'At either side of the weapon is a frame: over each frame is stretched a skein of sinew-rope: in the centre of the skein is embedded the heel of a recurved bow limb. When fully tensioned, the spring of twisted sinew exerts a powerful leverage on the heel of the bow limb: the tips of the limbs are connected by a cord . '
Invented by the Greeks, (who called them 'Katapeltes Ozubeles') and copied by the Romans, the description is of an arrow-shooting catapult of the third century B.C. a good representation of one of these is carved on a frieze set up in about 228 B.C. by King Attalus I on a terrace of the temple to Athena in Pergamum. The carvings, representing captured weapons, were commissioned to commemorate victories by Pergamum over the forces of Antiochus Hierax and his allies the Tectosages and Tolistoagii (two tribes from Galacia).
The proportions and detail showed that the sculptor (perhaps Eumenes himself) knew his weaponry: comparing the size of the Ionian type of round shield depicted, with the visible bow limb, the latter must have been quite short, not more than 30cm. or so in fact, not unlike the bow limbs of the 'Oneida Eagle'; and it is clear from the outline that this catapult bow limb was of composite construction. This weapon, with its stock, frames, and supply of war arrows, would have needed two men, perhaps with a mule, to transport it. Yet the principle -applying leverage to the base of a short recurved bow limb- is very like that of the 'Oneida Eagle'. The modern weapon has one advantage: the user does not need an ear for music! The 'Oneida Eagle' has its own built-in 'tuner'; a timing wheel is attached to the cam which boosts the spring. A cable runs from the timing wheel through the handle riser to the equivalent timing wheel at the other end of the weapon, ensuring that both cam assemblies and bow limbs move in synchronisation as the bow is drawn and shot.
For ordinary compound bows, Tom Jennings, who first spotted their potential back in 1967, now claims to have solved the problem of tuning (timing) with the 'one-cam system': "the one-cam, un-cam bow that never goes out of time", claim the advertisements for Jennings' latest design, the 'Uniforce'. (It was in fact one Matt McPherson who invented the one-cam system; and the patent rights were purchased by Bear Archery). How did Tom Jennings get involved?
By an extraordinary twist of fate, Jennings Compound Bows became involved in a bitter legal dispute with the Allen Corporation, and in 1983 was 'taken over' by the Bear Archery Company: Wisely, they also 'took over' Tom Jennings as their chief designer. He had long recognised that the action of cams at each limb-tip must be exactly synchronised. The Jennings 'Unistar' was one of the first attempts to prevent the problem; twin cams were attached together, back-to-back on a pylon just below the centre of the handle riser, while the wheels at the limb-tips were plain pulley-wheels, (idler wheels), which had no multiplying effect, merely changing the direction of the string.