The Artics in USA have huge tractor units, different shape to our units here and obviously have the engines front mounted.
Why and how has this difference came about?
Are the American ones petrol driven / diesel, or a mix of both? I am guessing majority are petrol as they can fair belt along the interstates at speeds of up to 80mph so I am assuming there are no speed restrictions. Interestingly however, when it came to hills ( and not particularly steep ones), the units seem to run out of power very quickly and end up slogging up the right hand lane with their hazard lights flashing. Does this highlight the difference between speed and torque?
I only saw diesel in one station and worryingly, it was the green pump whilst the unleaded was the black pump. It took a couple of mins of checking and double checking before I picked up the black petrol - not helped by a pickup that came in beside me and filled up from the green pump! I had to doublecheck with the driver that he was indeed filling up with diesel!
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All diesel, plus they can tow more weight.
They're not as restricted on length, either. Think ferries and the like.
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All diesel. Petrol still in Canada I think. 2 mpg!
Dimensions and axle loadings are much more generous.
Black for petrol and green for diesel applies in some parts of Europe, too, IIRC.
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We have overall length restrictions which make conventional cabs (i.e., those with bonnets) wasteful of payload space. So, in the UK if you see a truck with a bonnet, usually two things are in play 1) the owner's ego, and 2) the truck being used for a dense load so that it reaches maximum weight far before the trailer runs out of available volume.
As for overall top speed, our trucks are limited to 56 mph, and have been since 1988. Before that, trucks could and did speed along at 70+. Since 1988, installed power per tonne has gone up significantly, which is why crawling is much less common than it used to be.
As an example, when my father added the first Scammell / Leyland Constructor 8 to the fleet in 1982, with 265 BHP pulling a gross vehicle weight of 30 tonnes, it was considered to be the flying machine among our trucks. For a modern truck, that power to weight ratio would be considered rather puny.
The trucks in the US will be geared to enable a fast cruising speed, where the trucks here are geared to give good economy around 56 mph.
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>> The trucks in the US will be geared to enable a fast cruising speed,
Yes indeed... they may need to go down through 18 ratios to climb a long steep hill, but downhill or on the flat they can slowly wind up to well over 100mph. Prudent drivers are careful where they do that though because the trucks take a bit of stopping...
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Lorries in USA - Dave
