MP33 looked out of place to me too. I would have expected it to be between the MP24 and the MP99, and for stiffness to be MP33 > MP27 > MP24 Not being up-to-the-minute with Yonex products I don't know which of all those are Long. Cooler, does your stiffness test take into account that a short racquet will seem stiffer than a long racquet?
cooler. i see. i see. i am sure cooler's measurement will no doubt generate a lot of interests as it is the first objective and quantitative measurements we've seen. however, while we do so, i like to applaud cooler for being the 'guy of action', who actually took the time and effort to make all these measurements for everybody.
last question first. Yes, i did normalized to each their own length, that is why i showed relative stiffness, not absolute nor total stiffness. That was the purpose of going through the rigorous testing so that we subjective human being can see the racket specification objectively. Yes, normal logic would lead us to say mp33 performance to fit within trend of other mp's numerical model naming convention. However, if we apply this logic to the MP88, then MP88 stiffness should fall between MP99>MP88>MP77 but this is not the case. MP88 is more flexy than the beginner racket mp24. I'm sure most of you out there had felt the mp88 and it has a very flexible shaft.
2003 racket head balance point Thanks Kwun As the second part of this thread, the table shows the racket head balance point of the 2003 yonex rackets (from mp24 upward). Since each racket has difference length, i am showing the result in term of relative head heaviness or tippyness. Yes, some of the result may alarm you but that's how the data came out. All actual measurements are to 0.5 mm. No, i did not use my index finger as the fulcrum. The width of the fulcrum used was 0.5 mm, similar to a dull knife. 0 means balance similar to a 3U cab20M negative means relative percentage head lighter than a cab 20M positive means relative percentage head heavier than a cab 20M
with the 3 factors, weight, head balance and total length of the racket, we have sufficient data to measure the static head heaviness of each racket. cooler, can you calculate the head heaviness for us?
My expectations weren't based on the numerical naming of the racquets, but from Yonex's graph of whether each racquet is more for Singles or Doubles, and Offense or Defence. And then just comparing similar weight racquets, which is why I didn't mention MP88. Maybe what we are seeing with the MP33 is because it does not have the Ultimum-Ti shaft, whereas the MP77/99/100 do.
neil, Utimium Ti doesn't dictate shaft stiffness. MP88 has Utimium Ti shaft as well. That is the whole point of my exercise, to bypass generalized terms like extra stiff, stiff, Med stiff, Med, Med flex, flex. It's different from year to year, brand to brand. MP88 and MP33 are i think very misundertood rackets. In yonex's chart it catergorized as a double racket and yet pros that i know who uses mp88 are peter gade, mia audina and ardy wiranta. I dont know yet any pros who use mp88 for double. Of course i dont know all the top players out there so i might missed some pros who do use mp88 for double. Last weekend i went to see the Jr national qualifying competition. The most common racket used by the U19 was the MP33. Of course common doesnt mean 50% or more like the shoes (shb89). It was more like 10%. Second was MP99. The rest were other yonex, forza, victor, black knight, etc
I didnt understand this question. I thought the table had showed how head heavy each racket compared to the cab20M. Ex. the balance point of AT700 is ~ 6% further up the racket than a cab20M.
that is not a sound conclusion. there are 3U MP100, 2U MP99, 3U cab22/cab20 Power, 3U MP88 out there which i havent got hold of but i'm confidence that their stiffness are comparable to each of their 2U's counterpart.
the balance point of a racket is not very useful a measure on its own. the true static "heaviness" of a racket should be the moment generated by the racket, ie, the distance to the CG of the racket multiplied by its weight (N*m). let's give an example, a 1m long uniformly thick steel rod may weight 20kg with a balance point at 50cm. while a 1m long plastic rod weighting 200g also has a balance point at 50cm. the steel rod has a higher moment and thus much harder to swing. the same can be said about badminton racket. a 80g racket and a 100g racket with the same balance point, the 100g racket will be harder to swing. and thus the real value we need to look at is not merely the balance, but the actual moment which is a combination of the balance and weight.
i wasn't making a conclusion, just merely an observation. i am not convince about your claim though, it'd be an interesting experiment now that you have the setup...
i see i see However, just for completeness, the rod example u have highlighted is straight forward, linearity. For an objects with irregular shape, moment of inertia would still be different even when these irregular shaped and density profile object have similar CG location and weigh similarly. If we assume the rackets to the ideal case of the rod (linear system), then the cg * mass comparison is pretty straight forward. It was this issue of irregular frame shape that held me back of not doing the moment calculation Before i make those calculation, please note the limitation of calculated moment of inertia from some excerpts that i got from a space industries measuring device manufacturer. Of course, the content contain some marketing messages as well. No , i do not plan to buy one of those MOI measuring instrument Why measure Moment of Inertia The MOI of simple shapes may be calculated by well known methods. However, reducing complex shapes or compound objects to an assemblage of simple objects and summing the moments of inertia can lead to large errors. It is more practical and faster to accurately determine the MOI of complex objects or of objects with varying density by direct measurement. Measuring MOI directly has these advantages: Greater Accuracy - Typical errors in calculated MOI can range to over 30% due to simplifying the part shape, or making assumptions about average density. If hanging wire or trifilar pendulums are used to measure MOI, large errors result from multiple mode oscillations. Cost Savings - Measurements can generally be made in a small fraction of the time required for exact MOI calculations. Cost savings in engineering time alone can quickly pay for the instrument. Furthermore, calculations do not account for manufacturing variations. Quality Assurance - Military and industrial specifications frequently set limits on MOI (and CG location), where these parameters are critical to the performance of rockets, projectiles, and re-entry components
You said it was a real life comparison, when in fact it was a lab comparison. In the real world, you only experience dynamic stiffness. Dynamic stiffness can be tested very cheaply. A small weight, pen, and paper is all you need. Since dynamic stiffness (not static stiffness) is the only number that matters and can be very cheaply measured, I don't see why it's unreasonable to ask for it.
understood. but the static moment is closer an indicator than just balance point alone. if we have equipment limitations that disallow us to get to the true value, we just have to settle for the closest approximation within our constraints.
Irregular shapes can be approximated to a rod if there is no angular rotation along the axis perpendicular to the rod. This is true for all strokes except a smash, in which there is a small 90 degree rotation that is negligible. Thus it's perfectly fine to approximate a racquet as a linear rod of non-uniform density. If you presume the hitter always hits in the same spot on the string bed, you can further approximate it as a point-mass or ball at some distance from the axis of rotation. With either approximation, MOI is easy to calculate.
brl, obviously you had taken my words out of context. I could have reported stiffness in term of deflection per unit length of racket shaft. Real life meant stiffness in relation to a known or common reference point like a cab 20, in my case i didnt have a cab 20 so i used cab20M. If you are so adamant about knowing real life dynamic, just ignore this thread and go read the racket review in the BC section. I can also tell you how to experience real life dynamic stiffness but i doubt kwun would let me elaborate in BF Dynamic stiffness can be tested very cheaply. A small weight, pen, and paper is all you need. Since dynamic stiffness (not static stiffness) is the only number that matters and can be very cheaply measured, I don't see why it's unreasonable to ask for it. Well, let see you run some dynamic stiffness test on your rackets. I don't see why it's unreasonable for me to ask for it.
kwun, brl, i agreed. I just want people here to understand the limitation of calculated MOI although it's very small in this case.
