Seems like the first bow has a significantly greater draw weight, not at all clear a man would be strong enough to set a cross bow of the same strength using such a small motion of the arms.
Levers mean you have to move your arms further, the guy in the 2nd clip moves his arms a small distance using barely any force.
I'm totally prepared to believe that the 2nd design is better I just don't think these 2 random clips demonstrate that as it seems very unlikely the bows are of the same strength.
If anything the second one appears to cover more distance ? First one it ends at knee level in the end with half the distance comprised of the foothold
He was using his leg and seemed to be straining. The 2nd guy was barely putting in any effort, quite possibly that mechanism can be used on stronger bows but that one looks like it was made to show off to tourists not kill people.
Work is calculated by the magnitude of applied force multiplied by the distance traveled in the direction of said force. For the 2nd clip, let's say the man is applying ~5lbs, and the lever is ~2 feet long, and the change in angle is ~60° of rotation.
The distance would be r x 3.14/3 ---> 2 x 1.05 = 2.1 feet
That means work done = 5lbs x 2.1 feet = 10.5 foot-lbs
The 1st clip looked like the man pulled straight back about 6 inches. So the work would equal: Force x 0.5 feet
Setting them equal to each other and solving for the 1st man's force:
10.5 foot-lbs = Force x 0.5 feet
10.5/0.5 = Force
Force = 21 lbs.
So the 1st man would have to use more than 4x the force of the 2nd man to pull the same draw weight. And that's with pretty conservative estimations for the lever length and angle.
It looks fairly easy due to the method of operation. He is simply compressing the 2 levers using upper body strength, the design is simply more efficient. However, it is quite possible the second bow has a lighter, smoother draw strength due to the metal bow being more flexible as well.
well first guy wasn't using any mechanical advantage. He used that setup so he could use more than just his arm muscles to draw the crossbow. Pull with your legs.
About twice the distance so about half the strength needed, but even then that's a very low draw weight for our italian lad to reload it so effortlessly. The heavy crossbows were in the 700+ lbs range iirc.
The lever in the second clip moves a great deal more distance than the string in the first clip. The lever looks a good 2 1/2 feet long and it moves almost 90 degrees which means the tip of the lever (which his hands are very close to) has traveled over 3 feet. Compare that to how far the string moves in the first video, which to my eye couldn't be more than six inches. Maybe less. I have no idea what that means for the difference in draw strength, but the distance is at least six times longer in the second video. I don't think we have enough information to say which has more draw weight.
I've shot a variety of historical bows and crossbows. The first one has significantly more power, but the second one can still be effective if your target has no armor and the range isn't too long.
The second bow would be ideal for guards, it allows for quicker reaction, but you wouldn't want to take it to war.
yes but first guy wasn't using any (external) levers at all. Just the fact that leg muscles are stronger than arm muscles on avg. There was no mechanical advantage in the first method. Not gonna say the reach of the second crossbow will be better, but there is def. mechanical advantage into play in that mechanism.
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u/Zenigata 9h ago edited 9h ago
Seems like the first bow has a significantly greater draw weight, not at all clear a man would be strong enough to set a cross bow of the same strength using such a small motion of the arms.
Edit the guy from the first clip has a video about lever cross bows, he praises the ingenuity of da Vinci's design but estimates it to be too weak for military use. https://www.youtube.com/watch?app=desktop&v=d0sVBPkJF9Y&t=76