Extension springs, which are not to be confused with compression springs, are one of those engineering tools that normal, everyday people actually get to see. Look up a picture and you will recognize them to be very similar to the springs in bed frames, and in your storm doors. Unlike hydraulic pumps, grease fittings, and tapered roller bearings, these springs are some of the least exotic tools in the materials handling and engineering toolbox. These springs are exceptional at cable tensioning, holding hatch doors closed, and making sure that air cylinders return to their starting positions. The beauty of these…