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New 'milk stool' design may save dollars, backs

by Don Branum
U.S. Air Force Academy Public Affairs

6/2/2011 - U.S. AIR FORCE ACADEMY, Colo. (AFNS) -- A C-130 Hercules ramp support platform designed by four cadets here in May could save not only Air Force dollars but also the backs of the loadmasters who currently drag around 75-pound monstrosities, officials said.

The newly designed "milk stool," as the ramp support platform is called, would weigh 20 pounds, while supporting a load of up to 61 tons, according to a presentation May 5 by Cadets Aadit Patel, Zachary Peters, Jeremy Robben and Joshua Yeaste to the Air Force Academy's Department of Mechanical Engineering.

The department has begun discussions with the Air Force engineering authority at Robins Air Force Base, Ga., to determine testing requirements for the new milk stool, said Maj. Trent Greenwell, a mechanical engineering instructor who served as the cadets' adviser for the redesign project. The new design could be incorporated into a technical order supplement as early as 2012, depending on when the milk stool fulfills the test requirements.

The cadets began their project in the spring semester as part of their Mechanical Engineering 499 class, an independent study on one of several topics approved by the department head.

Cadet Peters, now a senior with Cadet Squadron 24, said the ramp support platform interested him because of its potential application to the operational Air Force.

"One day, a loadmaster could be using what we designed," Cadet Peters said. "This could help the C-130 community."

Major Greenwell guided the four through a systems engineering process that included preliminary and critical design reviews, development of a prototype and procedure validation and verification.

The cadets began their semester-long project by researching users' requirements. To find out what loadmasters needed from a milk stool, they visited the 52nd Airlift Squadron, part of Air Force Reserve Command's 302nd Airlift Wing at Peterson Air Force Base, Colo.

"While in a deployed environment, a loadmaster may lift the milk stool more than 10 times on a normal mission," said Master Sgt. A.K. Roberts, the loadmaster superintendent for the 52nd Airlift Squadron at Peterson AFB. "That may not sound like much, but when you take into account the heat and hydration issues that come with flying these missions, a lightweight design would help tremendously."

Loadmasters must also lift the milk stool over cargo or carry it outside the aircraft and in through the crew door due to the cargo configuration, a process that Sergeant Roberts described as "very cumbersome."

In their Feb. 15 preliminary design review, the cadets concluded the new milk stool must support at least 27,700 pounds without failing, and be durable enough to survive the rough working environments in which C-130s take off and land.

It must also weigh 50 pounds or less, and preferably less than 35 pounds, Cadet Peters said.

"It has to be quickly deployable for combat environments," Cadet Peters said. "And it has to function anywhere in the world, from deserts to tropical environments to the Antarctic, because C-130s fly to all of those locations."

The team brainstormed ideas, including an inflatable bag and a one-column support structure.

They faced both budgetary and time constraints, Cadet Peters said.

"We took our timeline and (asked), 'What's feasible?'" he said.

They presented their ideas in the preliminary design review and opened the floor to suggestions from mechanical engineering instructors and staff.

They got support from instructor Maj. Matthew Obenchain and materials scientist Megan LaBahn, along with others, Cadet Peters said.

After the first review, the cadets split their responsibilities into the categories of materials, manufacturing, modeling and analysis. Cadet Peters took charge of materials.

"I started out with 7075 aluminum for initial analysis," he said. "I used some information that Ms. LaBahn gave me."

Aluminum 7075 is an alloy of aluminum, zinc, magnesium and copper used in some airframes. Unfortunately, it turned out to be too rare for the cadets to procure it, and the second option was also out.

The group went back to the drawing board.

"We ended up going with 6061-T6 aluminum," Cadet Peters said. "It's lightweight, really cheap and readily available in sizes we could work with."

While the 6061-T6 metal has less tensile strength than 7075 aluminum, it proved to be sufficient for the cadets. Their design, which incorporates four columns with flat top and bottom surfaces, withstood nearly 4.5 times the required weight without permanent deformation, Major Greenwell said.

The team received the prototype just in time to present it at the Colorado Springs Undergraduate Research Forum, where it received glowing reviews, Cadet Peters said.

"People loved it. Everyone who was there for our presentations wanted to stay afterward and talk to us about it," he said.

One reason why visitors to CSURF liked the prototype might be the production cost, which is anywhere from $100 to $150 apiece, Major Greenwell said.

"A maintenance shop could build it from readily available parts," Cadet Peters said. "They could weld it together ... and put the wooden deck on top of it to fit the ramp if they needed a spare."

The simplicity and ease of construction would allow Air Force officials to bypass the process of seeking outside vendors or sourcing a contract to build the new ramp supports, Major Greenwell said.

Cadet Peters said he was pleased with the outcome of the project.

"I enjoyed the project a lot," he said. "Our team really worked well together, and Major Greenwell and the people in the (mechanical engineering) lab helped us out a lot. We worked hard, but we had fun, and we're happy with what we got out of it."



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