Calibrating an Alpha Blu

[NiteFly]

I finally received the Alpha blue I got from the auction site. The machine looks to be in good shape and is very sturdy. The clamps don't slip and the string gripper holds the string steady.

I went to calibrate it tonight and I run out of tension screw before I reach the desired tension. I am using an Alpha tension calibrator. Does this mean that I need to replace a spring or something? It gets close, it shows 50lbs on the calibrator when I have the tension head set at 53. The higher I go, the more it is off though. It shows 70 lbs when I am set at 76. Any thoughts?

I figure I can string like this, but it seems like I will have to check tension every time.

[Mansewerz]

Alpha blu? Was this an earlier model?

[Zhou]

Here is a picture of the machine. It is an earlier model of Alpha.

[SW Stringer]

Originally Posted by NiteFly

I finally received the Alpha blue I got from the auction site. The machine looks to be in good shape and is very sturdy. The clamps don't slip and the string gripper holds the string steady.

I went to calibrate it tonight and I run out of tension screw before I reach the desired tension. I am using an Alpha tension calibrator. Does this mean that I need to replace a spring or something? It gets close, it shows 50lbs on the calibrator when I have the tension head set at 53. The higher I go, the more it is off though. It shows 70 lbs when I am set at 76. Any thoughts?

I figure I can string like this, but it seems like I will have to check tension every time.

Take a bunch of readings that cover the range that you expect to use. For example: take readings every five pounds from 45 to 75 pounds - at least two at each setting. If you took two readings per setting you will have fourteen sets of data points, an x (machine reference tension) and a y (actual tension). Plug the numbers into a linear regression formula (Excel has one) and the program will spit out an equation of the form: y = m * x + b Use that equation to print out a chart that shows the machine reference tension vs actual tension from 45 to 75 pounds in one pound increments. Recallibrate and reprint a new chart as needed. (i.e. - every 50 racquets, every 3 months, and whenever you suspect the mechanism has shifted)

[dancraig]

You might also want to check the accuracy of your calibrator. You can do this with barbell weights. They can be "calibrated" too.

[william7gr]

It's a ratio. The machine isn't going to be off by three pounds when you set the tension to 10 but also it wont be off by three when you set it to 100.

[NiteFly]

Originally Posted by william7gr

It's a ratio. The machine isn't going to be off by three pounds when you set the tension to 10 but also it wont be off by three when you set it to 100.

Makes sense. Thanks.

[NiteFly]

Originally Posted by SW Stringer

Take a bunch of readings that cover the range that you expect to use. For example: take readings every five pounds from 45 to 75 pounds - at least two at each setting. If you took two readings per setting you will have fourteen sets of data points, an x (machine reference tension) and a y (actual tension). Plug the numbers into a linear regression formula (Excel has one) and the program will spit out an equation of the form: y = m * x + b Use that equation to print out a chart that shows the machine reference tension vs actual tension from 45 to 75 pounds in one pound increments. Recallibrate and reprint a new chart as needed. (i.e. - every 50 racquets, every 3 months, and whenever you suspect the mechanism has shifted)

This sounds like a great idea. Thanks. Is my tension head OK though? Would replacing any of the parts allow me to get to the correct tension in the calibration? I was reading through a Gamma manual and it had a little section on adjusting the tension brake after a lot of use. Could that be something I need to do on the Alpha?

[Zhou]

Originally Posted by NiteFly

This sounds like a great idea. Thanks. Is my tension head OK though? Would replacing any of the parts allow me to get to the correct tension in the calibration? I was reading through a Gamma manual and it had a little section on adjusting the tension brake after a lot of use. Could that be something I need to do on the Alpha?

I would give Mark a call at Alpha and ask him what he would recommend for you.

[NiteFly]

Originally Posted by Zhou

I would give Mark a call at Alpha and ask him what he would recommend for you.

I emailed him and he responded quickly. He sent me a pdf of the manual yesterday and he is mailing me a replacement tensioning adjustment screw today. As many on this board already know... you can't beat this customer service!

Mark thinks the screw might be stripped and it definately looks worn in the middle.