yes, but that does nothing to address the fundamental misunderstanding by @DuckFeet that just because the racket is stopped then all momentum must be transferred into the shuttle. I'm not sure any of that is any dispute. I just object to your terminology saying that a conservation law can be applied at an instant. A conservation law says that for a (closed) system whose state may change (for some definition of state), there exists an invariant quantity. If you are only considering a single instant, then you are only considering a single state and so a conservation law has no meaning. /pedant
I did tests using a tracker that spewed out the information for me. Due to the the swing and shuttle being so fast it was challenging to track, resulting in not being able to get fully behind this information, but here you go test 1 Vx of racket = 17.29m/s Vx of shuttle = 23.35m/s Ratio = 1.32 test 2 Vx of racket = 18.28m/s Vx of shuttle = 27.25m/s Ratio = 1.49 test 3 Vx of racket = 21.58m/s Vx of shuttle = 31.47m/s Ratio = 1.45 test 4 Vx of racket = 18.63m/s Vx of shuttle = 26.72m/s Ratio = 1.43 test 5 Vx of racket = 16.26m/s Vx of shuttle = 23.74m/s Ratio = 1.46 Average ratio is 1.43 This is not the speed of the shuttle as soon as it leaves the head as I could not capture this but it should be close enough. I can not give you any comparison on what racket head weights were either as I don't know most of the rackets used although the 1.46 was a zforce. Conclusion is I need a better camera and better tracking software
^ Interesting... here's one for you to measure... should have high enough frame rate to be accurate... Start at 1:47. [video=youtube;eH6qFJoySf8]http://www.youtube.com/watch?feature=player_detailpage&v=eH6qFJoySf8#t=107s[/video]
Sorry Visor tried that one but the results were too strange to include. The racket went faster then slower then faster then slower. Think this one is too slow and blurry to plot accurately.
@craigandy Please specify how you are doing your calculations. IE what's your general method, and what exact points are you using for racket speed - tip? head centre? contact point? The properties of the racket(s) used would be useful information as well. This would allow others to repeat your process and compare numbers.
I am not doing the calculations. I am using an already developed and tested tracker software. the software slows the video down and you mouse click the appropriate object frame by frame. I have been trying to click the center area of the racket string bed and for the shuttle the cork. You calibrate the video by putting in a known measurement in any of the frames that is near to where you are interested in reading speeds I.e you can use the players height or racket length to calibrate. I have checked the calibration on each video using several different points like the net height or tramlines width all give nearly the same figures, so happy with that. It processes the information and gives it to you on a graph. (their is also an axis you can tilt to offset any camera squint) Problems I have encountered: Their aren't enough frames per second. So one frame the shuttle would nearly be touching the racket but not quite next frame it is 5 foot away, so the shuttle speeds straight off the racket using better camera/software would most definitely be higher. It can be a bit blurry. Not every test(not included tests) has given numbers that in anyway correlate to whats happening(i.e dropping speed when it is gaining etc), so the software does struggle with the speeds. On a plus note the first 4 tests were the first four I did with no problems at all and all seem pretty consistent with each other. With regard to the rackets. I appreciate what you are saying and knowing the racket properties is probably the whole point of this exercise, but there is a major problem with this. Firstly have we come to an agreement that it is the weight in the head that is to be the measurement?? Next up is how can i accurately measure the head weight if this is what some want? Third and biggest problem I don't have access to most of the rackets used to value their properties. Sorry mate. I don't really have the time to do it all properly, but please if you all want to go out and video yourself's side on fairly close up and give up the specific racket properties that you used etc, Just post it here and we can go through it all together(nothing too fast though) p.S [MENTION=31680]amleto[/MENTION] Their is a velocity magnitude reading on the software as well that can be used for the swing.
thanks for the info! Unless you have access to a swing weight app, then just the racket weight and bp will be useful. Is the software open source?
https://www.youtube.com/watch?v=kwPTMLIBbTY&feature=youtube_gdata_player Interesting... Here, found an HD version. See if it works better. Start at 18:22. [video=youtube;kwPTMLIBbTY]https://www.youtube.com/watch?v=kwPTMLIBbTY&feature=youtube_gdata_player[/video]
why not just measure the overall displacement of the shuttle divided by the time taken upon contact to touching the ground? that will give you an average than trying to measure the speeds at different parts of its flight. at the very moment of contact, there is a split second when the shuttle is decelerated to zero velocity/zero kinetic energy before it changes its direction and flips over, where the force upon impact, accelerates the shuttle from zero velocity to "max"
Oh btw, try to pick the part where the frame rate is constant, as the video has 2 slow mo rates for special effect. Perhaps that was interfering with your first measurement.
There are already a lot of losses thru sound, inelasticity, etc, so I think we should measure max speed as much as possible. TBH tested the ZSlash (and currently testingI the NR Z Speed(?) ) with this method, so we want to see if we can get 421km/h. (half joking )
Still don't trust this one because of the other readings I can see but since your so adamant Vx racket = 1.22m/s Vx shuttle = 1.83m/s Ratio = 1.5
That is a bad idea because the further the shuttle travels the more air resistance affects the results.
Lol... yeah, but at least we got a good output to input ratio. Does the software need an input for frame rate? Because that FHF super slow mo section is very very high frame rate per sec. Meaning that one frame is probably like 1/1000th of a sec.
Lol, Yeah it is clearly not FHF real time. Tried to do quite a few things with regard to frame rates but to no avail. If the video is already in slo mo you can't input the frame rate of the vid into the software for translation, not that i would know what the fhf frame rate is(or maybe you can I don't know the software inside out and there is developer templates). But you can imagine whatever speed he usually hits the shuttle and divide it by 1.5 to get the real time racket speed.
air resistance is always affecting your results no matter what, whether you measure it when the shuttle has travelled more, or just left the bed of the racquet where it has barely travelled have you incorporated air resistance in your calculations then? if you have been ignoring it, then why not ignore it further? and it also depends on how hard the shuttle is being spun, if there is any slice component incorporated in the smash, the spin contributes.
The percentage of speed that air resistance subtracts over the first three feet is worth ignoring. It's a very small percent.
Just thinking about this point some more. This way of measuring is never going to be accurate enough to start being able to take into account bp racket weight etc etc. Their is nothing to show how much slice is on the shuttle, also we don't know the reduction off center hits make to speed even off by a few mm could be a lot. The video's can show us some things but no point in including racket details etc as the information is not good enough. I think if you want to compare what racket weight is best, you would be best forgetting about using a shuttle, and just record swings speed of only you(personally) seeing how fast you can swing the different weighted rackets, then use line and lengths formula!
