Custom Bats Cricket Forum
Equipment => Bats => Topic started by: tim2000s on March 28, 2012, 05:45:37 PM
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Sitting on the train on the way home, I was pondering ping and coefficient of restitution tests. It occurred to me that it would be interesting to conduct an experiment to compare rebound of various bats and see the impact of knocking in and age.
What I intend to do is rig up and experiment using a jig to hold a bat in a constant position and drop some form of spherical object onto it from a height of one metre. I will then judge the rebound based on measuring the height of the bounce off the bat using a video camera.
The intention is to test two similar bats, one knocked in and one not, and see what the effect on rebound is.
This will then provide a relative comparison of the effects of knocking in. I'm also thinking that cnc made bats should be used to provide consistency of production.
What do you guys think?
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Do scuffed and not scuffed also.
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sounds interesting, would like to see it, although holding the bat in position would be tricky. I am assuming you don't want the bat to move at all..
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Nothing like a vice or g-clamp to do that.
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University of Warwickshire did a similar test firing ball bearings onto pieces of willow. I'll try to find a video as it may help you with setting up.
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I'm going old school physics gcse approach, using gravity to provide acceleration and the classic move a trapdoor out of the way to ensure consistent drop.
Nowt high tech like firing ball bearings!
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Interesting idea, one I have considered myself. I see no problem with your plan, except in making sure the ball dropped in exactly the same place each time. I suppose too that if using a cricket ball you would have to try and arrange for the seam to not hit the blade as it may give an odd result.
I thought about doing it for a range of bats but gave up as it gets a bit complicated when testing bats with middles in different places.
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Thread of the week....
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Could you use a bola ball to ensure the seam doesn't interfere with bouncebackability?
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Tim,
There's a whole area of expertise called Design of Experiments (or DOE). You can get useful results without testing every combination of factors.
Google it, and if you need any help setting up your experiments and with statistical analysis of the data, I'd be happy to help:)
(Results are analysed using a method called Analysis of Variance or ANOVA)
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Ideally though, you'd want to test the same bat twice.
Regardless of knocking in, I would expect that 2 CNC'd bats from the same grade of willow might still perform differently - or am I totally wrong? Have batmakers nailed it to the point where they can take care of natural variations in the willow??
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Could you use a bola ball to ensure the seam doesn't interfere with bouncebackability?
I think that would make sense as long as a bat behaves the same with a machine ball as it would leather.
Quick question Tim but as there is some debate over where the middle of a bat actually lies, would you calculate the middle or choose an arbitrary point on both bats?
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Ideally though, you'd want to test the same bat twice.
Regardless of knocking in, I would expect that 2 CNC'd bats from the same grade of willow might still perform differently - or am I totally wrong? Have batmakers nailed it to the point where they can take care of natural variations in the willow??
Another good point that factored in to me giving up. If only it were something man-made and consistent!
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i dont think this test will produce definite results, you may gauge a general result say if you tested 10 knocked in bats and 10 bats that arent knocked in but the the fact is one bat may just be better than an another due to many factors
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Ideally though, you'd want to test the same bat twice.
Regardless of knocking in, I would expect that 2 CNC'd bats from the same grade of willow might still perform differently - or am I totally wrong? Have batmakers nailed it to the point where they can take care of natural variations in the willow??
spot on mate
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I had a conversation with James Laver regarding this once, apparently he has a grading system based on rebound. He said he used ball bearings.
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I'm not questioning anyone here, but how can we say a single test on a single bat will not give a true reflection of performance, yet we happily state 'this one mallets well, this has pro ping' etc etc?
Devil's advocate I know.
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if someone could come up with a reliable method for grading 'ping' on bats we could then have a true grading system- but im not sure this is ever going to happen
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I'm not questioning anyone here, but how can we say a single test on a single bat will not give a true reflection of performance, yet we happily state 'this one mallets well, this has pro ping' etc etc?
Devil's advocate I know.
Fair point. Again, what I'm really investigating is the effect of knocking in on two similar bats for the first part. There will be natural willow variations, but there are ways of managing this variation.
In addition, I'd like to test ageing but that also comes with its own problems...
Still in the design stages so advice and comment is welcome!
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happy to volunteer my icon for your test
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Good plan ;-)
Clamping position, grip tightness and handle stiffness
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happy to volunteer my icon for your test
What grade is it again?
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Good plan ;-)
Clamping position, grip tightness and handle stiffness
Would you grip handle or blade? Thinking out loud but if you gripped high up the blade then any variations in handle might be negated?
Interesting idea but so much to consider.
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606, but taps up a treat.
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Coefficient of Restitution is made of loads of stuff but for Tims tests where the bat remains the same it will be a solid constant. For different bats, even from the same manufacturer, it becomes very complex and you cant really simplify the test like this to measure performance
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I'm going old school physics gcse approach, using gravity to provide acceleration and the classic move a trapdoor out of the way to ensure consistent drop.
Nowt high tech like firing ball bearings!
got to make sure you hit the sweet spot perfectly for a like for like test - and thats difficult with the trapdoor method!
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Very hard to do and will not produce any clear results but will be a whole lot of fun.
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Depends on how you intend to operate your trapdoor method, the size of you projectile and the truth in the line that pressing is consistent in such a fashion that the scoop works...
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Tim you've got far too much time on your hands :)
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No scanners, once I've had brain juice o just think too much... ;) I think I share this with Norbs...
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Yep call me!
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A more accurate drop method would be to hold the ball with a vacuum cleaner tube and just switch the power off. If the distance wasn't too great the seam could be avoided more often than not and the landing spot could be controlled fairly easily.
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think thats the way forward John!
good second post btw :D
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think thats the way forward John!
good second post btw :D
The way forward if you choose to use a cricket ball... ;)
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keep the ball still and swing the bat into it. see how far the ball is displaced, repeate 20+ times, do stats.
If you drop a ball from 1 meter and film it you wont be able to measure the rebound difference, it will not bound very much at 10 ms-1, and a 25 frame rate wont cut it.
good luck...
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Right then, I've given this a little further thought and the result is the following hypothesis:
Knocking in a bat increases its coefficient of restitution (or blade surface based rebound)
I plan to prove or disprove this theory and the method will be as follows:
Using the following rig, I will drop a 10mm steel ball bearing on to the surface of the bat and measure the rebound. I will start at a distance from the toe and move up the bat in 10cm intervals, repeating the drop 10 times.
(http://i493.photobucket.com/albums/rr293/tim2000s/IMG_20120402_161459.jpg)
The bat will be held as close to the shoulders as possible, which will be marked for repeating the test.
Have completed the 80 or so rebounds, I will then knock the bat in for two hours, and repeat the test in the same way at the same intervals.
By using a new bat that is unknocked in, I will take into account the variance of willow (there will be none) and the variance in handle flex, which will be mostly eliminated by the way the bat is held.
I will publish alll videos on YouTube, and post results in a thread on here.
Using this method, and with a height of 1m, the CoR can be described as the square root of the bounce height, when all measurements are taken in metres.
I may also add a couple of additional bats to see if there is noticable difference in pressing (although this doesn't allow for willow variance).
Any thoughts?
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Any thoughts?
you are nuts?
you have to much time on your hands?
you should spend the time working on your batting?
you should spend more time with your girlfriend?
you should get out more?
but otherwise I am interested in the findings!!
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Right then, I've given this a little further thought and the result is the following hypothesis:
Knocking in a bat increases its coefficient of restitution (or blade surface based rebound)
I plan to prove or disprove this theory and the method will be as follows:
Using the following rig, I will drop a 10mm steel ball bearing on to the surface of the bat and measure the rebound. I will start at a distance from the toe and move up the bat in 10cm intervals, repeating the drop 10 times.
([url]http://i493.photobucket.com/albums/rr293/tim2000s/IMG_20120402_161459.jpg[/url])
The bat will be held as close to the shoulders as possible, which will be marked for repeating the test.
Have completed the 80 or so rebounds, I will then knock the bat in for two hours, and repeat the test in the same way at the same intervals.
By using a new bat that is unknocked in, I will take into account the variance of willow (there will be none) and the variance in handle flex, which will be mostly eliminated by the way the bat is held.
I will publish alll videos on YouTube, and post results in a thread on here.
Using this method, and with a height of 1m, the CoR can be described as the square root of the bounce height, when all measurements are taken in metres.
I may also add a couple of additional bats to see if there is noticable difference in pressing (although this doesn't allow for willow variance).
Any thoughts?
Love it.... really do... but yes more time with the girlfriend/wife is needed to.. ;)
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you are nuts?
Yup.
you have to much time on your hands?
I wish...
you should spend the time working on your batting?
lol. need to go to nets for that... See later point....
you should spend more time with your girlfriend?
She'll be away on business while I undertake the test. It will probably be accompanied by a session with a coach at the Oval...
you should get out more?
but otherwise I am interested in the findings!!
Don't tell her that ;)
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Can't wait to see your findings :D
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your hypotheses should be null, but I think you'll be OK this time.
Like I said before, I doubt you'll be able to tell the difference in rebound height with a standard speed camera, but good luck.
Ross
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your hypotheses should be null, but I think you'll be OK this time.
Like I said before, I doubt you'll be able to tell the difference in rebound height with a standard speed camera, but good luck.
Ross
It's all a bit of fun, and if the result is null, then it begs the question of whether spending a couple of hours knocking in a bat really makes much difference... Maybe I should do a vickers hardness test at the same time?
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It's all a bit of fun, and if the result is null, then it begs the question of whether spending a couple of hours knocking in a bat really makes much difference... Maybe I should do a vickers hardness test at the same time?
Sorry, what i mean is for hypotheses testing you need to test a Null hypotheses, not a directional one, anyway it doesn't matter, like you say it a bit of fun, your not going to publish the results in an journal!!! ;-)
I think the other benefit of knocking the bat in is that it does't brake of course so that might make a difference... ;-)
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I think the other benefit of knocking the bat in is that it does't brake of course so that might make a difference... ;-)
That raises the question of why doesn't it break, which is why I mention the Vickers Hardness Test pre- and post- knocking in.
With regard to the null hypothesis, the null is that Knocking in a bat has no impact on the coefficient of restitution. Or in other words, we won't see an improvement in surface based rebound using this mechanism and that the reasons for a knocked in bat seemingly performing better lie elsewhere...
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Would the knocking in process not increase the proportional limit of elasticity hence it not breaking so easily?
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.
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I'm renaming you Heath Robinson
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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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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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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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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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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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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
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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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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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The rig....
(http://i493.photobucket.com/albums/rr293/tim2000s/IMG_0106.png)
(http://i493.photobucket.com/albums/rr293/tim2000s/IMG_0103-1.jpg)
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I Like the books your using as a counterweight :D Genius
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mmm Jamie Oliver makes good food :D , rig looks more like Nigella's cooking though ;)
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Tim... you lost me at hello ;-)
Good luck
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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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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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Oi!! the American will arrive after most of the hard stuff is done and steal his wife.... :D
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This may sound completely barking but I was thinking about how you are going to record the height of the rebound, a standard video camera might not be good enough to be accurate so instead you could set up a D-SLR on a tripod and use a long exposure which in theory will just show the movement of the ball as a line of blur.
As long as the ball bounces back up on a slightly different track to the release you should be able to easily identify the stall point of the upward motion from the rebound.
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This may sound completely barking
In any other thread you'd be right. But you're safe here.
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Any results from this yet? :D