Robert Hooke and the Coil Spring

Robert Hooke was perhaps the single greatest experimental scientist of the 17th century, responsible for developing a concept hundreds of years ago that would result in coil springs that are still used widely today. About Robert Hooke   Hooke actually considered himself a philosopher, not an inventor. Born in 1635 on England’s Isle of Wight, he studied classics in school, then went on to Oxford University where he worked as an assistant to Thomas Willis, a physician. Hooke became a member of the Royal Society and is credited with discovering cells.   Hooke was peering through a microscope one day in 1665 when he noticed pores or cells  in a piece of cork tree. He decided these were containers for the â€Å"noble juices† of the substance he was inspecting. He assumed at the time that these cells were unique to plants, not to all living matter, but he is nonetheless given credit for discovering them. The Coil Spring Hooke conceived of what would become known as â€Å"Hooke’s Law 13 years later in 1678. This premise explains the elasticity of solid bodies, a discovery which led to the development of tension increasing and decreasing in a spring coil. He observed that when an elastic body is subjected to stress, its dimension or shape changes in proportion to the applied stress over a range. On the basis of his experiments with springs, stretching wires and coils, Hooke stated a rule between extension and force which would become known as Hooke’s Law: Strain and the relative change in dimension is proportional to stress. If the stress applied to a body goes beyond a certain value known as the elastic limit, the body does not return to its original state once the stress is removed. Hookes law applies only in the region below the elastic limit. Algebraically, this rule has the following form: F kx. Hookes Law would eventually become the science behind coil springs.  He died in 1703, never having married or had children. Hooke’s Law Today Automobile suspension systems, playground toys, furniture, and even retractable ballpoint pens employ springs these days. Most have an easily predicted behavior when force is applied. But someone had to take Hooke’s philosophy and put it to use before all these useful tools could be developed. R. Tradwell received the first patent for a coil spring in 1763 in Great Britain. Leaf springs were all the rage at the time, but they required significant maintenance, including regular oiling. The coil spring was much more efficient and  less squeaky.   It would be almost another hundred years before the first coil spring made of steel found its way into furniture: It was used in an armchair in 1857.