A Step frame tailer is a type of trailer that differs from the Normal type of trailer used with Articulated lorrys. The frame steps down from the 'neck' section with the kingpin mounted on, to a lower level (generally parallel to the floor). These trailers use smaller size wheels & a slimmer chassis to get a lower deck height.
The Lower loading height is often used for machinery transport. Other applications are to allow taller loads to be moved or when used as a 'box van' chassis to carry far more bulky goods.
The smaller wheel size can result in a lower load capacity but improvements in tyre technology has countered this problem.
The smaller wheels have a smaller circumference so tyre wear is greater due to shorter distance traveled per revolution, compared to a 'normal' truck tyre.
Most trailer makers offer step frames.
The Specialist trailer builders offer versions for heavy haulage with 4 & 5 axles with steering and features such as wheel wells for transporting Combine harvesters and ADT type dump trucks without removing the wheels or using a Low loader. Other versions have ramps to the neck to load vehicles to the front and rear ramps for self loading vehicles.
A specialist version fitted with very large Cranes are used by industrial machinery movers & installers transporting items like Printing presses or machine tools and rolling mill parts. the low height helps keep the center of gravity down on items that often ave a lot of weight high up or are very tall.
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