Slinging.org Forum - What ways are there to measure sling projectile speed?

Drakolith Funditor Offline Posts: 675 U.S.	What ways are there to measure sling projectile speed? Apr 10^th, 2017 at 7:40pm Any ideas?
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johan

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Re: What ways are there to measure sling projectile speed?
Reply #1 - Apr 11^th, 2017 at 2:20am

derived from max distance achieved with different projectiles(tennis ball , lead bullet, bbs) with use of programs with airdrag calculation
time over some defined distance (10-30m) but that's the average speed
use of video frames
radar gun/pocket radar or other athletic devices
chrony (this will need high accuracy or at least some protection for the device)
ballistic pendulum (accuracy and some physics needed, also difficult to make or transport)http://hyperphysics.phy-astr.gsu.edu/hbase/balpen.html

that's all i remember
without a good piece of equipment(high speed camera or chrony or pocket radar or speed gun) which is expensive you will not do more than a guesstimate.

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Drakolith Funditor Offline Posts: 675 U.S.	Re: What ways are there to measure sling projectile speed? Reply #2 - Apr 12^th, 2017 at 9:52pm I've found a app on my iPhone that looks promising, the way it works makes sense, and the reviews are great. If I have the time and conditions permit it, I will see if it works.
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johan Funditor Offline no longer active:keep the flame of slinging alive Posts: 531	Re: What ways are there to measure sling projectile speed? Reply #3 - Apr 13^th, 2017 at 3:31am i know of an app that could measure speed but it would require you to sling the iphone what app are you thinking?
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Drakolith Funditor Offline Posts: 675 U.S.	Re: What ways are there to measure sling projectile speed? Reply #4 - Apr 13^th, 2017 at 8:33am SpeedClock it has many different ways to measure it.
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Curious Aardvark Forum Moderation Offline Taller than the average Dwarf Posts: 13965 Midlands England Gender:	Re: What ways are there to measure sling projectile speed? Reply #5 - Apr 22^nd, 2017 at 8:50am get usian bolt to run past you and sling at the moment he gets level. Then ask him how fast he thought it was going when it went past
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Drakolith Funditor Offline Posts: 675 U.S.	Re: What ways are there to measure sling projectile speed? Reply #6 - Apr 22^nd, 2017 at 8:31pm I think it would be cheaper to get a radar gun
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jlasud Interfector Viris Spurii Offline Programming stones Posts: 2358 Transilvania Gender:	Re: What ways are there to measure sling projectile speed? Reply #7 - Apr 23^rd, 2017 at 4:52am Pocket radar. Measured distance slinging,recorded on video, calculated using audio with audacity prog.
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johan

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Re: What ways are there to measure sling projectile speed?
Reply #8 - May 21^st, 2017 at 10:20am

today i tried to measure projectile speeds.
i slung parallel to a stick of known length while filming with an 50fps camera( in the past i had done this with an 30fps camera so i thought i may have more accurate results now )

i filmed 8 throws
the projectiles stayed on camera for 2-4 frames
(the more the frames with the projectile in them the better the accuracy of the results)
results from each clip were:

50-60m/s
65-70m/s
32-48m/s (this clip must be the most accurate one but i used a heavier stone)
75-113m/s
36-55m/s
70-105m/s
58-87m/s
78-117m/s

what results have you got out of this method?

with time over 30m i get about 44m/s (0,67s) which is much more logical than 70-100m/s Tongue

but time over 30m gives an average speed not max speed reached Sad

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WojtekimbieR

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Re: What ways are there to measure sling projectile speed?
Reply #9 - May 25^th, 2017 at 12:18pm

johan wrote on May 21^st, 2017 at 10:20am:

50-60m/s
65-70m/s
32-48m/s (this clip must be the most accurate one but i used a heavier stone)
75-113m/s
36-55m/s
70-105m/s
58-87m/s
78-117m/s

How did you calculate the error of measurements? With known positions A and B and time you should have the exact speed, not 36-55 etc. so how did you come up with those numbers?

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JudoP Funditor Offline Rocks away! Posts: 936 UK	Re: What ways are there to measure sling projectile speed? Reply #10 - May 25^th, 2017 at 4:28pm Parm, out of interest- Roughly how much did the stones you sling weigh? What sort of distance would those shots achieve if shot for range? What type/length of sling did you use?
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johan

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Re: What ways are there to measure sling projectile speed?
Reply #11 - May 26^th, 2017 at 9:33am

WojtekimbieR wrote on May 25^th, 2017 at 12:18pm:

How did you calculate the error of measurements? With known positions A and B and time you should have the exact speed, not 36-55 etc. so how did you come up with those numbers?

that's what frustrated me the most.
i measured the distance between frames (with known positions A and B) the strange thing is that in some frames the stone travelled less distance per frame and at others travelled more distance (same clip,same throw) hence the 36-55m/s . it's probably a camera thing, although it is 50fps camera.

JudoP wrote on May 25^th, 2017 at 4:28pm:

Roughly how much did the stones you sling weigh?

50grams

JudoP wrote on May 25^th, 2017 at 4:28pm:

What sort of distance would those shots achieve if shot for range?

since i don't believe i achieved more than 55m/s
i would probably reach 200m as usually..

JudoP wrote on May 25^th, 2017 at 4:28pm:

What type/length of sling did you use?

linen split pouch 65cm

i will measure again with the good old 30fps camera

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johan

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Re: What ways are there to measure sling projectile speed?
Reply #12 - Jun 3^rd, 2017 at 3:24pm

i did measurements with 30fps camera
the main difference i noticed between 50fps and 30fps is that at 30fps the stone is blurred in contrast with the 50 fps.

i did measurements with the camera 3 meters away and then with the camera 10m away. 10m away produced more accurate consistent and realistic results.

3m away throws
1: 61,5m/s
2:68,7 m/s
3: 62,34m/s

10m away throws
1: 40m/s (heavier stone)
2: 54,75 m/s
3: 48 m/s
4: 55,92 m/s
5: 51 m/s
6: 52,41 m/s
7: 57,5m/s

sling is 72cm this time
i threw horizontaly overarm so if i throw for distance i'll probably achieve smaller speeds

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wanderer

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Re: What ways are there to measure sling projectile speed?
Reply #13 - Jun 5^th, 2017 at 11:47am

Quote:

that's what frustrated me the most.
i measured the distance between frames (with known positions A and B) the strange thing is that in some frames the stone travelled less distance per frame and at others travelled more distance (same clip,same throw) hence the 36-55m/s . it's probably a camera thing, although it is 50fps camera.

Perhaps you are suffering from 'rolling shutter syndrome'? https://en.wikipedia.org/wiki/Rolling_shutter

The pixels at different points on a single video frame can correspond to significantly different instants, so knowing the 'delta T' between two images of the moving projectile is not at all trivial.

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johan Funditor Offline no longer active:keep the flame of slinging alive Posts: 531	Re: What ways are there to measure sling projectile speed? Reply #14 - Jun 5^th, 2017 at 12:17pm wanderer wrote on Jun 5^th, 2017 at 11:47am: Perhaps you are suffering from 'rolling shutter syndrome'? https://en.wikipedia.org/wiki/Rolling_shutter thank you for sharing. probably thats the problem.
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