It's pretty cut-and-dry.. it's an axle which can be raised and lowered. Normal five axle units don't have them - they tend to be exclusive to heavy haulers. You see them on a lot of straight trucks, as well, such as dump trucks.
Five
You need to be more specific about the configuration. Is a single axle straight truck, a tandem axle straight truck, a tandem axle straight truck with additional lift axles, a tractor trailer...?
A ten foot spread axle trailer is allowed 20,000 lbs. per axle, for a total of 40,000 lbs.
Yes
An 18 wheeler consists of a tractor (meaning something that pulls) and a trailer (meaning something that follows.) A semi tractor-trailer rig has a trailer that sits on top of the frame of the tractor on a coupling device called a "fifth wheel." The tractor has ten wheels with two on the front axle and four on each drive axle in the rear. The trailer has two axles with 4 wheels each. The tractor and trailer together are informally called a rig. Is that what you were after?
A Class 8 truck is a vehicle with a Gross Vehicle Weight Rating of over 33,000 lbs. Single axle trucks with an additional lift axle, tandem axle trucks, tandem axle trucks with additional lift axles, and tractor-trailer dumps are all Class 8 trucks.
Yes, a strong enough tornado could lift a tractor trailer. It would probably take a a strong EF2 or EF3 to do so.
you can find a tractor and a trailer at Angel Pine Saw Mill (south of the mountain),the truck and trailer is by a fork lift.
A tandem truck usually refers to the amount of axles on the trailer or tractor. A single drive axle on a tractor would be referred to as a single, or the same for one axle on the trailer. I have seen it referred to the amount of tires on the end of an axle. When there are two tires on the end of the axle, that would be referred to as a dual, not a tandem.
What type of truck and trailer? For all I know, you could be talking about a Ford F650 and a single axle utility trailer. If you're referring to Class 8 vehicles, something like a single axle tractor towing a single axle trailer would be allowed an interstate GVW of 52,000 lbs.
$70 for a 5 axle tractor trailer
"18 wheeler" referred to tractor-trailer units with a total of five axles (four wheels per drive and trailer axle plus two wheels on the steer axle = 18 wheels). However, it has become a common expression for tractor-trailer units in general, whether or not they have 18 wheels.