Sizing longer wind trunking

Everyone discussing a remote organ blower installation has agreed that
a remote blower installation requires larger diameter wind trunking.
The reason is, as Mr. Bullock and others have pointed out, is that
pipes produce pressure losses due to friction, which are greater as the
pipe length increases, but are smaller as the pipe diameter increases,
for a given volume of flow.  If you want the same volume of air with a
longer trunk, the trunk has to be bigger.

In order to put some numbers to this concept, I have run a pipe sizing
program to create a table of equivalent pipe sizes versus length.  I
used PVC pipe for the smaller sizes, and steel pipe for sizes larger
than PVC pipe is made.  Although different materials have different
"Friction factors", the proportional lengths are approximately the
same, so this table can be used as a guide, as long as the new trunk
material is at least as smooth as the original.

For 10' of 1" pipe, 84' of 1-1/2" pipe, or 283' of 2" pipe has the same
pressure loss for the same flow.  The following entries have the same
format.

For 1-1/2" pipe, 34' of 2" or 232' of 3" are equivalent to 10'.
For 2" pipe, 69' of 3" or 258' of 4" are equivalent to 10'.
For 3" pipe, 39' of 4" or 293' of 6" are equivalent to 10'.
For 4" pipe, 70' of 6" or 273' of 8" are equivalent to 10'.
For 6" pipe, 40' of 8" or 144' of 10" are equivalent to 10'.
For 8" pipe, 34' of 10", 81' of 12" or 128' of 14" are equivalent.
For 10" pipe, 24' of 12", 39' of 14", 79' of 16" or 140' of 18"
For 12" pipe, 16' of 14", 33' of 16", 59' of 18" or 98' of 20"

One can extrapolate from these figures for any other cases.

Answering Mr. Bullock's question of yesterday; in pipe sizing, one adds
equivalent lengths of straight pipe for each elbow.  Use this table,
copied from the universally used "Crane Handbook".  When planning a new
equivalent trunking run, don't forget to allow for the elbows that were
in the original installation.

For each additional 1" elbow, add 2.7' feet of pipe.
For each additional 1-1/2" elbow, add 4.3' feet of pipe.
For each additional 2" elbow, add 5.5' feet of pipe.
For each additional 3" elbow, add 8' feet of pipe.
For each additional 4" elbow, add 12' feet of pipe.
For each additional 6" elbow, add 16' feet of pipe.
For each additional 8" elbow, add 20' feet of pipe.
For each additional 10" elbow, add 26' feet of pipe.
For each additional 12" elbow, add 31' feet of pipe.

These are only general guides.  If anyone has is planning a specific
new installation, e-mail me the diameter and dimensioned layout of the
old installation, and the dimensioned layout of the new installation,
and I can run the program to calculate the new size required.

But don't forget Mr. Loesch's and Mr. Bullock's warnings about other
possible effects of a remote wind supply with long, large trunks.  As
an example, many Aeolian residence organs had large reservoirs, or had
the blower remotely located in a distant cellar.  Each windchest that
had a trem also had a pressure regulator mounted directly at the
windchest inlet.  It was not really needed for pressure control; it
only took the already well regulated pressure from 4" WC to 3-1/2" WC.
But it was needed to isolate the chest from the supply system; without
it, the trem pulses would be lost in the huge volume of the reservoir
and trunking system.

Richard Vance