Gripper on drop weight scruffing strings

[abgoosht5]

Hi folks,

I’m new to stringing and I just bought a used Gamma Progression II 602FC. My problem is that I can feel with my fingers that the gripper on the drop-weight is scruffing up my strings each time I pull tension. The gripper looks clean to me. It has a rough surface, presumably for gripping, but that seems to be imparted to the strings near the mouth.

I tried to find this issue discussed in the forums but couldn’t see it anywhere. Is there something I can do, technique or otherwise, to protect the strings better?

Many thanks in advance for advice and guidance.

 

[Irvin]

No telling how old your machine is and how much it has been used. But a dirty gripper can cause string slippage, and string slippage can cause scruffing. Maybe @Gamma Tech has more to add.

 

[esgee48]

Clean the gripping surfaces with rubbing alcohol. Pull tension with scraps and see if the string slips. If the surface is no longer scuffed, then you've fixed the issue. If the marks are still there, take the lower jaw off and see if the surfaces are too roughed.

 

[Irvin]

Just thought of another idea. If the gripper drum is not rotated far enough clockwise before you start pulling tension the string may not apply enough pressure on the top (moving part of gripper) to grip string securely.

EDIT: And remember to wrap the string around the gripper drum 360 degrees clockwise and then insert the string in the gripper jaws. Hold the top portion of the gripper down as you apply so the string does not slip.

 

[Icsa]

I also use an old Gamma dropweight stringer and I see the same thing - the gripper is creating small dents/scratches on the string that I can feel with my fingers. Since it didn't cause premature string breakage, I assumed it is normal.

 

[MaxSwing]

I have a second hand very used Pros Pro Challenger II and had a problem with it initially pinching the strings in the grippers (and resulting in a few breakages) My post here. I resolved it by not only wrapping the string around the drum but also sticking a small block between the drum and the gripper to limit how far the gripper could move - obviously allowing it to move sufficiently to actually grip the string but without the pinching. However looking at your machine I dont think there is any ability to limit the grippers movement.

However as others have said a good clean will always help to avoid any slippage - what tension were you trying to pull? Have you got a tension calibrator to validate what you were pulling?

 

[abgoosht5]

Thank everyone for the helpful comments and suggestion!

@Irvin: I will try again cleaning the gripper with alcohol. I do suspect the surfaces are rougher than they might need to be, but there doesn't seem to be an easy way to adjust that roughness without putting tape or something over it, which I suppose could be ill-advised. @MaxSwing, I am concerned that by trying to limit the grip, I might cause slippage which could be even worse for the string. This is a drop-weight, so I was under the impression no calibration would be needed. Is that not correct?

@Irvin I did try adjusting my technique. I always wrap all the way around the drum. I have also now started rotating the knob manually to close the gripper drum prior to pulling tension by raising/dropping the weight. It seems that might have helped, some, but hasn't quite solved it.

@Icsa I agree that scruffing is very subtle. Can't see it by eye, only by feel, and probably only on more sensitive strings. Still, I will try to keep experimenting and see if I can do better. It's reassuring that other comments are on the same page. Thanks!

 

[MaxSwing]

I still check the pulled weight but yes drop weight won't change unlike any spring driven system (electric or crank). I just found the stuck on markers to be slightly off. I only mention if it's worth checking the pulled tension is correct as marked.

Limiting the grip was definitely my last resort but just did tiny shims until I was happy it didn't slip and it didn't crimp the string.

 

[diredesire]

If the scuffing is subtle, then it's normal. I think I've only worked on the 602 FC once, so my memory is very unreliable, but looking at photos, it seems like the 602 FC basically has the same drum gripper as the Progression ES, which is the predecessor to a machine I've worked on a lot in the past, the ESII+. IIRC, the gripping plate has a similar diamond dusted insert surface as their old (not sure what the design is like now) starting clamp. The old inserts were mildly textured, and gummed up quickly, which reduced their holding power a lot. They were also hard to clean with solvents, which is to say that the reduction in gripping power more or less stayed permanent without frequent maintenance. I didn't try to keep up with maintenance too much since the machines weren't mine, but soaking a rag in isopropyl alcohol (90%+ is better) and then shutting the wet rag into the gripper with my off hand and yanking it out (and repeating as needed) worked for a short term fix.

As time went on, I resorted to double wrapping the drum, which essentially increases the shutting pressure once the gripper is engaged. This has obvious downsides, including requiring more string on the final pull(s). You can back up the gripper with a starting clamp, which is janky, but works. You can also grip the drum shut with your off-hand when the tensioner is getting started. I recall the gripper still slipping on occasion while doing so. This was probably just under 20 years ago now, so take that recollection FWIW.

If you're not slipping, you're fine is my 2c. You can try backing up with a starting clamp (or a floater if that's all you got) and see if it makes things better. If you do, then you just have the texture/scuffing from the starting clamp to contend with, so I wouldn't worry about it

 

[Irvin]

I will try again cleaning the gripper with alcohol. I do suspect the surfaces are rougher than they might need to be, but there doesn't seem to be an easy way to adjust that roughness without putting tape or something over it, which I suppose could be ill-advised.

I would not suggest using just alcohol, I would use WD40 and alcohol. Take the lower section of the gripper drum off, but be careful there are 2 springs you don’t want to lose. Leave the top portion of the drum gripper on to make putting it all back together easier. Clean both surfaces of the gripper with WD40 and a stiff toothbrush. Wipe all surfaces clean with a dry rack the use 91% alcohol to remove any residue.

 

[eah123]

If there’s no premature breakage then I wouldn’t worry about it. I play on clay and the whole string bed gets scuffed on the first outing.

 

[Gamma Tech]

@abgoosht5 there's lots of good advice in the thread here but keep in mind it could also depend on the type of string you use. With a stiff poly you might not notice any scuffing or imprints but on a very soft multi filament you will often see some small scuff marks or discoloration where clamping force is applied. It is very important to recognize the difference between marks from the clamping force and marks from the string slipping through jaws and clamps. Watch the string closely for any sign of movement or even place your finger on the string next to the jaws to feel if the string moves when it should not.

 

[abgoosht5]

Thanks @Irvin I washed both surfaces of the gripper with WD50 and isopropyl alcohol. I thought I did a decent job of it, but it did not seem to solve the scruffing.

@Gamma Tech Surprisingly, I have noticed that I feel the roughness on the stiff polys actually, but I can’t feel them on the soft multis. Maybe because the stiffer strings give way less, so that the rough surface of the gripper leaves more of a mark on them. So the good news for me is that the softer, more vulnerable strings, seem to be just fine. All this is leading me to @eah123 ’s conclusion not to worry about it too much. The tougher poly strings I use for the most part are less likely to break or show any practical signs of the scruffing.

 

[Icsa]

Yeah, the scuff marks are move obvious on polys, and are caused by the clamping force of the gripper. I don't know if the gripper can be adjusted to avoid the scuffs..

 

[Irvin]

Thanks @Irvin I washed both surfaces of the gripper with WD50 and isopropyl alcohol. I thought I did a decent job of it, but it did not seem to solve the scruffing.

I know this may sound weird but my guess is you didn’t clean it well enough. If you take the gripper plates apart you should not see much if any wear on the gripper plated. gamma Tech has actually recommended using WD40 and a stone to clean clamp and gripper surfaces. I personally think that might be too aggressive. I would soak the surfaces for 10-15 minutes in WD40, or just lay a WD40 soaked rag on the surfaces for a while. The wet them down good again wi5h WD40 and scrupulous them well with a stiff brush to remove any sign of residue from string wear. Then clean them with 91% alcohol. Some times you think you have all the residue off but any remaining residue can cause slipping and that could be what’s causing the scuffing.

EDIT: If that doesn’t fix your issue I would consider buying a new gripper, but they’re expensive IMO. Another option would be to call Tennis Machines or Gamma Sports and see if you can talk to JC and TM or Gamma Tech.

 

[Radicalized]

Gamma's cleaning stone is $8, but you'd probably have to pay shipping because it isn't just sold everywhere. A replacement Gamma Composite Rotational Gripper is probably at least $50 (They used to be $30 in red, blue, or black.). If your displeasure with the scuffing is enough and you've clean as noted in various posts above, these are your only other options to try. You can try the double wrap around the rotational gripper before inserting between the jaws and being sure the string is pulled tightly when exiting the racquet. Other factors such as string material or user issues are often difficult to address if they exist.

Note: The Idea is the diamond coated surface is harder than the stone. I'm just making you aware that this product is available and used to be noted in the official manual, and perhaps still.

 

[Irvin]

I like @Radicalized’s picture above, but IMO the drum should have been rotated more clockwise so the string put pressure on the top movable portion of the gripper for better gripping. I’m sure the diagram will work well on strings that stretch more but on stiffer string like poly or Kevlar you could have slipping. Slipping causes string residue to build up in the diamond dusted gripper, which in turn causes less gripper bite, and more scuffing.

 

[Radicalized]

I like @Radicalized’s picture above, but IMO the drum should have been rotated more clockwise so the string put pressure on the top movable portion of the gripper for better gripping. I’m sure the diagram will work well on strings that stretch more but on stiffer string like poly or Kevlar you could have slipping. Slipping causes string residue to build up in the diamond dusted gripper, which in turn causes less gripper bite, and more scuffing.

Thank you for noticing that 14 years after the original post of the image where it was not intended be be an all-encompassing composite of rotational gripper stringing practice.