A better small-engine starter pull cord

Gasoline engines are used on power tools, such as chain saws and snow blowers, and on vehicles, such as snowmobiles, personal water craft, and all-terrain vehicles. Many of these tools and vehicles have a manual starter pull cord mechanism to provide the initial impetus to start the engine. The pull cord is wound around a starter pulley connected to the engine's flywheel and crankshaft. To start the engine, a user pulls the starter cord to unwind it from the pulley and impart rotation to the flywheel and crankshaft. Engine starter pull cords are typically made of nylon fiber. Nylon pull cords sometimes do not provide enough impetus to start the engine on the first pull, or even on subsequent tries. These nylon starter cords wear out and break, rendering the engine and hence the tool or vehicle inoperable. In some applications, for example - outboard engines, all-terrain vehicles and especially snowmobiles inability to start the engine can be life threatening. This paper describes an improved engine starter pull cord made of high-modulus fiber. High-modulus fibers are much stiffer than nylon and other conventional fibers. High-modulus fibers are also significantly stronger and are generally more resistant to wear than conventional fibers. The improved starter pull cord is made from melt-spun Liquid Crystal Aromatic Polyester (LCAP), known as Vectran™. The improved starter pull cord is now available as the product know as ArmorCord™. In laboratory abrasion tests, a typical nylon starter cord failed at an average of 22,677 pulls. The improved starter pull cord failed at an average of 1,431,852 pulls. In field trials with power tool engines equipped with the ArmorCord improved starter pull cord cords, experienced users reported that it is easier to start the engine than the same engine equipped with a conventional nylon pull cord. The reason that it is easier to start the engine is that the engine flywheel turns much faster with an ArmorCord pull cord. An analysis shows that a typical power tool flywheel can turn about 45% faster with the ArmorCord pull cord than with a nylon pull cord.