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Leo Todeschini
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Location: Oxford, UK
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PostPosted: Tue 14 May, 2019 1:40 am    Post subject: The power of different crossbow spanning devices         Reply with quote

Hi All,

I started making crossbows years ago so I could find out about them as there was so little reliable information. As part of this push, I try to disseminate what I find out using originally this site and now You Tube as well, where I have a channel with videos on such subjects as how far does a windlass bow shoot and how a two Axel crossbow trigger works as well as sword related bits and pieces.

This particular video looks at 9 different ways to span a crossbow and how powerful a bow you can span using that system and what the ratio of mechanical advantage of the system actually is. https://youtu.be/2IdfmaC_t-Q

Hopefully it will be useful to some of you.

Tod



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Jean Thibodeau




PostPosted: Tue 14 May, 2019 5:21 pm    Post subject:         Reply with quote

Note to everyone the video is well worth taking the time to look at.

Tod, really informative about the relative draw weights and leverage advantages of the different ways to span the prod.

I was really surprised to find out that the cranequin leverage ratio was better than the windlass as far as how heavy a draw it could manage.

As to the 1:1 ratio when not using a system with a leverage/mechanical advantage I think your numbers are in the ballpark, but some hugely strong guy might be able to span a bit heavier ..... If the guy was the size and strength of " THE MOUNTAIN " from the Game of Thrones ...... Wink Laughing Out Loud

But then that guy might be able to draw a 300 pound longbow if he trained for it a little bit ..... Eek! Laughing Out Loud

Very good video, well presented and very informative and entertaining.

You can easily give up your freedom. You have to fight hard to get it back!
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Bartek Strojek




Location: Poland
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PostPosted: Wed 15 May, 2019 3:18 am    Post subject:         Reply with quote

Jean Thibodeau wrote:


As to the 1:1 ratio when not using a system with a leverage/mechanical advantage I think your numbers are in the ballpark, but some hugely strong guy might be able to span a bit heavier ..... If the guy was the size and strength of " THE MOUNTAIN " from the Game of Thrones ...... Wink Laughing Out Loud

But then that guy might be able to draw a 300 pound longbow if he trained for it a little bit ..... Eek! Laughing Out Loud

.


Bjornson is unrealistic option, obviously he's so much stronger than 99.999% of people ever, likely.


However, at your local amateur deadlift competition you can easily find a ~170 pounds guy who can deadlift about 465 pounds.

https://www.sfd.pl/Zawody_Martwy_Ci%C4%85g_o_Puchar_Romana_Szymkowiaka__Ko%C5%9Bcian_11.03.2017_r.-t1140544-s2.html

Even under 20 guy can do it as well, though he's a bit bigger.

Of course those are 1 repetition maxes, but most calculators show that someone doping 465 max should be able to do 370 around 8 times.

Those guys , even amateurs, are very likely on some hormonal assistance, obviously unavailable to medieval man. Cool

I'm not sure how to calculate mechanical differences between standard deadlift and drawing the crossbow in different ways with your back, but it would probably be staggered stance dead-lift - one leg forward.

https://www.youtube.com/watch?v=b_h87ttec3k&ytbChannel=null


He are accounts from Pero NiŮo, about best way of using crossbow being spanning with girdle, and strong archers were obviously valued.

https://myArmoury.com/talk/viewtopic.php?p=244850
https://myArmoury.com/talk/viewtopic.php?p=256937

Similarly there's record, from early 15th century about Stanisław Ciołek, polish knight who was spanning mighty crossbows by hand, while archers had to use some help, not sure what, can't follow Medieval Latin at all.

Quote:

Nulla eciam balista tam tensa potuit fabricari, quin absque omni instrumentum pedibus et manibus illam tetendisset


He was supposed to be mightily strong though. In any case, spanning heavy crossbows without/with less cumbersome levers was obviously valued feat.



And here's very interesting video, with very nice replica.

https://www.youtube.com/watch?v=Yogv2dDnx64

Author claimed that he could draw this almost 900 pound bow with such simple instrument, thanks to very long lever arm , it seems. l. Very quick way to span a bow, though the device is obviously really bulky and unwieldy.
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Michael P. Smith




Location: Muncie, Indiana
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PostPosted: Sat 15 Jun, 2019 8:53 pm    Post subject:         Reply with quote

Tod has made at least a couple bows that use a gaffle like that. His opinion is that they are less effective and less easy to use that a gotís foot, if I recall, if not, I hope he corrects me. I canít measure the gaffle of course, but it looks like maybe a 4 to one advantage? A goatís foot is interesting in that if has a variable advantage that is quite high near full draw.

Iím sure super beefy guys can draw more directly. But one advantage of a cross bow with a good spanning device is that huge beefy arms arenít necessary.
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