News | Dec 6, 2017

Army’s ‘third arm’ rifle platform licensed to Tennessee engineering firm

With assistance from TechLink, Short Fuse Engineering licenses patent-pending design

News Article Image of Army’s ‘third arm’ rifle platform licensed to Tennessee engineering firm

Zac Wingard, a mechanical engineer at the Army Research Laboratory, explains the "third arm" body-worn weapon mount during the Association of the United States Army's Global Force Symposium in Huntsville, Ala., March 14, 2017. (Sean Kimmons/Army)

Update: On August 27, 2019, the U.S. Army was issued U.S. Patent 10,393,476.

CHURCH HILL, Tenn. – Dr. Justin Stacy focused on mobile robotic welding for shipbuilding applications during his 2013 doctorate in mechanical engineering at Tennessee Technological University, but now he’s working on an Army idea.

After a few years of teaching and work as a design engineer, the 35-year-old Stacy has founded his first business, Short Fuse Engineering, and on December 1 closed a deal to begin working on a futuristic “third arm” device designed by the Army Research Laboratory that can support the weight of a soldier’s weapon.

With a provisional patent application filed on the device by the Army, Stacy, who saw a prototype on an unrelated visit to the lab, was able to quickly license the third arm design with plans to sell it as an assistive device for disabled hunters and shooting hobbyists.

Dr. Justin Stacy

Dr. Justin Stacy licensed the patent-pending design from the Army.

“I already have the attachment re-designed as a quick detach that will clear scopes and sights,” Stacy said in an email to TechLink after the licensing deal closed.

Weighing about 4 pounds, the mobile weapons platform was designed by Army researchers so soldiers wearing it could accurately fire heavier weapons.

The modern soldier, they say, is often weighed down by combat loads that exceed 110 pounds. Those heavy loads may worsen as new weapons, ammunition, and attachments, are developed for future warfare.

“You wind up pushing that soldier’s combat load up beyond 120 pounds and they’re already overburdened,” said Zac Wingard, a mechanical engineer for the lab’s Weapons and Materials Research Directorate and co-inventor. “We [now] have soldiers in their late teens and early 20s and they’re getting broken sometimes in training before they see a day in combat.”

The third arm device redirects a weapon’s weight to the body making it easier to shoulder. An early prototype of the device can transfer up to 20 pounds from the arms to the body. This redirecting of the weight from the arms has potential other benefits besides user fatigue.

“Removing the weight of the weapon system from the user’s arms allows people with limited arm strength to safely enjoy shooting sports, such as hunting. And the system offers added safety to anyone carrying a weapon since the weapon is attached to the body and not just the user’s hands,” a spokesman for Short Fuse Engineering said.

TechLink’s Austin Leach helped negotiate the license agreement between Stacy and ARL’s Technology Transfer Office, a necessary first step in getting the Army’s design into the private sector and one TechLink specializes in.

“It’ll be exciting to see Dr. Stacy’s improvements on what’s already a very exciting invention,” Leach said. “The Army loves to see small, innovative companies grow with technology developed in their labs.”

And Stacy hopes to share new designs and improvements with the Army.

“The research and development we’re focused on now is refining this device,” said co-inventor Dan Baechle, also an Army mechanical engineer.

Baechle said they plan to investigate other types of weapons with different calibers, like the 20-pound M249 squad automatic weapon or the 25-pound M240B machine gun.

“Imagine shoulder firing either of these (weapons) without the weight on your arms, and without all the recoil going into your shoulder,” he said.

Troy Carter can be reached at or 406-994-7798.

Headshot Image of Austin Leach, PhD, CLP

Is your business interested in one of these hot technologies?

Contact Us