9 MEDIEVAL CROSSBOW DEVICES - How do they work?

[Applause] [Music] hi it's tired of Tubbs workshop and Todd Cutler and today we're going to talk about the mechanical advantage different spanning methods of crossbows so I've got a mess of crossbows here I've got four standing up here and little tiny one here all be made by by me through the toes workshop brand this goes from one hundred and twenty pounds in draw weight so fifty kilos 55 kilos in draw weight through to the windows bows the biggest of this lot which is nine hundred and sixty pounds in draw weight so round about three hundred and ninety kilos in draw weight something like that and then we're also gonna have a very quick mention of this book this is the book of the crossbow by Ralph Paine Galway it's basically sort of like the Bible really of crossbow making salt off it's a really good primer work it's a really good primal work before looking at crossbows but do not take it as gospel truth it just simply is men who were writing these sort of historical books around about the year 1900 or a little bit before they they seem to have their own agendas and their own theories and their own ideas which may or may not get backed up by research and unless you're quite painstaking about identifying what's true and what's not they're difficult books to use in the sense of you can't say that they're all correct so the example I've just taken a frame here of some crossbow bolts from the pen Galway book that he goes here are some bulbs well basically most of those I've never seen in my life and I look in a lot of museums now part of that is he talks about the mechanical advantage of the different systems we're going to have a quick look at that and look at what advantage you get with pulleys and chronic winds and so on not going to calculate it right we're not gonna calculate it we're gonna actually measure it we're going to measure for one rotation on the handles what kind of distance you get and that way we'll get an absolute ratio so here we have less our 13th century crossbow you can put the butt of the stock into your chest or onto our belly here and you can draw back and you can get about 150 pounds maximum I've shown that on another couple of videos I've got that stone go and knock a blister now an Akuma are roundabouts late 11th century she was talking about Crusaders there who are spanning their bows by sitting on the ground and putting a foot on either side of the stirrup and pulling the string back that's actually a very powerful motion and you can span if you practice up to about 280 300 pounds in draw worked so literally you pick your feet there on the top and you just pull the string back blacks say that limits you to about let's say 300 pounds in draw way we've got a stirrup stirrups were don't have fairly radically new at this time so the early crossbows didn't have a stirrup in fact when you introduced the stirrup what that does is it actually reduces the amount of power you can spend you want powerful spanning sitting on your back and pulling this back because now that you're doing it like this you've got your foot in one side and it it's it's an awkward off you're off-center it's it's it's not an easy maneuver really to do it so that actually limits you back again it takes you down to about maybe 250 maximum but it what it does do is it stops you having to sit down cut your bows stand up shoots it down cut your bows stand up [ __ ] so it makes the whole process much faster so the stirrup is a great invention but it is now reduced the power again the next thing that you can do is you can use a spanning belt buckle goes at the back this rather inelegant dangly bit makes it very difficult to run and curiously goes at the front and then what happens is you simply hook that on you put your foot in and then actually you go in this pose and you can push down with your with your hand here and pull this and you can go straight on and there you're in right terms a mechanical advantage it's a one-to-one it's a straight pole it allows you a little bit more using the spanning belt maybe up to about 300 320 pounds if you're a chunky guy done without a spanning bill so it definitely has an advantage but it's a one-to-one okay and it uses your big muscles here in your legs and your big back muscles as well as your arms now what then happened is of course we all know about pulleys and pulleys are very easy and certainly the medieval people absolutely knew that so you can make what's got a double of that you've got a roller here and a hook just as you over for and a funny little catch now I don't have a crossbow that suits this at the moment but that hooks onto a peg on the boat so if you imagine that there is a peg here that hooks onto the peg that goes on now then when I put my foot in and pull you now have a two to one action because of the pulley so now you can span up to 450 pound draw weight something like that now the obvious thing of course is you might think it's a doubler pulley you should be able to double the amount of load but actually you can't yes you get some friction losses but the other thing is very easy straight that movement becomes a much longer longer movement to get that doubler and that becomes a little bit awkward again so so it's a double pulley yes but you can't actually draw double the way foot here we have one of my munition grade crossbows with a 300 X bound to draw weight still on 380 pounds to span the string from here to here I cannot do that by hand they'll being some chunky bodybuilder boys out there watching this or one you can do that I am NOT one of them so I use a goats foot lever now this is an interesting thing because it's not a straight mechanical advantage I can't tell you exactly what this is because it changes continuously now obviously to pull the string from here to here takes a lot less work than to pull the string from here to here because this boat increases in power the more you pull it back to higher the draw weight so these curves on there allow continuously changing mechanical advantage so like I said 380 pounds so I can pull it back now at that point there and they see I'm now on one finger I'm on one finger holding that bow back it's not quite 380 pounds at that point it's probably about 320 330 because it's not quite at the nut well we'll do the best we can to do measure and we'll get an average mechanical advantage that's all I can give you what I can do is measure the radius from there through to the end I'll just do that again see where the end register is and we'll get a radius on it okay looks to be about six degrees okay so let's measure that as best we can right okay so we've got 700 millimeters divided by 135 mill which is the distance it comes back that gives you a ratio an average ratio ratio of 5.2 okay so the mechanical advantage of the goats foot lever is 5.2 as an average through its travel that is not what it is at the end because I can hold that back like I said of one finger and the reason for that is that it's the mechanical advantage changes radically at the end so if it's averaging at 5.2 I would think at the end the mechanical advantages it's maybe 12 to 1 on the ratio that the average through travel is 5 to them big ole boy this one nine hundred and sixty pounds at Rahway now this is going to be a little bit easier because we've got an absolute relationship between a rotation here and a travel down okay 22 centimeters 9 inches 1878 to 1 so a six fully windlass is a 78 to one the last of the proper bows as a cranek window this one is coming in at I think it was about six hundred and twenty pounds and draw out something like that and we have a little vlog on the back here that the back of the chronic win is is just catching on to so again we'll do exactly the same method now that I will calculate how far it is to rotate one and how far the string actually moves 30 centimeters 13 inches 11 millimeters 182 to 1 so a chronic win 182 to 1 then the last thing we're just gonna have a quick look at is this rather funny little oddity which is a ballast RINO now these were Italian Spanish round about the earth 1616 50-something them so they are in the age of gunpowder they're commonly known as assassins bows I don't think they are I don't think they ever were I've got a nice look video on that it's got screw jack built into now this is gonna be wildly different for all different bows but again we'll just do exactly the same method again because I can just put a little mark on here with a marker pen rotate one whole revolution and just measure off 30 millimeter diameter so 94 millimeters is a complete revolution 2 millimeters so the mechanical advantage on the balestrero system is a forty seven to one yeah a cute little bow this that's it really we've got windlass we've got goats foot we've got chronicling bows they all come in with different mechanical advantages that are dependent on the power I mean what was interesting is the cranek window had a much higher ratio than the windlass still but chronic wound bows were very often much more powerful than 600-pound but that was so if you look at some of the museum examples and well you've got a bow which is maybe 60 centimetres long but it might be 50 50 mil so two inches high and 20 mil or 3/4 of an inch thick I really can't begin to hazard a power of that I would think a minimum 1,500 pounds probably 2,000 pounds real weight and possibly even more than that say although that chronic one is driving a fairly low powered vote for one of these the chronic wound itself as a system is capable of driving 1,500 pounds 2,000 pounds maybe and that's why the mechanical advantage is is very high on anyway I hope you learned something and we'll have a quick look at those and the last thing you'll see is part of the scan over of the bows there is we're going to have a look at the bolts because it's kind of a comedy range of bolts really from the very small crew to the very big thank you very much [Music]

Channel: Tod's Workshop

Views: 230,956

Rating: 4.9568954 out of 5

Keywords: Medieval, reenactment, goats foot lever, Cranequin, Windlass, Balestrino, spanning belt, doubler belt, todcutler, todsworkshop

Id: 2IdfmaC_t-Q

Length: 11min 42sec (702 seconds)

Published: Mon May 13 2019