Does recoilweight calculation need to be adjusted for extended length rackets?

[ryohazuki222]

I’ve thoroughly confused myself in regards to recoilweight calculation:

does it matter how long the racket is?

it comes down to the balance point of the racket. For different length rackets the balance point changes relatively in terms of points headlight and head heavy but it doesn’t change objectively from the cm/in from handle.

for example: for a standard length ezone, 13.07 inches balance is something less than 4pts headlight. But for an ezone 98+ that same 13.07 inch balance point is now 5pts headlight.

from what I’ve seen looking at RW equations (and other equations dependent on sw, mass, balance), they just ask for the cm balance not the points headlight.

what’s the best way to ensure I’m comparing apples to apples in regards to computing these data points for extended length sticks?

 

[Irvin]

does it matter how long the racket is?

No, not for inertia, RW, generally speaking. But for longer racket with more weight distributed farther out the inertia will be greater.

what’s the best way to ensure I’m comparing apples to apples in regards to computing these data points for extended length sticks?

SW = RW + mrr or you can solve for RW = SW - mrr where m is mass in kg and r is balance point in cm minus 10.

EDIT: RW is the inertia at the center of mass. SW uses the parallel axis theorem to calculate the inertia 10 cm from the butt.

 

[ryohazuki222]

Very helpful. Thanks!

so to summarize:
If I wanted to target a recoilweight for an extended length racket, I’d have the same balance point in cm. Exactly what I was after.

then next question @Irvin

if that’s the case, what that means is that the extended length racket vs standard length racket that matches recoil weight WILL have different relative balance (Ie converting to points HL/HH).

ive never found a use for points HL/HH so I’ve just ignored that and always focused on the balance point distance from the butt.

im going to test this out myself but what would you EXPECT to happen when on the court with this:

scenario A: matched RW two different length rackets, but different balance in terms of points HL

scenario B: matched points HL two different length rackets, but difference RW due to different balance point length from butt.

 

[Irvin]

so to summarize:
If I wanted to target a recoilweight for an extended length racket, I’d have the same balance point in cm. Exactly what I was after.

Not true. Let’s say I have a 27“ and 28” and both have a balance of 32 cm. The RWs of the 2 rackets could be the same or different. If they are difference and I wanted to match up RW then the balance points may or may or may not match. I could raise the RW by add mass to either the butt or the tip. Adding mass to the butt lower the balance while adding it to the head raises the balance. Adding mass above and below the balance point could result in maintaining balance.

what that means is that the extended length racket vs standard length racket that matches recoil weight WILL have different relative balance (Ie converting to points HL/HH).

Thae a 27” And 28” racket again, if each were 4 pts HL the balance would be 13” (33.02 cm) for the 27” and 13.5” (34.29 cm) for the 28”.

Im not sure what you’re trying to do here but it appears you’re on the wrong track.

 

[Irvin]

You can take any 2 rackets no matter what the lengths and balances are. Let’s say one has a recoil weight of 160 and the other is 170. If you want to match the 2 RWs you would have to add 10 kgcm^2 to the 160 kgcm^2 racket. As long as the added mass times the distance squared is 10 kgcm^2 they match. I = mrr

 

[ryohazuki222]

You can take any 2 rackets no matter what the lengths and balances are. Let’s say one has a recoil weight of 160 and the other is 170. If you want to match the 2 RWs you would have to add 10 kgcm^2 to the 160 kgcm^2 racket. As long as the added mass times the distance squared is 10 kgcm^2 they match. I = mrr

Agreed.
I was meaning this scenario:

If I hypothetically have a 27" racket and a 27.5" racket both with 340sw, 340g and 33cm balance... looks like the math will check out that they both have the same RW of ~160 (this was my original question -- tell me if this is wrong because if it is I'm misunderstanding completely). In this scenario the length of the racket is not relevant to the RW calculation for the two rackets.

That said, in the same hypothetical scenario, the 27" racket will be 4 points HL, while the 27.5" racket will be 6 points HL. The longer racket is specced the same except that it is more relatively headlight than the standard length racket. So I suspect, at least in hand and static, the 2 rackets will feel a bit different.

What I'm trying to determine is which setup would play more similarly to each other and *why* (for the sake of argument assume such setups are even possible):
Setup A: Different length, different HL spec, same RW, same SW, same m, and same balance point.
Setup B: Different length, same HL spec, different RW, same SW, same m, and different balance point.
Setup C: something I haven't considered

(would MGR/I and polarization also be calculated independent of the racket length like RW? every calculator i've ever used just asks for sw, m, balance point then spits out these numbers... I don't actually know or understand the calculations themselves -- hence my struggle. But, I DO know my spec preferences and what adjusting each does to the feel when hitting tennis balls with a standard length racket. I'm about to start exploring with non-standard length rackets are trying to better understand how that does or doesn't change what I already know for regular length.)

 

[Irvin]

If I hypothetically have a 27" racket and a 27.5" racket both with 340sw, 340g and 33cm balance... looks like the math will check out that they both have the same RW of ~160 (this was my original question -- tell me if this is wrong because if it is I'm misunderstanding completely). In this scenario the length of the racket is not relevant to the RW calculation for the two rackets.

That is not true. You can not determining inertia measurements from weight, length and balance.

That said, in the same hypothetical scenario, the 27" racket will be 4 points HL, while the 27.5" racket will be 6 points HL. The longer racket is specced the same except that it is more relatively headlight than the standard length racket. So I suspect, at least in hand and static, the 2 rackets will feel a bit diff

That much is true but whether a racket is HL or HH means nothing.

What I'm trying to determine is which setup would play more similarly to each other and *why* (for the sake of argument assume such setups are even possible):
Setup A: Different length, different HL spec, same RW, same SW, same m, and same balance point.
Setup B: Different length, same HL spec, different RW, same SW, same m, and different balance point.
Setup C: something I haven't considered

Forget about HH and HL it is worthless misinformation.
Setup A would play more similarity, dependent on TW and racket stiffness.

EDIT: But I have a question now. How do you know the RW and SW are the same if you can’t measure them? You can’t not go be length, weight, and balance to determine inertia.

 

[ryohazuki222]

Forget about HH and HL it is worthless misinformation.
Setup A would play more similarity, dependent on TW and racket stiffness.

Thanks. This is exactly what I’m looking for, because intuitively to me it’s hard for me to believe that the relative balance means nothing in the case of different length sticks.

I’m not calculating SW — Assume SW is a measured value using a sw measuring device.

essentially with the hypothetical scenario above:
Assume SW is based on measurement, balance is based on measurement and mass is based on measurement. Others like RW, mgri, polarization would be based on calculation using the aforementioned measured values. This makes sense no?

 

[Irvin]

I’ve thoroughly confused myself in regards to recoilweight calculation

RW is nothing more than the racket‘s inertia measured at the center of mass. Assume you had a 340 g racket, 27” long, SW of 340, and an even balance. What is the RW?

RW = SW (340) - mr^2 (.34*24.29*24.29)
RW = 140

What if the balance point was 31.45, would the RW be the same?

If a racket weighed 340 g, and a balance of 31.45, do you need any other data to determine inertia a any point?

How does an RDC measure SW when it does not know how long the racket is, where the balance point is, or how long the racket is?

 

[Irvin]

Assume SW is based on measurement, balance is based on measurement and mass is based on measurement. Others like RW, mgri, polarization would be based on calculation using the aforementioned measured values. This makes sense no?

This makes sense I agree but there is no measurement for polarization that I’m aware of.

 

[ryohazuki222]

No. I'm just calculating polarization with this equation: P = RW/m

This makes sense I agree but there is no measurement for polarization that I’m aware of.

 

[Irvin]

No. I'm just calculating polarization with this equation: P = RW/m

And?