The higher the total sp losses in a duct system, the more powerful
the collector must be to overcome them. In the original scenario, the
woodworker would have 0.72 in. sp loss per foot. Over 26 ft. of
straight duct (no elbows or turns), this would amount to a whopping
18.72 in. of sp loss—enough to choke even a huge collector. By way
of comparison, a heavy-duty, 3-hp collector can handle only about
9 in. of sp loss when moving 400 cfm (about what you’d need for a
shaper and less than is recommended for a bandsaw).
I told the woodworker to stick with a typical small-shop dust col-
lector and connect it to his machines with large-diameter ductwork. A
5-in. main line with 4-in. branch lines should be about right. These
ducts are large enough to carry the volume of air and chips from most
shop machines while maintaining recommended air velocities. And for
the relatively short 26-ft. run he is planning, I’d guess a 2-hp unit
should be able to handle the modest friction losses in the 4-in.- and
5-in.-dia. ducts.
—SANDORNAGYSZALANCZY,Santa Cruz, Calif.,
from a question by Ted Baca, Evans, Colo.
CHAPTER ONE