While skimming a recent copy of "Land Rover International", I came across an article about a Police constabulary (can't remember which) that use the new Range Rover as their M'way patrol vehicle of choice.
What surprised me was a claim and I can't remember the exact phrasing but words to the effect that a 4.4l Range Rover can easily tow a 44 tonne artic - is that plausible?
As I said, I was only skimming and didn't get a chance to fully read the arcticle so may have got the wrong end of the stick....
Chad.
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I've seen a few Traffic RR Vogue's hanging around the Merseyside end of the M58. Don't know how much they can tow though.
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Adam
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Absolutely true. I've seen an ordinary LandRover series 2 pull a big lorry up the incline from the roundabout at Aust Services.
In low range bottom gear LandRovers and Range Rovers have incredibly high gearing. You could get out and leave it idling along and it would be hard to walk slowly enough to keep pace.
I once watched a farmer pulling down a derelict house with an old LandRover. He just hitched a cable through two windows and drove away. It pulled the wall over.
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Pulling a heavy load is easy, witness the "World's Strongest Man" tv shows where a single man can pull a truck, train carriage or aeroplane over a short distance.
There must be someone in the Backroom who paid enough attention at school to work out the force needed to move such a truck from a standstill. Force = Mass x Acceleration is all I can recall.
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Local Mitsubishi dealer told us of a local haulier who runs an L200 as his personal vehicle. One of his rigs got stuck in a field coming away from a festival so he unhitched the tractor unit, towed that out with the L200 then went back for the rest of the rig. No problems.
Mental not to self; check previous owner history on any locally registered L200s when buying secondhand.
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To get a truck moving on the flat, you need to overcome the rolling resistance. This means in practice that you have to apply enough force to 'breakout' all of the parts of the drive train that will turn with the vehicle in neutral. Although most rolling resistance comes from deforming the tyres, removing the half shafts would help a bit so that you don't have to get the whole drivetrain turning too.
As the force required to acheive 'breakout' is more than that required when everything is turning (dynamic friction being less that static friction), excess force is avaialable to provide some (possibly small!) acceleration once the truck is moving.
If the vehicle is on a gradient, then an extra towing force of mg sine(theta) is required, where m is the towed mass, g, the acceleration due to gravity, and theta is the angle made by the road from the horizontal. (Extra tractive effort is, of course, also required to propell the towing vehicle up the slope)
The capability of a hypothetical towing road vehicle with any gear ratio at its disposal is essentially limited by the maximum tractive effort it can put down through its wheels before slipping occurs, which is mg multiplied by the coefficient of friction between tyre and road. m here is the mass of the towing vehicle only.
number_cruncher
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Good Post Crunch!
So, after all that, what sort of numbers are we looking at? Could a normal car have enough grunt to move such a Truck? (discounting any permanent damage that might occur) :-)
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Purely as a 'guesstimate', I would imagine about 2000 Newtons would be enough to start a large, laden truck rolling on the flat - this force corresponds to an equivalent of about 200 kilogrammes mass hanging off a pulley.
number_cruncher
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I think this thread is really about the difference between towing and pulling.
I would not like to even think about the consequences of a Range Rover towing a 44 ton trailer on public roads for any distance, the braking and weight are just not there to control this "rig".
However I feel that most reasonable size off road vehicles working in low ratio could pull trucks like this out of trouble for a few yards.
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However I feel that most reasonable size off road vehicles working in low ratio could pull trucks like this out of trouble for a few yards.
I think this must be it - the ability to pull a trailer a short distance on to the hard shoulder or out of harms way wherever ..... not the ability to tow it like a caravan for miles and miles at speed.
Chad.
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Quite so. That presumably is what the police want it for - quick action to drag obstructing vehicles out of the way.
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Some years ago I saw one of the early police Range Rovers tow a fully loaded fire engine - complete with crew - most of the way up Reigate Hill. I have no idea why this was necessary (no spare vehicles available perhaps?!). It was quite slow, but made it to the top in one piece. Most impressive.
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