the vehicle floats on the loose ground, it will only be able to pass the track. A light and wide wheeled Niva has walked away where the heavy vehicle is buried up to the chassis. Well, in what % of mud tracks this is the case. It’s not even 10% that I’ve experienced so far. So then it would be more accurate to comment according to the 90% part. This is how I come to the conclusion that a vehicle with a large tire diameter and a suitable pattern, which can generally reach and hold the hard floor on the mud, makes a more successful ride. Is there no exception, yes, there is the niva we gave an example above.

Or let me give you the opposite example, a heavy vehicle in the sand is considered as trouble. Whereas, a vehicle with heavy but wide tires will probably be more successful in driving while maintaining its momentum, than a vehicle with light but very narrow tires. What happened, the light vehicle sank, the heavy vehicle passed. Even so, the main thing is that the laws of physics work according to the vehicle and track conditions for the moment.

Conclusion and Suggestions:

As I mentioned above, provided that the parameters affecting the friction coefficient are equalized, the friction force, which is the upper limit of the traction force of heavy vehicles, will be higher, so it is expected to drive more successfully in the offroad with at least 80% accuracy. The exceptions that we call the opposite situation do not break this rule, they have already produced their own results in a different way within the framework of the same physics rules.

It is expected that a vehicle with a wheelbase between 100”-120”, around 2000 kg in its equipped state, with suitable approach and departure angles, will have a higher off-road performance than other vehicles with the right tire choice.

Even though the big brothers appearing in the field with their weight based on the 3000 kg limit, 39”-42” big tires and fuel tanks up to 200 liters dazzle you in the videos, when considered as a whole, they are not very acceptable vehicles for us ordinary offroaders .

Despite its small size, it should not be overlooked that vehicles that are heavier than normal may experience breakage problems in the driveline.

Let me put it in the last word , do not buy a vehicle without a middle lock, if possible, choose a vehicle that has a minimum rear lock or can be installed without much expense.