The present acceptance criteria for trailer safety chain deals only with strength related to trailer gross weight. In case of primary hitch separation, simple calculations allow estimation of the trailer kinetic energy relative to the towing vehicle and the extent to which this energy must be absorbed by the chain. In some cases approved chains are shown to be grossly inadequate. This energy absorption capability can be improved by using annealed chain with alternating twists in the links. Tensile tests of as purchased commercial chain as well as chains modified as just described can be improved in their energy absorption capabilities by as much as a factor of three. The author was awarded a patent (4,467,598) for this concept.
