The rebound test... A little experiment.
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norbs

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Re: The rebound test... A little experiment.
« Reply #45 on: April 03, 2012, 03:05:05 PM »

I'm renaming you Heath Robinson

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Re: The rebound test... A little experiment.
« Reply #46 on: April 03, 2012, 03:25:18 PM »

Tim how will you ensure the vice is gripping each bat with the same pressure as I can imagine that will affect the results
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tim2000s

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Re: The rebound test... A little experiment.
« Reply #47 on: April 03, 2012, 03:56:37 PM »

Tim how will you ensure the vice is gripping each bat with the same pressure as I can imagine that will affect the results
I'm planning on using the same bat, and as it is a workmate, it will be possible to count the number of turns to hold the bat ina steady position, which can be repeated. Not ideal but near enough.
Have you considered using a snooker ball, the size and mass is more akin to a cricket ball than that of a ball bearing? Good experiment though, looking forward to seeing the results.
Ball bearing means less leverage on the bat handle, hence less likelihood of the contraption moving as the ball is dropped. A heavier cricket or snooker ball runs the risk of causing tipping more on a relatively unstable structure.
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John

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Re: The rebound test... A little experiment.
« Reply #48 on: April 03, 2012, 05:02:22 PM »

I'd support the back of the bat on something semi-solid. Maybe a shaped pad of foam insulation or similar. That would take out the effect of the handle and would be more easily repeatable.
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Nespresco

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Re: The rebound test... A little experiment.
« Reply #49 on: April 03, 2012, 10:47:44 PM »

An interesting experiment, I was reading a PhD Thesis based on an experiment produced to be able to quantify racquet power for a tennis authority as part of my degree. In short the level of mechanics and general engineering knowledge to design an experiment and execute it successfully extends beyond undergraduate degree level.
As someone mentioned design of experiments is a huge area and when doing this properly (i.e. commissioned to undertake research on behalf of a large sports equipment manufacturer) it would take a significant amount of time and money to attain reliable results.  I fear this experiment is flawed on a number of issues, even presuming you have modelled the impact suitably your method of recording the results could well be flawed. How many FPS are you recording with? Have you investigated by simple projectile motion how far the ball bearing could have travelled in between frames, or have you guessed by averaging frames? Have you accounted for cosine errors in reading the rebound height since you won’t have the lens level with the bearing at its highest point, or are these negligible due to the distance between the lens and ball bearing relative to the ball bearing and ruler? Is the use of a ball bearing even an accurate representation of the interaction between a cricket ball and the face of the bat? All of these create uncertainty in your results.  I ask you to what degree of confidence can you present your results?
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tim2000s

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Re: The rebound test... A little experiment.
« Reply #50 on: April 03, 2012, 11:00:20 PM »

Thank you for your questions. There are indeed many errors that can be introduced into my experiment and I do not intend to counter them all. It is first and foremost a bit of fun to raise some discussion. It is secondly intended to try and quantify many discussions about knocking in. There are many things that I can do but won't due to these factors however, if it raises anything real I'd be happy to see someone take it up properly and improve on it.
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Nespresco

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Re: The rebound test... A little experiment.
« Reply #51 on: April 04, 2012, 01:29:42 AM »

I realise that it is a 'fun' experiment to provoke related intellectual discussion. I was just questioning how confident you were in the accuracy of your data, if all the sources of uncertainties are not accounted for then the issue of 'to what extent is this data useful' may become relevant.  Even for this simple hypothesis test I would be skeptical that the test setup is suitable to accept or reject the null hypothesis even to a 10% confidence level. A couple of things, consider mounting a pair of laser pointer on a firm tripod and mark 2 small points a few inches apart on the bat, this should ensure the bat is in the same place each time, also i would imagine a ball bearing to not be a suitable substitution for a cricket ball unless it is quite heavy, Think about what happens to the fibers when the bat strikes the ball outside the experiment, dropping a ball bearing wont replicate this. My thoughts into this involved a bat attached to a speed controlled rotating arm using a light gate to remotely trigger a ball to relase into the path of the bat and using high speed photography to determine the velocity of the ball, It should be possible to ensure, with the correct delay, that the ball strikes the same spot on the bat consistently and that the path of the ball is perpendicular to the face of the bat. It would then be possible to calculate a 'power factor' using some formula involving the MoI of the bat, and the K.E of the ball after the impact, It would also be possible to deduce does the resultant K.E of the ball increase linearly with the MoI of the bat. I.e. the old bat speed vs bat weight discussion. 

Another key part of the test, is that any bat maker should be able to submit a bat for non destructive testing, perhaps one from each tree to account for natural variation within willow
« Last Edit: April 04, 2012, 01:42:43 AM by Nespresco »
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tushar sehgal

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Re: The rebound test... A little experiment.
« Reply #52 on: April 04, 2012, 01:43:23 AM »

I just have a simple question, when someone tries to do something why are there so many of us trying fortell doom? Sure its not scientific, sure its not accurate but atleast he is trying...

I used to watch Dale Styen videos so i could coach myself outswing, had a lot of negative ppl arnd but I will try and make a video on sunday to show what can be done if you just want it bad enough...

I am rooting for tim2000s, even if its flawed it will be a fun little video to watch...
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tim2000s

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Re: The rebound test... A little experiment.
« Reply #53 on: April 04, 2012, 06:28:33 AM »

I just have a simple question, when someone tries to do something why are there so many of us trying fortell doom? Sure its not scientific, sure its not accurate but atleast he is trying...

I used to watch Dale Styen videos so i could coach myself outswing, had a lot of negative ppl arnd but I will try and make a video on sunday to show what can be done if you just want it bad enough...

I am rooting for tim2000s, even if its flawed it will be a fun little video to watch...
Its okay Tushar, all it demonstrates is that a lot of us cricketers are just complete geeks, and I have to include myself in that one... ;)
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tim2000s

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Re: The rebound test... A little experiment.
« Reply #54 on: April 23, 2012, 05:44:07 PM »

The rig....



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ajm90

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Re: The rebound test... A little experiment.
« Reply #55 on: April 23, 2012, 05:46:35 PM »

I Like the books your using as a counterweight  :D Genius
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tushar sehgal

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Re: The rebound test... A little experiment.
« Reply #56 on: April 23, 2012, 06:03:24 PM »

mmm Jamie Oliver makes good food :D , rig looks more like Nigella's cooking though ;)
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MrFATBATS

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Re: The rebound test... A little experiment.
« Reply #57 on: April 24, 2012, 07:38:02 AM »

Tim... you lost me at hello ;-)

Good luck

PedalsMcgrew

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Re: The rebound test... A little experiment.
« Reply #58 on: April 24, 2012, 08:05:41 AM »

This is the kind of ingenuity that won us two world wars! Great work sir..........I have no idea what you're doing though. 
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Kulli

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Re: The rebound test... A little experiment.
« Reply #59 on: April 24, 2012, 08:06:57 AM »

This is the kind of ingenuity that won us two world wars! Great work sir..........I have no idea what you're doing though.

Are you implying that it won't work and he'll need an American to come and complete the job?
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