[pianotech] Fixing flexy stage dolly

[Norman Cantrell]

Mark
I forgot to mention that the finished product was painted black and is practically unnoticeable when the piano is on stage.  If anyone asks you can always claim that you had to install a "spit valve" on the piano.
Norman

--- On Mon, 1/28/13, Mark Schecter <mark at schecterpiano.com> wrote:

From: Mark Schecter <mark at schecterpiano.com>
Subject: Re: [pianotech] Fixing flexy stage dolly
To: "pianotech at ptg.org" <pianotech at ptg.org>
Cc: "pianotech at ptg.org" <pianotech at ptg.org>
Date: Monday, January 28, 2013, 5:52 PM

Norman, Thanks. 
The possibility of conserving sound energy had crossed my mind, but it's great to hear you actually noticed an improvement. 
So you're using 1/2" OD threaded rod, slip fit into 1/2" ID pipe, and the nut threading down the rod provides the length increase that pushes the dolly down, right? Excellent!

~Mark Schecter
On Jan 28, 2013, at 3:30 PM, Norman Cantrell <normancantrell at sbcglobal.net> wrote:

Mark
I have encountered this same problem in the past.  I made an adjustable post from 1/2" black pipe, a pipe floor flange, a 1/2' threaded rod with two locking nuts and a washer.  The threaded rod is epoxied into a small block of pinblock material with a third nut to spread out the contact load to the beam under the piano.  It is placed in the center of the spider and contacts the beam.  You unscrew the threaded rod like a screw jack to make the dolly arms parallel to the floor.  The piano then becomes very stable and you will also notice an increase in the volume under fortissimo playing as you are removing the spring that is absorbing the sound energy.
Norman Cantrell

--- On Mon, 1/28/13, Mark Schecter <mark at schecterpiano.com> wrote:

From: Mark Schecter <mark at schecterpiano.com>
Subject: [pianotech] Fixing flexy stage dolly
To: "Pianotech List" <pianotech at ptg.org>
Date: Monday, January 28, 2013, 3:39 PM

Hi, all.

I take care of a Steinway D at a local school which rides on a stage dolly. Yesterday I tuned for a pianist who found the movement of the piano under heavy playing to be disturbing. When he would play big octaves in both hands, the piano shook in a way he could feel through the keyboard. As Jurgen mentioned recently, the arms of the dolly are like big leaf springs. I have an idea to improve this for which I'd like to get your feedback.

Because the piano legs rest on the ends of the dolly arms, outboard of the wheel location, the wheels act as fulcrums, and the weight of the piano lifts the central arm-connecting part of the
 dolly. If you press down on the rim of the piano, the center of the dolly rises toward the main rim braces. I am thinking if I put a vertical post between the dolly and a main rim brace, it will greatly reduce the dolly's freedom to move, thus less flexible. I would make it long enough to be in compression, rising from the central arm connecting plates of the dolly, upward toward the underside of the brace, and wedged between the two.

Has anybody tried this? What were the results or problems? Do you have any suggestions for improvements to this idea? Thanks very much!

~Mark Schecter
<Assembled post.jpg>
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