Kinetic Energy and Arrow Speed Measurements

[Riverbc]

So where does one measure arrow speed and kinetic energy? 5 yards, 10 yards, right as the arrow leaves the bow? If you know your arrow speed and kinetic energy at this yardage, and you know the weight of your arrow, draw length, etc... Is there a formula to determine what the speed and kinetic energy are at other yardages? Thanks in advance. :-D

[358win]

Arrow speed is right off the rest. Energy is complete arrow weight V/s speed. Distance and arrow weight will factor in both.
I'm not a pro like Bowzone_mikey, Bow Walker or others. They will guide you through better when they get back from shooting :)

[Riverbc]

thanks,,,I will wait patiently! :D

[Eagle1]

arrow speed x arrow speed x arrow weight divided by 450,240

I shoot thru my chrony about 3 ft away.

60#, 29 draw, 327g arrow shooting 327 fps getting around 79.79 KE
I also shot a 407g arrow at 300 fps getting around 81 KE

Bowwalker is always on the computor,{ well a lot of the time, LOL } he can tell you where to find some of these formulas

[Vader]

If you know arrow weight and speed use this easy calculator http://www.dewclawarchery.com/Kinetic_Engery_Calculator-a/157.htm.
I measure as close as I can to where the arrow has just cleared the string.

[Bowzone_Mikey]

I measure about speed 3 yards off the bow ... to measure downrange you need to know the BC of your arrow construction ... how well it retains energy ... your fletch configeration and its properties etc.....

in short there is a number of variables for downrange calculation and there is no "rule of thumb"

[Bow Walker]

There are some sites that have the calculators ready to go for you - here are a couple...

http://archeryreport.com/calculators.html

http://www.goldtip.com/calculators.aspx (if the link doesn't work, just go to http://www.goldtip.com and follow the Calculators link)

Generally speaking, Eagle1 has it right ( spend way too much time on here) test your arrow speed by shooting through your Chrony at a distance of 3 - 5 feet. Make sure you have a decent target to shoot into so your arrow is safe.

[Riverbc]

Thanks for the answers and the links. I'll have to get my hands on a chrony (always thought that was short for chironimid ;)) and get my actual arrow speed and then go from there.

[brad ferris]

I've often wondered myself how much arrow speed is lost down range. Is it a significant loss of velocity at say 40 yards. The KE at 3 yards is great to know if you are going to shoot your bison at spear thowin distance but most of us are trying to put the arrow into our quarry out a little further. Maybe one of you archery technicians can fling a few through your cronies um chrony's a bit further out. Maybe with a couple different arrow weights. I'll speculate your heavy arrows lose less speed as they fly down range. Mass in motion and all that stuff newton came up with.

[Bowzone_Mikey]

Brad .. I will pump a few thru my chrony at distance ... say about 20 yards ... but once again ... it would depend on your fletching ... for example .. NAP quickspins are great out to about 30/35 yards ... then the arrow just drops like like a rock after that compared to say Blazers of the same size. (reason being is that quick spins have ... wings to induce spin ... and therefore robbing arrow of forward energy) .

I have found that differant arrow composition makes a differance as well ... 400 Grain ACC (Aluminum / Carbon/ Composite) arrows will have differant impact points than 400 grain pure carbon arrows ... as both have very similar speed comming off my bow (281 fps average) with the ACC having a higher point of impact at 40 yards than the pure carbons ... both made with glue in points and micro-blazer fletchings at 2 degree offset

[Bow Walker]

I'd try that experiment, but I've put all my archery stuff in temporary storage. Upcoming relocation of residence. When I get set up again and/or settled, I'll dig out the chrony and see what the numbers are with my particular arrows and bow.

Like a lot of people, I've wondered why no one has done the ballistic thing for a "common" archery setup, like they do for coming up with the advertised bow speeds (fps). Mikey, I'll be very interested in what you come up with. Even if you shoot different arrows and arrow weights than I do. Please be sure to list all the technical details of your experiment. If you feel like it - try shooting through your chrony at 25 or 30 yards - like in a hunting scenario.

Start a new thread or add it to this one, I'll find it.

[Bowzone_Mikey]

I'll shoot my target set up thru chrony ... 339 grain ACE ... that come off my Bow at 313 or so .. at 15 25 35 45 yards ... map a base line with those

[Riverbc]

now we're talking!! :D

[Riverbc]

I did find this a couple of weeks ago. http://backcountrybowhunting.com/articles/calc/ Had to do some googling to find out about Manufacturer's IBO speed, and now I'm much wiser! ;)

[Bow Walker]

I did find this a couple of weeks ago. http://backcountrybowhunting.com/articles/calc/ Had to do some googling to find out about Manufacturer's IBO speed, and now I'm much wiser! ;)

That calculator is pretty good for finding out what your particular setup is doing - and also for playing "what if" when you want to change a variable on your arrows or bow. Thanks for the link.

[Bow Walker]

I found this little chart that will let you know how fast your arrow will travel (in seconds) over a given distance.

http://www.huntingbc.ca/photos/data/500/Arrow_flight_time_10_to_50_yards.jpg

Interesting, no?

[Riverbc]

yes...3% loss....so if I'm thinking correctly, at 50 yards, the velocity of your arrow at 50 yards will be 15 % less then when the arrow left the bow? Therefore if my 356.15 grain arrow leaves my bow at 290 fps, it's KE is 67 ft-lbs, then at 50 yards my arrow speed would be 246.5 fps, and it's KE would be 48 ft-lbs?

[Bow Walker]

I'm not at all sure how the percentage of speed loss "ramps" up in relation to the distance, but I suspect (off the top of my somewhat flat head) that it isn't as easy as that to multiply it upwards. I don't know - I'd like to be either corrected or confirmed in my thinking.