gamma II drop weight test and adjusment

#1
Hi all,

just got a gamma progression ii table top drop weight flying clamp machine used pretty cheap.

seller told me he used his spring tension calibrator and that it was stringing about 3 pounds off.

I got a deal on a starting clamp and tension checker (the thing that looks like a fish weighing scale)

2 questions:

1. How exactly do I use this tension checker? add string, hook it to a post and pull tension? or what?

2. Assuming the guy was right and it is 3 lbs. off, is there anyway to adjust the bar the drop weight is on so that the bar markings are accurate?

Many thanks in advance for your expertise!
 

tennytive

Professional
#2
When I used the drop weight on my Alpha DC there were lines only for every 10 pounds, so I had to make my best guess as to 57 or 63 etc. Not sure how you test your calibrator, but I would think you should somehow attach it to your 12 0'clock post, attach your string, pull tension on the string with your weight and see what the scale reads. With experience you may be able to make a small adjustment on your bar to compensate for those missing 3 pounds.
 
#4
You can't really pry the scale off and reattach. I would just determine the offset at 40, 50 and perhaps 60 lbs ref tension and go with that. You do want to use a string that does not stretch and Kevlar or a thick poly is good for this. FWIW, do a search and all of your questions have mainly been answered.
 
#5
How can the drop weight be 'off'? There is nothing to move or get changed. Could just be technique or the nature of the machine. Just string a raquet, test the tension and compensate from there...
 
#6
the bar has markings every pound for where to put the drop weight for this or that tension. I just figurerd that there might be some sort of way to adjust (like a thread on the bar that you could pull the bar out a little or in a little) to fine tune the markings to reflect the true tension being pulled when the weight is properly placed there. BTW - I had gone to the gamma site and googled it with no real help prior to posting here.
 
#7
also, I just did about 5 diff searches re bar adjustment, gamma etc. varaiations with this web pages search feature. Only result was my original post
 

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Hall of Fame
#8
the bar has markings every pound for where to put the drop weight for this or that tension. I just figurerd that there might be some sort of way to adjust (like a thread on the bar that you could pull the bar out a little or in a little) to fine tune the markings to reflect the true tension being pulled when the weight is properly placed there. BTW - I had gone to the gamma site and googled it with no real help prior to posting here.
I think the best thing to do is string your racquet, then use Racquet Tune to measure the finished tension against the reference. Play with your racquet for a few hours, RT again. See what tension you are grooving with or think you will groove with and make adjustments. Your stringing technique will probably add more variables to the finished tension then any fine tuning of the tension gradient on the bar.

Comparing to some of the folks that get their racquets strung on a LO machine, my finished tensions are always a bit off. Also, some pull higher tension on their tie-off pull and that makes a slight difference in the final tension as well.

Any sort of variation in time from the start of your pull to clamping off your string would affect the final tension by performing variable pre-stretching before clamping off. The number of iterations of dropping the bar, ratcheting and raising the bar and dropping it again would also impact pre-stretching. Having your bar perfectly level (or not) will affect tension.

So if you are a beginner, there are many ways to have inconsistent tensions in your job.
 
#9
I'd trust the "fish scale" over a spring tension calibrator. Tie a loop of tennis string to one end of the digital scale and secure one end to the stringing machine's racquet mount. Then tie a solid piece of scrap tennis string to the scale. Set a weight like 50 lbs, pull tension on the string attached to the scale, and see what you get on the digital scale. Then try 40 lbs and 60 lbs to see if the offset (if any) is consistent. Of course if you have a known weight to test the fish scale with, even better.

When I did this on my drop weight, I found that my digital scale gave me a reading within 0.08 lbs of the tension I set on the bar regardless of the range (30-70lbs) as long as the bar was horizontal after pulling tension. I was honestly surprised to find that the drop weight was so accurate, and has the bonus of constant pull. Of course it's as slow as it gets for stringing, but the accuracy is solid.
 
#10
One thing to note is that the weight may need to be installed on the rod in a particular orientation?
Not sure that would throw off anything or not, sometimes the weights come in two pieces (little piece
for badminton.

Use Kevlar string on the calibrator if you can (or doube/triple more stretchy string.)

I have both a spring calibrator and two cheap electronic luggage scales. I kinda fudge the data
between them all. But honestly, since i got my WISE i don't bother checking it. Haven't in some time anyhow.

Three pounds isn't much on a spring scale. You're probably dialed in. It's a DW, after all........
really need no for calibration.

Newton did that for you many years ago.
 
#13
A drop weight machine will not need calibrated, ever. The physics used will always produce a consistent result. As long as the drop weight bar is parallel to the floor whatever the weight is aligned to on the bar, that is what the tension will be. Even is the bar is up or down a few degrees, the better than average player will not notice.

That being said, since the machine was used who knows what the former owner may have done. If they removed the set screw locking the drop weight bar in position on the rotational drum, removed the bar, and did not install it properly, then yes the machine could be off. If the drop weight bar is not at the factory set position, there could be a problem.
 
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