Triggerfish
The triggerfish (or caable or pierrière ) is an offensive military machine of the Moyen-âge, driven by Ressort S and cords attached, suitable to launch stones.
The principal part is the rod has , whose lower end passes in a beam of twisted cords by means of keys B and of wheels with teeth C , stopped by pawls. The cords passed in two rings holding with the stem to which the wheel with teeth comes to adapt, as the detail D indicates it. These cords or nerves twisted at will at the lower part of the rod had a great force of rappel 1 . But to further increase the speed of movements which the rod was to take, of the springs out of wooden and nerves surrounded by cords, forming two branches of arcs E attached through the cross-obstacle forced the rod to come to strike violently this cross-piece F , when by means of the winch G one had brought this rod to the horizontal position. When the rod has was lowered as much as possible, a man drawing on the cord H , made escape the branch from iron I (cf detail K ), and the rod brought back quickly to the driving position, stopped by the cross-obstacle F , sent to far the projectile placed in the spoon L .
One regulated the shooting by adding or removing furs in inside of the cross-piece F , so as to advance or to move back the obstacle, or by attaching cushions of leather stuffed of rags to the former wall of the tree of the rod. The more advanced the obstacle was, the more the shooting was high; the more it was moved back, the more the shooting was shaving. The projectile obeyed the Centrifugal force determined by the rotation movement of the spoon, and the horizontal impetus determined by the stop of the cross-piece F . The lower part of the rod presented the section M , in order to prevent the deviation of the tree which, moreover, was maintained in its plan by two pullings of the branches of the spring E .
The hooks O were used to fix the carriage in place, by means of cords related to stakes inserted out of ground, and to attach the features and swing bars necessary when it was need to trail it. Four men could lower the rod while operating the winch G . So that a similar machine was not ruined promptly by the terrible jolt which the rod was to cause while striking the cross-obstacle, it was necessarily necessary that this cross-piece was maintained by braces out of frame and iron supports, as shows it the figure.
The profile géométral below shown the rod lowered by means of the winch, and the rod striking the cross-obstacle, as well as the departure of the projectile of the spoon, the springs tended when the rod is lowered, and slackened when it returned to its normal position.
Similar machines were also used to launch features, such as large the Arbalètes of turn.
Source: Purple the Duke
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1 : It is known that the carpenters tightened the webs by means of cords thus twisted and attached by a small piece of wood which absolutely makes the effect of rod of our machine.
triggerfish
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