Custom Bats Cricket Forum
Equipment => Bats => Topic started by: frankspop on March 22, 2023, 09:22:19 PM
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It's quite niche, and many on here already know about this. If you really want to optimise your bat selection then, materials and quality aside, forget static bat mass and 'pick-up' and use Moment of Inertia. Normally a tricky thing to measure, and one reason why it's never been adopted by bat makers. I have now made it simple for players and bat makers alike. Have a look at my little website that shows you how, with links to a new blog for details on the what, why, and how, and a peer-reviewed journal article that explains the science.
The method is sound and validated. It's simple and although an estimation it's accurate. In summary the estimation uses a one-dimenional beam model approach, which has been shown to be within 1% of measured values. The calculation tool on the website pushes your input data through a set of equations derived through the research.
https://cricketbatmoi.info
The website is newly finished. I would welcome any feedback on the user experience, any errors thrown up, or flaws in the measurement instructions. Could be through 'Contact' on the website, or here. And of course happy to discuss any aspect on the forum here - not least on whether MOI is seen as important enough to warrant its adoption in bat making and retail.
Thanks for reading.
David Curtis
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Firstly, thanks for doing this. After a quick play the first thing I noticed is that you said you use a 30cm ruler and the first measurement you made and would be the case for some handles is more than 30 cm.
Second, blade length only allows input to 2 decimal points.
When I get a result, it's a number with no interpretation. Do I have to go somewhere else to work out what it means, or is it main purpose to compare to the same measure for other bats? I'll measure a couple of my bats at different extremes of weight and pick up and see what the results are.
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What does my reading of 0.594 mean though?
Or rather what do I do with this information?
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What does my reading of 0.594 mean though?
Or rather what do I do with this information?
Compare it with other (future) bats I guess.
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Compare it with other (future) bats I guess.
😀😀😀
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It's quite niche, and many on here already know about this. If you really want to optimise your bat selection then, materials and quality aside, forget static bat mass and 'pick-up' and use Moment of Inertia. Normally a tricky thing to measure, and one reason why it's never been adopted by bat makers. I have now made it simple for players and bat makers alike. Have a look at my little website that shows you how, with links to a new blog for details on the what, why, and how, and a peer-reviewed journal article that explains the science.
The method is sound and validated. It's simple and although an estimation it's accurate. In summary the estimation uses a one-dimenional beam model approach, which has been shown to be within 1% of measured values. The calculation tool on the website pushes your input data through a set of equations derived through the research.
https://cricketbatmoi.info
The website is newly finished. I would welcome any feedback on the user experience, any errors thrown up, or flaws in the measurement instructions. Could be through 'Contact' on the website, or here. And of course happy to discuss any aspect on the forum here - not least on whether MOI is seen as important enough to warrant its adoption in bat making and retail.
Thanks for reading.
David Curtis
Forget bat mass and pickup, hmmmm
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I've measured 7 bats of various weights, profiles and handle length and the correlation between dead weight and score is exceptionally strong. So it really wasn't more useful than dead weight.
I have a blank bats B1 and a kook ghost that weigh exactly the same to the gram. I find the pick up and balance of the ghost horrible and never been able to use it well in the nets as it always felt awkward. The B1 on the other hand is the total opposite. This had a 1% higher measure than the ghost, so a negligible difference.
The only interesting thing that I could get from the data was my very light small adult bat had a lower result than expected. This has a regular length blade but a super short handle.
If I can find the time I might play around with adding extra weight at various points along the same bat.
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Firstly, thanks for doing this. After a quick play the first thing I noticed is that you said you use a 30cm ruler and the first measurement you made and would be the case for some handles is more than 30 cm.
Second, blade length only allows input to 2 decimal points.
When I get a result, it's a number with no interpretation. Do I have to go somewhere else to work out what it means, or is it main purpose to compare to the same measure for other bats? I'll measure a couple of my bats at different extremes of weight and pick up and see what the results are.
Thanks for the feedback.
A tape measure is equally as good or a longer ruler. I will amend the site to make that clear.
Blade length field will be changed to 3 dec places shortly. In fact all field will be set to 3 dec. places as this is appropriate. The site was create for me by a pal, who hosts at the moment, so a small delay in any changes needed is possible
Its a good observation that there is no reference for how to use it yet, except as a comparator to your own bats, and other peoples. Only through its wider use as a measure will you get a sense of scale and what is a value that suits your abilities. As a comparison to bridge to the traditional measure of static mass, MOI ranges from 0.3 - 0.39 Kgm/s2, across bat weights of 2lb5oz - 2lb14oz.
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Forget bat mass and pickup, hmmmm
My mistake, a bit hasty while trying to write a catchy post last night. Bat mass can still be useful, but MOI can replace the subjective 'pick-up'. Bat mass is a useful indicator when looking at what is your optimum. At the end of my blog article I discuss this, and the idea of effective momentum, as there is a trade-off between low MOI to generate more bat speed, but still needing sufficient mass to generate batted ball speed in the impact. I've done some pilot work with this to show the principle. How we help players build a swing characteristic profile is future challenge and natural evolution, but only if MOI gets a foothold in the sport.
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Thanks for the range of expected values. I suspect I'm doing something wrong as all of mine are above your range. Re-reading it, I'm a little confused, am I supposed to calculate the balance point myself? If so, wouldn't it be simpler to plug in the values on the website to avoid user error,like I may have made. Also I'm a little confused about your statement about expected range but then stating someone's value much bigger than this is too small.
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I've measured 7 bats of various weights, profiles and handle length and the correlation between dead weight and score is exceptionally strong. So it really wasn't more useful than dead weight.
I have a blank bats B1 and a kook ghost that weigh exactly the same to the gram. I find the pick up and balance of the ghost horrible and never been able to use it well in the nets as it always felt awkward. The B1 on the other hand is the total opposite. This had a 1% higher measure than the ghost, so a negligible difference.
The only interesting thing that I could get from the data was my very light small adult bat had a lower result than expected. This has a regular length blade but a super short handle.
If I can find the time I might play around with adding extra weight at various points along the same bat.
You are right that there is a strong connection to dead weight. Bat mass and the location of centre of mass (balance point) are the main drivers for MOI, which is intuitive as MOI is a characteristic of the mass distribution in the bat.
I am interested in your observation of a minor change measured in MOI yet a significant difference in feel between those two bats. That is unexpected as a 1% difference would be barely detectable (if at all), but perfectly valid if the measurements are correct, and I would be interested to know what is creating this perception.
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What does my reading of 0.594 mean though?
Or rather what do I do with this information?
Firstly 0.594 seems very high. I would go back and check your input values. Typical range is 0.30 -0.39 (which covers bat masses 2lb50z to 2lb14oz)
In terms of how to use/interpret, see my reply to a previous post.
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I think I've worked out why my numbers are out, but consistently, they'd be spot on for 100cm bats.
Do handle length and blade length actually get used separately in your MOI calculations?
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I think I've worked out why my numbers are out, but consistently, they'd be spot on for 100cm bats.
Do handle length and blade length actually get used separately in your MOI calculations?
Yes, handle length and blade length are separate input parameters in the calculation, and each is needed.
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I think the numbers I put in are wrong
Phantom TK
31cm handle
52cm blade
0.665 kg W1
1.065 kg Total weight
The MOI = 0.453 Kg-M2
Burns TK
29.5cm handle
53.8cm balde
0.685 kg W1
1.240g Total weight
The MOI = 0.528 Kg-M2
I double-checked the weights too but no better. I think I may be weighing incorrectly
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This sort of thing is right up my alley!
The "calculate" button doesn't seem to be doing anything at the moment (using firefox), but I guess you may be tweaking it!
If you are making a calculator, it's probably best to not to ask the user to calculate and input "Balance point = (total bat length x w1) / total bat mass", when you have already asked them to measure and input all the data required and the calculator could be doing this automatically.
I'm used to physically balancing the bat and measuring that distance from the toe, while your calculated balance point appears to be measured from the handle, to within 3-8mm of what I've physically measured, so it's pretty close, allowing for scale weight issues.
Again, it helps to label what your figures actually mean. It took me a while to work out that your "balance point" is actually "balance point in mm when measured from the end of the handle". In the green input section, you could label "Bat mass Kg", "Handle Length M" etc to make it idiot proof.
Looking forward to playing around with it some more :)
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When I'm weighing the bat with the toe on the scale I've noticed that I can get a fair bit of variation in weight depending on how high I've raised the handle. For my measurements I got my scales and a pile of magazines at the same height of scales. However in the image shown, it appears that the book that the handle is resting on is quite a different height to the scales.
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When I'm weighing the bat with the ton the scale I've noticed that I can get a fair bit of variation in weight depending on how high I've raised the handle. Fory measurements I got my scales and a pile of magazines at the same height of scales. However in the image shown, it appears that the book that the handle is resting on is quite a different height to the scales.
Agreed. I've had problems getting toe and handle scale weights before, and it can be inconsistent, so my preferred method of getting POB is to physically balance the bat and measure that exact point. When I tested 4 bats with the 'calculated POB' versus the physical measurement, the differences were -3.94, -8.95, -5.15 and +2.82mm
Yes, I have all this sort of stuff on spreadsheets, and tend to overthink all these details. When I hear people go on about 'pickup' and 'feel' my eyes roll to the back of my head. Quantifying this sort of thing with facts and numbers is something I've tried to do before, but few people actually get it. Many prefer to say "this bat weighs 2 lb 10oz but feels like 2 lb 7" ;) , so I applaud your work on this David! Interesting to read your blog and paper, although a lot of the paper goes over my head! I'll did a bit deeper another time.
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From a batmakers perspective, I can appreciate some benefits and many drawbacks personally.
Obviously for people buying online, it may give a measurement for then to work from. But would they have this initially and what determines if that measurement they're working from is their 'optimum'?
Just not sure if it's a little confusing for consumers. Most people who come into my workshop are already confused over balance points, dead weights, middle position, Grade, pick up etc etc. There's already a lot going on and just not sure this, although intended to simplify, may just confuse matters more. Especially for people coming into the sport.
I'd certainly need to understand it more to advertise it with my bats, as I'd need to be confident in explaining it to customers. Who personally, I think in the main, would still go on scale weight and feel. As In said, this could benefit people buying blind. But they'd still have to know what their optimum was, not something I'm sure many would take time or have the ability to find out.
I think in order for it to be adopted to the masses, you'd have to clearly sell the performance benefits. (If I'm at my optimum MOI, what does that mean in terms of performance gains?) As there are so many variables determining a bats performance (not least the batter), would this measurement be overall that useful? It's fine having the right MOI, but if it's a plank with a poor handle, is that measurement worthwhile? Appreciate that these things should be a given, but they're not always.
No doubt I'll be called old fashioned by many, but I kind of like that some sport isn't over engineered. I don't like that it's sometimes sanitised somewhat, but then I'm not adverse to technology either. I've got wrapped up in it at times in golf, but at no point did in improve my game more than practice, education and playing more.
If you were in Leeds anytime, I'd gladly welcome you into the workshop to explain it further and test some bats out though.
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I think the numbers I put in are wrong
Phantom TK
31cm handle
52cm blade
0.665 kg W1
1.065 kg Total weight
The MOI = 0.453 Kg-M2
Burns TK
29.5cm handle
53.8cm balde
0.685 kg W1
1.240g Total weight
The MOI = 0.528 Kg-M2
I double-checked the weights too but no better. I think I may be weighing incorrectly
Looks like you might be inputting W1 into the form instead of balance point.
The way it is set you have to do a manual calculation of BP, and the instructions are there under the last bat image before the form.
Balance Point = ((total bat length) x W1) / Total bat mass
where total bat length is simply the sum of handle and blade lengths that you measured already.
I'll think about whether to change the form to do the BP calculation for the user. The way it is currently set out was meant to show the importance of those 4 parameters for MOI
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@frankspop Perfect, thank you :D
When I'm multiplying the total bat length, is that in cm or meters?
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Ignore that, I found the answer ahah :D
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Updated and likely correct numbers
Bat MOI
Phantom
31cm handle
52cm blade
83cm Total bat length
0.665 kg W1
1.065 kg Total weight
Balance point = (0.88 x 0.67) / 1.07 (length measurements need to be in units of metres, and mass in units of Kg)
The MOI = 0.355 Kg-M2
Burns
29.5cm handle
53.8cm blade
83.3cm total bat length
0.685 kg W1
1.240g Total weight
Balance point = (0.833m x 0.685) / 1.24 (length measurements need to be in units of metres, and mass in units of Kg)
The MOI = 0.327 Kg-M2
The Burns bat is 2 lb 8 oz 'natural' (with stickers, toe guard, and grip) but I didn't like the pick up so I added lead tape to the knobby bit at the top of the handle it's now 2 lb 11.5 oz. I used the 2 lb 11.5 oz for these calculations as its how I'll be using the bat.
Thank you all!
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Some feedback for your friend who did the site - I had another go today and the "calculate" button still did nothing - the page didn't change at all! Was confused seeing that others were obviously getting it to work.
Finally worked out that I had the display size too large on my PC(poor eyes here!), and CTRL mouse zoom out gave me a smaller size, and presto - found the result under the calculate button, where previously there was a white background where the "about" section started.
Now to play around with it!
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I'm having some trouble entering the formulas from your paper into a spreadsheet - seem to get all the wrong numbers.
Forgive my ignorance, but what's the significance of the physical size of the digits, e.g.
Ix′=MBL2B3. (copy/paste loses the formatting) You've explained what MB and LB are, but, what does L(small2)B(large3) mean?
Same thing with Ix′=MhL2h3+(MbL2b12+Mb(Lh+(Lb2))2). You've explained Lh and Lb but what's L(small2)h(big3) and L(small2)b(big12) etc?
I've been using POBmm from handle x MB as a measure of 'pickup' for years, but didn't know how accurate it worked out as a measure of inertia. Your calculated MOI seems to have a more pronounced difference between weights and POB, and it's good to see some proof that it's an accurate measure of what you feel through your hands.
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I've had a great time measuring every bat I could get my hands on. Generally the calculated balance point matched well with what I estimated while balancing bats.
I did the MOI for 17 bats and had a few interesting findings. I always found the claim that longer handle and shorter blade bats picking up better a little dubious as it pushes the mass lower. My data supported my scepticism.
The most difficult to interpret finding was between my two bats that weigh exactly. 1169 grams, a Blank Bats B1 and a Kook Ghost. The former feels beautiful to bat with, the latter completely awkward and heavy. They both returned almost exactly the same MOI. There are a few differences between the bats, the BB is a completely full profile while the Kook has a couple mm of concaving, the BB is far more bowed, the BB is a slightly longer handle and shorter blade option (this is my only example where I had matching bats and the subjective "pick up" was better in the long handle and short blade combo). The thing I suspect may make the difference in feel is that the ghost is about 8mm longer overall, and I'm only average height, so it may just be that the bat is too long for me.
The other thing that stood out is that I have a GM Haze and Noir of the same weight, and subjectively ifeel the Noir picks up way better even though it had a much lower swell, and the MOI measure confirmed this with the Noir having the clearly lower measure. I hcan only speculate as to the reason, but maybe it's due to willow density varying throughout the blades.
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Really interesting, need to get my bats out to try this today.
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Does the website save the data? We need a scatter plot! Maybe needs to be filterable by brand as well
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From a batmakers perspective, I can appreciate some benefits and many drawbacks personally.
Obviously for people buying online, it may give a measurement for then to work from. But would they have this initially and what determines if that measurement they're working from is their 'optimum'?
Just not sure if it's a little confusing for consumers. Most people who come into my workshop are already confused over balance points, dead weights, middle position, Grade, pick up etc etc. There's already a lot going on and just not sure this, although intended to simplify, may just confuse matters more. Especially for people coming into the sport.
I'd certainly need to understand it more to advertise it with my bats, as I'd need to be confident in explaining it to customers. Who personally, I think in the main, would still go on scale weight and feel. As In said, this could benefit people buying blind. But they'd still have to know what their optimum was, not something I'm sure many would take time or have the ability to find out.
I think in order for it to be adopted to the masses, you'd have to clearly sell the performance benefits. (If I'm at my optimum MOI, what does that mean in terms of performance gains?) As there are so many variables determining a bats performance (not least the batter), would this measurement be overall that useful? It's fine having the right MOI, but if it's a plank with a poor handle, is that measurement worthwhile? Appreciate that these things should be a given, but they're not always.
No doubt I'll be called old fashioned by many, but I kind of like that some sport isn't over engineered. I don't like that it's sometimes sanitised somewhat, but then I'm not adverse to technology either. I've got wrapped up in it at times in golf, but at no point did in improve my game more than practice, education and playing more.
If you were in Leeds anytime, I'd gladly welcome you into the workshop to explain it further and test some bats out though.
All good points.
Firstly, your true optimum is still objectively unacheivable until a player can do a test session with a range of bat MOIs where swing performance could be measured i.e. from one of the bat sensors now on the market. A player would need to get data on the main shots in the vertical plane (driving), and horizontal plane (cut/pull/sweep), and build a swing profile. This is unlikely a level the masses would be interested in, but could be possible for Pros and those with the interest and money to pay for it. Technically straightforward to do, but would be epensive at the moment. Until that is possible then MOI knowledge complements your probable 'preferred' bat that is based on feel and performance in nets and in matches. So that when you come to buy another, you know what to look for or specifiy if able to through custom bat makers.
MOI as you say may be marginal in terms of what it might give a customer, given all the other factors at play, but for some marginal is still valuable.
Transition to using MOI with customers is like anything new. If we believe this is a valuable parameter to base bat selection on, it is then a matter of education/explanation to shift to a new paradigm.
I'd be happy to pop up to Leeds for a chat on this. DM me and we can arrange something.
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I'm having some trouble entering the formulas from your paper into a spreadsheet - seem to get all the wrong numbers.
Forgive my ignorance, but what's the significance of the physical size of the digits, e.g.
Ix′=MBL2B3. (copy/paste loses the formatting) You've explained what MB and LB are, but, what does L(small2)B(large3) mean?
Same thing with Ix′=MhL2h3+(MbL2b12+Mb(Lh+(Lb2))2). You've explained Lh and Lb but what's L(small2)h(big3) and L(small2)b(big12) etc?
I've been using POBmm from handle x MB as a measure of 'pickup' for years, but didn't know how accurate it worked out as a measure of inertia. Your calculated MOI seems to have a more pronounced difference between weights and POB, and it's good to see some proof that it's an accurate measure of what you feel through your hands.
Your question on the equations seems to relate to the fact that through the copy/paste it is losing the division operator. L(small2)h(big3) is Lh squared divided by 3, and same for the other one bu 12 is the denominator.
If it would help you can DM me I can send you a spreadsheet with all the equations in. One I prepared a while ago. I'm happy to share it to anyone who would like it.
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All good points.
Firstly, your true optimum is still objectively unacheivable until a player can do a test session with a range of bat MOIs where swing performance could be measured i.e. from one of the bat sensors now on the market. A player would need to get data on the main shots in the vertical plane (driving), and horizontal plane (cut/pull/sweep), and build a swing profile. This is unlikely a level the masses would be interested in, but could be possible for Pros and those with the interest and money to pay for it. Technically straightforward to do, but would be epensive at the moment. Until that is possible then MOI knowledge complements your probable 'preferred' bat that is based on feel and performance in nets and in matches. So that when you come to buy another, you know what to look for or specifiy if able to through custom bat makers.
MOI as you say may be marginal in terms of what it might give a customer, given all the other factors at play, but for some marginal is still valuable.
Transition to using MOI with customers is like anything new. If we believe this is a valuable parameter to base bat selection on, it is then a matter of education/explanation to shift to a new paradigm.
I'd be happy to pop up to Leeds for a chat on this. DM me and we can arrange something.
I think there is a use case for the data. In a similar way to how people get fitted for golf clubs, using MOI with a range of bats in a standardised setting could give a customer better advice on what to use. And from that limited range of suitable bats then make their choice based on looks, quality, price etc.
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I've been using POBmm from handle x MB as a measure of 'pickup' for years, but didn't know how accurate it worked out as a measure of inertia. Your calculated MOI seems to have a more pronounced difference between weights and POB, and it's good to see some proof that it's an accurate measure of what you feel through your hands.
Interesting. what you have been 'using for years' is called First Moment. My research (writtne up in the journal paper) showed that First Moment is a very good 'proxy' measure for MOI but requires a calibration with MOI to establish the relationship for each shape of bat. This may be practical for a bat maker, as once the relationship has been derived they only need to measure mass and location of centre of mass for each bat produced (if handle and blade lengths are kept constant). The proxy is less applicable for one-off measurements where it is best to use the two-section beam model method, which is the one used on the website.
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Does the website save the data? We need a scatter plot! Maybe needs to be filterable by brand as well
No, unfortunatley I am not saving the data. That is another level of website functionality I could not ask my pal to create as it is probvably beyond his current skill level. I agree it would be ideal to save the data and visulaise some back, but wuodl need more data enrty form the user (bat brand/model), and I might be able to do it in time if there is suffient interest to warrant me paying for it.
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I reckon GM would be great brand to focus getting some data on as shapes are so consistent.
Thanks again for all your work on this!
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Your question on the equations seems to relate to the fact that through the copy/paste it is losing the division operator. L(small2)h(big3) is Lh squared divided by 3, and same for the other one bu 12 is the denominator.
If it would help you can DM me I can send you a spreadsheet with all the equations in. One I prepared a while ago. I'm happy to share it to anyone who would like it.
:( I had no idea about the division or power operators. I'm used to / * or ^ in everything :). My spreadsheet is now getting .264 when it should be .361, but I'm on the right track. Will send a DM - many thanks!
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It's quite niche, and many on here already know about this. If you really want to optimise your bat selection then, materials and quality aside, forget static bat mass and 'pick-up' and use Moment of Inertia. Normally a tricky thing to measure, and one reason why it's never been adopted by bat makers. I have now made it simple for players and bat makers alike. Have a look at my little website that shows you how, with links to a new blog for details on the what, why, and how, and a peer-reviewed journal article that explains the science.
The method is sound and validated. It's simple and although an estimation it's accurate. In summary the estimation uses a one-dimenional beam model approach, which has been shown to be within 1% of measured values. The calculation tool on the website pushes your input data through a set of equations derived through the research.
https://cricketbatmoi.info
The website is newly finished. I would welcome any feedback on the user experience, any errors thrown up, or flaws in the measurement instructions. Could be through 'Contact' on the website, or here. And of course happy to discuss any aspect on the forum here - not least on whether MOI is seen as important enough to warrant its adoption in bat making and retail.
Thanks for reading.
David Curtis
Thank you for sharing this!
It should be standardized for all bats. I have been talking about this for a long time! Buyers will save a lot of money and time if specs like this were standardized and available with every bat.