Is stringing on a crank similar to pre stretching?

[ryohazuki222]

Hear out my crazy thought from this week…

I was thinking about how on a crank, the machine pulls at the reference tension, but then after locking out, the tension starts dropping. I remember seeing this for myself when calibrating my neos with a digital scale.

And I’ve now start tracking DT with an ERT300. As you’d expect, the tension is some amount lower than the reference tension. This had me thinking…. I’ve always preferred the FEEL of stringing on a crank vs electric. But I’m about to start messing around with a WISE for various reasons.

So here’s my thought:

- wouldn’t pre stretching on an electric tensioner then actually be sort of similar to lockout (just more consistent)? Essentially you’d be overshooting the tension pulled and then bringing it back down, which to my simple human brain seems really similar.

Wdyt? Why or why not?

 

[Steve Huff]

I see your reasoning, but not quite the same. With a lockout, you string at a ref of 50#. As it relaxes, it settles in at about 44#. With a constant pull, using prestretch, you string at 50, 10% prestretch to 55, then the machine gradually lowers the tension to 50. It's not the string just relaxing. The idea is that the tension will settle closer to 50 and that some of it's elasticity will have been removed. The difference then is that with the LO, the string relaxes. With prestretch, you are trying to compensate for the relaxing of the string.

 

[ryohazuki222]

I see your reasoning, but not quite the same. With a lockout, you string at a ref of 50#. As it relaxes, it settles in at about 44#. With a constant pull, using prestretch, you string at 50, 10% prestretch to 55, then the machine gradually lowers the tension to 50. It's not the string just relaxing. The idea is that the tension will settle closer to 50 and that some of it's elasticity will have been removed. The difference then is that with the LO, the string relaxes. With prestretch, you are trying to compensate for the relaxing of the string.

Yes… but what if someone intentionally *tried* to make them more even for a final stringbed stiffness?

So riffing off your example above….

Ref tension at 50. But falls to 44 by the time you clamp. Via lockout.

Vs ref tension on constant pull at 45 with 10% pre stretch.

In both situations wouldn’t the string get stretched to about the same max tension (50) and then settle at about the same actual tension (44-45).

How would you predict those two string beds to result? Differences/similarities?

 

[10shoe]

So here’s my thought:

- wouldn’t pre stretching on an electric tensioner then actually be sort of similar to lockout (just more consistent)? Essentially you’d be overshooting the tension pulled and then bringing it back down, which to my simple human brain seems really similar.

Agree.

 

[MathieuR]

and that some of it's elasticity will have been removed

Pre-stretching does NOT remove elasticity. When you tension a string by stretching it, the elongation will be partly elastic (the part that holds the tension) and a "lasting elongation" part.

Pre-stretching removes a part of the lasting elongation. Actually, "removes" is misleading. It "creates" the lasting elongation that is linked to a tension, higher as ref.tension. The result is, that at ref.tension, there is less "creep", so the string will loose less tension while playing.

 

[diredesire]

Yes… but what if someone intentionally *tried* to make them more even for a final stringbed stiffness?

So riffing off your example above….

Ref tension at 50. But falls to 44 by the time you clamp. Via lockout.

Vs ref tension on constant pull at 45 with 10% pre stretch.

In both situations wouldn’t the string get stretched to about the same max tension (50) and then settle at about the same actual tension (44-45).

How would you predict those two string beds to result? Differences/similarities?

You probably need to be more precise in your language, here. What do you mean by "them," and what do you mean by "more even"? If you're trying to mimic a crank tensioning curve with a constant pull:

I think you're ignoring (or not taking into account) what the entire premise/purpose of "constant pull" means. Even if the string dynamics were more or less equal across achieving the initial pull maximum, and the string relaxing, you need to keep in mind that after the string elongates and the tension falls below the reference tension, the tensioner will begin to re-pull and stall, and repeat (accounting for some degree of hysteresis). I'd expect in general that the CP's string bed stiffness to be higher than the crank. This depends to a certain degree on the rate of the string "relaxing" and the speed of the stringer moving the clamps and moving on. The slower the machine operator is, the more the effect of the tensioner will be seen in the final string bed stiffness.

 

[ryohazuki222]

You probably need to be more precise in your language, here. What do you mean by "them," and what do you mean by "more even"? If you're trying to mimic a crank tensioning curve with a constant pull:

I think you're ignoring (or not taking into account) what the entire premise/purpose of "constant pull" means. Even if the string dynamics were more or less equal across achieving the initial pull maximum, and the string relaxing, you need to keep in mind that after the string elongates and the tension falls below the reference tension, the tensioner will begin to re-pull and stall, and repeat (accounting for some degree of hysteresis). I'd expect in general that the CP's string bed stiffness to be higher than the crank. This depends to a certain degree on the rate of the string "relaxing" and the speed of the stringer moving the clamps and moving on. The slower the machine operator is, the more the effect of the tensioner will be seen in the final string bed stiffness.

Good point.

For me:

In general, I’ve strongly preferred the feel of a racket strung on a crank vs electric. The crank would feel more comfortable and less harsh. Subjectively… I just like the feel more though.

I always assumed this was because the crank wasn’t constantly pulling as you say. But I recently realized that that isn’t *the only* difference. Hence some new thinking/wondering about how much of the feel I like is from being strung on a lockout vs being strung with a “poor man’s pre stretch”.

I’ve had zero interest in pre stretching my strings before. Wondering if anyone on here would save me some time telling me I’m wasting my time running an experiment like the above.

A small chunk of my justification on finally getting a WISE is to screw around with this and see what I take away. String on WISE with lock out. With constant pull. With constant pull plus pre stretch. So I’m definitely interested in hearing all the thoughts that come out of this…


But ya — I am ignoring that fact of the time under tension. Mostly because of my own brains limitations for now… trying to just understand one piece at a time.

 

[10shoe]

If you are interested in machine pre-stretch you might want to take a look at this video. The use of the cross string tool is not incidental, it's actual really significant. Without it, the drop down in tension after the initial pull would mostly be isolated to the portion of string between the tensioner and the outside of the racquet hoop.

Standard Stringing on Vimeo

 

[Irvin]

A small chunk of my justification on finally getting a WISE is to screw around with this and see what I take away. String on WISE with lock out. With constant pull. With constant pull plus pre stretch. So I’m definitely interested in hearing all the thoughts that come out of this…

A Wise on lock out more is not the same as a crank stringer. A wise on lock out stops pulling tension as soon and the tension in the string is reached then it stops pulling. A crank has a tension spring applying pressure against the gripper assembly holding the back of the gripper down. When tension is applied on a lockout a carriage assembly stretches the string until the gripper is pull up to engage the brake and lock the carriage from moving back farther. But the string and spring are still pulling against each other. The spring holding the gripper down, while the string pulls the gripper up. The spring won’t loose any tension as it manintains compression, or your reference tension would continually drop stringing a racket. But as the string’s resistance to being stretched falls tension in the string drops. Because the spring and string are in series with each other pulling in opposite directions the string is pulls by the spring as the string tension falls. You will loose some string tension still but not as much as a Wise in lockout.

You can not replicate a lock out with a Wise in lock out mode without modification.. You would be better off dropping the reference tension on the CP Wise depending on the string being used.

EDIT: As far as prestretching goes, if the lockout gripper is farther away from the racket as you apply tension that section of string between the racket and the gripper is pre-stretched when you apply tension. That pre-stretched section of string will be the section of string used to string the next main or cross.

 

[Steve Huff]

Pre-stretching does NOT remove elasticity. When you tension a string by stretching it, the elongation will be partly elastic (the part that holds the tension) and a "lasting elongation" part.

Pre-stretching removes a part of the lasting elongation. Actually, "removes" is misleading. It "creates" the lasting elongation that is linked to a tension, higher as ref.tension. The result is, that at ref.tension, there is less "creep", so the string will loose less tension while playing.

I agree with you. You worded it better than I did. Thanks. I think we agree that the stringbeds would be different though. I think the constant pull (with or without prestretch) makes the most difference on the cross strings. As DD stated, the speed at which you move the clamps would make difference too. If you pulled on a constant pull, and let it continue pulling for 30 seconds per string, you'd probably never need prestretch. If, on a lockout machine, you pulled tension 3 or 4 times on each string, you'd probably get close to what the constant pull machine could do.

 

[Agparj]

I....... If, on a lockout machine, you pulled tension 3 or 4 times on each string, you'd probably get close to what the constant pull machine could do........

I'm not all that knowledgeable about stringing yet, but this comment caught my attention. I came across an interesting channel on YouTube were a professional stringer tests these types of ideas.. was interesting!

Hope others find it interesting also:

 

[LocNetMonster]

In general, I’ve strongly preferred the feel of a racket strung on a crank vs electric. The crank would feel more comfortable and less harsh. Subjectively… I just like the feel more though.

This is my perception and preference as well. I feel a little more *pop* from a crank compared to an electric CP.

 

[ryohazuki222]

I'm not all that knowledgeable about stringing yet, but this comment caught my attention. I came across an interesting channel on YouTube were a professional stringer tests these types of ideas.. was interesting!

Hope others find it interesting also:

Really good share on the video. I’ve seen some of that guys stuff but never this one.

Very interesting.

 

[Agparj]

Really good share on the video. I’ve seen some of that guys stuff but never this one.

Very interesting.

Thanks!
I find his videos interesting.
I keep getting the impression that he must read or be on these boards as many of his videos tie very closely to "hot" topics.

If you are reading this AM Stringing: a test on string bed differences due to different crank pull speeds (fast, medium, slow) would be awesome!

 

[10shoe]

I enjoy his videos but I think I have yet to come to the same conclusions in my shop as he does in his. For instance, I think the difference between constant pull and lockout is more like 4 lbs.

 

[Rabbit]

I enjoy his videos but I think I have yet to come to the same conclusions in my shop as he does in his. For instance, I think the difference between constant pull and lockout is more like 4 lbs.

Me too. I remember backing tension down 8 pounds to get the close to the same feel.

 

[vokazu]

Maybe different type and brand of strings will require different tensioning too. That stringer should make another experiment with Kevlar string and also other brand of strings... Perhaps also different brands of stringing machine too!