A dolly is an unpowered vehicle designed for connection to a tractor unit,

truck A truck or lorry is a motor vehicle designed to transport cargo, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame constructi ...

or prime mover vehicle with strong traction power.

United States

Classification by axle configuration

There are several types of dolly

bogie A bogie ( ) (in some senses called a truck in North American English) is a chassis or framework that carries a wheelset, attached to a vehicle—a modular subassembly of wheels and axles. Bogies take various forms in various modes of transp ...

: * Full trailer - 2 axle (4 wheels), with a draw bar which also controls the trailer's front axle steering. The draw bar does not take load of the full trailer. Heavy full trailer needs to have its own brakes remotely controlled by the prime mover vehicle. * Semi-trailer - 1 axle (2 wheels), without the front axle but have a landing gear. Large semi-trailer of truck size is designed for connection via the fifth wheel on the tractor unit or the semi-trailer truck. Small semi-trailer such as

travel trailer A caravan, travel trailer, camper, tourer or camper trailer is a trailer towed behind a road vehicle to provide a place to sleep which is more comfortable and protected than a tent (although there are fold-down trailer tents). It provides th ...

and

boat trailer A boat trailer is designed to launch, retrieve, carry and sometimes store boats. Commercial boat trailers Commercial hydraulic boat trailers are used by marinas, boat yards, boat haulers, boat dealers and boat builders This is a list of boa ...

is designed for connection via a

tow hitch A tow hitch (or tow bar or trailer hitch in North America) is a device attached to the chassis of a vehicle for towing, or a towbar to an aircraft nose gear. It can take the form of a tow ball to allow swiveling and articulation of a trailer, ...

of a passenger vehicle. Either the fifth wheel or the tow hitch takes up to half the load of the semi-trailer. * Road train - special large dolly

equipped with a fifth wheel for further connection by the gooseneck type drawbar of another similar dolly and form a road train. The last dolly in a road train needs its own rear lights, brakes remotely controlled by the prime mover vehicle, and

registration plate A vehicle registration plate, also known as a number plate (British English), license plate (American English), or licence plate (Canadian English), is a metal or plastic plate attached to a motor vehicle or trailer for official identificatio ...

. * Tow dolly - a semi-trailer designed as automobile rescue equipment. It is designed to couple to the concerned automobile's powered wheel, i.e. the front wheel of a

Front-wheel drive Front-wheel drive (FWD) is a form of engine and transmission layout used in motor vehicles, where the engine drives the front wheels only. Most modern front-wheel drive vehicles feature a transverse engine, rather than the conventional longitu ...

automobile, or the rear wheel of a rear-wheel drive automobile, by locking the powered wheels onto the tow dolly's tray. The tow dolly is

connected to a

tractor A tractor is an engineering vehicle specifically designed to deliver a high tractive effort (or torque) at slow speeds, for the purposes of hauling a trailer or machinery such as that used in agriculture, mining or construction. Most commo ...

. Tow dollies are legal in all 50 US states and Canada. In the U.S. and Canada brakes are required on any loaded car tow dolly.

Classification by coupling configuration

There are two basic types: * ''Converter dolly'', equipped with between one and three axles and designed to connect to a towbar on the rear of the truck or trailer in front. There are two variants of this: ** An ''A-dolly'' has a single drawbar with a centred coupling. ** A ''C-dolly'' has two separate couplings side-by-side. * '' Low loader'' dolly, equipped with a ''gooseneck'' type drawbar that attaches to the fifth wheel coupling on the rear of a

prime mover Prime mover may refer to: Philosophy *Unmoved mover, a concept in Aristotle's writings Engineering * Prime mover (engine), motor, a machine that converts various other forms of energy (chemical, electrical, fluid pressure/flow, etc) into energy ...

to distribute the mass on the fifth wheel on the dolly between the prime mover and the wheels of the dolly. These are predominantly fitted with two axles.

Australia

Converter dollies are used in road trains in

Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

, most commonly with two or three axles and a hinged drawbar. They are also frequently referred to as ''road train dollies''. The C-dolly design is not allowed in Australia, as it prevents articulation between the dolly wheels and the axles of the truck or trailer in front of the dolly. Australian rules require articulation between axle groups. Low-loader dollies – which present a kingpin rather than a drawbar coupling – are used with many low loaders to allow heavy cargo to be carried without overloading the wheels of the prime mover or the low loader.

Airport dolly

Dollies are used for the transportation of loose

baggage Baggage or luggage consists of bags, cases, and containers which hold a traveler's personal articles while the traveler is in transit. A modern traveler can be expected to have packages containing clothing, toiletries, small possessions, tri ...

s, oversized bags,

mail The mail or post is a system for physically transporting postcards, letters, and parcels. A postal service can be private or public, though many governments place restrictions on private systems. Since the mid-19th century, national postal sys ...

bags, loose cargo carton boxes, etc. between an aircraft and the terminal or sorting facility. In the US, these dollies are called baggage carts, but in Europe baggage cart means baggage trolleys used by individual passengers.

References

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External links

Diagrams of A-dolly & C-dolly.

Evaluation of dollies, University of Michigan

Legal definition of a dolly
in

Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...

, USA
Images of trailer dollies
Trucks