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View Full Version : Tensioner question - lockout vs. drop/electric


byteme45
06-15-2004, 06:35 AM
I've just taken delivery of an Alpha Revo4000 lockout machine. I had been using a Silent Partner eStringer w/ flying clamps. The quality of the Alpha is awesome. My question is on the tensioner. I typically use one of those spring tension gauges to check the tension after stringing for reference only - to determine if the racquet has lost tension to the point where I need to restring. However, with the Silent Partner if I strung at 68lbs. the tension gauge was pretty close to 68. Now, in using the lockout on the Revo if I string at 68 the tension gauge reads about 58lbs.

I talked to Alpha and they said try bumping up tension by as much as 10% as compared to constant pull. So I tried it last night, strung my Pure Drive Plus at 76lbs on the lockout and it came up 63 on the tension gauge. Is there something I'm missing, doing wrong, not taking into account? I just find it hard to believe that a constant pull machine would make that much difference.

I went away from the SP machine because of the flying clamps and I really grew to hate the tension head on it. The alpha is great build quality, love the clamps, it's easy to use - but this tension thing might get to me.

Thanks!

SW Stringer
06-15-2004, 08:16 AM
"I just find it hard to believe that a constant pull machine would make that much difference." You just performed the experiment that PROVES what the resulting tension difference is between the way you operated your SP and the way you operate the Revo. Believe it. Now all you have to do is fiddle with the reference tension on the Revo to get an equivalent tension on the finished product. You may be able to operate the Revo differently to get a smaller difference in resulting tension. I've never operated a crank machine myself but have observed seasoned pros and they seem to turn that crank very slowly and methodically - ie it has to be the same rpm everytime to be consistant, and that's the key - consistency. Tension starts dropping on the lockout machines the instant it "clicks". On CT machines it's from the instant you clamp off. Since you still have both machines (assuming here) you could measure the difference in time between the two methods, and that time difference PLUS the tensioning error of the cranks reference tension would tell you where the differences are coming from. You would need an accurate calibrator to find the error in the cranks ref tension device.

SW Stringer
06-15-2004, 08:54 AM
Just had another thought. If you haven't already purchased a tension calibrator device this method will save you the expense. I'm assuming you still have both machines so here goes. You can calibrate the Revo against the SP by pulling tension on a single string (on both machines) and plucking the strings to compare the frequency - once the frequency is the same between the two machines (the fret length of the strings has to be the same too) then the pulling tension is the same. To make it easier use a stiff string , i.e. - polyester or kevlar will give better results than a stretchy taffy-like string such as Gamma TNT. The fret length should be as long as you can make it - 12" would be good. Just lock your turntable, clamp a piece of string around the mounting post using your flying clamp and put the other end in the tensioning device. Measure the string distance from the edge of the flying clamp to the point where it's being constrained in the tensioning device. If you can guarantee the lengths to be within a sixteenth of an inch over a twelve inch span then you will have half a percent accuracy in tension between the two machines. In other words if your SP is pulling 60 lbs tension and the frequencies are the same, the Revo should be pulling between 59.7 and 60.3 lbs tension. Good luck!

David Pavlich
06-15-2004, 08:58 AM
Alpha has great quality control, but strange things can happen. Did you check the calibration on your new Revo? It may have gotten jarred or something during shipping. Are you sure the clamps aren't slipping a little? Mark your string with a crayon right next to the clamp after it's clamped to see if it's creeping.

Or...is it possible that the calibration on the SP is off? Perhaps it's pulling more than the reference tension.

David

byteme45
06-15-2004, 10:03 AM
Good thoughts. First, I did check the calibration on the Alpha, it's dead on at 50lbs., I've got to come up with a method for testing at higher levels because the string keeps breaking. I know what I need, now it's just getting to the hardware store! As for the SP, I calibrated it quite a while ago and since I used the gauge didn't really bother after that. I know the string isn't slipping on the Alpha, every time there is a bit of string with printing on it near the clamp I always note where it is at lockout and then at release. Very nice clamps!

It's entirely possible that the SP tension was off, I know it varied during a racquet - that combined with the tension head and flying clamps were why it had to go.

One thing I picked up on is that maybe I should crank more slowly, also I'll have to remember to prestrech string from now on.

David Pavlich
06-17-2004, 07:12 PM
The speed with which you crank it will make a little difference, but not enough to cause the huge discrepencies you've described.

I'm sticking with the SP calibration being off, seeing as how you checked the calibration on your Revo and it was good.

I do have a question. You mentioned that you want to check at higher tension but the string keeps breaking. What kind of string are you using for your tension gauge that it breaks?

David

byteme45
06-18-2004, 08:22 AM
The speed with which you crank it will make a little difference, but not enough to cause the huge discrepencies you've described.

I'm sticking with the SP calibration being off, seeing as how you checked the calibration on your Revo and it was good.

I do have a question. You mentioned that you want to check at higher tension but the string keeps breaking. What kind of string are you using for your tension gauge that it breaks?

David I'm just using scraps of old string. The issue isn't the string it's that the calibrator has one end that was smoothed after they drilled the hole for the string and the other was never smoothed after being drilled, it's actually quite sharp so when you pull to check tension it's like pulling the string across a knife edge. I'm going to get a heavy duty key ring or a small screw shut chain link type thing to remedy this.

After playing with both racquets for a while I don't think the tension is that low. I think the SP was overshooting the tension - who knows how high they were really strung, I'm surprised that the racquets didn't just blow up!