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RE: KE vs Momentum
From my experience shaft diameter does provide an advantage in penetration This is in spite of the fact that the Aluminum arrows had a higher momentum rating than my current carbon arrows. There are other factors beyond just KE or momentum. A stiffly spined carbon arrow that stabalizes quicker off the bow, flexes less on impact and is subjected to less friction because of its smaller diameter has some of those "OTHER" factors going for it. IF I'm wrong then you explain how I get consistently better penetration from the carbons fired from the same bow, using the same broadhead even though the aluminums were much heavier and had a far better momentum rating? |
RE: KE vs Momentum
ORIGINAL: Todd1700 I get consistently better penetration from the carbons fired from the same bow, using the same broadhead even though the aluminums were much heavier and had a far better momentum rating.... That said, I believe alum has way too much going for it otherwise to dismiss it |
RE: KE vs Momentum
what I fail to understand why so many people are so bent to discredit this phenomenon without really examining it. My question was entirely serious. I thought we were discussing momentum vs. KE as a better indicator of penetration potential. In order to do proper testing, one needs to eliminate as many variables as possible. Since you are stating stiff spine is where it's at, I am wondering if you've ever tested your current speed pro arrow against say perhaps one just like it only with the internal cavity filled with some weight bearing medium, such as fine sand or even lead powder (no idea how much space is available in these things, never seen one). That should yield similar spined arrows with the only difference being weight and fps. It's not a set up question, I'm genuinely curious... In my mind, I would suspect the heavier arrow to have slightly more ke, but a lot more momentum, giving us a closer glimpse at the truth. That is why I asked, not trying to whiz on the speed pro parade. I just feel that until such an in my mind more accurate test is performed, everything else is just apples and oranges... |
RE: KE vs Momentum
BPS...
speed is another factor that seems to be over looked concerning the lighter arrows what you should keep in mind is that my current hunting arrow is traveling 350+ FPS off the string and is traveling over 340 at 20 yards, speed does equal deeper penetration. what I fail to understand why so many people are so bent to discredit this phenomenon without really examining it. I agree about momentum/KE being over-argued. Like I said, you don't have one without the other. Like YOU said, with a high performance bow you can stack up a pile of KE and do well. On the other hand, while you're stacking up that KE with speed, you're also stacking up the momentum. That's why a high KE arrow will penetrate. Not so much because of the energy but because it's also carrying a lot of momentum. Don't take my word for it. Do the math! It's easier and quicker to pile on the momentum with arrow weight than it is to get it with speed, but you do get it with speed. Still, momentum is the key, as far as I'm concerned. By definition, KE is scalar. You have a certain amount of energy in an arrow, some of which is going forward, some is rotating around the axis of the arrow as the fletching spins it, some is being transferred into noise and heat from it's interaction with the atmosphere. You've got energy going in all directions. That's because KE is a scalar quantity. Momentum is a vector. Momentum is mass and speed in a specific direction over a specific amount of time. BY SCIENTIFIC DEFINITION, momentum is the deciding factor when it comes to penetration potential. It's not my opinion, it's physical law. Blame Issac Newton. It's his fault, not mine. So.... Your results are due to the momentum your speed is giving you, not the speed itself. Your momentum for those 350 gn arrows at 350 fps and 95 ft lbs of energy is .54 lb/secs. Let's look at some other setups that will give the same momentum: 400 gn arrow at 304 fps and 82 ft lbs 450 gn arrow at 270 fps and 73 ft lbs 500 gn arrow at 243 fps and 66 ft lbs 550 gn arrow at 221 fps and 60 ft lbs In other words, my 2315's at 220 fps from my Accuwheel mounted ProTec at 60 pounds and 33" draw will skewer any critter just as easily as your 350+, 95 ft lb arrows. What's the problem? Can you do things your way? Certainly... but your way keeps taking archery and bowhunting closer to the realm of brain surgery and rocket science.  On the other hand, if one can't handle the draw weight or the draw force curves that come with the cams needed to get that kind of arrow speed, then the bowhunter can easily achieve exactly the same penetration potential you've got with much less extreme setups by increasing their arrow weight. I've got other issues with high speed arrows, as an archery club officer, that are totally unrelated to bowhunting. Specifically, safety issues and being able to contain stray arrows within the club's boundaries. We're on the verge of having to enact speed limits at our club's range because our formerly rural location is rapidly becoming suburban. Someone with a rig like yours would be limited to our practice area only. |
RE: KE vs Momentum
I have Norb Mullaney's take on KE vs. Momentum in a nice article he wrote about all this. Anyone want to read it? ....(waiting for the roar of the crowd pleading for more......) [8D]
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RE: KE vs Momentum
ORIGINAL: Black Frog I have Norb Mullaney's take on KE vs. Momentum in a nice article he wrote about all this. Anyone want to read it? ....(waiting for the roar of the crowd pleading for more......) [8D] [&:] What was that you said Todd? :eek: :yawn: Oh...ok..sure...go ahead.. :D;) Seriously..I'd like to see what Norb has to say, or anyone else for that matter. I don't always agree with what I read, but I always enjoy seeing other's perspective :) |
RE: KE vs Momentum
:)
It's a rather lengthy 3pg article- after lunch today I'll scan it in 3 jpeg pics and post them on our band website for everyone to read. Good article and he makes some interesting points.... 'Ol Norb is pretty thorough. |
RE: KE vs Momentum
Before I read it can you tell me who Norbs data supports.....................us light fast guys or the heavy slow guys:)
I don't like reading material that contradicts my open minded beliefs......LOL  |
RE: KE vs Momentum
okay, so what's the argument here? is it carbon vs. aluminum for better penetration, or is it which is the better indicator for penetration, ke vs. p? [&:]
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RE: KE vs Momentum
What? You expected this to stay on topic?? Well, you're fairly new to the forum. Once you've been here a spell, you'll find out these KE vs momentum discussions always devolve into aluminum vs carbon, old school vs new wave, science vs sci-fi...
[8D] I think I read Norb's treatise on this subject and he came down on the KE side. I'd like to see Norb and Sir Isaac debate the issue.;) |
RE: KE vs Momentum
Todd.
Hurry up and eat already, would ya? :) |
RE: KE vs Momentum
Here ya go, hopefully you can read it ok. It may depend on your monitor size....
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RE: KE vs Momentum
page 2...
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RE: KE vs Momentum
page 3.
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RE: KE vs Momentum
So Norb sees it as a "photo finish"- that either value is a good judge of penatration potential, but KE has the right unit label for his analysis of comparing penatration to work.
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RE: KE vs Momentum
Sorry, but these debates remind me of my current workplace. All the engineering, mathematical calculations and Kaizan idea instituting has done nothing but got us behind in deliveries and made setups much slower, when it was supposed to be the opposite!
Proof is in actual bowhunting situations............not on paper! Calculations are a good starting point, but that is all they are. I find it more necessary in finding an arrow stiff enough and heavy enough to not be hard on the bow, making the bow quieter, and good accuracy. If everything on paper worked, the Lakers would be the NBA champs and the Yankees have already locked up the World Series.[&:] |
RE: KE vs Momentum
ORIGINAL: Black Frog So Norb sees it as a "photo finish"- that either value is a good judge of penatration potential, but KE has the right unit label for his analysis of comparing penatration to work. But also note while his tests compare arrow weight and velocity, that arrow diameter & differing material is not used as testing factor (all tests were done with "22XX" alums). Easton did a ton of testing for the AXIS using equal weights vs. diameter (and I would have to think since they are the #1 sellers of alum arrows and I also believe Carbons, they would be loathe to skew their own testing in favor of one or the other shaft material). But it would be interesting to see an equal diameter, equal weight, different material test too. I'd like to see Norb do an updated test using all these other criteria (diameter, material type) as well. |
RE: KE vs Momentum
Excellent summation, Cougar Mag!
What great benefit is gained by possibly putting the setup on the edge of reliable and forgiving performance and durability by trying to increase the KE and momentum beyond what the appropriate setup naturally and best provides, and what is generally necessary? In the end, regardless of all of the computations, for most bowhunters it will still boil down to a common and long-established requirement; the shaft must be correctly matched to the specs of the bow and shooter. Any compound that has a draw-weight suitable for hunting (specific) large game will do the job as long as the arrow is appropriately matched to the particular bow and shooter. Most "spine" guides will indicate the correct shaft(s) to use without having to engage in a lot of physics and math. From that point, you simply tweak the bow and arrow until flight and accuracy is good. If your gear is tuned properly and your shooting skills are fitting, a shaft through both lungs will put the deer down, regardless of not getting full penetration and a blood trail In the end, a scientific application of KE/momentum is an individual thing and does no harm unless the performance of the bow and arrow is adversely affected. |
RE: KE vs Momentum
Proof is in actual bowhunting situations............not on paper! |
RE: KE vs Momentum
But also note while his tests compare arrow weight and velocity, that arrow diameter & differing material is not used as testing factor (all tests were done with "22XX" alums). And to me, the problem with doing test of "real hunting situations" is that there is very little, if any, consistency to the impact material. How do you get consistent material from an animal body to shoot shot after shot into for testing? Even if your 1/2" off from where the first shot went, who knows what sort of density differences you may encounter in an animal's body. I suppose if you had enough time and animal bodies to use, you could do lots of "averaging" to get some credible results. |
RE: KE vs Momentum
There's a thread going on at AT that has some interesting commentary in it I thought some of you would enjoy reading.
AT Momentum vs. KE thread |
RE: KE vs Momentum
ORIGINAL: Black Frog But also note while his tests compare arrow weight and velocity, that arrow diameter & differing material is not used as testing factor (all tests were done with "22XX" alums). And to me, the problem with doing test of "real hunting situations" is that there is very little, if any, consistency to the impact material. How do you get consistent material from an animal body to shoot shot after shot into for testing? Even if your 1/2" off from where the first shot went, who knows what sort of density differences you may encounter in an animal's body. I suppose if you had enough time and animal bodies to use, you could do lots of "averaging" to get some credible results. it's all nitpicking. Everyone should shoot what they feel confident in. In my case thats' a fairly high speed carbon with a greater emphasis on KE than momentum. |
RE: KE vs Momentum
Everyone should shoot what they feel confident in. In my case thats' a fairly high speed carbon with a greater emphasis on KE than momentum. More than adequate, I think. |
RE: KE vs Momentum
I remember how surprised I was after shooting my first deer many years ago with a compound set at 53# or so, and how far my aluminum arrow was burried in the dirt after the pass-through of the boiler room.......
Unless I'm hunting moose or grizzly, I really not too concerned with KE or Momentum to begin with. Any modern compound is way beyond the recurves that have killed thousands of animals just fine. It is fun to get into the technical aspects of the physics though! :) |
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