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View Full Version : Why I don't get the same exact tension in each main and its opposite??


Tron
08-29-2007, 12:55 PM
Hi all, I have a dropweight machine, the Alpha Pioneer DC Plus.

When I string the mains, most of the time each main and its opposite don't have the exact same tension, I can realize that because for the same string with the same tension and the same length you should get the same pitch if you "play" them (I am a guitar player by the way).

I am stringing two piece and I am sure I am doing everything ok.

I alternate mains 1 by 1, I always leave the bar horizontaly (matching the marks) and since the clamps have a little movement when you release the tension (because they don't fit exactly in the clamp base but a little loose) I always lock the clamps in a way that there is no movement when I release the tension.

So... I don't know why I don't get the exact same tension in each opposite main.

Probably the string is slipping in the clamp? I don't like to overtighten the strings to not mark them, there is no other thing that I might think of.

Any ideas?

Thanks

sigep1967
08-29-2007, 01:07 PM
you will lose tension off of the other main as soon as you clamp it so the one you just pulled will be tighter than the one previous. if you wait a few minutes they should even out or at least mine do because that same thing was driving me nuts at first too.

Tron
08-29-2007, 01:18 PM
The problem I mean is not with the previous main but with the exact opposite, it's normal than the previous main has less tension since it's always a little bit longer (as you string the mains they get shorter) and a longer string with the same tension applied will be looser.

Hidious
08-29-2007, 02:21 PM
I had the same problem when checking out the sound of the mains and i also am a guitar player. Came to the conclusion that mains were not meant to be "played" and that i should not worry about that. A lot of factors could change the pitch i guess.

Tron
08-29-2007, 03:25 PM
The problem is that, as in the guitar, a chagen of pitch means a chage of tension...

Pathy01
08-29-2007, 03:32 PM
The problem I mean is not with the previous main but with the exact opposite, it's normal than the previous main has less tension since it's always a little bit longer (as you string the mains they get shorter) and a longer string with the same tension applied will be looser.

I think what sigep1967 was saying is that of the two exact opposite strings, whichever you pulled first will have lost slightly more tension then the one you pulled second, because they were not both tensioned simultaneously. After a little while they should balance out. Or maybe you're not as perfect in your method of clamping to keep the clamps from moving, or the clamp on one side moves more or doesn't hold as tight as the other. There are a lot of variables, but I doubt that unless you are one of the best players in the world, you'd notice any difference in play.

Tron
08-29-2007, 04:54 PM
I'm kind of worried for the health of the frames having to support uneven tensions rather than how it can affect my play

Pathy01
08-29-2007, 05:02 PM
I'm kind of worried for the health of the frames having to support uneven tensions rather than how it can affect my play

I doubt that the minor difference will have any effect on your frame. It's probably a pound of difference at the most. Different length strings, tie-offs, etc all cause greater differences in stress on the racquet. Racquets are really quite sturdy as long as they're not abused.

dancraig
08-29-2007, 07:04 PM
You could try cleaning your gripper and clamps. Years ago I used to do the "pitch test" with my Klippermate that I started stringing with. The corresponding mains would usually be very close in pitch. When I upgraded to a lockout, I could never get the same good results.

Gmedlo
08-29-2007, 07:57 PM
Someone with a DT meter and a really accurate tuner (chromatic, etc) should come up with a formula for pitch = tension for different strings and lengths.

Several things could contribute to the change in tension/pitch– WHERE you clamped, how much drawback there was (one clamp might have more than another), WHEN it was tensioned as others have said, and the possibility that you aren't tensioning the exact same every time. If all of these things are off just a wee bit, it could make a large impact on the tension.

I wouldn't be surprised if the difference you notice in pitch, even as different as 50-100 cents, could be less than .5lbs. Just a guess though.

psp2
08-29-2007, 09:48 PM
In a perfect situation it's theoretically possible to get the same "pitch" when you pluck the matching opposite mains. However, said perfect situation will NEVER be achieved.

With that said, I wouldn't worry too much about being that perfect. I simply try to achieve a consistent stringjob that provides consistent play time after time.

Tron
08-29-2007, 09:57 PM
Do you think that's not even possible with a professional electronic machine with real constant pull and with perfect clamps that don't even move a milimeter when reliasing the tension? (take into account that a dropweight is not a real constant pull machine as it pulls constantly but with less force as it pass the horizontal plane)

gjoc
08-30-2007, 03:21 AM
Do you think that's not even possible with a professional electronic machine with real constant pull and with perfect clamps that don't even move a milimeter when reliasing the tension? (take into account that a dropweight is not a real constant pull machine as it pulls constantly but with less force as it pass the horizontal plane)

No, your drop-weight machine is a real constant-pull machine.

If the arm descends past horizontal you have to take up slack so as to get it back to horizontal.

The arm should be stably at rest at horizontal before you clamp.

As far as the different tones, I think even a very minor change in tension can produce a drastically (to your ear) different pitch.

Have you calculated or experimented to see how much change in tension it takes to change the pitch of your shortest string to match the pitch of your longest string?

I wonder if it’s a pound or an ounce, or more or less...

Tron
08-30-2007, 03:48 AM
What I mean saying is not a "real" constant pull is that you have to adjust the bar manually if, for instance, you are stringing a monofilament and you leave the bar completelly horizontal but waiting a little makes the string strech and the bar go below horizontal. In that case an electronic constant pull machine would automatically adjust the tension each time the string streches.

Regarding the experimentation, I just tensioned one string to 60 lbs and then to 50 lbs to hear the difference but I didn't do that on different sounding opposite mains.

I'm gonna record the worst case of difference in pitch between opposite mains and then I will recreate those 2 sounds (tunning with the recording) pulling one string in the place of one of the mains until I tune with the recording the 2 different pitches to see what's the difference in tension.

I'm sure that the pitch difference is completely string dependent, meaning that the same pitch difference in two different strings (material, construction, gauge) might give a completely different tension difference.

SW Stringer
08-30-2007, 09:12 AM
You can use MarcR's Freqmess program (available for download at stringforum dot net) to measure the frequency of the individually plucked mains. The tension is proportional to the square of the frequency so if you got 512 Hz for one main and 505 Hz for the other equal length main then (assuming 60 pound reference tension) the tension of the lower sounding main would be = 60*(505*505/512*512) = 58.37 pounds.

Tron
08-30-2007, 12:59 PM
I use that program, is an amazing program but It calculates the tension of the whole string bed and with that program it's not possible to calculate only 1 string.. if you look the formula that comes with the PDF they provide you'll see that the Head Size is involved in the calculation.

Anyway, probably the formula you give is OK.