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DIY Chronograph, am I doing it right?

A place to ask general spud cannon related questions.
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Unread postAuthor: rp181 » Thu Jul 03, 2008 5:18 pm

ahh, i see the way you do it. I dont have a scope, but agilent might give me a 40mhz handheld, that will be usefull.

Ile keep the resistors out, i use NiMH rechargables, so they last awhile, and there rechargable =p. its used for short periods anyway.

Im well aware of the diode needed antiparrallel across thecoil, i have 4 1200v 5500A surge fast recovery diodes.

I clocked a rubberband today, does 30FPS sound about right?
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Unread postAuthor: jimmy101 » Fri Jul 04, 2008 10:18 am

rp181 wrote:I clocked a rubberband today, does 30FPS sound about right?

If you launch the rubber band horizontally and measure the distance it takes to fall to the ground from a known height you can get a rough estimate of the velocity;
v = (horizontal distance) / SQRT(2*height/g)
if g is 32 feet/second^2
v = 4*(horizontal distance) / SQRT(height)
where both distance and height are in feet

So, for a 3 foot drop and a 30 FPS velocity the rubber band should carry about 13 feet.
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