Hi All, It's interesting to note that there really is no easy formula
for figuring out how much tubing is needed to retube a trackerbar.
There are simply too many variables.
It seems that most people accept the general formula
[ (S+L)/2 ] x N = T
as relatively accurate. And once I saw it again, I did remember it
from my early high school days... ;-) But that was over 40 years ago
and I've never had the need to estimate how much tubing I would require
to do a particular mechanism.
Like Spencer Chase said, "Since tracker tubing comes in 100 foot
rolls and since an upright is going to use more than one roll,
a precise formula would probably not be of much practical use."
However, at Player-Care, I sell tubing in lengths as short as two feet,
and I've had people order 11 feet and 111 feet of trackerbar tubing.
So, having a formula so that people can estimate what they need _is_
useful, to a degree.
I think most of the rebuilders in this group would be a little
surprised by the number of requests I get from people who want to buy
a 'retubing kit' for their player piano. I explain to them that
no one has ever taken the time to record the various sizes and lengths
required for the 70 or so mechanisms, and that they will have to
measure the fittings and estimate the lengths. While some of them
act a bit discouraged to learn that a kit isn't available, the vast
majority do the work and submit an order.
The mechanisms that seem to confuse people the most are the Gulbransen
and the Lauter-Humana. This is especially true if the tubing has
already been removed or if it is badly cracked and falling out of
the piano. The problem is that those mechanism are designed to 'fold
open'. And if the mechanism is retubed in the 'upright' (or unfolded)
position, the tubing will pull off when it's folded open.
It's always been a point of curiosity to me to know if the
manufacturers had a template for cutting the tubing for units like
the Gulbransen. Having seen perhaps hundreds of them, they all seem
virtually identical. And the tubing droops in such a fashion that it's
hard to believe that a factory worker could consistently lay the tubing
in such a precise manner year after year without a template.
On the other side of coin, I envision the worker whose sole
responsibility was to cut precise lengths of tubing and keep them all
in perfect order until they were installed. Or, the cut and install
each piece hour after hour, day after day, year after year... I can't
imagine having to do that job -- I'd go nuts in a week!
In closing, I want to thank everyone who contributed their ideas.
For what it's worth, Jack Breen was the first person to contact me
with the above formula, which has been included on the Tubing page at
Player-Care. Hopefully it will help some people figure out about how
much tubing they'll need for the trackerbar.
John A Tuttle
Brick, New Jersey, USA