I’ve been recently reading about ballistæ (and their many relatives!), and I’ve come across the assertion that early such weapons were tension-based (like any ordinary bow) while more advanced ones would work akin to a crossbow (torsion-based).
My question is: how the heck do the two differ after all? I can see that the energy-storage mechanism is fundamentally the same (pulled elastic string held back), and I thought it was about the different ways you could pull the string itself, but then I had a look at the Wiki page of the oxybeles (supposedly tension engine), which looks EXACTLY like a torsion ballista. Besides – don’t some crossbows get their string pulled by hand? Are those torsion weapons too?
Bonus: [these](https://www.stormthecastle.com/catapult/images/oxybeles-drawing1.jpg) two [images](https://www.stormthecastle.com/catapult/images/ballista-drawing1.jpg) attempt to explain the concept; I still don’t get it. Can anyone please explain it to me?
Thank you!
In: 8
The pulled string *isn’t* elastic. It transfers the force to (and from, when released) the bow or the twisted (torsioned) ropes.
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