Cut a rope by Bow shot.

Nicely described memeengine.

I wonder if this particular myth might only apply to wooden bows, since unlike metal and carbon fiber wood is not a consistent material. It is possible that the warning came about because there could be weaknesses in a length of wood that even the best bowmakers couldn't detect. Major weaknesses would be detected very quickly, as the bow would probably have failed as soon as it was first tensioned. But minor ones might not be evident unless you dry fired a bow, which might have caused the weak point to fail. (Or of course less scrupulous bow makers may have been using this line so potential buyers didn't try to fire a bow that was likely defective and discover this when they were still around)

That said there was a line in Arrow regarding dry firing a bow. Oliver is sitting there with a bow in one of the flashbacks (set five years before the events we see in the modern day stories). He is warned not to play with the bow because it was a carbon fiber long bow tensioned to 150lbs and if it shattered they'd be picking bits of the bow out of his face. The interesting thing about this claim is that Oliver wasn't pulling the bow back to anything close to full draw - in fact it was specifically noted that he was incapable of doing so at this time.

The rig doesn't have to perfectly duplicate the actions of an archer, it just has to be close enough that the forces are moving in the correct direction. The myth is that dry firing can damage the bow or cause it to 'explode'/shatter and harm the user.

The point about using real arrows as a point of comparison is a good one. However like duplicating the actions of an archer accurately this is probably the sort of rig that would be impractical if not impossible to do on the show. Both would require rigs that were too complex or that had to be manned throughout the testing - using real arrows would require an automatic loader and someone to turn the machine off while the fired arrows were removed from the target. (And given the nature of the rig chances are fairly good that a fair number of arrows would get damaged when they hit each other, further adding to the difficulties of the rig as you'd have to buy a lot of spare arrows). This wouldn't be a problem if we had reason to think that a bow might fail after maybe a hundred shots or so, but as we might well be talking about several thousand shots or more which would make such a setup impractical. They'd end up having to test the bow for a month to get this number of shots with an arrow in the bow, have the rig manned at all times (if only for safety) and have to take up badly needed space in the shop for the rig.

Ideally of course would be trying to figure out a way that the stresses and stress patterns in a bow could be modeled and shown visually to see if there was/is any difference between a bow firing an arrow and a bow that is fired without one. They might be able to do a computer simulation for this, but such simulations are limited and not exactly the 'hands on' type of testing MB prefer to do*.

(*Yes, I get the irony of using 'hands on' when discussing a rig that is intended to be anything but that)



Figure that the arrow would be 31 inches, or just under 78cm, long. This seems to be the longest commercially available arrow size - historical bows may have used longer arrows than this on occasion but I've not actually seen specific figures for arrow lengths. If they are testing to see if you could parry/deflect an arrow they would most likely be looking at buying the longest arrows they can find in bulk, which would give us the 31 inches figure.

Speed is harder to calculate, but for tradition bows you can look here; www.greenmanlongbows.co.uk/SPEED%20TESTING%20Measuring%20the%20arrow%20speed%20of%20bows%20and%20longbows%20using%20a%20chronometer.htm

Figures range from 136-183 fps, with a approximate average of around 160 fps/49ms - so your calculations are accurate. Not bad for a quick guess.

Humm, a side by side shot would be the best practical option. Assuming that they wanted to test rope-cutting (and some trick arrows) using a static rig anyway they could simply remove the arrow for one of the shots. Everything else needed would already be in place, so it wouldn't require a separate rig or any extra work. The high speed would also serve an additional function in that it would allow them to see how the string is acting, allowing them to fine tune any automatic dry-firing rig to be as close to real as they can manage. They would also be able to use the high speed to compare against a real archer using the same bow (although it probably wouldn't be in the rig at the time) so they could get their firing rig as accurate as possible. All useful information using the exact same rig and basic set up. Maybe add some markers on the bow so they can compare the vibrations directly against each other - assuming the exact same bow in the exact same rig any difference should be easy to spot if the superimpose the two images over each other.

Would something like say a small light piece of cloth on the ends of the limbs allow them to judge if the bow was releasing/containing more energy when dry fired? If the explanation as to what the reason for the difference is correct (that a lot of the energy goes into the arrow rather than the bow) then a dry fired bow should move that length of cloth further out than the same bow firing an arrow. Or at least that is what I would imagine happening.

Thinking on, I suspect that an automatic arrow reloader would most likely be dismissed on safety grounds. If, say, the rear wall of the box fell over or arrows started to be deflected upwards and over the box they'd end up with arrows bouncing around the shop. They have stated on multiple occasions that they never load guns in rigs with more than a single round purely because they don't want to risk having to deal with what might happen if anything goes wrong with the rig. Yes, there are multiple ways they could limit such risk, but I'd expect them to rule out such a rig anyway on these grounds even before thinking about what kind of rig would be needed.

The fail point of a bow could be many thousands of hours.....

However, the reason for not keeping old bows strung all the time was the failure of the string.
They didnt have the technology to make good strings, so they had to un-string the bow when not in use to stop it stretching and snapping.

I think maybe someone needs to talk to someone who is specialised in laminated materials under tension ...
Find out exactly what may fail and why and under what circumstances.

it is kind of a "keeping things under tension causes unnecessary wear" factor.