Dolly (trailer)

European type dolly trailer

A dolly is a small trailer that can be coupled to a truck or trailer so as to support a semi-trailer. The dolly is equipped with a fifth wheel to which the semi-trailer is coupled. This dolly needs its own rear lights and a registration plate.

A tow dolly is little more than two wheels, an axle and a tow-hitch, used to tow a Front-wheel drive suspension car behind a recreational vehicle or other larger vehicle.

There are two basic types of dolly:

• 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 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.

Dollies are popular in Finland and Sweden, where the law allows longer vehicle combinations than in the rest of the European Union. By using a dolly, a semi-trailer can be attached as a regular trailer to the towing truck.

Australia

Converter dollies are used in road trains in Australia, 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.

See also

• Axle track
• Road train
• Wheelbase

References

• Diagrams of A-dolly & C-dolly.