"Phil L" wrote in message
...
Arfa Daily wrote:
On last week's episode of Eddie Stobart Trucks and Trailers, they
showed driver Mark working with a new illegal-length trailer that
they have been given special dispensation to trial on UK roads, by
the DoT. They said that it was called an "Eco-trailer" because being
some 2 metres longer than a 'standard' trailer, it would be able to
carry nine more cages of Tesco goods, which would mean less lorries
on the road leading to a fuel and pollution saving.

Fair enough, I thought. But later whilst giving it a bit more
consideration, I started to think about the 'not getting owt for
nowt' principle, and started to doubt whether there really is any
'free lunch' to be had here. If the 'standard' trailer is about 13 m
long, then this one at 2 m longer represents about an extra sixth of
a truck. So for every six of these new trailers, you'd save one
standard tractor unit and trailer. But then, you've got to take into
account that the extra 2 m of trailer is going to weigh quite a bit,
as is the extra axle and tyres that it had, and the extra equipment
to make the rear axles steerable so that it can get round
roundabouts, and manoeuvre in tight yards. On top of that, there will
be the additional frictional drag from the extra axle, plus the
weight of the nine extra cages, and the goods in them. Hauling those
additional weights and losses, is going to take more engine power,
and will thus use more fuel. So how much fuel usage advantage would
really be gained from these extra long trailers ? Any ? Rather less
than was implied ? And as for reducing pollution, I know that diesels
aren't the cleanest of engines, but as far as I am aware, they
produce little or no carbon dioxide, which is the one that the green
mist brigade are terrified of, and only small amounts of carbon
monoxide, so is this just another case of adding the word "Eco" to
the front of some existing item, to justify getting what might be a
contentious change to that item, accepted ? Or am I just being
cynical in thinking that if Stobarts got the approval to roll this
out across their fleet of curtain-siders, they would save the wages
of one sixth of their drivers ... ?

The majority of the weight of a fully loaded HGV heading for Tesco will be
the truck itself, I mean, what do forty pallets of crisps weigh?
bread?
teabags?
There's loads of light goods that take up space but weigh next to nothing,
yet it costs the same as a 250kg pallet of lager to get to the
destination...what I'm saying here is that instead of thinking in terms of
weight versus fuel savings, it's capacity, IE space


I would dispute that it costs the same to haul 50 cubic feet of crisps, as
it does to haul 50 cubic feet of cans of lager. The weight of the goods
being hauled is a significant part of the overall equation, as is the weight
of the trailer. Another two metres of that, plus the additional axle and the
equipment to make the rear axles steerable, is not going to be
insignificant, and when you add in the (potential) weight of the extra
goods - probably somewhere in the region of 500 cubic feet in the additional
capacity afforded by this trailer - the overall weight of the trailer will
be a fair percentage higher than that of a 'standard' trailer. The energy to
move this, and keep it moving, comes from the tractor unit's engine, and the
energy to make this happen, is derived from the diesel that it burns. If the
engine has to output more power to haul the extra weight, then it must use
more diesel. I was just interested in how much more diesel, as this
obviously at least partially negates any claims of using less diesel and
producing less pollution than having an additional sixth of a conventional
trailer on the road.

Arfa