Medieval crossbow replica

[stuckinthemud]

I am trying to get a reasonable idea of the actual power of medieval wooden crossbows. This is very niche research. There are only 9 wood crossbow laths (Europe the bow is called lath or lathe, US they are called prods) that I am aware of, out of which 2 are sinewed.
If you want fulldetails check out my thread at [solved]Skane/Lillohus crossbow thread - Page 2

Also I am slowly posting material to my blog (not a commercial site, any adverts are from my hosting service).

So, after much work, I have got the lath to brace height and it looks like this: (image 2 and 3 are the lath unstrung, it is not straight and I am not planning on steaming it straight as the medieval bow is also a bit wonky)

 

[stuckinthemud]

Happy to answer questions. I have work to do to get to full draw length (10.5”). No idea what the power will be but I am 2 or 3 mm below target thickness- 10 percent below - which is annoying. I’m way over the 50kg of my scale. Common wisdom says bows of this type and period (hand drawn bows, 14th century) would be about 250lb. This seems an arbitrary amount based on what an academic thinks a strong man can press, well, hopefully we’ll find out…

 

[mwinfrance]

Following with interest..thanks for posting this

 

[mwinfrance]

You could measure the draw force by hanging it vertically, supporting the "bow" either side of the "shaft" ( rather like one would hang a garden rake on a wall ) attaching a loop at the centre of the cord and hanging a sack or a container from it .As you add known weight of sand ( or water 1ltr water weighing 1kg or 2.2lbs) to the container you will eventually get the weight ( and thus draw force required to pull the cord back ( or down ) as far as just behind the "pin".

 

[stuckinthemud]

I think hanging known weights is the only way forward. Going to visit the village blacksmith and see if he can help

 

[Droogs]

Have a look at - Todds workshop & Richard Head Longbows channels on the tube of you. They cover the subject very well overall

 

[stuckinthemud]

I am familiar with Todd’s work, his work on metal bow laths is well respected, Andreas Bichler and Historia Vivens 1300 (not the Italian site) is an amazing resource

 

[stuckinthemud]

The blacksmith has a 100kg scales and is well up for a bit of experimental archaeology

 

[mwinfrance]

You can also ( may involves taking them apart ) measure force with a pair of bathroom scales, "reworked" to measure pull as opposed to push.Imagine that you attach the bow to the wall and pull the cord towards you .You then place the scales between the cord and the bow (with the "read out" of the scales facing you ) .Place a small block on the scales, so as to hold the cord clear of the part that you would stand on.If the cord still touches the platform you may need to take the scales apart to get to the mechanism.When you pull the cord towards you, the force is shown as the weight on the scales.Moving this ( bow and scales and block ) assembly to a vertical plane , allows you to attach weights ( you don't need to know how much they weigh ) to the cord. You can also do the same sort of thing using a scissor jack or a bottle jack in combination with a bathroom scale, most bathroom scales will measure to over 100kgs.

 

[Inspector]

Would a small crane scale work? https://www.amazon.ca/Outmate-Digit...aWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl&th=1

Pete

 

[MF1000]

By using a lever with a 10:1 ratio to pull down on a centrally mounted rope on the draw chord you could measure up to 250kg effective force with a 25Kg spring balance

 

[Inspector]

By using a lever with a 10:1 ratio to pull down on a centrally mounted rope on the draw chord you could measure up to 250kg effective force with a 25Kg spring balance

Would the built in errors in the scale also be increased 10 times too?

Pete

 

[MF1000]

True but a lot simpler to sort than obtain a crane scales etc …let alone the cost too. If it was +/- 1kg accurate then that would be 10Kg error ….in 250 Kg for a replica setup I’d be happy with that

 

[Inspector]

The scale I linked wouldn't have to be hung to use. A table or beam with the crossbow at one end and a come along pulling from the other end. The scale between the two measuring the force. Heck you could use a fencepost and the bumper of a car to anchor them to. There are other ways to apply the pull that are only limited by what you have, your ability to adapt, can get or access.

Pete

 

[mwinfrance]

Your "come along" costs about 5 or 6 times that price here.

 

[Inspector]

Your "come along" costs about 5 or 6 times that price here.

You can find them if you look under the right rocks.

https://www.ebay.co.uk/itm/40410657...dXeuMrZn%2B6RA%3D%3D|ampid:PL_CLK|clp:2047675
You could also make a boat winch work too.

https://www.ebay.co.uk/itm/16514080...19rZL8NR8zj%2BC5w%3D|ampid:PL_CLK|clp:2047675
Pete

 

[mrpercysnodgrass]

I am trying to get a reasonable idea of the actual power of medieval wooden crossbows. This is very niche research. There are only 9 wood crossbow laths (Europe the bow is called lath or lathe, US they are called prods) that I am aware of, out of which 2 are sinewed.
If you want fulldetails check out my thread at [solved]Skane/Lillohus crossbow thread - Page 2

Also I am slowly posting material to my blog (not a commercial site, any adverts are from my hosting service).

So, after much work, I have got the lath to brace height and it looks like this: (image 2 and 3 are the lath unstrung, it is not straight and I am not planning on steaming it straight as the medieval bow is also a bit wonky)

My father in law was a longbow maker and wrote a book on making them which you can still buy for about a fiver. I don't know if the power calculations are the same for cross bows but I would think they would be!

 

[Fergie 307]

If you watch th series Sword Musket and Machine gun on BBC in the first episode the presenter has some time with a guy demonstrating some medieval design crossbows, which I assume he has probably made. Might be worth giving him a shout.

 

[mwinfrance]

Pete..I'm in France..since Brexit almost all UK companies don't ship to the EU, and vice-versa.

 

[Inspector]

I know you are in France and if you take a little time and search you can find the same stuff directly from China where it is made, Alibaba, Aliexpress and Banggood. You need to play with the search phrases as what works here are a little different there. Besides I thought the OP hangs his hat in the UK.

Pete