PDA

View Full Version : Using a Crank Stringing Machine


Athans87
10-19-2006, 10:19 PM
I was wondering, because crank machines are not constant-pull like gravitational/drop-weight machines, should I increase the tension setting while stringing so that the actual tension is closer to where I want it when the string sets in and adjusts?

For example, if I wanted to achieve a tension of 60lbs with a crank, should I set the brake tension to 66ish?

Also, if this is what I should do, by how much should the increase in brake tension be? Would +10% suffice?

Thank you,
Athans

kchau
10-19-2006, 10:21 PM
it woudl really depend on string to string, some strings lose tension faster than others, im pretty sure 2 pounds with be sufficient, but then i have never used a crank.

it also depends on how fast you can clamp it off.

jonolau
10-19-2006, 11:36 PM
I think you shouldn't worry too much about this even though a crank isn't a constant pull. Most important, ensure that you calibrate it, I was reading somewhere with every 20 stringing jobs.

I have a crank and a digital fishing scale. After it locks out at the target tension, it will lose not more than 0.5lbs of tension by the time you clamp off.

Hope this helps.

Athans87
10-19-2006, 11:46 PM
It does help, thanks for the replies.

I am under the impression that relative tension is not as important as consistency in tension, which makes sense to me.

Gamma Tech
10-20-2006, 04:48 AM
I was wondering, because crank machines are not constant-pull like gravitational/drop-weight machines, should I increase the tension setting while stringing so that the actual tension is closer to where I want it when the string sets in and adjusts?

For example, if I wanted to achieve a tension of 60lbs with a crank, should I set the brake tension to 66ish?

Also, if this is what I should do, by how much should the increase in brake tension be? Would +10% suffice?

Thank you,
Athans
You are correct. You want to increase the tension if you are going from dropweight or electric (CP) machine by 5-10%, as a good starting point. You can then fine tune your tension. It depends a lot on the string construction and how quickly it relaxes.

Consistancy is also very important, ie how quickly you clamp the string, speed you rotate crank handle, etc.

bret

jonolau
10-20-2006, 05:00 AM
You are correct. You want to increase the tension if you are going from dropweight or electric (CP) machine by 5-10%, as a good starting point. You can then fine tune your tension. It depends a lot on the string construction and how quickly it relaxes.

Consistancy is also very important, ie how quickly you clamp the string, speed you rotate crank handle, etc.

bret
This is interesting, Bret. Does this apply to all types of strings for a crank machine?

If I target a post-stringing tension of 60 lbs on my poly mains, this means I have to set the crank at 63-66 lbs. Correct me if I'm wrong.

Kind regards
Jon

LttlElvis
10-20-2006, 06:00 AM
I think you shouldn't worry too much about this even though a crank isn't a constant pull. Most important, ensure that you calibrate it, I was reading somewhere with every 20 stringing jobs.

I have a crank and a digital fishing scale. After it locks out at the target tension, it will lose not more than 0.5lbs of tension by the time you clamp off.

Hope this helps.

jonolau,

I have to disagree with you here. I think you lose alot more than 0.5 lbs. depending on the type of string. I use gut, and testing on the digital fish scale, I lost over 7 lbs. with Babolat VS Gut 17 g. The way I tested the loss is, with a string sample, I slowly cranked, read the initial reading, waited, then read the stablilized reading.

I lost about 5 lbs with Wilson NXT. I lost around 1.5 lbs with Luxilon.

My point is, with a crank, you have to know the string to know how many lbs. you need to increase IF you decide to increase. That is why a lot of people say to increase your tension 5% to 10% if you are used to a dropweight stringer.

Cranks work well, but they are all about consistencey. I used to string my racquets @ 60 lbs. with a crank. There was always small variances between the racquets. Switching to an constant pull electronic stringer, I strung @ 60 lbs and it killed my arm. Finally found my magic number @ 48 lbs. Gut really stretched alot, so on a crank I was getting inconsistent results. Now with constant pull electronics, I can't tell the differences between my racquets and I no longer have a favorite one.

Cranks are nice and fast and with experience, can be consistent. Switching to constant pull electronics took away all of my guess work for how much to increase.

jonolau
10-20-2006, 06:15 AM
jonolau,

I have to disagree with you here. I think you lose alot more than 0.5 lbs. depending on the type of string. I use gut, and testing on the digital fish scale, I lost over 7 lbs. with Babolat VS Gut 17 g. The way I tested the loss is, with a string sample, I slowly cranked, read the initial reading, waited, then read the stablilized reading.

I lost about 5 lbs with Wilson NXT. I lost around 1.5 lbs with Luxilon.

My point is, with a crank, you have to know the string to know how many lbs. you need to increase IF you decide to increase. That is why a lot of people say to increase your tension 5% to 10% if you are used to a dropweight stringer.

Cranks work well, but they are all about consistencey. I used to string my racquets @ 60 lbs. with a crank. There was always small variances between the racquets. Switching to an constant pull electronic stringer, I strung @ 60 lbs and it killed my arm. Finally found my magic number @ 48 lbs. Gut really stretched alot, so on a crank I was getting inconsistent results. Now with constant pull electronics, I can't tell the differences between my racquets and I no longer have a favorite one.

Cranks are nice and fast and with experience, can be consistent. Switching to constant pull electronics took away all of my guess work for how much to increase.

No worries, I enjoy healthy discussion.

Yes, I also find a big loss if the string is allowed to stabilize and I get similar results. In fact, with most polys, the tension loss can be as much as 10lbs within half and hour of stringing.

That is why I posted the question back to Bret.

What would MRTs do in cases with polys or other strings for that matter? What is the recommended increase in tension on the crank? The packaging on SPPP recommends that we set tension at 10% below target tension.

Hope someone can shed some light.

Jon

varuscelli
10-20-2006, 07:08 AM
I have to disagree with you here. I think you lose alot more than 0.5 lbs. depending on the type of string. I use gut, and testing on the digital fish scale, I lost over 7 lbs. with Babolat VS Gut 17 g. The way I tested the loss is, with a string sample, I slowly cranked, read the initial reading, waited, then read the stablilized reading.

I lost about 5 lbs with Wilson NXT. I lost around 1.5 lbs with Luxilon.


Please excuse the intrusion where I don't really have knowledge to contribute, but I'm curious.

Seems like there'd be some kind of documentation on that or a database where some very experienced person or group has info on tension loss for various strings in your typical stringing situation (and how it applies to different types of machines, perhaps).

I mean, if tension loss with various strings can be actually measured in some way that's consistent (and say, given the most likely situation of stringing in a climate controlled environment where temperature changes are rather moderate, etc.) -- is it impractical to say there should be some kind of associated database if there's this much of a variation in tension loss? Or do people just go by the philosophy of "once you've got enough experience, you'll develop your own feel for it"?

Just curious.

LttlElvis
10-20-2006, 08:37 AM
[QUOTE=varuscelli]

Seems like there'd be some kind of documentation on that or a database where some very experienced person or group has info on tension loss for various strings in your typical stringing situation (and how it applies to different types of machines, perhaps).
QUOTE]

I think the general rule among experienced stringers, when compared to dropweight or constant pull, is that you do need to increase your crank tension 5% to 10% as Gamma Tech mentioned.

If you are used to a crank and you get consistent results, stick with your method. When using a crank, I never made it a set rule to increase my lbs a certain % because that just got too confusing. 5% to 10% could be a big increase for many people. In other words, my 60 lbs on a crank is what it is. If that was too loose, I could tell my customer next job we can try 65 lbs. I never would string at 65lbs and say it is a 60 lbs job. Too confusing.

varuscelli
10-20-2006, 08:45 AM
I guess my question was more about how different types of strings might lose tension differently on the same machine, as here:

I lost about 5 lbs with Wilson NXT. I lost around 1.5 lbs with Luxilon.

Or is that more the exception to the rule and thus maybe something not really worthy of tracking in any kind of detail?

Hope I'm asking that the right way... :confused:

LttlElvis
10-20-2006, 10:04 AM
I am not sure if I am answering your question, but here goes:

On the same crank machine, using the same technique, every string will lose tension at different rates. The feel of one particular string will feel very different from another, not only because of the type string, but also the tension loss and loss of elasticity. Therefore, on a crank, when I string @ 60 lbs., no matter what, I will call that 60 lbs. I do not make adjustments 5% to 10% to make it feel like 6O lbs. from another machine. If I make adjustments, I am no longer consistent. I would rather say I will string the racquet @ 65 lbs.

Because of this, I did switch to electronic constant pull for my own simplicity. You can still get great results with a crank.

Athans87
10-20-2006, 04:40 PM
Well, usually I string mainly for myself and people I know on a ATS Traveler, so I was mainly asking so that I could get a stringbed that was fairly close to the stringbed I was used to. Was just trying to get an idea of how the two tensions would compare without compensation. I plan on eventually adding a Wise unit, so hopefully that will make things easier for me. :p

Midlife crisis
10-21-2006, 09:33 AM
I guess my question was more about how different types of strings might lose tension differently on the same machine, as here:



Or is that more the exception to the rule and thus maybe something not really worthy of tracking in any kind of detail?

Hope I'm asking that the right way... :confused:

The USRSA publishes a guide on strings late every fall. In it, they test strings for tension loss using the same protocol. While they may not be accurate for your exact situation, you can usually be confident that if one string is shown to have more tension loss than another string, that their relative difference will be what you observe when you string.

Here's their latest:

http://www.racquetsportsindustry.com/issues/200609/200609stringselector.html

varuscelli
10-21-2006, 09:40 AM
The USRSA publishes a guide on strings late every fall. In it, they test strings for tension loss using the same protocol. While they may not be accurate for your exact situation, you can usually be confident that if one string is shown to have more tension loss than another string, that their relative difference will be what you observe when you string.

Here's their latest:

http://www.racquetsportsindustry.com/issues/200609/200609stringselector.html

Thanks! That's exactly what I was getting at. (But perhaps not asking the question as clearly as I should have.)

Davai
10-21-2006, 03:29 PM
The way I see it is that Electronic (CP) machines are regarded to produce more accurate stringbeds is becuase of two factors: time and psychology.
When stringing on a CP you can wait for the machine to reach tension and you can clamp it off almost immediately becuase you have both hands on the clamp. On a crank it will take a second longer - to get your hand from the crank to the clamp base. The clamp off time is almost immediate in both cases - so whatever string relaxation occurs it does so under conditions that are no longer influnced by the tensioner. The big assumption here is that both heads reach the exact same tension when they lock/beep. Therefore unlesss any string will lose a radical amount of tension in one second the difference is insignificant.
Psychological factor: you expect the CP to produce a more accurate, stiff, responsive stringbed and therefore it comes true in your head.
I don't contest that indeed after a relatively long time strings tensioned with a crank lose far more tension than CP. However such a scenario isn't very realistic since you don't wait even five seonds between the time tensioned is reached and clamp off.

jj300
10-21-2006, 05:30 PM
Davai,
I agree and disagree with you. A cp machine is no doubt going to be tighter than a crank at the same tension. That said, different cp machines have different levels of tension accuracy, for example a cheap eagnas does not repull after the same tension loss as my silent partner aria. I believe gamma tech posted some of the gamma machines number and you can see that some have range of 2-4 lbs of string tension drop before the machine repulls, my aria is a lot less than that so it will probably be a litlte more accurate and tighter.

I'm not sure what machine you have but with my aria, it many times finishes pulling before I can get my hand to the clamp to unlock it unlock the base. It pulls the string to the desired tension in about 2-3 seconds so sometimes it does finish pulling before I get my hands to the clamps. Since its so accurate, I don't have to worry that one string might be at 60 and one might be at 64lbs when I clamp off.


The psych part I totally disagree. I'll give you two rackets, one strung on my aria and one strung on a alpha revo at 60lbs. If the player using the rackets is at all a good player they will definetly notice the difference, no doubt about it. Even a simple stringmeter will show you the difference between crank and cp machines on a rackets strung at the same tensions. It's as simple as that, usrsa did plenty of research and its proven that cp machines do produce higher tensions, unless again you go with the super cheap electrics.

Gamma Tech
10-23-2006, 05:38 AM
I'm going to have to agree with jj300. I did serveral test with different Gamma machines and tested the racquets string beds stiffness (RA Test) after stringing. The dropwieghts and electric machines were close to each other and the spring tension machines were less when I used the same rqt, string and tension (calibrated machines @ maximum). if there wasn't a difference in a lock out and a CP machine then why spend and extra $500-$2000 for an electric CP?

compensating for different machines is only important if you are running a business and you get new customers that have had their rqts. strung on CP machines and then are moving to lock out machines. If your happy with your results on a lock out machine then just keep stringing at that same tension.

here is some more technical info from the USRSA.
http://65.19.168.133/lockout_vs_constant_pull.pdf

bret

SW Stringer
10-23-2006, 10:44 AM
. . . The clamp off time is almost immediate in both cases - so whatever string relaxation occurs it does so under conditions that are no longer influnced by the tensioner. The big assumption here is that both heads reach the exact same tension when they lock/beep. Therefore unlesss any string will lose a radical amount of tension in one second the difference is insignificant. . .

Typical nylon strings do lose significant tension immediately. From a chart labeled Clamping Off Creep Tension Loss from Chapter 33, p. 304, of the Physics and Technology of Tennis, I've extracted the following data:

Tension /Total Tension lost /Time in seconds after clamping
55 0 0
51.1 3.9 1
48 7.0 2
46.6 8.4 3
45.1 9.9 4
44 11.0 10
40.4 14.6 60

From the above actual real laboratory data you can see that in less than 2 seconds after clamp-off the string has lost more than 10% of it's original tension. Any constant pull electric or electronic with a hysteresis less than 5.5 pounds would already be repulling.

Bret mentions doing several tests with different Gamma machines at his disposal and testing the resulting string beds with the RA tester showing what is commonly accepted in the industry that CP machines (both dropweight and electric(onic)) produce stiffer stringbeds than the crank machines. A common misconception that permeates this and all similar threads is that a higher stiffness number (RA or RDC) is better.

The actual figure of merit or Quality Factor is the deviation (or the statistical number - standard deviation of the RA or RDC) of the same frame, string, tension, etc, done many times over.

Hypothetically if one were to string the same racquet five times in succession under the same conditions on a dropweight, CP electronic and crank machine and the RA data were:

DW: 72, 75, 74, 76, 74 Avg= 74.2 SD= 1.483
CP El:74, 76, 77, 79, 78 Avg= 76.8 SD= 1.924
Crnk: 66, 65, 66, 67, 65 Avg= 65.8 SD= 0.837


You would conclude that even though the DW and CPEL strung tighter stringbeds than the Crank machine, the overall consistency as measured by the Standard Deviation was better on the crank machine.

The above data was made up, purely hypothetical, but presented to make the point that consistency is the mantra. But wouldn't it be nice to see some actual field data (like the above) showing what various machines are capable of in this department?