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Unread 10-01-2006, 22:54
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DonRotolo DonRotolo is offline
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Re: How will FIRST measure muzzle velocity?

It seems trivial to me that you could use an optical sensor (like the Allen-Bradley...) and measure how long it takes for the ball to pass. If it is an 18 cm ball (about) and the speed is 1200 cm/sec, then 18/1200 = 0.015 or 15 milliseconds. less than that, it's going too fast.

You should be able to build something like that into a 10" diameter tube perhaps 6" long and just hold it at the end of the launcher, with the launched ball going into a net for safety.

If you want to build one: Note that the A-B sensor has a 1.0 mS 'on' delay and a 1.5 mS 'off' delay, which needs to me measured to see if it is consistent. Also, the RC probably cannot measure time accurately enough. Easiest would be to use an oscilloscope - even a cheap one would be OK.

Have fun. Post photos.

Don
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