前面有人提動能不受距離影響， 又有人提出十字弓與長弓誇張的磅數比。 我發現有人好像混用了弓拉到滿的最大磅數，以及十字弓儲存能量的"磅數" 基本上前者乘以"拉的長度"之後大致除以2才會變後者。 http://science.howstuffworks.com/crossbow.htm/printable Two factors determine the amount of energy a bow can hold. Its draw weight is the amount of force required to draw the bow. A bow's draw weight increases the farther back you pull the string. Its draw length is the distance between the bowstring's position at rest and its position when drawn. The total amount of energy that a bow can hold is approximately equal to its draw weight times its draw length, divided by two. In other words, a bow's overall strength depends on how hard it is for you to pull the string and how far back you are able to pull it. Bow manufacturers express this strength in terms of: The bow's energy, measured in foot-pounds or joules The arrow's velocity, measured in feet or meters per second 另外補充一個連結 http://www.thebeckoning.com/medieval/crossbow/cross_l_v_c.html W.F. Paterson (1990) published data from Stephen V. Grancsay about an experiment comparing a longbow and a crossbow that was spanned with a cranequin. Type of Weapon @ Draw weight @ Bolt weight @ Speed of bolt @ Difference Longbow 68 lbs. 2.5 oz 133.7 fps Not much!! Crossbow 740 lbs 1.25 oz. 138.7 fps Not much!! ps.下面都是簡短意譯 裡面也有做些比較，並說明除了拉的距離不夠長以外，弓臂彈回的速度無法達到該動能 所能允許的最大速度，因此造就了較低之速度，以及相對無效的系統。 Although it is impossible for any bow to be perfectly efficient, crossbows are particularly inefficient when compared to longbows. The reason for this is that the draw length and the lath (also called a prod) of crossbows are much shorter than those of longbows. So even though a crossbow may have more stored energy when spanned, the tips of the lathe do not have enough time to reach the maximum velocity that the amount of stored energy would otherwise allow. It is the lathe tip velocity that determines the speed of the bolt that is loosed. (Crossbows are not "fired", which is a term related to gunpowder.) 而現代十字弓則有辦法在較低之拉力下達到更高速度。 NOTE: through the use of modern engineering and advanced materials, modern crossbows are now much more efficient. The Excalibur Exomag has a draw weight of 185 pounds, and is able to send a bolt at 290 fps. The 165 pound draw weight Excalibur Exocet looses bolts at 270 fps, and the 150 pound draw weight Excalibur Vixen looses bolts at 250 fps. Special thanks to Excalibur Crossbows for the use of crossbow specs. --

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