GRADUATE AEROSPACE LABORATORIES
California Institute of Technology
Division of Engineering and Applied Science
1200 E. California Boulevard, MS 105-50, Pasadena, CA 91125

Historical
AWT construction
Ten-Foot Tunnel

AWT Construction
Beginnings
Preparations
Test Section
First Wave
Second Wave
Fan
Test Section Walls
Exteriors
Interiors

Lucas AWT Construction

Assembly of the Test Section

The test section is the part of the tunnel in which models are mounted for testing.  In most wind tunnels, this is a rigid tube with framework all around it, much like the return sections in the Lucas tunnel.  In our test section, however, the floor and ceiling are flexible and adjustable, while the side walls are rigid.  This requires a different kind of structure, which is shown in the images below.  The test section frame provides attachment points for the rigid side walls,  and crossmembers for attachment of the actuators along the top and bottom.  All of frame's interior space must be kept clear for the actuators, walls, and of course, the airflow.  To avoid interference with the windows, there are also no intermediate supports along the length of the test section.  Therefore, deep I-beams had to be selected to support the load and minimize deflections over the 25-foot span.

The primary frameworks of the top and bottom are mirror images of each other, long I-beams with square tubular crossmembers.  However, to simplify alignment and welding, the lower framework was built upside-down,  The legs were welded on, and then the structure was flipped over using the overhead gantry.  The main columns were set into place and welded, and then the upper assembly was lifted into place, aligned, and welded.

Once the upper structure was welded into place, we decided to "top" the test section.  The Topping-Out ceremony, in which an evergreen tree (and usually a flag) is placed atop the highest point on a structure, is a common practice in the construction industry.  The tradition dates back many centuries,  to times when all structures were built from wood, and spirits were believed to live in the trees.  The topmost leafy branch from the tree used to build a house was placed atop the highest point, as a symbol of respect and thanks to the spirits. 

Click on images to enlarge.

Bottom of test section being flipped over into its proper orientation.	Bottom of test section upright, with foot plates installed.
First pair of columns positioned for hoisting.	First pair of columns clamped to hoisting beam.

Columns squared and attached to bottom of test section.	Hoisting upper part of test section into place.
Topping of the test section.