Primitive Archer
Main Discussion Area => Bows => Topic started by: zenmonkeyman on April 12, 2010, 01:50:51 am
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I just shot 3 arrows through a chronograph. The arrows are 401, 463, and 478 grains respectively. They chronoed at 166fps, 166fps, and... uh... What was it now?... Oh yeah: 166fps. But not necessarily in that order. What can this mean?
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I'm just guessing that your bow just doesn't shoot any faster than 166fps. As I understand it that "dry fire" speed is related to limb mass and limb profile. It may shoot somewhat heavier arrows just as fast, esp. if it's a heavy draw weight bow. Ron
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You could always shoot some other bow through the chrono just to rule out some weird malfunction. Ron
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Thanks Ron, I had a half-formed notion to the effect of what you're telling me. I've used the chrono before and I think it's fine. It's good there's no temptation to skimp on arrow weight to try for a few more fps!
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Zen, what was the draw weight of your bow. I have never seen different weight arrows chrono at the same speed unless the chrono is malfuntioning. If your bow is around 50# you should be seeing between 10 and 12 fps difference between the lightest and heaviest arrows. Not really physicaly possible. I would test again under different light. The 401 gran arrow is getting 24# of energy and the 478 is getting 29# of energy. Steve
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It is possible that the chrono is displaying the fastest fps all the time.
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Thanks guys, I'll go try it again. The bow is (to the best of my scale's ability) about 54#. The second and third shots flashed "DUPL", which I figured was the chrono's way of telling me that it did indeed get a new number, but it just happened to be the same as the last number.
Steve, is it possible the bow just has a maximum response speed? There has to be an end to gains at some point, or a 1gr arrow would be approaching the speed of light... The bow design isn't ideal, either, it's another skinny serviceberry, only an inch wide at the handle, 68" N2N, and about 19oz. There's a deflex kink near the handle I had to heat twice to prevent hinging, even though the bow was left almost untillered at that point for the same reason. An ideal bow design should have arrows leaving at 180fps at my 30" draw I would think.
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Zen, there is a final speed it will reach but that would be with a weight of about 20 grains or so. Your terminal speed is probably about 220 fps with that bow. Not really that hard to calculate if you know how much energy your bow stores.
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That's what it sounds like to me also Justin.... I know that mine will do the same... if you don't set it right
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:DGood one Justin.
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Just shoot the three arrows a few times at a target from the same distance If they hit the kill zone, hut um ;D