Sandia LabNews

Sandia completes ground-up redesign of new DOE Armored Tractor

[Armored tractor]
THE FIRST PRODUCTION UNIT Peterbilt Armored Tractor rolls up Central Ave. in Albuquerque on a test drive. To the untrained eye the new tractor is indistinguishable from a commercial 18-wheeler. (Photo by Randy Montoya)

DOE special agents who transport weapons cargo across the country in armored 18-wheelers are getting new, more comfortable rides this year as the first of 51 improved Armored Tractors (ATs) rolls off the production line.

DOE special agents who transport weapons cargo across the country in armored 18-wheelers are getting new, more comfortable rides this year as the first of 51 improved Armored Tractors (ATs) rolls off the production line.

The rigs were redesigned from the ground up by a Sandia team of engineers with feedback from the federal agents who, during a typical mission, often must drive the trucks and remain vigilant against hostile attack for several days at a time without a break. Predictably, a primary concern is ergonomics.

But the new rigs feature more than just improved comfort. They’re also lighter than the previous design, and in many ways safer. They incorporate numerous communication-system upgrades.

And, says design team leader Robert Baca (5851), unlike the previous armored trucks that were easy to spot because of their "Wells Fargo" appearance, the new Peterbilt rigs blend in with the rest of the 18-wheelers on the highways, which has obvious benefits when you want to avoid attention.

The new tractors are purchased from Peterbilt in stripped-down form and modified to Sandia’s specs in a Honeywell plant near the Albuquerque International Sunport. Sandia has supported the nation’s transportation safeguards needs since 1970 when DOE’s predecessor agency, the Atomic Energy Commission, asked then-Sandia President John Hornbeck to develop technologies to reduce the vulnerabilities of weapons shipments. Labs engineers designed the first two generations of ATs in 1971 and 1984.

Today Sandia remains the design agency responsible for the development of and modifications to the Armored Tractors and their custom armored trailers, called Safeguards Transporters, under the guidance of DOE’s Transportation Safeguards Division (TSD).

The new tractor was created by Sandia for DOE in an accelerated 21/2-year design project guided by a set of requirements from the Armored Tractor Working Group. The working group included DOE federal agents; representatives of TSD, Sandia, and Honeywell; and Armored Tractor maintenance personnel from Sandia, Mason & Hangar, Pantex, and Lockheed Martin Energy Systems, Oak Ridge.

Marmon, the company that manufactured the tractor the previous AT design was based on, discontinued that model, so a new design based on a different model was needed. In addition, says Robert, a lot of data had been gathered over the years that showed there were some real ergonomic issues with the previous design, especially considering the amount of time the federal agents spend in the rigs.

Improved comfort, safety, & more

With the added communications equipment and armor, the Marmons were cramped and dark, with very little headroom, leg room, or other amenities. The bunks were uncomfortable. Some driver controls were not easily accessible.

In contrast the new Peterbilt tractor has:

  • An air-ride-suspended integral cab sleeper with windows for a comfortable ride.
  • 12 inches more headroom in the cab than the Marmon.
  • A rounded-down hood, wider driver field of vision, and reduced windshield glare for improved safety.
  • A better air conditioning system and improved air flow.
  • Communications equipment consolidated in the cab and sleeper area, providing more room for occupants and improved accessibility for maintenance.
  • A modular communication system that allows for upgrades as technology evolves.
  • Reduced cab noise partly as a result of exhaust pipes being routed underneath the frame rather than mounted to the back of the tractor.

Designing an Armored Tractor is more complicated than just adding features until it meets the requirements, adds Robert. A lot of engineering work went into the new design.

"Every improvement presented a new set of design challenges," he says. "It wasn’t just buy a bigger tractor and go to town. We had to use Sandia’s capabilities across the breadth of the laboratory to get the design right."

Engineers in Sandia’s analytical testing groups, for example, developed a dynamics model that quantified ride comfort — the amount of vibration from the road that is transferred to the occupants — based on tractor weight, suspension type, axle width, chassis and frame length, and other variables.

The new custom composite armor and lightweight armored glass was designed and developed at Sandia with extensive testing at Sandia’s Ballistics Test Facility.

Acoustic sampling inside the cab guided decisions about features that reduce cab noise, "which is a serious problem when you’re driving several days straight," Robert says. "Exceeding the OSHA standard is one thing. Establishing a level of comfort is another."

Vibration testing using human-like dummies helped assess the response of the sleeper mattress to road conditions and showed that the old spring mattress created a resonance that resulted in a bouncier ride for an agent trying to sleep. The Peterbilt’s new viscoelastic foam mattress mitigates vibrations and "holds" the person sleeping. One of the early design challenges was satisfying the ergonomic need to relocate the communications equipment within the constraints of the Peterbilt cab, says communications engineer John Barnum (5852). And to reconfigure the antennas on top of the cab, the communications team had to investigate and test the effects of the tractor’s fiberglass structure, metallic paints, and vehicle profile on antenna performance.

Designing a super truck

Robert says he never dreamed his job might include helping design a super truck. Seeing the new AT go from ideas on paper to a tangible product hitting the road, and watching all the people in different disciplines doing their jobs in parallel to make it happen, has been extremely satisfying, he says.

Also, having the engineering and fleet support facilities (Sandia) in the same city as the production facility (Honeywell) "played a huge role in Sandia being able to complete the redesign from a piece of paper to the first unit in less than two years," he adds. "It meant a lot having the designers, the engineers, the maintenance people, and the federal agents right there to solve problems and come up with ideas on the spot." A total of 51 new rigs are scheduled to roll off the production line and into the TSD fleet by 2003.

Last modified: February 29, 2000