Tension Weapons vs Torsion Weapons

Dec 2016
33
Australia
I have long held the belief that tension weapons such as crossbows were superior to their torsion counterparts.

Today, I read an old post from twcenter that claims that torsion weapons are superior than tension ones.

My questions are:

1. By what criteria do we judge a weapon.

2. Which mechanism is better according to those criteria.
 

Chlodio

Forum Staff
Aug 2016
5,015
Dispargum
What do we want a weapon to do?

How well does it succeed at that task?

Criteria for tension and torsion weapons:
Range
Accuracy
Weight of shot
Rate of shot (reload time)
Mechanical reliability
Ease of use

I have no idea what these statistics are for various tension and torsion weapons.

We could also look at historical armies that experimented with different tension and torsion weapons and assume that they made rational decisions in choosing which weapons to use and which to not use.
 

Guaporense

Ad Honorem
Mar 2011
5,050
Brazil
Torsion is basically a way to store more energy in a given amount of space compared to tension. Hence why Ancient Greeks first developed tension catapults and then those developed into torsion catapults.

Torsion is more adequate for artillery while tension is more adequate for hand held weapons that cannot be very powerful due to the restriction of the strength of their users.
 

Ichon

Ad Honorem
Mar 2013
3,781
Torsion is basically a way to store more energy in a given amount of space compared to tension. Hence why Ancient Greeks first developed tension catapults and then those developed into torsion catapults.

Torsion is more adequate for artillery while tension is more adequate for hand held weapons that cannot be very powerful due to the restriction of the strength of their users.
Good post.

Tension can not only store more energy it usually can release it more efficiently as well but gravity is ultimately the most efficient for larger siege weapons.
 
Sep 2017
119
Pennsylvania
Good post.

Tension can not only store more energy it usually can release it more efficiently as well but gravity is ultimately the most efficient for larger siege weapons.
I would agree with this overall. Concerning gravity weapons I agree that they're more efficient mechanically but I think that they could present logistical difficulties.

Since a gravity driven siege engine provides less mechanical advantage to the crew loading and resetting it than a torsion weapon wouldn't it require longer to load, set and fire?

Am I over-thinking the issue with that? If not how does that fact balance against the fact that even the largest siege weapons weren't getting through the walls of larger cities prior to the advent of gunpowder?
 

Dan Howard

Ad Honorem
Aug 2014
5,161
Australia
I would agree with this overall. Concerning gravity weapons I agree that they're more efficient mechanically but I think that they could present logistical difficulties.

Since a gravity driven siege engine provides less mechanical advantage to the crew loading and resetting it than a torsion weapon wouldn't it require longer to load, set and fire?

Am I over-thinking the issue with that? If not how does that fact balance against the fact that even the largest siege weapons weren't getting through the walls of larger cities prior to the advent of gunpowder?

The amount of energy is the same, the difference is how you put it into the system. The faster you want to load it, the more energy you have to expend every second, which increases the effort involved. A crannequin lets you span a crossbow with one hand but it takes a minute or so. A windlass can span the same crossbow in around 15 seconds but it requires two hands and more effort. A goats foot lever can span it in just a few seconds but it requires the most effort of all. Generally it won't work on heavier crossbows because a human doesn't have the strength required. The main problem is efficiency. The larger the machine, the less efficient it is because the machine absorbs more energy itself, leaving less to apply to the projectile. So you can keep making it larger and larger until there comes a point where the machine can't put any more energy into the projectile. Gunpowder enabled more energy to be contained in a more compact device so a much higher proportion of the generated energy could be applied to the projectile.
 
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heavenlykaghan

Ad Honorem
Mar 2012
4,563
I would agree with this overall. Concerning gravity weapons I agree that they're more efficient mechanically but I think that they could present logistical difficulties.

Since a gravity driven siege engine provides less mechanical advantage to the crew loading and resetting it than a torsion weapon wouldn't it require longer to load, set and fire?

Am I over-thinking the issue with that? If not how does that fact balance against the fact that even the largest siege weapons weren't getting through the walls of larger cities prior to the advent of gunpowder?
Nope. On the contrast, because tension catapults have far more complex parts to put together, they are a much greater burden logistically. To quote the well known catapult historian WTS Tarver:
""The findings of this project support several conclusions. First, the traction trebuchet was a serious engine of war in its own right, and not merely a diminutive version of the counterweight trebuchet. This machine provided a viable alternative to the onager soon after the collapse of the Roman empire and long before the introduction of the counterweight trebuchet in the 12th century. Moreover, the advantages of the onager appear minimal: more expensive, troublesome, and dangerous to build, use, and maintain, its advantage of greater range appears negligible in a world before the Welsh longbow and the steel crossbow.
"

"Renaissance and Enlightenment scholars considered this transition from the complex war machines of the ancient world to the comparatively simple design of the medieval trebuchet as proof of the superiority of classical knowledge. More recent investigation, however, has revealed that the trebuchet's simplified design offers significant advantages over its more technically complex forebears
Lacking any components capable of achieving high-energy states of elasticity, the trebuchet was not subject to the catastrophic failures that plagued earlier machines if they were not fastidiously maintained. Whereas torsion and tension engines required numerous precision-made parts — such as metallic gears, locks and frames — a trebuchet could be constructed in the field almost entirely out of rough-cut lumber and using natural stones. Siege engineers, masters of adaptation, seem to have recognized a superior design when they saw it."