Drop Weight Linear Gripper Challenge

[Leftorium]

Backstory: Worked in a tennis shop in the 90s, strung around 500 rackets during that time. Took a hiatus from tennis, came back 5 years ago. Got access to the tennis shop´s Babolat Star 5 stringing machine. I have strung circa 50 rackets on the machine with very consistent results. I string two piece, with the Yusuki starting method for the mains. Didn't wanna take advantage of the tennis shop, so I bought my own machine this Summer. I bought the Penta Preimuim 3600 drop weight machine. I like the 6-point mounting system, fixed clamps with base locking system. Went with the upgraded diamond dusted clamps.

My issue is the linear gripper/tensioning system. With two different accurate fishing and baggage scales my pulled tension varies. Usually 2-5 lbs less than set reference tension, but 1 in 10 pulls are very close to set reference tension. I start with the drop weight in the down position, my theory right now is that the issue is varying degrees of string slack and the position the linear gripper ends up. The quick fix would be to set reference tension a couple of lbs higher in the future, but the problem is that ocassionally the tension is dead on.

CHALLENGE:
For people that string on a drop weight with a linear gripper, using a accurate scale. Are you able on 10 pulls to average set reference tension within 0,5 of a pound?

Sry, for the long wind up/write up!

 

[esgee48]

If the bar is level, the drop weight is pulling the right tension. What the final tension may be could be less if string is rubbing against grommet or frame before going into the gripper. So my question is are you going straight or at an angle? Rubbing anything? Happens on throat mains only? If not and while still pulling, move that string so it momentary loses contact with the grommet or frame. An easier solution is to lube the grommet holes as part of cleaning before mounting. Or just move the string while pulling if it is in contact with anything. If the bar drops, that's your answer.

 

[Irvin]

CHALLENGE:
For people that string on a drop weight with a linear gripper, using an accurate scale. Are you able on 10 pulls to average set reference tension within 0,5 of a pound?

How could it make a difference in how you’re holding the string? As long as the string is touching the drum the tension should be the same as long as the bar is level. If the bar is within 5 degrees of level the tension should be no more than -0.2 lbs off pulling 55 lbs reference tension.

if you’re pulling any string through a grommet, or if the string in touching anything, you’re introducing a friction error into the equation.

 

[Leftorium]

Thank you guys! Friction was the issue. Taught that it was negilable, but it was the culprit.