Main Discussion Area > Arrows

Energy storage and light arrows

<< < (3/4) > >>

Del the cat:
Easy way to look at it... some energy goes into the limbs and some into the arrow.
If we ignore all the fancy stuff and say for the sake of argument that the limbs and the arrow weigh effectively the same and that half the energy goes into the arrow and half into the limbs.
The energy is getting shared in 2 parts 1 part to the limbs, 1 part to the arrow
So if we make the arrow weigh twice as much then the energy gets shared in 3 parts, 1 part in the limbs and 2 parts in the arrow.
So the arrow now has a bigger share of that energy. :)
Exactly the same logic applies to lightening the limbs.

Of course this is a huge simplification just to illustrate the principle.
Del

willie:

--- Quote ---The energy is getting shared in 2 parts 1 part to the limbs, 1 part to the arrow
So if we make the arrow weigh twice as much then the energy gets shared in 3 parts, 1 part in the limbs and 2 parts in the arrow.
--- End quote ---
That looks like a good way to start understanding the concept. There are explanations out there on the web that are heavy on the math...... a full understanding might take a while.

Can someone illustrate a practical usage of the principle? Seems like the calculation would only be useful for small changes in velocity or weight. that is, where efficiencies remain relatively constant?

willie:

--- Quote ---And any disagreement between me and.........
--- End quote ---
Not looking at disagreement at all, just trying to understand.

ok, compare two scenarios

the first, a very heavy arrow leaves a bow at limited velocity . from sleeks example, it is an arrow that reached its velocity during the first half of the powerstroke, with the implication being that the last half of the powerstroke was ineffective or a wasted opportunity. For that bow, a slightly lighter arrow that accelerates thru the full powerstroke will be more efficient

in the the second, a much lighter arrow is shot. It continues to accelerate right up to the moment it leaves the string. In this case, the bow is only as efficient as mass of that arrow lets it be, the implication being if a slightly heavier arrow could have also been accelerated  to the same moment of release (with of course a slighty lower velocity), the bow would be more "efficient" with the slightly heavier arrow.

the bowyers job is to design and tiller a bow that delivers acceleration thru the full powerstroke, to an arrow of the design weight, no more, no less?

Badger:
 Willie, all of them accelerate all the way through the power stroke, the last 1/2 of the power stroke has less weight pushing but gives the arrow better leverage over the limbs sucking the power back out of them. The bowyer can try to reduce string angles in the last 1/2 of the stroke to improve the leverage the arrow has.

willie:

--- Quote --- Willie, all of them accelerate all the way through the power stroke
--- End quote ---
well ok, then I suppose that there might be a difference between a strong  usable acceleration (one that adds the final 20 or 30 fps,) and an acceleration that only nominally increases the arrow speed during the last part of the power stroke.

I read somewhere, (but I can not remember where at the moment), about using a chronograph when tillering out the last 6 inches or so of a new bow. something about seeing if the bow is coming in as expected, and using speed readings to help with decision making during the final tillering. Have you ever tried anything similar?

Navigation

[0] Message Index

[#] Next page

[*] Previous page