In defense of TAR (Was S&S retrofit rails ?)

[John Hartman]

In defense of TAR

I think the tubular action rail (TAR) works well and serves a definite
function. I believe the rails were designed to virtually eliminate wood
movement problems. This design dates from the 1870 and if you are
familiar with the wood rails used in the Steinway grand piano before
this time you can appreciate what a huge improvement they were. The
brackets on the earlier wood rails were glued to the key frame. The new
design allowed for easy access to the keys and the removal of the upper
part of the action as a subassembly. The old wood brackets and wood
rails exhibited undue wood movement that effected the stability of
action regulating. The new tubular rails eliminated wood movement
between the rails. They also were rigid and would maintain alignment
when removed from the key frame. Tubular rails are at least as stiff as
these earlier wood rails.

Maybe another aspect can be seen in how the new rail shape brings the
action centers closer inline along the grain to where the flange is
screwed to the rail. This will reduce the amount the flange centers will
move in relation to the rails. Also the rail profile allows the flange
screw to pass through less wood. The thickness of the Renner Steinway
hammer flange is less than 6mm. The same measurement on an average flat
rail flange is 8mm. The Steinway design reduces the stresses on the
flange due to wood movement. There are other factors as well such as
allowing for a lower string height and less room needed at the breaks
for the rail to fit. Ever notice how hard it is to access the front
screws on smaller M&Hs and how much the keys have to be altered to
accommodate the flanges.

Here are some pointers on working with TARs.
1. Use the pre-glued felt sold by Steinway under the hammer shanks. This
will help the shanks stay adjusted.
2. Use shanks that have screw holes larger than the screws to help with
spacing. Renner parts come this way but some others will need to be
re-drilled.
3. Use high quality cut thread hammer flange screws. Cost more but will
reduce hole stripping.
4. Do not over twist shank flanges to space. Instead travel the shanks
in areas were the string pacing is to close together or erratic. The
hammer should be evenly space at rest but may travel a little to hit the
strings.
5. Space the strings to the hammers in the De-capo area.
6. For fine spacing get the spacing tool Renner sells. Grind the sides
to fit between the flanges better.
7. Either set up to replace action rails or find some one to do it for
you. 

John Hartman
Beacon NY
Rebuilding Steinway piano with minimum re-engineering since 1979.