This reasoning lets us work out how a relatively simple trebuchet would work but my trebuchet has two extra details in the construction. The first is the sling which is present on most trebuchets. This sling changes slightly the working of the trebuchet however analysis of its motion is much more complex I will therefore not write about its working in detail. The sling is accelerated by the arm and increases the length of the projectile arm without adding much inertia to the trebuchet, thus allowing greater range. The sling is constantly in acceleration. I bent the pin such that it releases the sling when the optimal angle is reached.

The second feature of the design of my trebuchet is the wheel from which the counterweight is suspended. A hanging counterweight is the limit of this idea, with a wheel of radius 0 at the very end of the counterweight arm. Having this wheel with a radius as big as the length of the counterweight arm greatly improves the efficiency of the counterweight. It falls straight down, with no sidewards movement, thus wasting minimal energy on sideways movement. All the force is normal to the wheel at every position of the arm. This counterweight creates a tension on the string which pulls the trebuchet. The force from the counterweight is always applied to the same point, with the same angle, and thus the counterweight can be omitted when calculating the moment of inertia of the trebuchet arm, greatly decreasing the moment of inertia allowing a greater angular acceleration with the same forces. The wheel from which the counterweight hangs does however have a moment of inertia which must be added to the moment of inertia. The inertia is . This is equal to because r is constant (assuming the spokes weigh nothing) and that in turn is equal to mr

© Filip Radlinski 1996, 1997