Struggling to calibrate Gamma Progression STII to 60 lbs

[eb_tennis_247]

@Gamma Tech, others,

I have a Gamma Professional ST II and I am struggling to calibrate it to pull calibrating 60 lbs.

When I set 60 lbs on its linear tension scale, it gives me 50 lbs on a calibrator, with an (oldish) synthetic gut. I do mark the string on both ends to make sure there is no slippage.

To try to calibrate it, I keep unscrewing the adjustment screw until it is almost all the way out (almost 2”), but I am barely getting 55 lbs on a calibrator. If I go to 65 lbs on linear scale tensioner, I see some increase on a calibrator towards 60.

It is an older machine.
Is it possible that tension spring lost the springiness/elasticity?

Should I use Kevlar string?

Am I doing something else obviously wrong?

I have pictures of all steps and the state of the machine.

Please let me know if contacting Gamma customer support is more appropriate.

 

[Irvin]

Should I use Kevlar string

It does not matter Gamma Tech has suggested in the past to use the string that came with their calibrator and it SG

Am I doing something else obviously wrong

You’re probably pulling tension and allowing the string to stretch out. The machine should be calibrated at the peek when the machine locks out. Some users measure the tension inside the racket and not directly. Also it is possible you have a faulty calI rat or.

I have pictures of all steps and the state of the machine

You could have posted them

Please let me know if contacting Gamma customer support is more appropriate

Easy enough to just call Gamma and ask to speak to %Gamma Tech

It is an older machine.
Is it possible that tension spring lost the springiness/elasticity

The springs are made to last a life time and should be fine.

There is also the possibility that every thing your doing is fine and someone has maladjusted the tension spring assembly trying to change tension calibration, or maybe they took it apart to clean it.

 

[Gamma Tech]

@eb_tennis_247 tennis247 Sounds like you're doing everything right, but there are probably a few additional steps you can take highlighted in this video here:

. I think you will need to play around with the cam I point out in the video as well as the positioning of the latch block. You can also ship me your tensioner and I can do a tune up in my shop.

As far as the strings you want to use for calibration, always use an elesatic string as these give the most accurate end result. Always avoid polyester. Kevlar is probably fine but I would stick with the SG. Multifilaments work as well but tend to be less durable and will need to be replaced after only a couple calibrations.

 

[eb_tennis_247]

@eb_tennis_247 tennis247 Sounds like you're doing everything right, but there are probably a few additional steps you can take highlighted in this video here. I think you will need to play around with the cam I point out in the video as well as the positioning of the latch block. You can also ship me your tensioner and I can do a tune up in my shop.

As far as the strings you want to use for calibration, always use an elesatic string as these give the most accurate end result. Always avoid polyester. Kevlar is probably fine but I would stick with the SG. Multifilaments work as well but tend to be less durable and will need to be replaced after only a couple calibrations.

Thanks for sharing this. I will watch, review, try to apply, and report on the progress.

 

[Irvin]

@Gamma Tech Ewen it is also best to use a spring tensioner and not a digital luggage scale. What tension gauge are you using in the video?

 

[eb_tennis_247]

I think you will need to play around with the cam I point out in the video as well as the positioning of the latch block. You can also ship me your tensioner and I can do a tune up in my shop.

@Gamma Tech — this was very helpful. I am getting much better range of 30-60 lbs.

Do you have any other video or best practice to recommend for producing a consistent tension on this machine?

I see all kinds of tips on the forum — keep the crank lever hand strand straight, pull slowly, etc., but would like to know from what is the “official” best practice.

 

[USMC-615]

@Gamma Tech Ewen it is also best to use a spring tensioner and not a digital luggage scale. What tension gauge are you using in the video?

Are you suggesting using a mechanical, spring calibration tool that has hashmarks/lines every 5 lbs is more accurate than a digital Wise 2090 or luggage scale?

 

[Irvin]

Are you suggesting using a mechanical, spring calibration tool that has hashmarks/lines every 5 lbs is more accurate than a digital Wise 2090 or luggage scale?

No as a matter of fact I use a digital luggage scale myself. A digital scale works with a load deal and often especially with an eCP machine can fluctuate as the eCP turn off and on. A spring scale is more stable as the spring tends to cushion the fluctuations. That’s why I asked Ewe. What type scale he was using. Maybe @Gamma Tech can offer his suggestion.

I think one like the one below is reasonably priced and would work well.

https://amzn.to/3Ya9r1E

Its always good to keep in mind the scale you’re using could be off a little. If you check the linearity of the scale at 30 and 60# though there’s a good change both readings would be off the same. Even if you’re off a little you are still in the ball park.

 

[Irvin]

@USMC-615 abllee2198 the last few Gamma Techs before Ewen have mentioned that a spring calibrator should always be used checking the tension head calibration. Here is just one of several by albllee2198

Babolat star4 born again

Here is my old star4. It was in the garage of local shop with out of order but I fixed w/ help of @abllee2198 . (Thanks again for your help Albert) After calibration and changing the clamps, it works fine and tenstion output is perfect. Pull @ 50 Lbs

tt.tennis-warehouse.com

 

[Gamma Tech]

@Gamma Tech — this was very helpful. I am getting much better range of 30-60 lbs.

Do you have any other video or best practice to recommend for producing a consistent tension on this machine?

I see all kinds of tips on the forum — keep the crank lever hand strand straight, pull slowly, etc., but would like to know from what is the “official” best practice.

Glad it was helpful! I don't have a video like that but that's a great idea for one in the future. Those are certainly good tips, all I would add is that I always have the crank in the same starting position before pulling the string. The easiest way to do this is to get the tensioner a good working distance from the racquet where the handle is hanging straight down, gravity will keep the crank in that spot assuming the brake is not too tight. Hopefuly that makes sense. Also pulling fast or slow is not as important in my opinion as making sure you pull the same speed each time.

 

[Gamma Tech]

@Irvin @USMC-615 I would trust the thoughts of my predescessors on the spring/digital scale debate here. That logic makes sense to me. That being said I know the Wise digital calibrator works well for a lot of people. What I have in my shop here is a push/ pull spring scale from a Japanese company called IMADA. I think mine is from the 90s and it was part of the Gamma shop when I started here. The best part about my scale is it has the ability to lock the needle at the highest reading on each pull which is very important for crank machines as the string starts relaxing and losing tension immediatley.

 

[Irvin]

@Irvin @USMC-615 I would trust the thoughts of my predescessors on the spring/digital scale debate here. That logic makes sense to me. That being said I know the Wise digital calibrator works well for a lot of people. What I have in my shop here is a push/ pull spring scale from a Japanese company called IMADA. I think mine is from the 90s and it was part of the Gamma shop when I started here. The best part about my scale is it has the ability to lock the needle at the highest reading on each pull which is very important for crank machines as the string starts relaxing and losing tension immediatley.

You may want to modifying your calibration video to point out you’re taking max readings. Many users calibrate the lockouts using the reading after the string relaxes, which IMO is not the correct way to do it. When I had my lockout I would double pull each string to duplicate the pull from a constant pull machine.