Fan assembly

1. A fan assembly comprising:

(a) a metal outer chamber with a plurality of adjoining planar sidewall segments, wherein each planar sidewall segment forms an obtuse angle with the adjoining sidewall segments to form a tubular structure having a polygonal cross-sectional shape having at least five sides, the outer chamber defining a longitudinal axis extending between a first open end and an opposite second open end, wherein the outer chamber is formed by a first section part and a second section part mechanically fastened to the first section part, wherein each of the first and second section parts include at least two interior obtuse angles formed by the planar sidewall segments, wherein each of the first and second section parts includes a plurality of separate bent tab sections extending orthogonally from the planar sidewall segments in a direction away from the longitudinal axis to form a first end flange at the first open end and a second end flange at the second open end;

(b) a first adapter ring attached to the first end flange, the first adapter ring defining a circular outer perimeter;

(c) a second adapter ring attached to the second end flange, the second adapter ring defining a circular outer perimeter; and

(d) a rotatable fan assembly disposed within the outer chamber, the rotatable fan assembly being configured to move an airflow stream through the outer chamber from the first open end to the second open end.

2. The fan assembly of claim 1 , wherein the outer chamber has eight planar sidewall segments separated by bend lines to form an octagonal cross-sectional shape.

3. The fan assembly of claim 1 , wherein the first section part and the second section part have an equal number of planar sidewall segments.

4. The fan assembly of claim 1 , wherein the outer chamber first and second section parts each have a first side flange and a second side flange, and wherein the first side flanges of the first and second section parts are secured together by mechanical fasteners, and wherein the second side flanges of the first and second section parts are secured together by mechanical fasteners.

5. The fan assembly of claim 1 , wherein each of the planar sidewall segments is provided with the bent tab sections at opposite ends to form the first end flange and the second end flange.

6. The fan assembly of claim 1 , further comprising:

(a) an inlet cone secured to the first adapter ring;

(b) wherein the rotatable fan assembly is a mixed-flow type fan assembly having a rotor inlet adjacent the inlet cone.

7. The fan assembly of claim 1 , further comprising:

(a) a motor plate mechanically fastened to the outer chamber, the motor plate being configured to support a motor for driving a fan wheel of the fan assembly;

(b) a motor cover for covering the motor and being mechanically fastened to the outer chamber, the motor cover being formed from a plurality of planar segments;

(c) a belt seal housing mechanically fastened to the outer chamber proximate the motor plate, the belt seal being housing a belt extending through the outer chamber and coupling the motor to the fan wheel.

8. The fan assembly of claim 1 , further comprising:

(a) an inner chamber having a plurality of planar sidewall segments that together form a tubular structure with a cross-sectional polygonal shape, the inner chamber being disposed within the outer chamber and supporting the rotatable fan assembly; and

(b) a bearing plate securing the inner chamber to the outer chamber, the bearing plate being mechanically fastened to the inner chamber and to the outer chamber.