I didn't see this discussion right away, so hopefully I can help.
There are no new complete Steinway stacks available that I know of, but our shop can install one, two or all new rails on the existing stack brackets. We can increase the spread if either the wippen or hammer rail is replaced, both replaced as a set lets us set everything up optimally.
Are you having any issues? 111 mm is a little too tight, but it will probably be functional. The minimum we ever want to see is 112 mm, and 112.5 to 112.75 is our target.`
You may be able to increase the spread by switching the hammer flanges from New York to Hamburg, if NY flanges is what you have. If memory serves, Hamburg flanges are 1 mm shorter from the screw hole. That may actually be the root cause of the short 111 mm spread, someone installed NY flanges on a Hamburg stack.
We're using Hamburg size hammer flanges on everything currently as that's what's most easily available and that's what both NY and German Steinways are using now.
Another way to increase the spread 1 mm is to install #17 music wire between the top of the wippen flange and the rail. Of course that changes the wippen ratio but that change may be beneficial or detrimental, depending on what's there now.
In 1917 the knuckle distance was probably 16 mm or so, but whether the action is working correctly depends on the rest of the geometry. The key ratio varied widely so some old Steinways can use 17 mm knuckles, some won't work well.
If you can fill out this web form, I can analyze the geometry and tell you if 16 mm or 17 mm is better, and probably more. See
There's a PDF with instructions on the above page, lots of pictures. The first time this takes an hour. The second time, 30 minutes or less. This is a free service for any PTG member or anyone in the piano rebuilding business. I use the same custom software to analyze your action that we're using the Reyburn Pianoworks shop to design new actions and keysets.
Sometimes a capstan move can help accommodate a knuckle distance change, I can tell you that from filling out the above web form. A capstan move takes some time, but it's not that hard. It's plugging the old holes nice and neat that's the trick. I can comment on that if needed as we've done it a number times in our shop.
Hope that helps,
Dean Reyburn, RPT
Sent: 02-01-2023 08:00
From: Alan Eder
Subject: Replace action frame in 1917 Hamburg Steinway model A?
The piano is a 1917 Hamburg Steinway model "A" with 111mm action spread. The hammers, shanks and flanges have been recently replaced with Renner parts of modern specs (17mm knuckle placement).
We will be replacing the repetitions and are considering replacing the action frame with current production which should increase the action spread to 112.5mm.
Has anyone out there done this before? And is there any down-side to doing this?
Alan Eder, RPT
Herb Alpert School of Music
California Institute of the Arts