Chrono setup

[Bigggcountry]

how far away should I put the chrono?

 

[ILbowhntr]

Set mine up about 2-3' away.

 

[HardLoadHunter]

The same with firearms, you want to get the speed of project the second it leaves the bow/rifle. So you want your arrow entering the Chrono as soon as it leaves you string. Or like the rest of us 2-3 ft should work good

 

[Bigggcountry]

I tried the 3' and got 246fps out of curiosity I moved to 20 yds and got 270fps. What am I doing wrong?

 

[HardLoadHunter]

That makes no sense try it again! Lol

 

[Micarden3]

That makes no sense try it again! Lol

Does your arrow have a mini engine on it that turns on after 3yds? haha, tha doesn't make sense, perhaps you were to close to the chrono and it was measuring speed before it left the string.

 

[HardLoadHunter]

What kind of arrows and vanes are you running? You may be on to something!!! 

 

[Micarden3]

When i was talking to the guy at my proshop, i was asking about being able to shoot two different arrows that weigh within 10 grain of each other. One for hunting, and one for ground squirrel cheapos. He said up close i would notice as much of a difference because the arrow isn't at full speed yet, but once it starts on the downward slope of the trajectory it builds up more speed. This beingsaid, if he is correct, your chrono could also be reading correctly.

 

[HardLoadHunter]

that makes no sense, with the air friction(resistance)  gravity etc   ive never herd of such a thing i will do some more research

 

[HardLoadHunter]

fletchings are the only thing i think could allow this

 

[HardLoadHunter]

just found this


The arrow starts at zero rotation but depending on the degree of offset or helical can accelerate its spin quickly. As the arrow continues on, the spin rate speeds up. There are now two velocities in play, the arrow velocity and the fletching velocity. The fletchings velocity is its rotation at a right angle to the shaft. The drag on the entire arrow is the sum of the arrows speed and the fletchings spin rate. The spin velocity increases until at some point the speed of the arrow is not sufficient to continue the spin acceleration and it will have reached peak rotation speed. All of this is happening while the arrow is oscillating, complicating all the simple factors that we just talked about. What this means is that there is additional drag on the whole arrow but mostly on the rear of the arrow, where the fletching is, as it bends and wobbles through the air. Part of the drag on the fletching is trying to straighten the arrow out instead of spinning it. So much for perfect arrow flight




posted the question on archery talk and they say not possible


was the wind at your back??

 

[HardLoadHunter]

im gonna say you got a cheap chrono

 

[ILbowhntr]

Any pro shop that tells you an arrow speeds up down range is the one to stay away from. The arrow has ALL the energy it will have the instant it leaves the spring. It starts losing energy/velocity at that point. The rotation of the arrow is one of the factors that stabilizes the arrow, but the rotation is caused by the drag of air over the vanes which by nature slows the arrow down.

 

[HardLoadHunter]

My thoughts exactly

 

[Micarden3]

Any pro shop that tells you an arrow speeds up down range is the one to stay away from. The arrow has ALL the energy it will have the instant it leaves the spring. It starts losing energy/velocity at that point. The rotation of the arrow is one of the factors that stabilizes the arrow, but the rotation is caused by the drag of air over the vanes which by nature slows the arrow down.

I just called it a "proshop". It was a new Sportsmans that just opened up, after all he said most the bows they sell are low end. This is definitely not my bow shop that i have work done at! I would think that as so as the string stops accelerating it, they would slow down!

 

[ILbowhntr]

I think that's what I said.

 

[Bigggcountry]

It must have been the downward angle I was shooting off my deck to make my chrono read incorrectly. I was able to get a flatter arrow flight across it today and 7 arrows averaged 280fps at 3 yards. Correct me if I'm wrong, but isn't your arrow still gaining speed when your string hits your stop?  I'm shooting a Hoyt Charger, Easton FMJ arrows with 3" helical vanes with 100gr tips, I have a 31" draw.

 

[Micarden3]

It must have been the downward angle I was shooting off my deck to make my chrono read incorrectly. I was able to get a flatter arrow flight across it today and 7 arrows averaged 280fps at 3 yards. Correct me if I'm wrong, but isn't your arrow still gaining speed when your string hits your stop?  I'm shooting a Hoyt Charger, Easton FMJ arrows with 3" helical vanes with 100gr tips, I have a 31" draw.

As far as i understand, the string is the only thing that accelerates your arrow. Everything elseslows it down. I beleive even a helical curve has drag therefore slowing it down. The positive of a helical is a stabilized arrow flight just like a bullet.