When off-road heavy equipment and construction vehicles fail in the field, it can cause big-time problems. The article cited below tells about how a coupler manufacturer learned from Spirol engineers that it needed to switch from using slotted pins to coiled pins. The end results: the coiled pin's design ensures flexibility after installation. For the life of the assembly, the coiled pin can absorb impact loads without damaging the host of the pin. Unlike the slotted pin, it remains an active member of the joint, continuously absorbing loads.

Does your coupler design use slotted or coiled pins? Why?

http://www.designworldonline.com/articles/5411/16/Coiled-Pins-for-H...