前面有人提动能不受距离影响， 又有人提出十字弓与长弓夸张的磅数比。 我发现有人好像混用了弓拉到满的最大磅数，以及十字弓储存能量的"磅数" 基本上前者乘以"拉的长度"之後大致除以2才会变後者。 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 另外补充一个连结 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.下面都是简短意译 里面也有做些比较，并说明除了拉的距离不够长以外，弓臂弹回的速度无法达到该动能 所能允许的最大速度，因此造就了较低之速度，以及相对无效的系统。 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.) 而现代十字弓则有办法在较低之拉力下达到更高速度。 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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