Low Friction Pianos

Here’s a Steigerman with a low bearing on the agraffes. Tuning it, I had the feeling the pitch was sliding quite easily. Even with long non-speaking length, I was getting pitch changes when I removed the hammer force after a slow pull.

I performed a friction test. I flexed the pin towards the string, removed force, whacked, and measured. Did the same flexing away from the string.

This test measures the friction at the agraffes, and the residual friction in the pinblock. Usually I get 15 – 20 cents. On this piano, it was 5 cents.

This explains why the pitch so easily followed the pin.

To improved tuning sensation, I might add thicker felt under the strings.

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5 Responses to “Low Friction Pianos”

  1. Cobrun Sells says:

    Is low friction not good? It’d almost seem preferrable so that there doesn’t need to be as much massaging of the pin during tuning, and there would be less chance of the string changing pitch too far in the future if the NSL tension band was too high or too low.

    • Low friction is not good, if the difficulty I have had tuning those pianos is any indication. With the pin bending/twisting and unbending/untwisting, there needs to be friction to give us a target window.

      Also, on hard playing, speaking length tension rises. Low friction would result in poor stability in those situations.

      The piano in this picture was a customer’s piano. She hadn’t had me tune it in years. (I’m not the cheapest!) I asked her when the piano was tuned last. She had it tuned six months ago. “Not by me” I said. The piano sounded like it hadn’t been tuned in 4 years. That’s because the low friction, and poor stability, allowed the string to slip on the v-bar with the slightest change in tensions, perhaps due to hard playing, or even just humidity swings.

    • Low friction is not good, if the difficulty I have had tuning those pianos is any indication. With the pin bending/twisting and unbending/untwisting, there needs to be friction to give us a target window.

      Also, on hard playing, speaking length tension rises. Low friction would result in poor stability in those situations.

      The piano in this picture was a customer’s piano. She hadn’t had me tune it in years. (I’m not the cheapest!) I asked her when the piano was tuned last. She had it tuned six months ago. “Not by me” I said. The piano sounded like it hadn’t been tuned in 4 years. That’s because the low friction, and poor stability, allowed the string to slip on the v-bar with the slightest change in tensions, perhaps due to hard playing, or even just humidity swings.

      “..there would be less chance of the string changing pitch too far in the future if the NSL tension band was too high or too low.”

      Think about that. Low friction means a narrow Tension Band and more chance to have NSL tension near the limit of the Tension Band. So, there would be more chance of the string slipping.

  2. Cobrun Sells says:

    What I meant to say was since the string slippage is already present during tuning then that means there will be less slippage after tuning the entire piano (since any slipping will have happened during tuning). (?)

    • I suppose that could be said for any piano with any amount of friction.

      The problem occurs when we play hard. The speaking length tension increases and the v-bar friction decreases. That’s when the string slips. (But you know that already since you took a course with me, LOL)

      One benefit for low friction pianos may be that the amount that the friction drops during hard playing is low, since there is not a lot of friction to begin with.

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