Nurse, graphician/designer, engineer, all the same to me....

If the weight of the vehicle was enough and the power was enough, 10mm profile tyre would easily saw into asphalt or ice?

Really, it would!

I know, speaking as a nurse....

 

[QUOTE=richard thomas;630755][QUOTE=sandy85;630749]thinner tire have lower forward resistance (think of how much sand/snow you have to separate by moving forward) then wide tire - less resistance, less traction you need. That is one big plus. Friction is function of weight at surface (that is basic school). So more weight on smaller surface - again better for thin tire. You need wide tire only in case where thin tire comes to limits - for example if surface is so bad that you would sink by trying to apply that huge force per surface what thin tires do and you cannot make as tall thin tire to overcome the step.

 

Would the tank not change direction so that it was heading not only across the hill, but also upwards to maintain momentum in the correct direction?

The 'angle of attack'?

 

I don't drive my Jag in the snow-there's no point as I couldn't enjoy the power & handling without having a huge crash, as you have to consider other road users.

So if I have to drive in the snow then I use my old BMW 525tds with the tyre pressures dropped by 30%.

Driving in good weather conditions is all about driving enjoyment. Driving in snow/ice/heavy rain is all about getting to your destination & remaining alive-there's no driving satisfaction in terrible weather conditions, so the Jag stays in the driveway & the BMW is used instead.

On a wet day-even if it is warm enough for the standard tyre tread to be soft & supple-the XJR still scrabbles for traction in 1st gear at full throttle if the tyre pressures are at the higher level. Drop the pressures 10% & traction improves noticeably.

In this country the roads are already so bad that it doesn't matter about metal spikes damaging roads-and that's another reason for lower tyre pressures, to give a more comfortable ride over our terrible potholed roads

 

[QUOTE=sandy85;630766][QUOTE=richard thomas;630755]I think you have it - it all depends on the friction that the surface can take? Once the friction becomes more that the surface can take then the tyre will eat into the surface?

For instance, a vehicle weighing 30 tons with 4 wheels of 10mm width on a soft ground would sink up to the axles before any forward movement is attempted?

Or also, on ice where the available friction is almost nothing - it is better to use more area of the tyre tread (skate edges) to maximise friction?

I could be wrong...

 

Aah, I am a lucky man - for the snow, I break out the Land Rover!

(Or the Jag if I fance some fun....)

 

The T34 tank managed to travel a couple of thousand km's over Europe in all weather conditions, from the icy snowfields through to the muddy roads in the Russian spring thaw. It was so flexible because it had very wide tracks for it's weight & could travel over terrain thought to be impassable by other vehicles & tank designs.

However, a tank has different priorities in life compared to a tractor or a Jaguar

 

[QUOTE=sandy85;630776][QUOTE=richard thomas;630771]Aaahh, but we are back to friction - is it untrue that Formula 1 cars were given narrower tyres to reduce the traction in order to slow down the cars and make the sport safer?

 

I think this upholds the entire discussion - the T34 was given the best means of traction to support the worst ground conditions that could be? It was a sacrifice of traction on good (asphalt/hard ground where a narrow track could be used) ground against bad (muddy/wet/icy) ground?

 

I think that main purpose of the tank was to travel anywhere without any consideration at all for the ground or streets?

However I do agree that Landrover has travelled more that a Russian tank :-) although it is about 20 tons lighter....and slightly better on fuel efficiency (but only slightly)

 

[QUOTE=richard thomas;630781][QUOTE=sandy85;630776]This is usually first what drivers argue with on LR Course - race cars have big tires to get traction.
It is not that simple. But it is still the same. They have big tires so they can have softer compound to decrease the effect of weight and more importantly the sliding to side. You cannot bite into the asphalt if you want to put down 7 tons needed for acceleration. You reach limit of how you can bite, so only way is to go wide.
And in case of F1, the tires also play huge role as gyroscope, same as on bikes.

 

Sandy, please admit that you are an engineer really? If you are not, then I am going back to school to learn to be a nurse....your logic is better than mine....

F1 cars do actually weigh a lot (even though they are very light when not moving) as the downforce created by aerodynamics makes the tyres think the car is a lot heavier than it really is.

 

exactly. Tracks are not better then wheels in any case, but are friendlier to environment, more durable (shots, explosions, wear) and the disadvantages can be overcome by driving skills or throwing raw power at it (20 fuel tanks following it). But you see that even war vehicles are mostly with wheels. Tanks are only single purpose and even nowadays not really used anymore.

 

I'd like to see a Land Rover operating in the middle of Siberia in winter when the temperature is -50C

The Russian tanks were not really bothered about damaging the road surface anyway-it was a war machine designed to get from one place to the next.

Here's a thought about traction & grip...

If you have very thin tyres & very heavy vehicle on snow, then there is only a small contact point with the surface which will have a very high pressure on it. If you squash snow very hard, then it turns to ice & then you have no traction at all

That's why the T34 had very wide tracks-the Russians know something about winter, you see

When I was in Moscow walking in the snow, thin shoes would just sink in the snow & it was difficult to walk. When I wore wider boots, they didn't sink in the snow as much & it was much easier to walk around.

My thin shoes crushed the snow into ice & then my feet slipped on the ice-so I wore wide boots & the problem disappeared

 

Tracks have the advantage of much more surface area grip (friction/traction) - I am led to believe that they need replacing and maintenance quite a lot?

However they are not so capable of coping with high speeds compared to a wheeled vehicle.

 

dont know about replacing, but high speed is not really the case. If you have the power and moneys, you can build tracks able to do it. War trucks carrying similar load are not race machines either. They just damage the roads and would be too expensive / weird to have such big tires to get through typical mud fields.
I said it earlier. Tracks or heavily deflated tires are best if you would sink too deep. You came more often to scenario where 20t car would sink then to scenario where you would slide on muddy hill. So good trade off.
Normal cars drive on roads. They do not sink, so no need for trade off.

 

Downforce is directly related to speed, an F1 car can accelerate quickly - the downforce is good for cornering - it makes the tyres use the available grip better (due to compound/width). However downforce has an effect on speed - the greater aerodynamic downforce created, the greater the drag created which limits top speed. More downforce = More drag. Drag is turbulent air which tries to suck the vehicle backwards....

At high speed the downforce created by an F1 car is more that the car weighs - so in theory only an F1 car could drive upside down in a tunnel at top speed....this is theoretically only of course - but if aircraft aerodynamics are anything to go by it is true....

 

[QUOTE=sandy85;630813]dont know about replacing, but high speed is not really the case. If you have the power and moneys, you can build tracks able to do it. QUOTE]

As I am led to believe, tank tracks have a very short life whatever the use mainly down to the forces (weight/power) involved.

Although it is true that there are 'rubber' tracks available for minimum damage to tarmac roads.....not sure these are considered in times of conflict though...

Hasn't this thread wandered a bit though :-)

 

They weren't really that bothered, as they still managed to get where they wanted to go & somehow they always had a supply of fuel from behind

The Russian war horses didn't need much feeding either-they would simply stop in the villages & eat the straw roofs from the primitive houses.

The main reason I had problems walking in snow with thin shoes was that the pressure caused the soft snow to change state into hard ice-something that didn't happen with wide boots as they didn't put a concentrated area of very high pressure onto a very small contact patch & cause a change of material state.

 

it is more then F1 car weight but maybe not more then normal car weight, because the F1 car can accelerate quicker then some 2t Ferrari with same power specs.?