Hondero
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Madrid-SPAIN
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Sometimes has surprised to all of us the humming that an elongated or irregular sling projectile has made, and we have thought about the possibility of designing an aerophonic missile, that is to say, a sound producer projectile like the whistling arrows. Nevertheless, there is not archaeological or historical evidence (I do not know them at least) of the existence of a projectile like that, in spite of existing projectiles of very special and strange forms, but that respond to other ballistic functions, to economy or simplicity of construction. I have tried replicas of glandes that one could imagine as aerophones, but they emit a weak humming, having to conclude that its design was fortuitous or based on economy criteria, like the hemiglandes or those made by hammering and irregular shape. So, apparently do not exist specific sling aerophonic projectiles, which could have been used in war to send signals or to bring about panic in the enemy troops, (we can imagine a rain of whistling glandes falling over they), either in agriculture and cattle ranch to frighten birds from seeded fields or predators on the prowl. That warns us either of the difficulty of its construction or more likely of its little effectiveness for the tried aim. Nevertheless, even as an entertainment, it would be attractive to throw whistling projectiles by the same reason that we made crack the strap of the sling to enjoy the sensation of the weapon power.
I would like to go at a thorough project of construction and experimentation of aerophonic projectiles in this forum, giving besides continuity to several previous works on the matter that have been posted here. The task of design and experimentation is very wide and requires the collaboration of enough people to try variations of the designs and to imagine other new ones, since a single person does not have generally sufficient time to do it alone.
From the point of view of the acoustic theory I have seen two main possibilities of design:
Type 1:
Aerophone of internal vibration, in which the projectile has a cavity where the vibration of the air takes place and therefore the sound. Thus are constructed the whistling arrows, putting in head an aerophone type whistle or spherical cavity with several holes. But on the contrary that you shoot an arrow, with a straight and stable flight that allows the regular entrance of the air by the holes of the whistle, a sling projectile is not easy to orient point-first of permanent way, nor to secure a perfect alignment of the axis of the projectile with the trajectory. That would be the first challenge to surpass, to acquire a perfect technique (and the sling and the suitable shape of projectile) to secure consistent launchings. The point-first technique is well known and has been discussed enough in the forum years ago, but what we looked for now it is an extreme perfection of this technique. On the other hand, to tune a musical aerophone instrument, like a flute, ocarina, etc, is a delicate process in which any small variation in the design, size of the holes, etc., can spoil the result. For that reason it would be necessary to design carefully aerophonic projectiles type 1, doing numerous tests until securing a good design.
Type 2:
Aerophone of external vibration, in which the shape of the projectile and its movement produce eddies and disturbances in the air doing it to vibrate and to emit sound. It is the principle of bull-roarer, in which the combination of the displacement of the apparatus and its spinning, perpendicular to each other, create in the air vortices of sound. The movements of the sling projectile are similar, since it moves in its trajectory and simultaneously spin, but is necessary that both movements are perpendicular one to other, like in the bull-roarer. The technique that we have to use is the contrary to point-first, having to release the projectile with its axis perpendicular to the trajectory, which is equally easy to obtain with a position of the palm downwards in the instant of release, and not forwards like in the point-first.
There are nevertheless some important differences between bull-roarer and the aerophonic projectile type 2, since the spinning of the bull-roarer is autogenerated when moving in the trajectory, and the spinning of the sling projectile is produced by the sling in the launching, more energetic than the first. On the other hand, bull roarer is simply an aerophone and nothing else, but our projectile must be first of all a projectile, that is to say, able to produce a good impact and reach. We are not going to try to throw a bull-rorarer with the sling by the simple fact that it sounds well. Our projectile must be small and of similar relative proportions to a bull-rorarer, a sort of elongated and flat glans, but of good weight (lead, steel). The pitch will be more high and continuous, since the spin of the projectile do not invert its sense like in the bull-roarer.
I am making and testing different designs and the affair seems promising, although at the moment the sound is not too spectacular. Some conclusions, rather obvious, are:
- Wide designs produce lower tones than the narrow ones and they suffer much more the air drag, disabling a good reach and a precise trajectory.
- Material like terra-cotta or stone sounds well but the trajectories and the reach are very bad since the air push them to unexpected trajectories. The lead, and even the steel, with its great inertia, makes the air to vibrate without modifying its trajectory.
- The best design I´ve found till now is the rectangular, of length/width ratio around 7/1, and not too thin if it is made of lead, since thin designs bend the lead projectile in the flight due to the vibration of the air. As far as the weight, I have experimented with light weights, like glandes from 30 to 50 gr., mainly by economy since all projectiles are generally lost.
-There are many designs to try and could work very well typical forms of bull-roarer like the rhombic one, the oval one, the dentiform, etc.
-The projectiles of type 2 are easier to make and cheaper than those of type 1, although the sound that they will produce is probably more weak.
-Besides type 1 and 2 projectiles, it´s very possible than others approaches to problem could be made, and so it would be very interesting that those who have had experiences with buzzing projectiles tell them here, as well as the shape of the projectiles, to glimpse different solutions.
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Aerophonic projectiles (Read 57430 times)
