[QUOTE=richard thomas;630819]i think the tracks do not damage the road when tank is not turning. They just lay there and car drives over them. The damaging part was mainly to the fields and simply environment it drives over. 30t truck damages any unpaved road so that none car passes over it again.
though we could agree that car with 20m tall thin tires would get better traction everywhere, would be better option as war machine, but is not realistic.

 

[QUOTE=sandy85;630824]I think a car with 20m tall thin tyres would be so tall that you couldn't climb up into it, and it would also blow over easily in a strong wind-however, it would be great to service such a vehicle & do oil changes from underneath with all that space to look up into

I'm sure a psychologist would be very interested in the direction this thread has now taken

 

A normal F1 car can get to 100Kph i less than 2 seconds. It weighs 640 Kg with fuel and driver.

At 190Kph it's downforce is twice the weight of the car. The car has enough power to overcome the drag created by the downforce (imagine putting your hand out of the car window at speed - as you tilt your hand upwards it gets pushed backwards - this is drag)

So a ferrari would need to generate considerably more downforce to do the same at he same speed.

But it is all a matter of power/weight?

For instance, one of my other cars weighs 480kg and gets to 100Kph in 3.6 seconds...but does not have the same top speed as either the F1 car or the ferrari....this is due to gearing and available engine power....

So it would need considerable downforce to do the same - which would probably create so much drag it would prevent the car achieving the top speed in the first place?

 

[QUOTE=Red October;630827]Do not worry, I am an engineer during the week, but at the weekend I am a nurse and psychologist...we are all fine here:-)

 

imho drag is aerodynamics and power or torque (never knew that) is needed to overcome weight. Weight of the car is same as downforce. Both need to be overcome same.
So if you have 640kg car generating 640kg downforce with its on purpose "bad" aerodynamic, it is same as having 1280kg car which have no downforce. But you still want it to be as light as possible, because downforce helps you brake, while car weight creates momentum and as you said, downforce is there only when you need it (high speeds). But to get the speed, you need same power, regardless if it is weight or downforce. So i assumed that downforce is smaller then weight of same fast ferrari is heavy and you confirmed it. F1 is faster because its downforce combined with its weight is smaller then ferraris with same power and (in theory) aerodynamics.

 

The two references are the electrical diagrams at 11.4 and JEPC to lookup part numbers. I was deliberately looking to see if the power fold mirrors had a second motor, and it is not listed. The only motor is listed as different between with and without memory function, but the same whether or not power fold.

The harness is similar but instead the part number is different between with and without power fold.

 

Ok, so as speed doubles - drag quadruples - this is unavoidable in air.

A car weighing 640 Kg has a downforce at standstill of 640 Kg (which is to say 1G - one times the force of gravity which is equivilent to 9.8 Metres per second squared (9.81M/S2))

To increase the downforce to a point where the car could overcome it's own weight and theoretically drive upside down it would need to achieve a downforce (upforce in this case as the car is inverted) of greater than 1280Kg (2G)

But to get there the power required is massive as the drag has increased by much more than the downforce achieved - the car wants naturally wants to slow down the faster it goes - this is due to the resistance created by the viscosity of the air....

Am I boring you yet?

 

I would think this is due to the ommision of the 2 wires for the fold motor (grey and red)

Could you post a link to the diagram - I have to admit that I am not an I.T. guru...

Thanks,

Rich.

 

The reason for using narrower tires is that in deep snow the front tires can cut through the snow better. It is also true to a lesser extent for the rear tires. They benefit from following the track made by the front tires. However, on packed snow or ice, more foot print is beneficial.

Remembering that the contact patch is oval, lowering the inflation pressure lengthens the contact patch in addition to making it slightly wider. In most circumstances, the recommended inflation pressure is best as you also need to consider speed rating once traffic clears and you are on the highway.

In the same vein, narrower tires are also better in slush because they hydroplane less.

 

[QUOTE=sandy85;630840]Yes, I totally understand - I have confused my friends by not only owning a Landrover which takes considerable maintenance but supplementing it with a Jag which means more of the same....likes alike as you said?

 

This is, of course, assuming that the tyre pressure is high enough to maintain an oval footprint - if low enough the shoulders of the tyre are in better contact than the centre which would create an 'H' shaped footprint - which is how tyres wear at the outside first when under inflated.

 

Not sure I do either - it's probably that earlier lubrication....or because it is now Saturday and I am now a nurse/Psychologist not an engineer...

 

In the middle of a war situation, the Russians did not have the luxury to be careful about damaging the landscape-most of it was already damaged anyway by bombs & artillery shells, so the Russians needed a tank with wide tracks to travel over widely variable terrain.

My shoes were sliding as they had crushed the soft snow into hard ice-I saw this quite clearly when I lifted my foot out of the snow, as there was now a patch of hard ice which was very slippy.

I have very long legs & I'm not a light person-I'm 1.88m tall & weigh 95 kg.

I do not need to worry about frontal resistance as I don't run fast enough for that to be a problem-haha

Anyway, going back to the original question-the gearbox on my XJR starts in 2nd gear in 'N' mode unless you use full throttle & make it kick down into 1st gear. Starting off in 2nd gear helps traction in snowy conditions.

In 'S' mode the gearbox starts in 1st gear & changes up later-at higher engine RPM-than in 'N' mode. In 'N' mode the gearbox changes up into the higher gears earlier.

I'm going to bed now as it's far too late

 

Mine does that too!!!

Another beer, anybody?

 

However, tracked vehicles are completely different from wheeled vehicles. The tracks can float over snow, or bite through ice. Turning is accomplished by differential speed on the tracks. In fact, you can spin a dual track vehicle in place by using opposite motion on each of the tracks.

Comparing the two is like comparing snowshoes to skis and those two even have greater similarities than would tracked versus wheeled.

 

Good point, well made.

It is down to ideal tyre for the condition again?

 

I agree. (I think)

Not sure they float over snow, it's down to surface area creating/using available friction?

 

It's like comparing Guinness to Newcastle Brown Ale & right now I could do with several pints of both after tonight's discussion

Goodnight-or should that be Good Morning as it's Saturday now

 

Jagermeister?

 

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