Brass Rail Repairs

[Tom Cole]

BSimon1234@AOL.COM wrote:
> 
> I was wondering, however, why the piano companies did not anneal the original
> rails. As you have shown, they easily could have, and I cannot imagine that
> they did not know about it. 
 

I don't imagine that the manufacturers thought much about how the rails
might work harden. It's such a unique application of the material.


Do you think that over time, continuous impact
> stresses from playing might bend the annealed tabs out of line? You are
> gaining a ductility and losing hardness. Do you forsee any downside risk?


This thought had occurred to me. Brass rails appear to have been stamped
and so I expect that they start out partially work hardened. But my
sense, having bent the tabs up and down with vicegrips, is that the
annealed tongues are plenty strong enough to do the job and might even
last longer than the originally made parts.

I don't think that hard playing alone could bend the tabs out of line
enough to deform them. Rather, I would be more suspicious of overzealous
tightening of the butt plates being the culprit. The reason is because
of the way they break. The groove near the end of the tongue is the weak
spot and the ends of this horizontally-mounted double flange break
downward, away from the pressure of the butt plate and in the opposite
direction of the upward striking jack. The butt plates break at the
fixing screw from the pressure of the screw. Note that on the piano I'm
repairing, at least one of the _damper_ tabs was broken from "natural
causes" (two more on the test section but I might have caused
intentionally). Maybe the manufacturers should have published torque
specs for tightening butt plates.

The notion that piano technicians may be partly or wholly responsible
for brass rail breakage only dawned on me as I wrote the above
paragraph. I am moved to check if the action in my shop needs to have
its screws _loosened_!

Excuse me while I put the impact wrench away.

Tom

-- 
Thomas A. Cole, RPT
Santa Cruz, CA
mailto:tcole@cruzio.com