Turning radius The turning radius (alternatively, turning diameter or turning circle) of a vehicle defines the minimum dimension (typically the radius or diameter) of available space required for that vehicle to make a semi-circular U-turn without skidding. Th ...

was a longstanding problem with

wagon A wagon (or waggon) is a heavy four-wheeled vehicle pulled by Working animal#Draft animals, draft animals or on occasion by humans, used for transporting goods, commodities, agricultural materials, supplies and sometimes people. Wagons are i ...

s, dictated by the distance between the front

wagon wheels Wagon Wheels are a sweet snack food sold in the United Kingdom as well as other Commonwealth countries such as Australia, Canada, New Zealand and India. They are also sold in Ireland. They consist of two biscuits that form a sandwich with a m ...

and the bed of the wagon—namely, the point where the rotating wheels collide with the side of the wagon when turning. Many earlier designs required a very large turning radius; however, shrinking the width of the bed means decreasing the size of the load. As this is a problem that

carts A cart or dray (Australia and New Zealand) is a vehicle designed for transport, using two wheels and normally pulled by draught animals such as horses, donkeys, mules and oxen, or even smaller animals such as goats or large dogs. A handcart ...

(by virtue of their two-wheeled nature) do not face, this factor, combined with their lighter weight, meant that carts were long preferred over wagons for many uses. The general solutions to this problem involved several modifications to the front-axle assembly. The front axle assembly of a wagon consists of an

axle An axle or axletree is a central shaft for a rotation, rotating wheel and axle, wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In ...

, a pair of

wheel A wheel is a rotating component (typically circular in shape) that is intended to turn on an axle Bearing (mechanical), bearing. The wheel is one of the key components of the wheel and axle which is one of the Simple machine, six simple machin ...

s and a round plate with a kingpin in its centre that sits halfway between the wheels, which may be mounted on spindles. A round plate with a hole in its centre is located on the underside of the wagon. The plate on the wagon, in turn, sits on the plate on the axle between the wheels. This arrangement allows the axle and wheels to turn horizontally. The pin and hole arrangement could be reversed. The

horse harness A horse harness is a device that connects a horse to a horse-drawn vehicle or another type of load to pull. There are two main designs of horse harness: (1) the Breastplate (tack)#Harness, breast collar or breaststrap, and (2) the Horse collar, ...

is attached to this assembly. To enable the wagon to turn in as little space as possible, the front pair of wheels are often made smaller than the rear pair to allow them to turn close under the vehicle sides, and to allow them to turn still further, the wagon body may be ''waisted''. This technique eventually led to further designs well-adapted to narrow areas; the front wheels of express wagons, trolleys and floats are small enough to turn under the vehicle's body.

References

{{Horse-drawn carriages Wagons Wheels Carts Horse-drawn vehicle parts

See also

References