Mr. Tuttle indicates that he is mathematically challenged, and wants
a quick and easy formula for estimating tracker bar tubing.  I am not
mathematically challenged, but would suggest that a formula isn't going
to work for all pianos.  If the tubing in all pianos is run in about
the same way, perhaps.  But I suspect that is not the case.

In any event, if I were doing it, I'd just take a look at the layout
and see if the change in length of the tracker bar tubes appeared to
be linear from the longest to the shortest.  If so, average the length
between the longest and shortest (in John's example, 10 + 24 divided
by two equals 17 inches avg.) then multiply this by the number of tubes.
Throw in 10% for error and 10% more for waste, and you got it. Then,
of course, you have to add all the control tubing in.

If the change in length of the tubes is not linear, then you aren't
going to get a simple formula.

These days I don't worry too much about calculating everything to a
gnat's eyebrow.  I just swag it (on the high side because I hate to run
short).  It's always nice to have extra materials for something later
anyway.

Ray Fairfield