Way easier to just use a chrono and faster.

 

And more accurate, but not everyone has a chrono in their backyard.

 

There are plenty of online calculators, but like your chart they don't take everything into consideration

 

The ones I've seen start with assuming an IBO or chrono speed and make adjustments based on draw weight, draw length, arrow weight, etc.
I'm attempting to take any bow and arrow combination and with a single shot, determine the actual arrow speed on the range. If the math is right, it will be mighty close.
Not everybody cares how fast their bow shoots and some have access to a chrono, but for some of us this could be an interesting tool.

 

Thanks for the chart.

 

Cool idea. Thanks for posting.

 

Very cool don't see why it wouldn't be pretty close

 

Pretty cool imo [emoji106]

Sent from my SM-G930V using Tapatalk

 

Chronograph can be found for less than a six pack of quality broadheads. There are a few things that aren't figured into the chart that may make the reading faulty like peep height, distance from peep to sight and probably others. The beauty of a chrono is identifying slight increases /decreases with tuning. Last week I was putting on speed nocks. One nock added, 3 fps faster. Another, 3 fps faster. 3rd nock, slowed down 4 fps. Same with twisting cables and strings. There isn't a graph that can pick up small changes that can affect efficiency. Jmho

 

I used the same chart for a couple years and I did it last week and I had a drop of 15.5” which is a bit over 300 FPS .shot through chronograph and it was 309 FPS. The charts and graphs are pretty damn close. There’s nothing to take into consideration. Arrow drop is arrow drop. Try it out you will pleasantly surprised how close it is. And yes if you shoot 3D you are concerned with speed . You want every FPS you can get .

 

With all due respect, I Don't think the chart can differentiate the addition of a speed nock. My chrono can. If the chart is all you have, use it. Just sayin chronograph are very cheap.

 

X10000. You buy a $1200 bow, $150 arrows, $200 sight, and $100 release and that's just for a target archer......then if you hunt it gets really crazy...…$45 broad heads or if you are a broad head snob maybe $200 but a $115 dollars for a Chrono is too much...…….lol

 

It's called guessing and only gets you close.....and that's if you are realistic with the data you use.

 

Most shops will let you chrono your bow for FREE.....sorry but that chart is just guessing, I really don't know what good it would do? I chrono my bows a few times throughout the year, I don't put too much into the results though.

 

A little off subject but for those who have a chrono how do get them to work indoors like in a basement.

 

You get the ones with the lighted shades.

 

light kit.

 

View attachment 7060485
Maybe this has been done before, but I've never seen it and it seemed like a fun exercise. This graph is intended to be used to determine arrow speed based on the arrow's drop over distance. It is used by shooting an arrow (or group of arrows) at 20 yards with a 20 yard pin and then backing up to a longer distance and shooting an arrow (or group) with the same pin. The difference between the two arrows (or groups) is the amount the arrow drops between those two distances. Using that measurement and the graph, you can determine the arrow's speed.

The example shown on the graph predicts that a bow that shoots an arrow at 272 fps would see an arrow drop 22 inches between 20 and 40 yards. This may require a pretty large target. Or (assuming your 20 yd pin is dialed in) you can skip the first part and just align your 20 yd pin with the top of the target or an aiming point above the target when shooting at 40 yds.

Note: this graph is based solely on gravity calculations and ignores air friction and some other variables, so it's not going to be perfect, but it should be close.

Anybody with a chrono care to give this a try and let us know how well it works?

Not accounting for air drag, rotation, vibration during flight, etc....makes the usefulness of such graphs extremely limited....I had my college physics students once, create a similar graph and at 20 yds it was overestimating by 15 FPs. At 40 yds was off by 26 FPS. Then I took the average of three shots at 80 yds and it underestimated by 12 FPS. I realized then that the I did not took into account the difference in the angle of launch. On the other hand, most cheap chronos are pretty useless also. The only devices that are highly reliable are the Labradar and the velocitip accelerometer...very expensive though...

It would make a great middle school science experiment though...

 

The "biggest" limitation of the curves is not the variables and forces affecting the arrow; I acknowledge these exist and are complementary to the simple gravitational based ballistic curve. But, the shooter's ability to replicate shots at 40 yards will result in greater uncertainty. The average shooter is not capable of sub 2-inch groups at 40 yards. A 2-inch variation is shown to result in approximately a 20 fps difference in arrow speed.

I would also concede that most chronos are pretty much a ballpark tool, semi-quantitative. Just do a search on chronos on AT and one can see the variability others have had with most chronos. Not owning one because I think they are a semi-quantitiave level instrument, I would like to know how a user calibrates the instrument to make sure it is giving accurate readings.

 

The average shooter is not capable of sub 2-inch groups at 40 yards. A 2-inch variation is shown to result in approximately a 20 fps difference in arrow speed.

Shoot 20, 50, 100? arrows, use a scoring app that has plot and analysis functions, and measure the difference between density centers.

 

Beings I have a chronograph.............

 

Interesting concept, here is something I have done a few times over the years when I was really concerned about my speed when I was a unknown shooter for asa in the semi pro class. I tried to keep my bow just under the asa speed limit of 299fps so I was legal and with my bow and arrow combo I could get 293 on the good chronos easily and be fast but safe just under the limit.

So once I knew my bow was at 293fps I would go to each of the marks on my sight tape for 20 30 40 50 and make sure I was perfect. Then I would go to 30 yards and dial in my sight and start walking back and aiming higher and higher until I got back to 50 yards. Once I was all the way to 50 yards I could then put a marker up high on the target or the back stop to aim at and then I put up a fresh piece of cardboard down where the arrows impacted. I then just started shooting at the marker up high and shot until I was sure where my arrows were hitting and I measured the distance between the aiming marker and the point of impact. Once I had that number I could do this simple little test the rest of the summer with that same bow and arrow combination and see if my bow was changing getting faster or slower.

In the years that I did this little trick the bow never got faster, it would get slower and show me a bigger distance usually when the bow lost its tune such as the cam sync or just general stretching of the string set. So then I would twist it back to perfect and be good to go.

 

There are a lot of variables that come in with things like this. Just yesterday I was playing with some new arrows and I got over 10fps differences in speed through an indoor chronograph. It took 10 or so arrows before I got a speed I was comfortable with by tossing out high and low and averaging the others. The included numbers were all within 3fps of each other.

This is a dark art and, really, don't believe anything.