Forest City Gear of Roscoe, IL, is a turnkey gear manufacturer, responsible to their customers for literally every facet of gear manufacturing, including prototyping, testing, production, finishing, quality and process validation, even packaging and delivery. One customer the gear manufacturer has increased their involvement with is Motion Control, Inc., of Salt Lake City, Utah, a world leader in myoelectric prosthetic devices and the makers of the Utah Arm, considered the most advanced prosthetic elbow/hand in the industry for above-elbow amputees.

The Utah Arm from Motion Control Inc. (top) provides an advanced prosthetic elbow/hand for above-elbow amputees. Forest City Gear machines the sector gears (bottom) for the Utah Arm.
The development of the Utah arm was done by Motion Control and the University of Utah’s Center for Engineering Design. Now in its third iteration called the Utah Arm 3, the devices incorporate two microcontrollers for the elbow and hand. Thus, separate and simultaneous control of both is possible, allowing the wearer a more natural feel and free-flow movement.

Many veterans of the Iraqi war have been fitted with the Utah Arm 3 at Walter Reed Medical Center and Brooke Army Medical Center. Motion Control also released the Myoelectric Hand and Electric Terminal Device (ETD) to complete its line. With a strong motor, strong fingers, a battery save feature, wider grip, and quick disconnect wrist, the hand offers speed and rugged wear performance. Motion Control follows the rigorous FDA and ISO quality control standards.

In 2002, Motion Control released the Myoelectric Hand, as well as the Electric Terminal Device (ETD) to complete its line of myoelectric products for the upper extremity amputee. With a strong motor, strong fingers, battery save feature, wide grip and quick-disconnect wrist, the Motion Control Hand offers higher speeds and rugged use. The MC Hand is the only electric hand to offer a Flexion Wrist feature, giving the wearer the ability to put the TD in a more natural position for performing tasks. The ETD is the first water-resistant electric terminal device available. Both hand and ETD are available with the controller inside so they may be used with other manufacturer’s systems.

For many years, the sector gears were made for the Utah Arm in a multi-step process that included machining two separate parts, welding those together, grinding down the weld, hardening the part, having Forest City Gear cut the teeth and doing some final machining. The time and cost involved merely to move the products from one vendor to another were substantial. Typically, a 10- 15% product loss was experienced in this process.

Forest City Gear proposed single sourcing for the product and the job was awarded to them. As Morandi puts it, “We now just send them an order and we concentrate on our customers. We know we’ll receive the highest precision gears from them quickly, at a better price than we were paying and without the hassle of chasing the products from one vendor to another.”

“Motion Control has partnered with Forest City Gear since its earliest versions of the Utah Arm. The company has provided gear design expertise and quality gear cutting performance for us, over the years,” according to Roger Morandi, documentation manager at Motion Control.

The Forest City Gear parts are key to the flexing of the elbow joint and, because the main gear functions as a single product, rather than the previously welded double-section part, there is substantially greater stability and power transmission possible.

“We actually seek out the tough jobs. Not because we’re masochists,” said Forest City CEO Fred Young. “Rather, it’s because we know a few things about the business of designing and being able to produce the right gear solution for the job at hand. That’s not as simple as it sounds,” Young explains.

This article was written by Everett Hawkins, Forest City Gear Company, Roscoe, IL. For more information, please contact Mr. Hawkins at 815-623-2168, e-mail him at This email address is being protected from spambots. You need JavaScript enabled to view it..


Motion Control Technology Magazine

This article first appeared in the June, 2009 issue of Motion Control Technology Magazine.

Read more articles from this issue here.

Read more articles from the archives here.