Slinging.org Forum - David and Goliath (Discovery Channel)

archeorob Descens Offline Know when to duck! Posts: 126 Wisconsin Gender:	Re: David and Goliath (Discovery Channel) Reply #15 - Jan 20^th, 2004 at 2:50pm Nuts, I missed it. The website said 7, and I missed the fact that that was 7 Eastern Standard time. Which means that I set the VCR for an hour too late. Ah well. Sounds like I didn't miss to much. Has anyone actually tested the speed of their sling stone before? Rob
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Yurek

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Re: David and Goliath (Discovery Channel)
Reply #16 - Jan 20^th, 2004 at 6:24pm

Quote:

Chris,

I think Yurek needs to write a note and attach it to one of his lead glandes and sling it over to the UK. The note could read something like, "Hey you whimpy Brits, I could sling the stone and the guy who slung it in the video faster than 80mph!" Grin

Signed Yurek the Great of Poland.

David,

We shouldn't forget that just the British has hurled 8 oz stone at 377 m or something about. Where was he durring the production?

Jurek

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In the shape, structure and position of each stone, there is recorded a small piece of history. So, slinging them, we add a bit of our history to them.

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Chris

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Re: David and Goliath (Discovery Channel)
Reply #17 - Jan 20^th, 2004 at 7:07pm

Oh, I thought you might be interested in this. They measured the speed by sticking two poles in the ground a meter apart and filmed the rock go by them with a high speed camera. They could count the number of frames it took from pole to pole (9 or something), which allowed them to figure out the time to cover one meter (because a frame was 1/100 of a second or something).

Anyone got a decent digital camcorder? Sounds like a pretty easy set up! I'll help with the rest.

Chris

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mgreenfield Funditor Offline Posts: 509 Milwaukee Wisconsin Gender:	Re: David and Goliath (Discovery Channel) Reply #18 - Jan 20^th, 2004 at 8:53pm 80mph??? Pitchers are regularly throwing fastballs at 90+mph. We gotta figger out how to routinely do a lot better or hang up our slings. mgreenfield
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Yurek

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Re: David and Goliath (Discovery Channel)
Reply #19 - Jan 21^st, 2004 at 7:36am

Quote:

Oh, I thought you might be interested in this. They measured the speed by sticking two poles in the ground a meter apart and filmed the rock go by them with a high speed camera. They could count the number of frames it took from pole to pole (9 or something), which allowed them to figure out the time to cover one meter (because a frame was 1/100 of a second or something).

Anyone got a decent digital camcorder? Sounds like a pretty easy set up! I'll help with the rest.

Chris

The expensive advanced digital camcoder is not necessery. You can use common cheap analog VHS or V8 one. Lots of them have "sport" (high speed shutter) mode. The "exposure time" of frame is 1/4000 s (it surely depend on model), every frame is taken in 1/25 s intervals (you should check it for your camera in the instruction book or somewhere). The each frame is composited with two "half-images" taken every 1/50 s. So if you view the tape "frame by frame" you will see that each frame oscillate between two "half-images". You will see two positions of the stone or sling cleary. If you can count the real distance between these positions, divide it by 1/50 s and you will get the velocity. In another way, you can measure the stone distance durring several frames and divide it by the numer of frames and by 1/25 s. I hope my explanation is clear.

Jurek

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In the shape, structure and position of each stone, there is recorded a small piece of history. So, slinging them, we add a bit of our history to them.

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