Why do trailer trucks have so much space between them?

Question

Why do trailer trucks have so much space between them?

Answer 1

For turning. Its because the front corners of the trailer will move in closer to the cab on sharp turns.

Answer 2

As a truck driver and former truck driving instructor...I think I can answer this one ok.  There is a place on the back of the tractor called the catwalk.  It allows the driver to hook up the air hoses that are needed for the trailer and the electrical line that makes the lights on the trailer work.  The space is needed to provide the driver with the ability to get up there and do these things.  Also, some need more space than others.  Like refridgerated trailers have a box on the front (usually) and when you turn the truck....you don't want to hit the box with the stacks or part of the truck.  It all depends on what type of truck or trailer you have as to the space there.  There is regular and stretch "california" type trucks.  but there are laws in many places that regulate how much space can be there.  If you are talking about when the driver switched the 5th wheel or the back axel on the trailer making the space bigger or smaller...then that is because of weight distribution and that's a longer story.  Hope this helps.

Answer 3

Two reasons the trailer needs clearance in turns so as not to contact the tractor with the front corners of the trailer in a turn.

If your learning truck driving you will also have a movable 5th wheel on the tractor. It moves forward and backwards. when this is moved you must check the clearance between the back tire and the landing gear on the trailer for the same reason as above

Answer 4

Without this space how would they backup or turn the truck and trailer ????????????

Answer 5

because of their blindspots and since they are so big, they need more space than regular cars. the cars behind them also need to give the trucks space so they can see whats ahead of the truck incase theres an accident

Answer 6

if you mean between the tractor and the trailer:  it is so the driver can back the trailer in tight spaces,

Answer 7

In terms of another vehicle being in front of them, they require what they commonly refer to as "cushion" space so they have enough time to stop. Tractor trailers cannot stop like cars--they require more time to slow down the engine with the weight they're hauling, and if a car or another tractor trailer is only a few feet away, they might rear-end them. And you NEVER want to pull up too close behind them, especially when they're on a hill, because although many are experienced, a lot of them still have trouble transitioning their clutch/gas/brake. You don't want them to roll back on you.

Answer 8

G'day Ev K!

Depends on what you mean by trailer trucks, and where you live.  I will give you a few options...

In most countries, there are regulations that apply to road networks to protect bridges and roads from extreme loading and overloading.  To give you an example, Australia for general road use use the formula 3L+12.5 to work out mass limits for axle spacing and gross combination mass.  To get the national limit of 42.5 tonnes, the front axle of the truck and the back axle of the trailer have to be 10 metres minimum apart.  (3 X 10 = 30, + 12.5 = 42.5 tonnes.)  To get maximum loading over two tandem axle groups of 16.5 tonnes each, a minimum of 7 metres is requiered. (7 X 3 = 21, + 12.5 = 33.5 tonnes.

In the U.S.A. and Australia, in the early days, many of the states had wooden bridges and these had to be protected.  To do this, bridge formulas were introduced, so that a large amount of weight was not over one span or section of bridge.  This is why you may see a modern day prime mover or tractor with a long, set forward front axle and a large gap between the cabin and the front of the trailer.  

On truck and trailer combinations, it is prudent to use a longer drawbar length as that seems to cut down on the swaying of dog trailer designs.  With the use of triple road trains, drawbar length (measured from the Ringfeder pin to the centre of the kingpin on the trailer) is normally 5 metres.  This is both for stability and for bridge spacing formulas.  

Most trailers can only hang forward so far, as there is a front projection clause in the law...  If they were allowed to go too far back with the siting of the king pin, when making a sharp turn near roadside furniture...  lights, telegraph poles, they would be wiped out by the front of the trailer.  The other thing that has a bearing on where the king pin goes is the siting of the landing legs, for when a semi trailer is unhooked from the hauling unit.  If the king pin is too far forward, the legs will get hooked up with the back of the chassis of the truck, or have the back mudguards wiped out that are over the drive axles!!!  

I do hope that this has been of some help to you.  

Ding.