Good morning everyone, compliments on the site, it is very interesting. I would like to ask a question regarding the dimensions of the white strings (non-wound). I have noticed that on certain pianos, on the bridge or on the cast iron, approximately every 4 tuning pins there is a number indicating the string diameter with a difference of 0.025 mm (17=0.975, 16/half = 0.950, 16=0.925, etc., etc.). Here is the question: I found myself in front of an old upright piano, 140 cm tall with 85 keys and some broken strings, which did not have any reference numbers on the bridge or on the cast iron, so I measured the strings. The strings immediately after the wound ones had a diameter of 1.100 across all 4 tuning pins, while the strings of the next 4 tuning pins measured 0.950 instead of 0.975... then I measured the strings of the next 4 tuning pins which, in my opinion, should have been 0.950, and indeed they were. Likewise, for the last treble strings, the first 8 tuning pins had a diameter of 0.800, while the subsequent ones increased by 0.025. So I wonder: is all this correct, to report the same measurements every 4 tuning pins, or has someone over time replaced the strings making a real mess without respecting the rule of the 0.025 difference? I hope I have explained myself well, otherwise excuse my ignorance if someone would like to answer me and explain the operation in a simple way. Thank you...
When it comes to century-old pianos with very long strings, during restoration the stringing is generally recalculated to reduce the load on the plate, staying below 75 kg of tension per string.
Based on the length of the string, its thickness determines the tension; it can happen that you have to skip even two sizes, depending on the project. There is certainly no progression rule, only calculation and choice. Century-old Blüthners, for example, have 3 or 4 courses before the crossing where the gauge suddenly decreases by two sizes instead of remaining constant or increasing.
Sometimes manufacturers don't even use half-measures; they start from 13 and go up to 19 or 20.... If you are unable to perform a new calculation, you can use Fenner's tables or copy the existing setup.
I thank you very much for your precious answer giovannig, it is certainly better for me to rewrite the existing situation since now you have given me the possibility to understand better, also because I wouldn't know how to do the new calculation. Also because I am not replacing the spun strings, so I think that if a recalculation is done, the entire stringing must be recalculated to avoid imbalances? Correct me if I am wrong. Anyway, while I'm at it, I would like to take a look at this Fenner table if you can tell me where and how I can find it. If it's not too much trouble, can you explain to me how to measure the load on the bridge and what measurement differences there are between the various compartments, so to speak.. I want to specify that the piano in question has no value in case damage is caused. I hope I haven't been too annoying with my inexperienced questions. Thank you from the bottom of my heart
What Giovanni says is correct. There isn't a precise rule. Let's say that the formula suggests, based on length, a possible diameter: I say possible because some passages can be recalculated by equalizing tensions or at least avoiding sudden jumps. However, it must be noted that by recalculating, one might encounter greater disharmony. The fact regarding the decrease in diameter near the crossover is also true. These strange things are compensations made by manufacturers on an experimental basis. In fact, on the last steel strings before the copper ones, the situation is quite critical, both in terms of disharmony and timbre. Many difficulties with hammer voicing/intonation are also encountered. It should be noted that a change occurs in material, in the bridge, and in the position of the bridge relative to the soundboard. Generally, one tries to "increase" the last steel strings before the copper ones... almost to make the transition of "dimension" smoother... but it doesn't always work. The situation is very, very complex. Trying to recalculate isn't bad. Aim for the goal of tension uniformity without increasing disharmony too much. You will certainly discover some interesting things! You must measure the exact length of the strings, which, together with frequency, are two values that cannot be modified. Compare the table obtained with the old strings and make decisions regarding uniformity. Naturally, tuning stability and the precision of certain passages will benefit, especially on the octaves. The instrument will also gain power. Of course, ensure that the frame is intact and robust and that there are no collapses on the bridges or cracks in the soundboard.
P.S. To measure the load of the bridges, a centesimal comparator would be necessary. Anyway, keep in mind that on old instruments one must lighten rather than load: the basses should have minimal load and the highs a bit more. The important thing here too is not to find strong discontinuities due to soundboard sagging, bridge detachment, and/or string block/plate issues. Giovanni, do you agree? Please add your opinions!!!!!
I have read your replies with great interest, admiring your expertise and especially the availability you show to people who want to understand something in this wonderful world of the piano. Sincerely, I wouldn't know how to redo the calculation; I tried to look for this Fenner table mentioned by giovannig but I couldn't find it, I would like to take a look at it if you could indicate where I can find it. Anyway, in these days I can provide you with the thicknesses of the strings for each course with relative lengths, perhaps it will be useful for you to manage to develop some calculations, naturally within the possible limits and anyway if it is feasible with this data. Bridges and soundboard are fine. Cast iron frame intact as well as the pedals and soundboard. Thank you again, kind regards.
Anyway, you could measure the length of the A3, A4, A5 and if possible the diameters so as to have an indication regarding the need to review the string gauge
Good morning, here are the lengths with relative diameters for la3, la4, and la5. For accuracy, I took measurements from both 3 strings (la3 lengths 101 - 99.7 - 97.7: diameter 10.50) (la4: 77.5 - 71.1 - 68.9: diameter 0.975) (la5: 55.5 - 50.5 - 48.2: diameter 0.925... Lengths taken from the hitch pin to the bridge pin without counting the wraps at the bridge, which would be about 7.5 cm. I am also reporting all the diameters of all the white strings if it might be useful. From the first one immediately after those wound in copper to the last of the trebles: 1.100 - 1.050 - 1.050 - 1.000 - 0.975 - 0.975 - 0.975 - 0.925 - 0.900 - 0.875 - 0.850 - 0.825 - 0.800 - 0.800. What I am wondering is, what operation needs to be done with this data to understand how many kg the string spreader is under? Bye, Giovanni.
