Newsgroups: comp.robotics
Path: brunix!uunet!zaphod.mps.ohio-state.edu!wupost!darwin.sura.net!news.duc.auburn.edu!gauss.cse!mdavoli
From: mdavoli@eng.auburn.edu (Michael Kenneth Davoli)
Subject: Re:  Measuring the acceleration of an arrow
Message-ID: <1992Dec7.212942.20544@news.duc.auburn.edu>
Keywords: arrow acceleration
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Reply-To: mdavoli@eng.auburn.edu
Organization: Auburn University Engineering
Date: Mon, 7 Dec 1992 21:29:42 GMT
Lines: 31



I do not claim a whole lot of physics knowledge, but I have shot an awful lot of
archery in the last 12 years.  I have seen 2 methods for ascertaining arrow
speeds, once the arrow has left the bow.  I think they are both marketed as
"chronographs".  One is simply a pair of fixed light "sensors" on a platform.
When one shoots over the sensors, I believe the arrow's shadow triggers the sensors and one obtains an instantaneous velocity.  I've seen this one used 
with both arrows and bullets.  Do this at as many distances as is reasonable and
you should be able to generate your acceleration (deceleration) curve.  A decent archer should be able to shoot a group about the size of the bottom of a soda
can at around 25 meters, past that your data might not be easy to obtain.

The other "chronograph" has a square (rectangular) frame through which you are
suppose to shoot.  I know nothing about how it works.........

I think going down to any reputable archery shop is all your friend would need
to do.  They would probably let him shoot over theirs for free.

If he's interested in the acceleration from anchor point, then maybe:

> From scott@psy.uwa.oz.au (Scott Fisher)
>.......
> how about a row of photo-diodes lined up along the path of the arrow flight,
> this need only be a strip of 20 of them spaced 1 inch a part, you could even
> attatch this strip to the bow itself using the stabilizer mounts.
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			Michael Davoli



