# M's and X's at the same tension = more stress horizontally?

Discussion in 'Stringing Techniques / Stringing Machines' started by Shangri La, Aug 30, 2010.

1. ### Shangri LaHall of Fame

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I was thinking about this: if a 16x18 frame is strung at 50 lbs, both mains and crosses, that would put an extra 100 lbs of pressure on the frame horizontally (18-16)X50=100 lbs. So, from a standpoint of maintaining the same press in both directions, one would need to string the mains higher, by (18-16)/16= 12.5%. So that’s M’s 56.25 lbs and X’s 50 lbs: 56.25*16(M)=900lbs=50*18(X). What do you think?

2. ### IrvinG.O.A.T.

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I don't think so, but I do think you should quit thinking so much.

Irvin

3. ### Shangri LaHall of Fame

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Lol... I started to think about this when considering tensions of a gut/poly hybrid. From playing point of view, you'd string the poly lower because of its stiffness. But, from preserving frame point of view, gut doesnt lose tension but poly losses quickly. So if you string gut in the mains higher by 2 lbs, after initial loss, mains tension can be easily 5-10 lbs higher than the cross. And I wanted to know how bad it is for the frame - but then I realized there are less mains than crosses, thus the question.

4. ### SW StringerSemi-Pro

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The mains go in with essentially all the reference tension applied. The crosses lose about half a pound per main string due to friction. So on average the crosses have around 3.5 to 4.5 fewer pounds of tension applied than the mains. The racquet designers take this into account. Don't worry about it.

5. ### Shangri LaHall of Fame

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Ah.. Thanks for the info, it really clears my doubt and shows my theory is not wrong

6. ### Shangri LaHall of Fame

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Here's a scenario: if I were to string poly mains and gut crosses in a 16/19 frame (not the best use of gut I know but just to make a point), I followed the 10% less tension rule on the poly and string them at 50/55.

After the initial tension loss, the poly mains will lose 20lbs and the gut crosses will have no more than 10 lbs of loss (the numbers come from USRSA string database), which makes the actual tension reading to be 30/45. Apply the crosses -5lbs factor SW Stringer mentioned, it will be 30/40.

Now, total vertical (mains) pressure: 30X16=480lbs,
total horizontal (crosses) pressure: 40X19=760 lbs.
Difference = 760-480=280lbs (!!)

That's a LOT of stress difference horizontally and vertically. Is that the reason people see frame warp after strung, and isnt it really bad for the frame?

7. ### SublimeSemi-Pro

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When you weave the crosses through the mains, you're forcing the mains to go a long distance from grommet to grommet. This effectively increases the tension of the mains.

When you pull tension on the crosses and the frame compresses from 3 to 9, the frame will distribute the force by trying to expand out from 12 to 6... also causing the tension of the mains to effectively increase.

If you start considering the dynamic tension during hitting (mains will increase more in tension than crosses), it's a miracle frames don't shatter in our hands :twisted:

Frames are roughly circles in order to be structurally sound. Forces in one dimension cause counter forces from the other direction. You'd really need no opposing force in the mains or cross to really cause damage.

8. ### esgee48Hall of Fame

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I would say that 16 mains times 16Ga (16 strings to one inch) at 50 # tension does not put 800 # of pressure on the frame. The area of the 16 mains translates to approx 78-79 # on the frame vertically. 19 crosses translates to approx 82-84 # on the frame horizontally. You also need to consider the horizontal and vertical components of the tension where the strings meet the frame. Most of these forces translate into tension and compression along the surface of the frame. Only the true vertical and true horizontal strings do not do this.