SSC-Natick Press Release
U.S. Army Soldier Systems Center-Natick
Public Affairs Office
Natick, MA 01760-5012
Contact: Chief, Public Affairs Office
Date: April 2, 2003
Boots take a beating
NATICK, Mass. -- After thrashing through 100,000 cycles in a puddle of water, checking for a leaky boot is as simple as removing the piece of absorbent paper tucked inside.
"We beat up boots here. We beat the heck out of them," said Michael Holthe, lead project engineer for footwear programs at the U.S. Army Soldier Systems Center here. "They have to be durable, but also help the person do their job. You could make a boot that lasts forever, but you really couldn't use it. It wouldn't be functional for the soldier."
The whole shoe flexer, modified for water penetration, is an often-used part of a collection of merciless machines gathered in the Footwear Performance Laboratory, the only facility of its kind in the Department of Defense. In operation for more than a year, the idea is to have one central location for technical testing or research and development for all military footwear, Holthe said.
"We're always trying to improve our users' products," he said. "We're lucky to have a facility with two trained people dedicated to studying the human performance aspects of footwear and materials testing."
Holthe and Valerie Banville, lab technician and project engineer, work primarily with the Army, Marine Corps and provide engineering support to Defense Supply Center-Philadelphia, but have helped the Navy and Air Force. Other jobs include testing footwear for law enforcement officers and firefighters under contract by the National Protection Center at the Soldier Systems Center. When time permits, industry can pay to use the lab's equipment.
One of the bigger contracts currently is the Army's new Infantry Combat Boot. Holthe and Banville are taking product demonstration models from different manufacturers that are submitting bids to check that they pass existing performance specifications.
When they're not checking product models, they may be adjusting existing performance standards to enhance performance, safety, comfort and durability, or researching and developing new boots.
"When it comes to boots, it's a different sort of item," Holthe said. "They can affect oxygen consumption, fatigue, and marksmanship in addition to lower leg injuries. We need to make footwear function in many environments but also protect the soldier and help him do the job more efficiently."
Military boots are categorized as extreme cold, cold-wet, temperate, hot weather wet and dry, and blast protective. The only footwear they don't currently handle is chemical-biological protective.
Besides the Infantry Combat Boot, other projects in progress or upcoming are improved hot weather combat boots for the Army, the Army's new modular footwear program and improving the current blast protective footwear used by Army engineers.
"In the past we would always tell industry what to make," Holthe said. "It's changed in that we do a lot more work with industry in determining what new footwear and component technologies are available and how we can implement them into our footwear quickly and efficiently to give our users added capability and safety."
Their research is sometimes collaborative between the U.S. Navy Clothing and Textile Research Facility and U.S. Army Research Institute of Environmental Medicine, both located on the installation, as well as the Textile Testing Facility at the Natick Soldier Center.
Equipment in the lab was assembled to create a specialized ability to test and evaluate footwear and checks heat insulation, shock attenuation, pressure distribution, water penetration, flex resistance and dynamic stiffness.
"None of this replaces field testing, but it helps us know if an item is going in the right direction. We can do the pre-testing here so we don't waste time," Holthe said.
A dry and wet testing version of the whole shoe flexer sits atop a black counter inside the lab. Once it's set up for flex angle and fitted with a boot, the machine pivots up and down along the boot's natural flexing line for a 12-hour test, cycling 140 repetitions per minute to assess the resistance of an item of footwear to repeated flexing. The boot is visually examined for damage. It produces results similar to having a soldier wear the boot in months of field use, according to Holthe.
For the wet version, only one intact boot is placed inside the machine where a stainless steel tank is filled with enough water to cover up to the ankle. It's pass or fail if the paper inside remains dry or gets wet.
"It does its job great," Holthe said. "The test we used to use didn't provide a real-world type application. This lets us know if it stays waterproof during wear and tear."
Similarly, the dynamic stiffness tester measures longitudinal and torsional stiffness, but unlike the flexer, data can be collected.
"What we can do is determine the flexibility to see how a boot changes as it's broken-in and then find the break-in point," Holthe said.
Used more as a research and development tool, the impact tester slams a steel piston onto a separate midsole or onto the entire manufactured boot sole system to assess shock attenuation, energy return and material deformation. A computer registers deceleration, a measurement of how much the material is absorbing the impact and time it takes to stop and rebound to its original shape.
"We're trying to find a way to protect our users. Much of the population currently entering the military is used to wearing cushioned soles," Holthe said. "Research has shown that, even with seasoned soldiers, providing enhanced shock attenuation leads to less lower leg injury, less down time for the soldier which translates into less money lost by the military as well as added capability for our warfighters."
Also helpful in research and development, the in-shoe pressure measurement device records data from sensor-embedded insoles placed inside footwear worn by a human research volunteer. By measuring impact and pressure along the entire length of his foot, researchers have an uncommon capability.
Data is logged with a portable device carried by the research volunteer either in a lab study walking on a treadmill or in a field study.
Heat insulation is another property the lab can measure. The heated sandbath consists of a metal tray incorporating a hotplate filled with sand. The entire sole is covered in sand heated to 150 degrees C. A probe is placed inside to measure the temperature increase. The standard is a temperature increase no higher than 22 degrees C in 30 minutes.
More than gauging comfort, the sandbath helps assess flame and heat protection required for aviators, according to Holthe.
The Army's Infantry Combat Boot is an example of the success of the footwear program, which hopes to expand in capability by bringing in more equipment and conducting more tests.
"To have one style of footwear for 450,000 people and get more than an 80 percent approval rating makes us feel like we're moving in the right direction," Holthe said.
For more information about SSC, please visit our website at http://www.natick.army.mil.