cracked steinway rails (long)

[John Dewey]

I may have missed some of this thread but here is what I found tonight. I
have saved about 40 old rails and about 20 old dowels from Steinway action
frames where I have replaced them. Before tonight I had not made a study of
the bad rails to see if there was a trend in the cracks.

If we look at the end of a rail it has what I will call 4 large diameter 1/4
circles and 4 small diameter 3/4 circles. The screws go through the brass in
the middle of one of the large diameter 1/4 circles that I will call the top
side. The two different diameter circles meet in what I will call a valley.
This is probably not the right terminology but I hope it lets us all talk
about the same part of the rail.

Upon studying the rails I found the following things.

Almost all the cracks were in the middle of one of the small diameter
circles that is on the top side of the rail. Some of the rails also had
cracks between the holes and a few had so many cracks that some of the brass
had fallen off. I only found 1 rail with a crack on the small diameter
circle on the bottom side of the rail that did not have also have cracks on
the top side. Most of the rails had cracks on the top side only.

There were a few cracks in the valleys but these rails usually had long
cracks in the middle of the small diameter circles also

Some of the rails had cracks between the holes and a few had cracks on both
of the top small diameter circles.

None of the badly cracked rails had visible cracks in the dowels.

Steinway appears to have used different thickness of brass at different
times. There were cracked rails with both thick and thin brass.

I only have 4 regulating rail rails (some of my customers want there old
rails back) but these all have cracks in the center of one small diameter
circles.

Of the dowels I have replaced only a couple had any cracks and these were
only a few holes in length.

I have found a fairly wide range of inside diameters in the brass rails when
I have replaced dowels.

My conclusion based on what I have observed are.

The idea of screw pressure being one of the contributing factors in causing
the cracks is probably right since almost all the cracks are on the side
with the screw holes. I am not sure that it is over tightening since I have
replaced dowels that were over tightened to the point of stripping out the
wood without cracking the brass. Over tightening can not explain the
cracking of regulating rails.

I think probably a major cause of cracking is the dowel being too large for
the brass rail. This might be caused by inconsistency in manufacturing, high
humidity, or inconsistency in the wood in the dowel.

I think there is something about the way the rails are made that introduces
the most stress in the brass in the middle of the small diameter circles.

John Dewey
jdent@soltec.net