Some Allegiance numbers to chew on
01-29-2005, 09:34 PM
#43
Nontypical Buck
Join Date: Jan 2005
Location: Upstate New York
Posts: 2,435
RE: Some Allegiance numbers to chew on
That is an amazing speed for 60#. My only explination is that the B.C. speed is not for the actual bow but a speed that this bow would shoot at standard IBO conditions. If that's not the answer then I guess Bowtech has made a giant leap forward and have gotten efficiency's for pretty light arrows up around the 85% mark.
01-29-2005, 09:39 PM
#44
Giant Nontypical
Thread Starter
Join Date: Aug 2003
Location: The OH-IO
Posts: 7,103
RE: Some Allegiance numbers to chew on
sylvan
The BC is what the bow you bought shot before leaving the factory. They test each bow at 5gpp through a chrono and fill out the BC with what it put out.
The BC speed includes 1 brass nock 2 elimantor buttons and the factory hush kit string silencers all on the string.
The BC is what the bow you bought shot before leaving the factory. They test each bow at 5gpp through a chrono and fill out the BC with what it put out.
The BC speed includes 1 brass nock 2 elimantor buttons and the factory hush kit string silencers all on the string.
01-30-2005, 05:34 AM
#47
Nontypical Buck
Join Date: Jan 2005
Location: Upstate New York
Posts: 2,435
RE: Some Allegiance numbers to chew on
walks with a gimp,
Using 91 grains for virtual mass I get:
wt S.E.P.
70=1.25
68=1.29
66=1.33
64=1.37
62=1.41
60=1.46
I don't know the draw length for this bow but if its not over 30" then the 1.4 value for S.E.P. is a pretty good value for upper end. So, if your shooting at least say 62 pounds I think the speed you quoted is reasonable. A guess would be you are around 66 lbs.
S.E.M. might have been a better indicator than S.E.P. because it takes the power stroke into consideration. S.E.M. is the ratio of the stored energy to the maximum possible stored energy the bow could contain if the peak weight were held over the entire power stroke. The value is not affected by brace and draw length where S.E.P. is.
Does anybody know if Bowtech makes public its S.E.P. for a given design? I doubt they use S.E.M. most don't but if I'd be very interested in that as well.
Using 91 grains for virtual mass I get:
wt S.E.P.
70=1.25
68=1.29
66=1.33
64=1.37
62=1.41
60=1.46
I don't know the draw length for this bow but if its not over 30" then the 1.4 value for S.E.P. is a pretty good value for upper end. So, if your shooting at least say 62 pounds I think the speed you quoted is reasonable. A guess would be you are around 66 lbs.
S.E.M. might have been a better indicator than S.E.P. because it takes the power stroke into consideration. S.E.M. is the ratio of the stored energy to the maximum possible stored energy the bow could contain if the peak weight were held over the entire power stroke. The value is not affected by brace and draw length where S.E.P. is.
Does anybody know if Bowtech makes public its S.E.P. for a given design? I doubt they use S.E.M. most don't but if I'd be very interested in that as well.
01-30-2005, 07:56 AM
#48
Join Date: Feb 2003
Location: NJ USA
Posts: 243
RE: Some Allegiance numbers to chew on
Sylvan,
Are you able to tell from the speeds I posted for a 60# bow if my SEP is right? They have 70# bows and I still find it hard to believe that they can crank them down to the same weight as mine and shoot 10 - 15 fps faster at the same draw length. I have to find the answer to this. Any input?
My bow specs are very close to theirs and I have compared cam positions and they look the same......
Are you able to tell from the speeds I posted for a 60# bow if my SEP is right? They have 70# bows and I still find it hard to believe that they can crank them down to the same weight as mine and shoot 10 - 15 fps faster at the same draw length. I have to find the answer to this. Any input?
My bow specs are very close to theirs and I have compared cam positions and they look the same......
01-30-2005, 10:56 AM
#49
Nontypical Buck
Join Date: Jan 2005
Location: Upstate New York
Posts: 2,435
RE: Some Allegiance numbers to chew on
Jerry/NJ
At 61#/29" draw length with a loop, kisser, peep and huskit
------------------vel-----SEP---predicted---sep----predicted
304 grain arrow = 308--- 1.36---------------1.29------------
332 grain arrow = 297--- 1.36--- 297.6------1.29---297.1
365 grain arrow = 285--- 1.35--- 286.7------1.29---285.6
381 grain arrow = 280--- 1.35--- 281.8------1.29---280.5
432 grain arrow = 265--- 1.34--- 267.7------1.28---265.8
What I did here was first to calculate sep for each of your data points using 91 grains of virtual mass. As you can see the sep's ran from 1.36 to 1.34 which are certainly reasonable values. Like I said, I believe 1.4 is kind of upper end. What I did next is to use the values from the first data point to predict how closely your real numbers would match a "theroretical" change in arrow mass. If you look close you will see its a pretty good match but the predicted velocity deviates more as you go up in arrow mass. To get a better "fit" I adjusted the virtual mass down to 70 grains and ran the numbers again. This is a better fit, the worst deviation of predicted to actual is less than 1 ft/sec. I should point out that 70 grains of virtual mass is very, very good. It translates to 81% efficient for the lightest arrow and 86% for the heaviest arrow. If your bow scale and chrony are giving you the correct values, and they appear to be, I am very impressed with Bowtech.
At 61#/29" draw length with a loop, kisser, peep and huskit
------------------vel-----SEP---predicted---sep----predicted
304 grain arrow = 308--- 1.36---------------1.29------------
332 grain arrow = 297--- 1.36--- 297.6------1.29---297.1
365 grain arrow = 285--- 1.35--- 286.7------1.29---285.6
381 grain arrow = 280--- 1.35--- 281.8------1.29---280.5
432 grain arrow = 265--- 1.34--- 267.7------1.28---265.8
What I did here was first to calculate sep for each of your data points using 91 grains of virtual mass. As you can see the sep's ran from 1.36 to 1.34 which are certainly reasonable values. Like I said, I believe 1.4 is kind of upper end. What I did next is to use the values from the first data point to predict how closely your real numbers would match a "theroretical" change in arrow mass. If you look close you will see its a pretty good match but the predicted velocity deviates more as you go up in arrow mass. To get a better "fit" I adjusted the virtual mass down to 70 grains and ran the numbers again. This is a better fit, the worst deviation of predicted to actual is less than 1 ft/sec. I should point out that 70 grains of virtual mass is very, very good. It translates to 81% efficient for the lightest arrow and 86% for the heaviest arrow. If your bow scale and chrony are giving you the correct values, and they appear to be, I am very impressed with Bowtech.