RX3 speed help - no chrono

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Jan 5, 2020
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I do not have a chrono within a 3 hour drive of me. Trying to get my arrow speed by those who have specs at somewhat similar specs to me.

Hoyt RX3, #3 cam, 29.5” draw, 68#, 520 grain Easton axis.

Trying to get as close as possible.
 
For why?
Sight tape?
I'd say 260-265
If you have your fixed pins set put an arrow wrap or masking tape on.
Use very fine print sharpie and walk it out.
Then compare it to the closest tape in the kit.
 
There’s online estimators that will give you a close number. But without a chrono you won’t get exact. Using the specs you just gave me and a quick google search for a calculator I come up with 270ish. Again it’s impossible to be exact without a chrono.
The real question is does it matter? Set the pins on your sight for the arrow tour shooting and go woth it. If the bow and arrow are tuned and the pins are on speed is just a number.
 
It’s for the Full Draw 4 rangefinder. I have a few methods with calculators as well. I know it’s a popular bow so just seeing if I could get some real numbers that’s all.

Pinwheel shows 276. Archers advantage showed over 280 from what I remember but need to check again.
 
Ohh.
It gives you a cut yardage.

Another way to do that it to throw in a close fps.
Actually shoot at an angle.
If your low decrease the fps, high increase etc.
Until it matches up.
What it tells you is what you're actually shooting.
 
Here's a method to get you in the ballpark:
  1. Take IBO speed and subtract 2 fps per lb of draw weight under 70 lb, then subtract 10 fps for every inch of draw length under 30"
  2. Calculate KE with a 350 gr arrow at the speed calculated in step 1
  3. Use the KE calculated in step 3 to calculate speed at any given arrow weight

For your setup, the calculations would be:
  1. 340 fps – (2 fps/lb) × (70 lb – 68 lb) – (10 fps/in) × (30 in – 29.5 in) = 331 fps
  2. (350 gr) × (331 fps)² / 450,240 = 85.2 ft-lb
  3. √[(85.2 ft-lb) × 450,240 / (520 gr)] = √73,770 = 272 fps
 
Awesome, thank you. My initial input was 271.

I was also going to go adjust up and down through testing. I appreciate the replies.
 
Rx3 turbo #3 cam @28 dl and 70 lb draw weight With Rip tko 300 @ 517-520 grains total. Used tape to make yardage marks (tommy Hogg) got the closest spot Hogg tape sighted in and used archers advantage online and put in all the info they asked for using 20&80 yard sight in marks and inputting them in to print an archers advantage tape @ 264.5 FPS and it’s pretty spot on to 100 yards with my custom tape and about 1-2 yards off on spott hoggs tape.
 
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