I have an Ohaus Dial-o-gram scale. I can measure total weight. I have leveled the rackets and taken a weight at the head, with the tip of the handle supported level. I have also weighed the handle, with the head supported level. I SHOULD be able to get an accurate balance this way, if I only knew the formula. It seems like this should be more accurate that balancing the rackets and measuring. Anyone know?
Is there a scientific way to calculate balance point?
- Thread starter Nikwho
- Start date
FuzzyYellowBalls
Legend
DIY: Balance Board
So after messing with a bunch of lead tape trying to weight a racquet correctly, I realized I really needed a balance board. Not wanting to throw down the cash for a commercial one, I decided to go DIY and devise one myself. This is super simple to make, less than 30 minutes to put together...
tt.tennis-warehouse.com
Grafil Injection
Hall of Fame
Find a flat surface like a table or desk. Put the handle end on the table and the head off the end of the table in a dead-straight line. Slowly move the racket off the table until the butt rises, but the whole racket does not fall off. Measure the distance from the edge of the table to the point where the butt is rising (or indeed, balancing).
Hey! I figured it out! The formula is:
Center of mass = (m1r1 + m2r2 + ... + mNrN) / (m1 + m2 + ... + mN)
m1 = weight at handle.
r1 = distance from end of raccqet that measurement is taken. I balanced each handle 0.25" in from the end of the end cap, for consistency, and to make sure that it didn't fall.
m2 = weight at head
r2 = distance from end of racquet.
So, for my Head Extreme racquet (317.2g total weight, as played) m1= 160.1g, r1=0.25", m2= 154.7g, r2= 27"
I came up with a center of mass of 13.396"(from the handle) With the racquet being 27" long, the center of that is 13.5". So, I came up with 0.104" HL, so just shy of 1 point (0.125") head light.
I'm trying to match my rackets, hence the nerdyness!
Center of mass = (m1r1 + m2r2 + ... + mNrN) / (m1 + m2 + ... + mN)
m1 = weight at handle.
r1 = distance from end of raccqet that measurement is taken. I balanced each handle 0.25" in from the end of the end cap, for consistency, and to make sure that it didn't fall.
m2 = weight at head
r2 = distance from end of racquet.
So, for my Head Extreme racquet (317.2g total weight, as played) m1= 160.1g, r1=0.25", m2= 154.7g, r2= 27"
I came up with a center of mass of 13.396"(from the handle) With the racquet being 27" long, the center of that is 13.5". So, I came up with 0.104" HL, so just shy of 1 point (0.125") head light.
I'm trying to match my rackets, hence the nerdyness!
FuzzyYellowBalls
Legend
That sounds amazingly accurate, me as a more dum dum just got a rolling pin from the kitchen and used the dining table and a ruler lol.
That was pretty quick, actually!
Here's my starting points for my racquets:
Head Extreme MP - 317.2g
Bob weights:
Handle: 160.1g
Head: 154.7g
Center of mass = 13.396"
0.832 pts HL.
Babolat Pure Aero La Decima - 316.9g
Bob weights:
Handle: 162g
Head: 152.8
Center of mass: 13.234"
2.128 points HL
Babolat Pure Aero - 318.5g
Bob weights:
Handle: 165.7g
Head: 150.7g
Center of mass: 12.991 in
0.509" Head light
4.072 pts. HL
Prince Ripstick 100 - 324.6g
Bob weights:
Handle: 166g
Head: 156.5g
Center of mass: 13.231 in.
0.269" HL
2.152 pts. HL
Now I'll start playing with some lead tape and try to get them all more closely matched.
Here's my starting points for my racquets:
Head Extreme MP - 317.2g
Bob weights:
Handle: 160.1g
Head: 154.7g
Center of mass = 13.396"
0.832 pts HL.
Babolat Pure Aero La Decima - 316.9g
Bob weights:
Handle: 162g
Head: 152.8
Center of mass: 13.234"
2.128 points HL
Babolat Pure Aero - 318.5g
Bob weights:
Handle: 165.7g
Head: 150.7g
Center of mass: 12.991 in
0.509" Head light
4.072 pts. HL
Prince Ripstick 100 - 324.6g
Bob weights:
Handle: 166g
Head: 156.5g
Center of mass: 13.231 in.
0.269" HL
2.152 pts. HL
Now I'll start playing with some lead tape and try to get them all more closely matched.
Grafil Injection
Hall of Fame
What do you get if you do the table method?
My Head Extreme is listed to be "0.7 HL". 0.7X0.125(")=0.0875. So, 0.0875−13.5= 13.4125" advertised center of mass (Balance point). My measurement yielded a 13.396" center of mass. The very small difference (0.0165") is what, 1/60th of an inch. Probably the difference in string choice, plus my dampener being installed.
But, realizing that you're probably just wanting to compare accuracy, I just checked. Using the table method on a pretty square edged table, I measured 13 13/32", or 13.406". That was measured with a laser measuring tool. 13.5-13.406=0.094". 0.094÷0.125=0.752, or 0.752 HL.
So, the table method got me right about in the middle of the advertised balance, and my measured balance. So, still very accurate, if done carefully. I don't know that anyone would feel the difference between those specs.
But, realizing that you're probably just wanting to compare accuracy, I just checked. Using the table method on a pretty square edged table, I measured 13 13/32", or 13.406". That was measured with a laser measuring tool. 13.5-13.406=0.094". 0.094÷0.125=0.752, or 0.752 HL.
So, the table method got me right about in the middle of the advertised balance, and my measured balance. So, still very accurate, if done carefully. I don't know that anyone would feel the difference between those specs.
Yea, test that formula to prove it works. I have a balance board but I've used the table and ruler method many times. I want to see the formula compare to the table and ruler method.
You probably saw it, but checked the table method to my formula in the post just above yours. Probably submitted them at roughly the same time.
Grafil Injection
Hall of Fame
Table method or your calculation on strung sticks are most reliable for comparing one racket to another. Manufacturer's specs are -/+ 0.5cm balance unstrung normally, which leads to a potential 3-5pt range balance difference when considering different string weights as well.
Return_Ace
Hall of Fame
Also just to say that Head historically can be a bit lazy with their printed specs.
I'm certain i have 2 rackets lying around here where they list the same 1"HL, but are supposed to be balanced differently.
I'm certain i have 2 rackets lying around here where they list the same 1"HL, but are supposed to be balanced differently.
Bud
Bionic Poster
Perhaps, you're the wise one
Irvin
Talk Tennis Guru
You can use that method but you must accturately measure you distance to the 2 support points. The closer to the support points the center of mass is located the more accurate the calculations will be. Say your handle support is Sh and your tip support were St. Sh and St are 20 and 40 cm from the butt of the racket. It is best to have a sharp edge on the points where the supports touch the racket and the scale. You also want your racket level so your distance measurements are accurate. The sum of the weight times the support point distance gives you the the force relative to the butt of the racket. Divide the force by the total weight and you have the center of mass.
Here is an example assuming a 325 g racket. Assume you St reads 167 g. Then ((20*158)+(40*167))/325 = 30.28 cm
EDIT: There is no need to make 2 support measurements. The 2 readings, if the racket is level, will add up to the total weight. If one point (St) supports 167 g the other must be total weight - 167. It is best to have a stop so your supports are always the same. The Sh should rest on the table and St on the scale. Rest the jig on the scale and Tare the scale. Then put the racket on the jig to make measurements.
Last edited:
Irvin
Talk Tennis Guru
The larger the diameter of the pivot, or if there are any flat spots on the pivot, the less accurate you measurements are.
Irvin
Talk Tennis Guru
Here is an example of another jig but requires 2 scales. If the 2 scale are not matched there’s a problem.
tt.tennis-warehouse.com
Manually Measuring Swingweight
When will the Briffidi SW machine be available for purchase/shipping in/to Europe?
tt.tennis-warehouse.com
Happi
Hall of Fame
Wouln’t Swing Weight be a better way to march racquets than weight and balance point ?
Irvin
Talk Tennis Guru
If I was going to MARCH rackets I’d play the Star Wars theme. LOL
Always best to match all parameters.
