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General >> General Slinging Discussion >> Sling release velocity vs. distance (video)
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Message started by IronGoober on Nov 21st, 2021 at 12:26am

Title: Sling release velocity vs. distance (video)
Post by IronGoober on Nov 21st, 2021 at 12:26am
I made a video trying to get confirmed release speeds vs distance (my max distance, I didn't get a bunch of distances in between, unfortunately).

Short version:
https://youtu.be/O3VPxMWtBZM

Long version:
https://youtu.be/v-jP9oKcpXE
(it's kind of like hangin' out on a hilltop, except you don't get to talk or interact)

Title: Re: Sling release velocity vs. distance (video)
Post by Mersa on Nov 21st, 2021 at 4:34am
So close to 250 confirmation and a great video!!!
I think if it were lead it would have got the extra meters but been much harder to see and find .
Congratulations!!

Title: Re: Sling release velocity vs. distance (video)
Post by Morphy on Nov 21st, 2021 at 3:08pm
Finally got to watch. Did you purposefully use a hilly area so you could see where they hit easier? That was my initial impression. Either way gorgeous area man it looked like a postcard.

Anyways on to the actual slinging. That was very good. I really, *really* wish that radar went up higher. I want so bad to see 140-150. I bet you could do it with an optimal set up.

What I really dont get, and Ive mentioned this before is how in the hell are people slinging 400m+? Because those shots you were slinging were zipping man. They were really moving fast.

Oh and I wonder if you could add some of that powder NOOC uses for slinging at children to get an initial impact spot? Just some random thoughts. Great vid.

Title: Re: Sling release velocity vs. distance (video)
Post by Archaic Arms on Nov 21st, 2021 at 6:16pm
Very fun video to watch!
The Rangefinder, radar, and jolly good slinger makes for a great combo. It's also nice to see it verify your hypothesis and calculations.
Good stuff!

Title: Re: Sling release velocity vs. distance (video)
Post by IronGoober on Nov 21st, 2021 at 11:05pm
Yes, I used a hilly area in the hopes that puffs of dust would be visible, and I could range find the hit location. In a lake you can see the location of the hit, but can't range find it.

Title: Re: Sling release velocity vs. distance (video)
Post by David Morningstar on Nov 22nd, 2021 at 7:36am
Love that video. Are there any suitable radar devices that go over 130 mph?

Title: Re: Sling release velocity vs. distance (video)
Post by IronGoober on Nov 22nd, 2021 at 9:39am
Affordable radar guns? not to my knowledge. But ones certainly exist that can do higher velocities. This one is actually only software limited if the internals are made the way I think they are. I emailed the company and they mentioned that they are working on expanding its velocity range. I don't know if they'll ever release a newer version of the software that will do it for this unit though, I think the firmware on the unit would have to be upgraded as well. It's just finding the peak in a Fourier transform and converting back to velocity, so it should be an easy software upgrade. But I think they probably do a lot of testing to make sure the readings come out accurately under a variety of conditions. The best part about this unit is that it works with the object moving toward or away from the radar gun, most of the police-grade or expensive baseball units only work when the object is moving toward the gun.

Title: Re: Sling release velocity vs. distance (video)
Post by joe_meadmaker on Nov 22nd, 2021 at 11:00am
Great demonstration IG!  And one heck of a throw! :thumb:

Title: Re: Sling release velocity vs. distance (video)
Post by Curious Aardvark on Nov 22nd, 2021 at 11:27am

IronGoober wrote on Nov 21st, 2021 at 12:26am:
(it's kind of like hangin' out on a hilltop, except you don't get to talk or interact)


lol having hung out on various hilltops with various slingers, I can say it's definitely a lot more fun if you're not on your own :-)
We've got a few texans around these days.
Shouldn't be impossible to set up a weekend or something similiar.


Nice video :-)

So what is the rader unit and what is it picking up and how ?

Normally you need to sling between a couple of antenna type things.

All i can see is what looks like a little box stuck on top of a phone.


Title: Re: Sling release velocity vs. distance (video)
Post by IronGoober on Nov 22nd, 2021 at 2:20pm
https://www.youtube.com/watch?v=5c6mf8-RqOI

@CA It works by sending out radio waves and receiving reflected radio waves from the object in motion. It calculates velocity from the Doppler effect (the frequency of the reflected radio wave shifts based on the speed of the object). It's the same thing that baseball coaches/scouts and the police use to clock speeds.

Since it works on a reflected wave and the object is moving and can change velocity, the reflected waves it receives will have a frequency that isn't constant. So, the value it reads out (displays on the screen) is the highest speed that it "sees".

Compared to one baseball scouts use a lot ($1500), it is within 1 mph ( in the video I linked above).

Timpa also has one, and claimed he's used it to get speeds from objects as small as a metal BB. (I think it being metal helps increase the radio wave reflection).
https://youtu.be/4FgcysbplWA


In related news, I saw a really neat video of a guy who made a simple version that would emit sound based on the speed of the object (much cheaper than the unit I bought). But from what I can tell, it would be really easy to use the Fourier spectrum from the oscilloscope to give a max velocity too.

https://youtu.be/Kzsh59TM4MY




Title: Re: Sling release velocity vs. distance (video)
Post by IronGoober on Nov 22nd, 2021 at 7:03pm

Archaic Arms wrote on Nov 21st, 2021 at 6:16pm:
Very fun video to watch!
The Rangefinder, radar, and jolly good slinger makes for a great combo. It's also nice to see it verify your hypothesis and calculations.
Good stuff!

AA, I didn't think to actually check this...but great idea!

Using the trajectory calculator and the mass/area ratio for a 70g sphere of rock (2.7g/cc, ratio ~70), the average drag coefficient for that release was ~0.2.

The Reynolds number for the recorded throw is approximately [(1.225kg/m3)*(57.67m/s)*(0.03m)]/(0.001 kg/(m*s))  ~ 2100

From looking at Wikipedia, the drag coefficient on a sphere in that range is about 0.4-0.5.  Given that the stone I used was not spherical (but not biconical either), I think this seems about right. A perfectly released biconical with a drag coefficient of 0.08 would have traveled >290m.

https://en.wikipedia.org/wiki/Drag_coefficient#/media/File:Drag_coefficient_on_a_sphere_vs._Reynolds_number_-_main_trends.svg


Title: Re: Sling release velocity vs. distance (video)
Post by Sarosh on Nov 23rd, 2021 at 6:49am

IronGoober wrote on Nov 22nd, 2021 at 7:03pm:
sing the trajectory calculator and the mass/area ratio for a 70g sphere of rock (2.7g/cc, ratio ~70), the average drag coefficient for that release was ~0.2.

what is the trajectory calculator and how did you find the drag force?
Edit: I realized what you mean, which trajectory calculator did you use?

Title: Re: Sling release velocity vs. distance (video)
Post by IronGoober on Nov 23rd, 2021 at 9:51am

Sarosh wrote on Nov 23rd, 2021 at 6:49am:

IronGoober wrote on Nov 22nd, 2021 at 7:03pm:
sing the trajectory calculator and the mass/area ratio for a 70g sphere of rock (2.7g/cc, ratio ~70), the average drag coefficient for that release was ~0.2.

what is the trajectory calculator and how did you find the drag force?
Edit: I realized what you mean, which trajectory calculator did you use?


I was using the one in this thread.

https://slinging.org/forum/YaBB.pl?num=1637205605

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