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Kevin S.





Joined: 25 Aug 2009

Posts: 54

PostPosted: Fri 11 Dec, 2009 3:51 pm    Post subject: GoatsFoot Crossbow         Reply with quote

Based on basic physics, I know that a lever can make the pulling of the crossbow much easier. However, I am not sure on the specifics.



Assuming that the person holds it in the same way as in the picture, what would be the draw-weight that he can easily pull with the lever (assuming a modestly strong soldier)? Is it safe to say 180-250lbs?

thank you
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Hanns Wiechman




Location: Minneapolis, MN
Joined: 17 Jun 2007

Posts: 21

PostPosted: Fri 11 Dec, 2009 6:36 pm    Post subject:         Reply with quote

Assuming a linear increase in tension with the curved pivot and what appears to be a 4:1 mechanical advantage 40-50 lbs of pull using the prod doesn't seem too high. FWIW,
Hanns
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Michael Curl




Location: Northern California, US
Joined: 06 Jan 2008

Posts: 486

PostPosted: Fri 11 Dec, 2009 8:41 pm    Post subject:         Reply with quote

plus if used with a stirup then you have even more power
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Leo Todeschini
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Location: Oxford, UK
Joined: 12 Nov 2006

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PostPosted: Sat 12 Dec, 2009 12:53 am    Post subject:         Reply with quote

in a nutshell Payne Gallwey got it wrong.

The distance from hook to hook pivot verses hook pivot to arm tip may well be 4:1 but this is not the important factor here.

If you look at the second picture down, the distance in height of hook pivot above hook verses hook pivot to tip arm is very very different from 4:1, maybe a 15:1?

I can span a 250lb bow with one finger and this is not a boast or an exageration to try to illustrate my point. I haven't gone higher because I haven't got round to it, but I am sure I can.

Goats foot bows are hand held when loaded, so a stirrup doesn't come into it and usually just a hanging ring was present at the front.

Tod

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