[pianotech] Brands prone to breaking plates

[Floyd Gadd]

I had my first plate break last month.  It was an old Doherty full sized
upright, certainly near the end of its life cycle.  I had installed threaded
rod through the top of the plate and pinblock on my previous visit, and had
brought it up to pitch (a significant pitch raise, probably about 30 cents)
without incident.  On this tuning some pitchraise was again necessary, and
as previously, I used my standard overpull settings of 15% in the bass, 25%
in the tenor and 32% in the treble.  Pitchraise pass went without incident.
On tweaking the treble tuning during the second pass, I heard a sound like a
gunshot.  The treble was gone.  Most of the treble strings were off their
hitchpins.  The tenor was still pretty much in tune.

Doherty is a Canadian brand,and on debriefing with my mentor, I discovered
that they are indeed prone to plate breakage.  A little research on the list
archives confirmed this.  It gave me pause to think that a few days earlier
I had blithely done a 50 cent or more pitch raise on another deteriorated
Doherty, probably overpulling a full 25 cents in the treble at times.  (I'm
using Tunelab Pocket, using 25 cents as my maximum overpull on the non-wound
strings.)

Interesting to see this issue come up right now, as I loaded the replacement
piano into a UHaul trailer this evening for delivery tomorrow, prior to
checking the list.  It's only slightly earlier in its life-cycle than the
Doherty was, but still has some music left in it.

Floyd Gadd
Manitoba Chapter