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View Full Version : losing tension from friction while stringing crosses


passerofgasses
01-25-2010, 09:16 PM
I did some tests pulling a cross string that was attached to a fish scale at the far end and came up with some interesting results. I set the tensioner to 50lbs and pulled a cross string through about the middle of the racket but with no mains laced. It wasn't surprising that virtually no tension was lost. Then I pulled a weaved cross string and got 42.7lbs. It was also very interesting that when I straightened the cross, the tension rose to 46.0lbs (static vs dynamic friction or better pulling angles or both?). Out of curiosity, I also did a pull of a cross that was between 2 tensioned crosses and the scale measured 38.0lbs (no straightening possible). I used old Toa Leoina 66 (a lightly textured nylon but I'm sure is less frictiony than other string types) on a 16 main 107 Prince.

I'd like to know what people's opinions are on this variability and if they think about it often when deciding on tension settings. How much does the finished tension of a racket depend on friction from the mains while pulling the crosses? Variables could include string type and texture, # of mains, gauge, style of straightening, amount of wax used with gut. Yeah, I mean this could get ridiculous.

I'd also like to ask people's opinion on whether they believe a racket's end result tension is significantly more affected by the cross tension rather than the main tension, with minute racket head shape warpage taking up the difference between the two. You might have guessed that I already believe that.

Blade0324
01-26-2010, 10:26 AM
Interesting results IMO. I'm not at all surprised that the tension is lower for a cross that is woven through the mains. Also I would think that the cross that you checked that was between two other tensioned crosses was lower because of the tension created on that string by the two on opposite sides exerting more resistance than one that only has tension on one side.

I do always consider this when stringing my frames and most of my customers as well. For myself I pull the tension 3-4 lb. higher on the crosses than the mains to make up some difference. I have a few customers that like this same method while others only want the crosses upped by about 2 lb.
I do still have a select few that want the crosses lower to keep the string bed even softer but they are slowly coming around to see that they get a much more consistant string bed if they up the crosses just a bit.

SW Stringer
01-26-2010, 12:45 PM
I did some tests pulling a cross string that was attached to a fish scale at the far end and came up with some interesting results. I set the tensioner to 50lbs and pulled a cross string through about the middle of the racket but with no mains laced. It wasn't surprising that virtually no tension was lost. Then I pulled a weaved cross string and got 42.7lbs. It was also very interesting that when I straightened the cross, the tension rose to 46.0lbs (static vs dynamic friction or better pulling angles or both?). Out of curiosity, I also did a pull of a cross that was between 2 tensioned crosses and the scale measured 38.0lbs (no straightening possible). I used old Toa Leoina 66 (a lightly textured nylon but I'm sure is less frictiony than other string types) on a 16 main 107 Prince.

I'd like to know what people's opinions are on this variability and if they think about it often when deciding on tension settings. How much does the finished tension of a racket depend on friction from the mains while pulling the crosses? Variables could include string type and texture, # of mains, gauge, style of straightening, amount of wax used with gut. Yeah, I mean this could get ridiculous.

I'd also like to ask people's opinion on whether they believe a racket's end result tension is significantly more affected by the cross tension rather than the main tension, with minute racket head shape warpage taking up the difference between the two. You might have guessed that I already believe that.

Can you imagine doing those tests with a standard spring calibration scale? Heck no. No where near the resolution of the digital scales with which anyone can do real experiments.

It probably wouldn't surprise one that the racquet designers have available to them laboratory grade instrumentation which make even the digital fish scale look crude by comparison. They've done the above simple test and dozens of other more complicated experiments to determine the stresses a racquet undergoes and design the carbon fiber layups accordingly.

Net result is all you have to do is keep the applied tension with recommended manufacturer specifications. Don't overthink the problem.

passerofgasses
01-26-2010, 10:14 PM
Net result is all you have to do is keep the applied tension with recommended manufacturer specifications. Don't overthink the problem.

I wish I could think that way, honestly. I'm not an extremely finicky tension snob, but even so, I can't ignore how different the tensions seem to be when I'm for instance pulling smooth syngut crosses over syngut mains vs pulling natural gut over textured pro supex blue gear mains. I mean if somebody said your tension could vary by 5 lbs depending on what string you use, would that catch your attention?

I think the best suggestion I've heard on here that (inadvertently) relates to this is to up the tension enough so the racket comes off the stringer without much force (ie. so the head/throat length does not shrink making removal more difficult). If it's the first time I'm doing a racket though, I'll be guessing at that increase. Also, if the customer asks for a certain tension, I'll be working around that figure too.

Maybe what I should do is get a pulley and start measuring some of the actual new crosses I install. I'll have a better idea what properties give more or less friction and how consistent that tension drop is.

Maybe what anybody else might do is hold that next cross in position with one hand, and pull it with the other and feel what friction there is. We've all done that to some extent. I'm sure there's something to what I'm saying.