New Stacell tensegrity structure
constructed in Langford atrium


A new tower honoring the memory of a former architecture professor is standing tall in the Langford Architecture Center atrium.

Designed by Ivan Farr, who earned a Bachelor of Environmental Design degree in May, the tower honors Alan Stacell, who taught architecture at Texas A&M for 40 years before his death from cancer in 2001.

The all-steel, 25-foot tall structure stands on a base used for the original tower honoring Stacell, a 43-foot tall edifice built in 2002 that was dismantled in July 2008 due to structural concerns.

Like its predecessor, Farr’s tower doesn’t use screws or nails to hold it together: its structural integrity is derived from the principles of tensegrity, one of Stacell’s academic interests.

The tower owes its structural integrity to 250 feet of galvanized steel cable running through steel pipe bound together by what Farr calls “propellers,” holders of a type that look like airplane propellers.

“These propellers serve in tension and the pipes in compression, while the cable threads the two elements together into a stable structure,” said Farr.

Materials for the tower were paid for by an endowment for a structure to stand in Stacell’s memory.

"Professor Stacell was in tune with his students and excited about teaching," said Patrick Winn, who was a senior architecture student when he began the original tower project. "As a result he instilled in us an incredible passion and in the process created an indelible legacy that lives on in the many students whose lives he has profoundly touched."

As a sophomore in Stacell’s structural design class, Winn was handed a sketch of a Stacell-designed tensegrity structure and asked to see if it worked.

Winn eventually developed a model of the sketch into the site’s original tower, which stood for 6 ½ years.

After it was dismantled, all that remained at the site was the anchoring concrete base. Rodney Hill, professor of architecture at Texas A&M and faculty advisor for the original tower project, was concerned the original tower would never be replaced.

“There was supposed to be a competition to select a new tower design, but I was worried that nobody besides faculty knew who Stacell was,” said Hill; then Farr came along.

Farr enrolled in an independent studio in the fall 2008 semester with Hill, focusing on theoretical structures.

“He knew what tensegrity was,” said Hill, who realized he had a student who could continue to honor Stacell’s legacy. “He could work independently and is a good designer. If Stacell had been here, Ivan would have been his star pupil.”

“I did a variety of scaled models of structural concepts, figuring out how to support something of an irregular shape,” said Farr, recounting his work in Hill’s studio.

About halfway through the semester, he said, he started designing vertical structures, then Hill suggested Farr create a design for a new Stacell tower.

Farr designed a structure roughly half the height of the original tower, as requested by the sponsors.

The new tower was fabricated and assembled at the Architecture Ranch at Texas A&M’s Riverside campus and had to be transported by truck whole to the Langford building. Both factors contributed to practical considerations about its height.

“It couldn’t have been made any bigger because when we raised it at the ranch, it came in a foot under the ceiling and it was within one-half inch of the maximum delivery truck space,” he said.

Farr’s initial designs of the tower called for high-strength plywood, but for structural and financial reasons, steel had to be used instead. 

“Purchasing carbon steel from local Aggie-friendly suppliers proved far more cost effective than importing prime plywood from other states,” said Farr.  “Choosing to construct the tower exclusively of steel gave one more crucial advantage, because it weighs less than wood in the manner used.” 

To give the tower the necessary stability with wood said Farr, significantly greater quantities of it would have to be used, whereas a 1/8” steel propeller weighing just a few pounds could serve the same purpose.  

Chuck Tedrick, digital fabrications manager at the Architecture Ranch, helped Farr assemble the tower in just a couple of hours, adjusting the amount of tension in the cables that ran through the pipes with winches underneath the tower’s base.

“Selecting the cable was a challenge, as it had to be sized in relation to the pipe’s inner diameter,” said Farr.  “A thin cable will rattle and be unable to provide the necessary shear resistance to the pipes in compression, and a thick cable will cause threading problems or may simply be too inflexible for general use.” 

Externally tensioning the final cables proved to be another challenge, he said.

“Not enough tension produces a flaccid structure, but overtensioning compresses the structure into failure,” he explained.

The biggest hurdle in the entire project came with obtaining the approval of an engineer.

 “An engineer had to sign off on the tower,” said Farr. “No signature, no tower. When I had visited with about 10 engineers who were hesitant to sign up on the project, I started doubting it would go through at all.”

He said engineers were reluctant to take on the liability issues the project presented.

“It took a very long time, months on end, where I was running around to engineers, hoping to get pointed in the right direction,” said Farr. “In the end we joined up with a local engineering firm and a university engineer from the physical plant.”

Hill lauded Farr for pressing on with the project.

“If Ivan hadn’t persevered, it never would have gotten done,” he said.

Farr thanked Shelley Holliday, an architecture lecturer, for her role in the project.

“She was an influence in the initial stages of my design and planning for the tower, and she gave me valuable advice on the sizing of the tower’s pipes and cables,” he said.

He also thanked Chuck Tedrick, digital fabrications manager at the Architecture Ranch. “He was a valuable part of the project for his input into the design of the tower, its assembly and delivery to Langford,” said Farr.

Others integral in making the tower a reality were engineers Thomas Gessner and Mikael Olsen, sponsors Jorge Vanegas and Rodney Hill, and suppliers Brazos Industries, Mack Bolt & Steel, Suncost Post-Tension, Harbor Freight and Texas Custom Coasters.

Farr’s memories of the original tower remain.
“I enjoyed the previous structure,” said Farr. “It was the pioneer for this project and a source of inspiration.”

- Posted: July 13, 2009 -

- the end -


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