Talk:Compound bow

The compound and composite bow are not one and the same, not sure if it's worth separating. (No they aren't. The composite bow is, usually, the horn/wood/sinew Asiatic weapon). Richard Keatinge 12:14, 23 July 2007 (UTC)

Draw weight - not force

Yes, the correct term in physics would be force, not weight, but the correct term in archery is "draw weight" - not "draw force". N0YKG 14:02, 10 July 2005 (UTC)[reply]

The pictures.

Why is there a picture of an incredibly outdated browning? It doesn't demonstrate the technology available in bows and the cam system is not good at all. Perhaps a Mathews switchback or bowtech allegiance would be more apropriate? The cam system works just fine. This bow is quite powerful, yet only has 20 pounds of force required when you draw it. Don't insult my bow.

I don't have a problem with the photo that is there now. It seems like a good basic representation of a compound bow.

What I would like to see is a diagram that shows the basic common components and term such as

where do the ends of the strings anchor to the frame?
what are the name and purpose of the bar in the middle that mounts near the grip and points back at the archer?-Crunchy Numbers 17:05, 21 November 2006 (UTC)[reply]

wording problem with acceleration

The string continues to accelerate from the release to rest so imparting more power (and hence speed) to the arrow.

I'm going to rework some of these types of statements. Any bow that puts force on the arrow until release is accelerating the arrow the whole time. A traditional bow has maximum acceleration just after release but there is still force and therefore still acceleration until the arrow leaves the string. A decrease in acceleration is not the same as deceleration or negative acceleration.-Crunchy Numbers 05:13, 31 October 2006 (UTC)[reply]

Schematic & explanation needed

This article needs some kind of schematic of a common type of compound bow, where all the mechanical parts are clearly visible, and an in-depth explanation of the physics behind the operation of the depicted bow. Shinobu 17:23, 2 December 2006 (UTC)[reply]

What is Let-off?

It's a term that is put in quotes, and apparently means something, but without knowledge of what that term means, the statement that the let-off is 99% is meaningless. Could someone who knows what it means put it in the article? 62.49.94.185 02:15, 31 December 2006 (UTC)[reply]

Changes 23 Feb 2007

I had to correct some serious misconceptions about how a compound bow works, the main one being the suggestion that energy is stored anywhere other than the limbs. While there might be a tiny amount of energy storage in the riser, string and cables resulting from the elasticity of those parts, it's not worth confuddling people over. Sorry if I've trodden on any toes. Mr Barndoor 16:44, 23 February 2007 (UTC)[reply]

Noise levels

In my limited experience compounds are usually noisier than traditional bows. I propose to delete the new section that says the opposite, unless anyone can come up with a good reference. Richard Keatinge 12:14, 23 July 2007 (UTC)

+++ Id say they are much quieter, though that that owes to other technological advancements that have also gone hand in hand with compound development, not necessarily due to the inclusion of cams and pulleys itself.

For instance, parallel limbs have perhaps done the most to bring down the volume of bows, these limbs of course being an exclusively available to compound bows. The fact of the matter is that a fully silenced compound bow is much quieter than a fully silenced long or recurve bow, the fact that a barebones compound in circumstances can be louder is a moot point as bows are rarely fired in this manner anyway. —Preceding unsigned comment added by 60.242.139.185 (talk) 02:24, 11 September 2007 (UTC)[reply]

You're moving goalposts. Compare a stock compound bow to a stock trad bow. The trad bow is quieter. — NRen2k5^(TALK), 10:55, 27 March 2008 (UTC)[reply]

Origins of the compound bow concept

I've always thought, and many sources suggest, that the compound bow was invented by H. Wilbur Allen. He was certainly the first to patent the concept. However, I recently had a conversation with a compound bow designer (Ben Jones of Merlin) who told me that the concept had been around since at least the 1950s, possibly the late 1940s, and Allen's patent was strongly disputed at the time. Does anyone have references for this earlier work on the concept? Mr Barndoor 11:31, 26 September 2007 (UTC)[reply]

It seems the concept of a “compound” bow is even older than that. I stumbled upon a webpage a while back showing a “compound” design that a Native American tribe used. It was basically a longbow with a shortbow attached to the back (to a layperson, the front). The string was tied to the limb tips of the shortbow and strung through the limb tips of the longbow. — NRen2k5^(TALK), 00:51, 12 April 2009 (UTC)[reply]

What you describe is pennobscot bow. It is not compound. It is two bows bundled together with string. —Preceding unsigned comment added by 193.184.83.234 (talk) 09:33, 2 May 2011 (UTC)[reply]

Confusing Lingo

As someone who does not have much prior knowledge of bows, I found this article difficult to understand. With all of the technical lingo used in it, I think some clarification is needed. Maguxmagu (talk) 02:31, 30 October 2010 (UTC)[reply]

Draw weight, fps & kinetic energy

We read "A draw weight can consist of 30 to 100 pounds creating speeds of 150 to 370 feet per second (46 to 113 m/s)"

--> according to http://www.huntersfriend.com/bowselection.htm#10-drawweights, we find that depending on the person's age, someone will only be able to pull around 30-40 lbs (=30x0,45= 13,5kg) The table from the page is useful:

Very Small Child (55-70 lbs.) 10-15 lbs.
Small Child (70-100 lbs.) 15-25 lbs.
Larger Child (100-130 lbs.) 25-35 lbs.
Small Frame Women (100-130 lbs.) 25-35 lbs.
Medium Frame Women (130-160 lbs) 30-40 lbs.
Athletic Older Child (Boys 130-150 lbs.) 40-50 lbs.
Small Frame Men (120-150 lbs.) 45-55 lbs.
Large Frame Women (160+ lbs.) 45-55 lbs.
Medium Frame Men (150-180 lbs.) 55-65 lbs.
Large Frame Men (180+ lbs.) 65-75 lbs.

we find that the speed of the arrow can vary between 280 and 340 fps (feet per second; for large frame men (65-75 lbs) see http://www.huntersfriend.com/bow-review-400-fps-bow/400-fps-compound-bow.htm ); that is probably using a 350 grain (= ? kg) arrow. It appears that arrows come in various sizes, and weights of 490 to 540 grains isn't unusual (see http://www.bghi.us/index.php?x=bowspeed )

How to determine kinetic energy --> This is draw weight X draw height ?

The shooter's KE formula is pretty simple: speed of the projectile squared (in fps) x mass of the projectile (in grains) divided by 450,240 (to yield an answer in standard ft-lbs). This result can then be multiplied by 1.35581795 to obtain the result in newton meter (Nm). But in order to use the mv²/450,240 formula, you must know the speed of the arrow (or bullet) and the mass. So this equation is rather after the fact (after the shot actually). An example:

We measure ft-lbs by actually firing an arrow of known mass and measuring its velocity with a chronograph device. Then using the archer's KE formula, we can compute the actual KE (since we then have values for m and v). For example, if we have a bow that fires a 350 grain arrow at a velocity of 315 fps (feet per second) and input the values ...

KE= mv²/450240
KE=(350)(315)²/450240
KE= 77.13 ft-lbs (or 104,57 Nm)

Typically and arrow's velocity is measured approximately 2 arrow lengths beyond the bow (so essentially point-blank range, or V1,4 ?). The arrow of course, loses velocity - and therefore KE - in flight due to air resistance. So a measurement at 100m would be less. For a overall graph at several meters, see http://www.excaliburcrossbow.com/content/arrow_ballistics (formula graph= Fx= ?)

Kinetic energy: fatal weight/velocity chart < 25 ft. lbs. Small Game (rabbit, groundhog, etc.) 25-41 ft. lbs. Medium Game (deer, antelope, etc.) 42-65 ft. lbs. Large Game (elk, black bear, wild boar, etc.) > 65 ft. lbs. Toughest Game (cape buffalo, grizzly, musk ox, etc.) —Preceding unsigned comment added by 91.182.241.204 (talk) 16:22, 30 November 2010 (UTC)[reply]

Most modern high-performance compound bows generate KE (in ft-lbs) roughly equal to the bow's peak draw weight (in-lbs). We test every bow we setup and compute actual KE output. So I can safely generalize that it is typical for a 70# compound bow to generate a final KE output of about 65-75 ft-lbs.

The best and burliest compound bows produce KE in the 80-100 ft-lb range. That's about the same energy as a boxer's punch, no where near the KE of any powder fired weapon. Bows kill by penetration - by hemorrhage. As a matter of killing large animals, the KE of a bow is just the energy used to push the knife into the target - so to speak - not to shock the target with impact force.

91.182.63.68 (talk) 15:32, 5 December 2010 (UTC)[reply]

Eccentrics working as pulleys ?

The function of the cams/eccentrics is to change the draw cycle, and not to provide a mechanical advantage. However, I was wondering whether the use of pulleys as indeed provides a mechanical pulling advantage ? 91.182.60.88 (talk) 09:05, 4 January 2011 (UTC)[reply]

Confusing Wording in Arrows Used Section

The Arrows Used section begins with a two-sentence paragraph:

Arrows used with compound bows differ significantly from arrows shot from recurve bows. Recurve bows can safely use wooden shafted arrows, or, alternatively, heavy aluminum shafted arrows, requiring in any case that arrows with more mass be used with recurve bows than with compound bows to avoid damaging recurve bows from experiencing problems from dry-firing the bow.

I cannot figure out what the second sentence is trying to say. As I don't know the subject matter, I'm afraid to touch the sentence as I don't wish to make it any worse.

[Update] A bit of Googling has let me find this and this which explain what "dry firing" is and the dangers of it.

I think I can update the article. It would be nice if someone were to review it and confirm that I didn't make things any worse and, hopefully, made things better.

Draw *weight* - not force