Tension calibrator

[Jeff]

I have an Eagnis Hawk 10 that isn't too bad a machine (after I tweaked it some).

I got a tension calibrator this week from Eagnis to make sure the tension was is accurate. It shows that at an indicated 65 lbs. pull I am actually pulling 90+ lbs.! I can't believe that, as I have strung a lot of racquets over the past year on it with no problem.

I called Eagnis and they said the calibrator (it's a spring type) won't work with a drop-weight machine. Huh??
Am I using it correctly?
Anyway, can someone clue me in? Thanks, Jeff

[Jens]

@Jeff
Can you make a picture of your weight arm and the scale and indicate where on the scale you read the weight? I have a feeling you might be reading the weight on the wrong side, since I haven't seen any drop weight so far that can pull more than 80 lbs.

[kwick]

@Jeff,

Seems highly unlikely that you are actually pulling 90lbs on a drop weight. What modifications have you done to your machine. Is that why you are checking calibation as normally you shouldn't need to on a drop weight. As long as it's level and flat, you are reading the scale correctly and you aren't suffereing from any friction loss through the pivot, it shouldn't change.

You could have a flaky calibrator so you could try measuring a variety of different tensions (eg. 20lbs, 50lbs, 65lbs, 80lbs) and see if the results are consistently bad across the range. You could try the calibrator on another machine to compare.

cheers,

kwick

[Jeff]

Thanks for your replies.
OK, I think I understand what the guy at Eagnis was saying - you don't need a calibrator for drop weight machines because of the way they're built. Makes sense to me.
Kwick;
I had to round over a part tension drum/gripper so that it wouldn't bend the string so sharply when it was wrapped around it. It did not change its radius, so I think it shouldn't have changed the leverage ratio. I was checking the tension just to make sure it was accurate. I didn't know enough about it to realize that drop weight machines don't need calibration. The quality control on the machine wasn't very good.
Joe;
You are right, my machine only goes to 80 lbs.
I had the weight set at 65 lbs. and the calibrator read 90 lbs. when the weight was horizontal. I think I am not going to worry about the whole thing anymore because of what Kwick said about drop weight machines, and I haven't had any problems with breaking strings from too much tension.
It's interesting see that you live in Cologne. My sister-in-law lives in Dusseldorf, and we were there in March for a couple weeks. I always enjoy visits to Germany. Thanks again to you both. Jeff
P.S. Great web site!

[Jens]

@Jeff
Ah sorry, I had turned your sentence around. So you have actually higher tension than you set. Hm, from my experience on the German discussion board, higher tension mostly results from people pressing down the weight arm into the horizontal position, which is of course an absolute no-no. So unless you do that, I have no idea why the calibrator shows such a high difference.
So next time you're in Dusseldorf, come by for a visit! :)

[Gaines Hillix]

Jeff, something is not right here. Eagnas is correct in that a drop weight should not need to be calibrated if it was correct when it was put together. However, there's nothing wrong with checking it with a calibration tool to make sure it's correct. The calibrator should NOT read 90 lbs. when the weight is set to 65 lbs. no matter what Eagnas tries to tell you. Either the mahine or the calibrator have a problem. If you have a friend that lifts free weights you can take 50 lbs. of Olympic bar bell weights and hang them from the calibration tool to check if it is close to being accurate. The weights themselves may be off by a pound or two, but they should be close enough. The spring based calibrators can be adjusted. There is a double locking nut mechanism in side that can be adjusted.

[Jeff]

Gaines, thanks for your reply. I think I'll do what you suggest (test the calibrator). I have been stringing for about a year with no probs breaking strings, and the strung racquets "feel" right.
However, I am looking at a Silent Partner elect. stringer mainly for the speed and consistency. What do you think of their intry level electric pull machine? Jeff

[moosryan]

it will be far less consistent than your dropweight. it isn't constant pull...and its an electric motor. run a search.

[Gaines Hillix]

Gaines, thanks for your reply. I think I'll do what you suggest (test the calibrator). I have been stringing for about a year with no probs breaking strings, and the strung racquets "feel" right.
However, I am looking at a Silent Partner elect. stringer mainly for the speed and consistency. What do you think of their intry level electric pull machine? Jeff

I have seen comments(mostly anecdotal) that the basic SP e-stringers are not very consistent in the tension that they pull and that they are subject to variations in voltage coming in from the power company. They also look "crude" to me. I just don't like seeing a machine with a tension head that is attached to the base with what look like pop rivets.

[Jeff]

I hear you. I did quite a bit of research and ordered a Laserfibre machine. Tim, at their distributo,r was VERY helpful and talked to me for about an hour, answered all my questions and explained a lot of things. I am very much looking forward to more consistency and accuracy in my stringing.
Thanks for your input. Jeff