Some Allegiance numbers to chew on
?
01-29-2005, 07:45 PM
#32
Giant Nontypical
Thread Starter
Join Date: Aug 2003
Location: The OH-IO
Posts: 7,103
RE: Some Allegiance numbers to chew on
Posted by Joe
Add 3-4 fps for 10 grains puts him at 314- 315fps. Not much different than mine 3 - 4fps.
Here are some numbers that I am getting with a 29in draw string loop, nock and peep.
@ 70#
360 grains at 311fps
@ 70#
360 grains at 311fps
01-29-2005, 08:13 PM
#33
Join Date: Feb 2003
Location: Los Alamos NM. USA
Posts: 34
RE: Some Allegiance numbers to chew on
I read where you said yours was a mess when it arrived? What was wrong? Maybe it is rooted from that?
I think he had the same problem that I did in that the cams rotation are a little off from eachother, which can be corrected by adding ar taking away a couple twists in the cables. I had to play with it a little because it also changes the let-off.
all-in-all it can be tuned pretty much any way a person would want.
01-29-2005, 08:33 PM
#34
Join Date: Feb 2003
Location: NJ USA
Posts: 243
RE: Some Allegiance numbers to chew on
Joe, I hear ya......I just posted on the other thread what Bowtech told me...to align the inside part of the bowstring post with the outer side of the limbs.
Can you and Buckeye.....email me pics of your cams?
My bow is a 60# max bow, are your's 70's?
Can you and Buckeye.....email me pics of your cams?
My bow is a 60# max bow, are your's 70's?
01-29-2005, 08:46 PM
#35
Nontypical Buck
Join Date: Jan 2005
Location: Upstate New York
Posts: 2,435
RE: Some Allegiance numbers to chew on
buckeyebuckhntr,
Sorry for the jargon…. Stored energy to peak ratio (S.E.P.) is simply the stored energy value divided by the peak weight on the draw curve. If a bow stores 60 foot pounds of energy and has a peak of 50 pounds its S.E.P is 60/50=1.2. S.E.P. is a measure of how severely cammed a bow is. Early compounds with simple round wheels typically had an S.E.P. of 1.0. The most severely cammed bows today are near 1.4. As I said the numbers you stated, that is 62 lbs, 310 grains and and 318 ft./sec, indicate an S.E.P. of 1.46. This would be an extremely high value. Now how did I arrive at this value?
Well you gave me the peak weight of 62 pounds so all I need now is the bows stored energy (SE). I used the standard equation SE=1/2(m1 +m2)V**2 where m1 is arrow mass and m2 is what is known as virtual mass. V of course is arrow velocity. Virtual mass can be thought of as the sum of all the resistance during the power stroke. Its not a real mass so that’s why its “virtual”. I often think of it as the mass that is accelerated if you were to dry fire the bow. Anyway, a typical value for virtual mass is around 100 grains. The higher the value for virtual mass, the lower the bow efficiency and of course the reverse is also true. Anyway I used 92.4 grains of virtual mass which would mean the bow under these conditions would be 77% efficient. That would be pretty good efficiency for a 310 grain arrow. So again, the stored energy calculated to 90.4 foot pounds and therefore 90.4/62 = 1.46. Hope this helps.
Actually I have a computer program that does the number crunching for me so I can do it pretty quickly. One of the things I find it usefull for is to predict what will happen when I make changes to a bow. Given the peak weight, draw length, brace height, arrow weight and a chronographed velocity for those conditions, I can usually predict within a few feet per second what will happen if any or all of these values are changed.
Sorry for the jargon…. Stored energy to peak ratio (S.E.P.) is simply the stored energy value divided by the peak weight on the draw curve. If a bow stores 60 foot pounds of energy and has a peak of 50 pounds its S.E.P is 60/50=1.2. S.E.P. is a measure of how severely cammed a bow is. Early compounds with simple round wheels typically had an S.E.P. of 1.0. The most severely cammed bows today are near 1.4. As I said the numbers you stated, that is 62 lbs, 310 grains and and 318 ft./sec, indicate an S.E.P. of 1.46. This would be an extremely high value. Now how did I arrive at this value?
Well you gave me the peak weight of 62 pounds so all I need now is the bows stored energy (SE). I used the standard equation SE=1/2(m1 +m2)V**2 where m1 is arrow mass and m2 is what is known as virtual mass. V of course is arrow velocity. Virtual mass can be thought of as the sum of all the resistance during the power stroke. Its not a real mass so that’s why its “virtual”. I often think of it as the mass that is accelerated if you were to dry fire the bow. Anyway, a typical value for virtual mass is around 100 grains. The higher the value for virtual mass, the lower the bow efficiency and of course the reverse is also true. Anyway I used 92.4 grains of virtual mass which would mean the bow under these conditions would be 77% efficient. That would be pretty good efficiency for a 310 grain arrow. So again, the stored energy calculated to 90.4 foot pounds and therefore 90.4/62 = 1.46. Hope this helps.
Actually I have a computer program that does the number crunching for me so I can do it pretty quickly. One of the things I find it usefull for is to predict what will happen when I make changes to a bow. Given the peak weight, draw length, brace height, arrow weight and a chronographed velocity for those conditions, I can usually predict within a few feet per second what will happen if any or all of these values are changed.
01-29-2005, 09:16 PM
#39
Giant Nontypical
Thread Starter
Join Date: Aug 2003
Location: The OH-IO
Posts: 7,103
RE: Some Allegiance numbers to chew on
Jerry
ATA is 33 9/16
Brace is 6 7/8's
Tiller is 9 7/8's.
I set the tiller even when I dropped from 70#. I used a yard stick to get a solid starting point for the measurement at the limb pocket.
My cams timing is right on with the lobes even with the limbs.
ATA is 33 9/16
Brace is 6 7/8's
Tiller is 9 7/8's.
I set the tiller even when I dropped from 70#. I used a yard stick to get a solid starting point for the measurement at the limb pocket.
My cams timing is right on with the lobes even with the limbs.