11-15-2013, 11:15 PM
Quote:Espringals often used silk skeins to power the bow arms, which might have been an improvement.I would doubt whether silk could be an improvement on sinew. It's elasticity characteristics are completely different. Consider why a bow-string can be made of silk: precisely because, like linen, it has a low energy storage capacity, which allows most of the energy to be transferred successfully into the missile. This is precisely the opposite of what is required in a torsion spring. (Like linen, silk also has a high tensile strength, meaning that it tolerates higher tractive stress -- exactly what you want in a bowstring.)
Quote:In case of silk as spring material, that is only mentioned in Eastern Roman manuals while in west, horse hair is used mostly.I would be interested to see where your information on silk has come from. Greek and Roman catapults used animal fibre for the torsion springs (ideally, sinew; otherwise horsehair; at a pinch, human hair) because of the peculiarities of its elasticity. Silk (similar to plant fibre) has nothing like the elasticity of animal fibre.