The problem is that the magnet pulls the strings into plane with one another, when used at the strike point. On uprights, it is a convenience, as putting the piano on its back takes extra effort and room. Also, it matters somewhat less whether the strings are "level" (perpendicular to the strike of the hammer) than that each unison is in a plane, since the action doesn't shift, and it is far less likely that we will be repeatedly mating the hammers over time. Filing the crown to a slight slant is pretty efficient to do.
You'll note that I suggest placing the magnet 10 - 15 mm from the V-bar. At that point, it will read the initial curvature of the wire, which will predict pretty well (not perfectly) what the alignment will be at the strike point. From my experience, making bends so that the strings are in a plane at that point produces pretty good results, assuming your magnets are as weak as possible (they have to have enough strength to make an audible tonal difference to the sound of a pluck). If you place a magnet there, and discern a problem with level, experiment and slide it down to the strike point. You will almost always discover that suddenly there is no problem - all three strings will be held by the magnet.
Bottom line is that it works well enough to make mating pretty quick, which is the whole point.
I did experiment with magnets for grands about ten years ago. I was disappointed to find out that the results were pretty bad. Part of this is due to the higher expectations for grands, and part of it due to the fact that, at least for critical instruments, you need to re-mate every time you file hammers - which means that if the strings are in a very good line parallel to the keybed, the hammer crowns can simply be put into a very good line and mating will be little effort. So centering the bubble of a level is worth the trouble. All of this is about efficiency, not about some magic achieved by leveling strings in and of itself.
------------------------------
Fred Sturm
University of New Mexico
fssturm@unm.eduhttp://fredsturm.nethttp://www.artoftuning.com"We either make ourselves happy or miserable. The amount of work is the same." - Carlos Casteneda
------------------------------
Original Message:
Sent: 06-29-2017 15:23
From: Benjamin Sanchez
Subject: Magnetic Leveling
To Mr. Sturm or anyone else who knows the answer:
I read your article in the May 2017 Journal on upright voicing, and liked the idea of using magnets. My question is, why don't we use them to help with grand voicing? Is it simply something that's not been done yet, or is there a reason behind it? If there is a reason behind not using them for grands, what makes it safe to use them for verticals?
Thanks,
------------------------------
Benjamin Sanchez
Professional Piano Services
(805)315-8050
www.professional-piano-services.com
BenPianoPro@comcast.net
------------------------------