Fifth-wheel coupling

The fifth-wheel coupling provides the link between a semi-trailer and the towing truck, tractor unit, leading trailer or dolly.

[inconsistent] A Thornycroft steam tractor with articulated trailer competed in the 1898 heavy vehicle trials in Liverpool which took place from May 24 to May 28.

[1] Built by the Steam Carriage and Wagon Company of Chiswick, the trailer and tractor unit were connected by a turntable though the details of the coupling are not revealed apart from a schematic.

Another early example of the fifth wheel in a motorised vehicle was the Messrs T. Toward & Co Steam Motor Tractor that was exhibited at the Northumberland Agricultural Society Show in Newcastle upon Tyne in July 1898,[2] and described in some detail in the September issue of the Automotor Journal.

Drawing a trailer loaded with 30 passengers on 6 August 1898 it travelled the 14 miles (23 km) from Newcastle to Durham without a stop for water.

After stopping at Market Place for 2 hours where it attracted a large crowd, it turned "nearly in its own length" and made the return journey without any problems on the hills between.

The September account also includes details of the delivery and successful testing of one of these vehicles for hauling loads of coal over the hilly roads in Morpeth.

The semi-trailer increased the capacity of trucks, but it was the fifth wheel that brought the flexibility for drivers to keep moving while receivers unloaded the loads they just delivered.

The Fruehauf Trailer Corporation helped to make the Martin Rocking 5th Wheel a success by installing them on their popular new semi-trailer design.

Opening a branch in Chicago and later in Des Moines their trailers and hence, the Martin Rocking 5th Wheel became the top selling commercial vehicle of this era.