Developing a Lightweight Trailer-Hitch

Trailer hitches are found on many non-commercial vehicles such as pickups; SUV's and even some cars and used to tow trailers, boats, campers etc. They are a safety critical item but do not get the checkups or preventive maintenance. Vehicle OEM's face pressure to reduce fuel consumption and mass reduction is an important means to accomplish that. This development work was undertaken for Alcoa with the goal to reduce the weight of a typical trailer hitch from over 30 lbs to under 15 lbs while maintaining safety, installation, towing capacity and durability and also minimizing impact on unit cost.

A typical trailer hitch (shown below) is an assembly of seven components made from steel sheet, tube and sometimes even a casting or a forging. The parts are typically joined together by welding and the assembly is bolted to the underside of the vehicle frame and sometimes to the rear bumper. It must fit into the available packaging space and also look good. To accomplish the goals of this program we chose to apply aluminum in two different product forms, namely hollow extrusion and casting, and integrate the parts - just two. The new design, shown in figure 2 below, conformed to the applicable SAE standard while the weight was reduced by one-half and all the other objectives were also met. The part consolidation, particularly in the cast hitch-receiver, resulted in optimizing material distribution and minimizing number of joints and resultant welding which improved durability, reliability and safety. The remaining weld joint was designed to be closed loop to eliminate open end points; which typically are fatigue initiators and cause quality problems. The casting design also provided a protective pocket to install the connector assembly so it would not get easily damaged during use and minimize road-salt-spray induced corrosion. Using computerized simulation tools for forming; a special oval extrusion shape with varying wall thickness around its perimeter was created, such that it could be formed into different cross-sectional shapes along its length. Special manufacturing process and press forming tools were also developed. This gave the assembly its strength and stiffness for minimal weight. The design's performance and ability to meet standards and other requirements was ensured using FEA and then prototypes were manufacturing and tested in the lab successfully. Common alloys were used to minimize cost impact. Technical cost modeling (TCM) was used to estimate the unit cost of the assembly and was determined to be within target levels.

Typical Steel Trailer Hitch

Lightweight Aluminum Trailer Hitch (figure 2 below)

The design is adaptable to use on a variety of vehicles and can be tailored for different capacities. It can also be scaled up to commercial vehicle applications. The details of this design and its development are published in an SAE paper and it is covered by a US patent. For more information, please contact this consultant directly.

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