Several years ago Dr. C N. Hickman published a series of articles dealing with the strains and stress in bows. He called attention to the fact that the belly side of the bow was badly overworked in the stacked bows then being manufactured. He recommended a cross section that was more nearly rectangular. Dr. P.E. Klopsteg brought these recommendations to the attention of archers in several articles in which he gave instructions for making bows of the rectangular section type. Today, almost all of the bows sold in America are patterned after the recommendations laid down by Hickman and Klopsteg.
Now, Dr. Hickman is recommending the use of chains on bows. Is it possible that most of the bows will soon have chains on them or is this last recommendation just a brain storm? We ask him to tell us something about the chains and how to put them on and here is what he has to say.
"It has been a well known fact for years that steel could be made stronger by working and in particular by drawing it. Piano wire is manufactured with tensile strengths as high as 400,000 pounds per square inch. This is accomplished by drawing it so that the grains are drawn out to long threads. The strength of the wire may also be increased by being sure that the grains are the proper size before the drawing starts. This is accomplished by heat treatment.
"It is also a fact, but not so well known, that organic substances may be put in such a form that they will behave like metals. Not only are they subject to tensile strength improvement by drawing, but the grain size may be obtained in at least two ways. One method is known as the condensation process and the other, polymerization.
"There are a great number of these materials on the market, but the one that is attracting attention at this time is Nylon. This is a product of coal air and water. It may be drawn out into fine threads which are twice as strong as silk and which has almost perfect elasticity up to the breaking point. In the fine silk like form, the breaking point is reached after an elongation of about 13%. Another characteristic of this material is that the modulus of elasticity increases with the elongation."
"Now it has taken civilization over 5000 years to learn how to make substances which the Chinese found the silk worm makes. The Physical Chemists tell us that these materials have what is known as long chain molecular construction. Take for example a cake of parafin, you can break it, it has no tensile strength. Yet, the same material may be produced by polymerication in a form (long chain molecular construction) so that no man is strong enough to break a cake of the same size as that of parafin. The strength of silk is due to the fact that it is of the long chain structure. The substance may be taken from the silk worm just prior to the time it starts spinning and may be drawn out by a man into very strong large threads. The process of drawing orients the molecules so that they are in long strong chains. This is exactly what takes place in drawing and rolling metals. The silk worm at the time it spins its cocoon does the same thing. There are two sacks of substance in the worm which have pasages to the spineret on the lower lip of the worm. The fluid from these sacs is forced out through these pasages through the spineret where they unite into one thread. There is a gumy substance on the outer side of each thread which serves to lubricate the pasages, stick the two threads together and to make it possible for the worm to attach the combined thread to the inner wall of the cocoon."