How much K.E. for mechanicals???
08-25-2003, 07:17 PM
#2
Nontypical Buck
Join Date: Feb 2003
Location: St. Cloud MN USA
Posts: 1,757
RE: How much K.E. for mechanicals???
Most people say 50 to 55 KE. But thats for a regular size head ( 1 1/8" to 1 3/16" ) Some of the great advantage of mechanicals is the large cutting diameter. (example My Wasp Jackhammer 100 have a cutting diameter of 1 3/4" ). If you shoot larger cut mechanicals I' d strongly recomend KE over 60 to 63. Good luck and if you' re not sure or on the edge.......shoot fixed!!!
08-25-2003, 07:46 PM
#3
Boone & Crockett
Join Date: Oct 1998
Location: Hughesville, PA USA
Posts: 18,322
RE: How much K.E. for mechanicals???
Back when mechanicals first came out and the failure rate was high....many of the manufacturers started recommending at least 55 ftlbs. of KE for adequate usage....you don' t read much about that anymore but I still feel that is a good rule of thumb.
08-26-2003, 03:17 AM
#4
Nontypical Buck
Join Date: Feb 2003
Location: Vinton VA
Posts: 2,978
RE: How much K.E. for mechanicals???
A lot depends on the head being used. The energy needed to open the heads is very small, but since most mechanicals have larger cutting diameters and longer ferules it they have more resistance, and this slows down penetration. a good rule of thumb is 50 to 55ft/lbs but some need much more and others a little less.
08-26-2003, 07:47 AM
#5
Boone & Crockett
Join Date: Feb 2003
Location: Lehigh County PA USA
Posts: 12,157
RE: How much K.E. for mechanicals???
...it also definitely depends on the size of the game you are pursuing. Most of the KE figures that get thrown around are in reference to whitetail deer sized animals. Go hunt Elk and you open up an entirely different can of worms. 
08-26-2003, 10:02 AM
#6
Typical Buck
Join Date: Feb 2003
Location: AR USA
Posts: 889
RE: How much K.E. for mechanicals???
I can tell you for sure that 50 ft lbs is plenty K/E for the rocket steelheads. 50 ft lbs was my K/E last season usin my G/E splitfire 36, shootin 245 fps with ICS 400' rds. I had no problem gettin a complete passthrough on the deer I took, one was at 25 yds. and the steelhead is a tough little head.
08-26-2003, 10:45 AM
#7
Join Date: Feb 2003
Location: medora Illinois
Posts: 434
RE: How much K.E. for mechanicals???
bogobble
the last couple of years i have used 100 grain steelheads and have harvested every deer that i shot at except the one that got stolen. i was shooting 53.4ft.pds. kenic energy via the math formula. i have harvested 8 deer with this head but i am going to change to a different head because i am unsatisfied. i would like to pass threw at least most of the time and i do not find this in the steelhead, at least with my set up. i do agree that it is a good head but i want pass threws. i am going to try the snyper this year. 5-Shot speeks highly of this head and so far it flys good. i am NOT trying to start an arguement. just letting you know what my experience has been with this head.
the last couple of years i have used 100 grain steelheads and have harvested every deer that i shot at except the one that got stolen. i was shooting 53.4ft.pds. kenic energy via the math formula. i have harvested 8 deer with this head but i am going to change to a different head because i am unsatisfied. i would like to pass threw at least most of the time and i do not find this in the steelhead, at least with my set up. i do agree that it is a good head but i want pass threws. i am going to try the snyper this year. 5-Shot speeks highly of this head and so far it flys good. i am NOT trying to start an arguement. just letting you know what my experience has been with this head.
08-29-2003, 08:56 AM
#8
Nontypical Buck
Join Date: Feb 2003
Location: Wisconsin
Posts: 3,903
RE: How much K.E. for mechanicals???
I emailed NAP for a buddy of mine who was curious about the kinetic energy of his setup and the NAP Scorpions. Here' s the reply from NAP.
We publish a minimum specification for all of our mechanicals of 50 FT/LBS. Depending on your set up and arrow weight you may be able to use a much lower KE than this. However that is a personal choice.
Few people realize that broadhead penetration has very little to do with broadheads. Rather, penetration has almost everything to do with arrow flight. A well tuned 50 pound bow with arrows that fly without wobble penetrates better than an 80 pound bow with aberrant arrow flight. Probably the greatest disadvantage of mechanicals in general is that as a group they tend to be much more critical of arrow spine than replaceable or fixed bladed broadheads. For instance, because there is a loss of energy of about 1 to 3 ft/lbs. when a Spitfire contacts a target, and because this energy loss is directly opposite the direction of travel, an improperly spined arrow will have an additive effect. Generally an improperly spined arrow fails to penetrate well regardless of broadhead style because the energy is partially lost in some direction other than straight forward when the arrow strikes an animal. A standard broadhead in this scenario would most likely penetrate and stick in the animal with enough of the shaft inside to lodge it until the animal does something that causes the shaft to break or possibly get pulled out during escape. Spitfires along with most other mechanicals will almost instantly back out because of the additive effect of the spine related energy loss, reverse energy of opening the blades and the fact the blades can close easily preventing any anchoring effect. Arrow flight is especially important on high angle shots. If the arrow is wobbling back and forth or up and down, then when it hits the target/animal the energy continues to the side rather than straight forward. On a mechanical this would have the effect of pivoting the broadhead and reducing penetration. Keep in mind that if your arrow flight is good then increased angle has NO effect.
Another thing to consider is momentum. Momentum is often disregarded in archery because people tend to concentrate on kinetic energy. Let me explain the difference. Kinetic energy is the impact energy of the projectile. It is a very good way to determine how efficient your bow transfers stored energy in the limbs to dynamic energy in the arrow. For the most part kinetic energy in the 50 ft/lbs. to 60 ft/lbs. range is ample for taking animals in the deer to elk range. Kinetic energy in the 60 ft/lbs. to 70 ft/lbs. will effectively take any animal in North America. For example, Chuck Adams took his 1400 pound Kodiak Grizzly Bear with about 65 ft/lbs. of kinetic energy. I believe he used an arrow in the 630 grain range that traveled about 220 fps. While there are several arrow/speed combinations that would produce 65 ft/lbs. of kinetic energy, Chuck opted for a heavier slower arrow because of the momentum. Momentum is the ability of the projectile to continue in motion. Momentum is a linear function of mass. The idea is the greater the mass the more resistance is required to slow or stop the object. Think of it this way if someone were to pitch a baseball and a bowling ball to a batter, and both balls had the identical amount of kinetic energy even though one is traveling very fast and the other is traveling very slow. The batter would be able to hit the baseball and move it in the opposite direction very easily while the bowling ball would most likely break the bat. The bowling ball has tremendously greater momentum and therefore is much more difficult to stop or slow down.
Hope this helps.
Cary J. Pickands
Technical Support Specialist
New Archery Products, Corp.
7500 Industrial Drive
Forest Park, IL 60130
800-323-1279
We publish a minimum specification for all of our mechanicals of 50 FT/LBS. Depending on your set up and arrow weight you may be able to use a much lower KE than this. However that is a personal choice.
Few people realize that broadhead penetration has very little to do with broadheads. Rather, penetration has almost everything to do with arrow flight. A well tuned 50 pound bow with arrows that fly without wobble penetrates better than an 80 pound bow with aberrant arrow flight. Probably the greatest disadvantage of mechanicals in general is that as a group they tend to be much more critical of arrow spine than replaceable or fixed bladed broadheads. For instance, because there is a loss of energy of about 1 to 3 ft/lbs. when a Spitfire contacts a target, and because this energy loss is directly opposite the direction of travel, an improperly spined arrow will have an additive effect. Generally an improperly spined arrow fails to penetrate well regardless of broadhead style because the energy is partially lost in some direction other than straight forward when the arrow strikes an animal. A standard broadhead in this scenario would most likely penetrate and stick in the animal with enough of the shaft inside to lodge it until the animal does something that causes the shaft to break or possibly get pulled out during escape. Spitfires along with most other mechanicals will almost instantly back out because of the additive effect of the spine related energy loss, reverse energy of opening the blades and the fact the blades can close easily preventing any anchoring effect. Arrow flight is especially important on high angle shots. If the arrow is wobbling back and forth or up and down, then when it hits the target/animal the energy continues to the side rather than straight forward. On a mechanical this would have the effect of pivoting the broadhead and reducing penetration. Keep in mind that if your arrow flight is good then increased angle has NO effect.
Another thing to consider is momentum. Momentum is often disregarded in archery because people tend to concentrate on kinetic energy. Let me explain the difference. Kinetic energy is the impact energy of the projectile. It is a very good way to determine how efficient your bow transfers stored energy in the limbs to dynamic energy in the arrow. For the most part kinetic energy in the 50 ft/lbs. to 60 ft/lbs. range is ample for taking animals in the deer to elk range. Kinetic energy in the 60 ft/lbs. to 70 ft/lbs. will effectively take any animal in North America. For example, Chuck Adams took his 1400 pound Kodiak Grizzly Bear with about 65 ft/lbs. of kinetic energy. I believe he used an arrow in the 630 grain range that traveled about 220 fps. While there are several arrow/speed combinations that would produce 65 ft/lbs. of kinetic energy, Chuck opted for a heavier slower arrow because of the momentum. Momentum is the ability of the projectile to continue in motion. Momentum is a linear function of mass. The idea is the greater the mass the more resistance is required to slow or stop the object. Think of it this way if someone were to pitch a baseball and a bowling ball to a batter, and both balls had the identical amount of kinetic energy even though one is traveling very fast and the other is traveling very slow. The batter would be able to hit the baseball and move it in the opposite direction very easily while the bowling ball would most likely break the bat. The bowling ball has tremendously greater momentum and therefore is much more difficult to stop or slow down.
Hope this helps.
Cary J. Pickands
Technical Support Specialist
New Archery Products, Corp.
7500 Industrial Drive
Forest Park, IL 60130
800-323-1279
08-31-2003, 12:23 AM
#10
Join Date: Aug 2003
Location:
Posts: 17
RE: How much K.E. for mechanicals???
I also shoot steel head 100' s and have shot 4 elk and never had one go more than 100 yards. As for the K.E I don' t know for sure what is needed for the mach. broad head I am using but do know that it can' t be much.
