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on 1:20 is exactly that, pay more attention

Oh ok! What threw me off was the plain background. A solid point of reference would have helped.

Thanks.
-chris

The foot does not ever "catch up" to the head when it is forced to move. The head "stays ahead" until the torque on the pin is released. During that time the head rotates back to where the foot is waiting for it. The head comes nearly back to the foot, as shown by the zero mark, but not quite. Those few tenths of a degree is the residual twist left in the portion of the pin in the pinblock.

Seems we cross posted. The point of reference is the zero on the card, which is affixed to the foot with a bent wire. (You can see it when the pointer is not at zero.) As the foot rotates, so does the card. The pointer is a wire affixed to the becket hole on the head and rotates along with the tuning lever. (Lever not shown, wanted the graduations to be easily readable.) When the pointer goes to the left, it means the lever is applying a CCW torque to the head and the amount of resulting twist is indicated on the graduations. It only goes so far, at which point the foot is turning, too.

Thanks Jeff for making this important video. Just some critiques if I may:

1. I am missing seeing the tuning pin itself, as well as the tip, apart of a fleeting and indistinct glimpse. Seeing the pin would put the demonstration into perspective and better demonstrate the purpose.

2. I would like to see a base line, or point of reference. The label is attached to the pin foot as I understand, but an extra external point of reference, such as an indicator fixed to the pin block, would show the twisting movement of the whole pin relative to the block.

3. It would be useful to know how the twist behaves with a range of torques. I think it should be repeated with torques across the range typically expected.

Thanks, Chris. You are correct on all points. I did what I could with what I had in the time I had. Since it does demonstrate the things I wanted it to, I'm just going to move on. But I bet you could SHOW me how to do better!

Thanks for doing this Jeff, very revealing! It shows what we all feel.

You're welcome, Bill. Don't think everyone does "feel it" based on some previous comments. That's why I made the video. Could have been better, but better than nothing.

It's excellent, and a vivid demonstration.

Now what I want is a video of a piano with a strain gauge in a string between tuning pin and agraffe/pressure bar, and another in the speaking length, to illuminate the question of the relative tensions in those two sections!

Great idea! Go ahead and do it. I made some suggestions for a mock up on another Topic you started:

http://forum.pianoworld.com/ubbthre...peaking-length-tensions.html#Post3071825