New Tracks for Bradleys, Abrams Tanks

New Tracks for Bradleys, Abrams Tanks
InsideDefense.com NewsStand | Libby John | May 24, 2006
The Army's Tank Automotive Research, Development and Engineering Center is developing new track systems for two major Army programs that have seen action in Iraq, a center official told Inside the Army May 17.

The new tracks for the Bradley Fighting Vehicles and Abrams tanks are currently going through tests at the Army's Yuma Proving Grounds, AZ, said Mike Blain, team leader for TARDEC's track and suspension team. The program managers for the heavy brigade combat team and the Tank-automotive and Armaments Command are also participating in the development of the tracks.

The objective of the track system is to provide “flotation and propulsion” of heavy combat vehicles over off-road conditions, he said. The track system is a mechanical system composed of individual segments called shoes. Each shoe is connected to the adjacent shoe by a track pin, end connectors and center guide assemblies.

The Bradley's new XT161 track system is designed to handle the weight the vehicle gained over the past several years because of the new add-on armor, weaponry and communication systems that have been added. When the vehicle was first fielded about 25 years ago, it weighed 25 tons. Its new capabilities increased the weight to 36.5 tons.

In Iraq, the track system had “very unacceptable levels of performance,” Blain said. “Normally it lasts around, let's say 2,000 miles before it wears out. Overseas, we were seeing it wear out at approximately 400 miles, prompting the government to initiate a new track system.”

He said the Army has applied short-term fixes to the track system. For example, the track bushings, the components of the track which failed first, were fixed. The bushing is an elastomer ring or doughnut used to isolate the track pin from the wall of the track bodies binocular tube, Blain said. The bushing prevents “metal to metal” contact that can quickly fail the steel track body through abrasion.

The problem with the current track is that it was not designed to handle the weight the current Bradley vehicles carry. The tanks “just increased in weight to such an extent that it's overloading the base track,” he said.

The metal pin was driven into the bushing, which was made out of rubber, Blain said. The pin was driven into the steel of the front binocular tube, the front connection to the rear of the next track.

“Once you receive a metal-to-metal contact of that pin made of high strength steel against the forged wall of a binocular tube, it's only a matter of time before it wears away the binocular tube wall and pulls through,” Blain said. “Once that happens it's only a matter of time before you have a catastrophic failure where the track separates and you have a mobility kill.”

The new track will have a double pin, or double block track, and the area of the bushing is designed to have a longer lifespan, he said.

The XT161 track system was tested last summer, and the pin that connected one track to the next developed a hairline crack, he said. The track was rebuilt using induction hardened pins, and that track will be evaluated this summer.

Induction hardening is a method used to harden the surface properties of steel, Blain said. The metallic object is exposed to extremely high temperatures that result in an extremely dense and wear resistant surface. In this case, an electric field is used to heat and harden the steel pins.

For the Army's tanks, TARDEC is working on the Abrams Enhanced T158 Track. There are two track systems being worked on: a non-interchangeable 5,000 mile track system and an interchangeable 3,000 mile track system.

The 3,000 mile track will be completely interchangeable with the existing track fleet and the 5,000 mile track cannot be put into the existing fleet. Both tracks are being tested at the Yuma Proving Grounds, and the program manager for the heavy brigade combat team will decide which direction to go in, Blain said.

Both tracks are going through durability tests, which will include scenarios on pavement, cross-country and rough off-road conditions, he said. They will also begin engineering tests later this year. Those tests examine the performance of the track, such as how fast it breaks, how well it climbs a hill and side slop performance.

Testing for all the tracks are being done in the summer because it is a more demanding time of the year, he said.