A tool-balancing arm, or zero-gravity arm, is an innovative solution that can hold heavy construction power tools while allowing workers to perform their tasks normally, significantly reducing fatigue and stress placed on upper extremities, and improving the workers’ accuracy and efficiency. More specifically, this tool is designed to increase the safety and productivity of workers who are working on mounted platforms such as scaffolds and lifts.

Several construction tasks (e.g., drilling, sanding, bolting) could involve working on aerial platforms and using powertools (e.g., grinders, impact drills, and chipping hammers) at the same time. Zero-gravity arm systems enable workers to operate these heavy tools comfortably for long time periods. The zero-gravity system can be attached via two spring-arms to scaffolds and aerial lifts to counterbalance the weight of power tools.

The system includes a double-arm unit and universal attachment accessories that ensure secure connection of the tool to aerial platforms (see Figure 1). The zero-gravity arm unit is made of aerospace-grade aluminum and steel, weighs around 35 lb., and can hold tools weighing up to 36 lb. Figure 2 displays the components of the tool: the gimbal emulates the function of hand and wrist; the unique spring and cam architecture of the zero-gravity arm enables uniform lifts throughout a range of vertical heights; and the mounting block helps transfer the payload to the platform.
 

Figure 2. Top‒three main components of the solution. Bottom‒more details of a zero-gravity arm (Photo courtesy of Ekso Bionics)

Installation of this solution on aerial platforms follows these steps (the accessories are designed and engineered to support a broad range of platform configurations):

•  Put the mount on the inside of the aerial basket by positioning the mounting hooks on the top and middle rails and locking them as shown in Figure 3-a.
•  Remove the lock pin, insert the arm into the mount, and replace the lock pin as depicted in Figure 3-b.
•  Secure the arm by locking the docking ring to the safety latch, then inserting the tool holder into the receiver (Figure 3-c).

Figure 3. Setting up the zero-gravity arm on an aerial basket. a) Set up and secure the mount. b) Set up the arm. c) Set up the tool holder. (Photo courtesy of Ekso Bionics)

After setting up the tool, there are three different ways to attach a power tool to the zero-gravity arm. Figure 4 shows these options.
 

Figure 4. Tool holders.  a) Gimbal. b) Universal. c) Slings and pigtail tool holders. (Photo courtesy of Ekso Bionics)

The gimbal technology (Figure 4-a) gives the worker better control over the tool because it allows the tool to rotate freely (although use of the gimbal is limited to specific tools). The slings and pigtail tool holder (Figure 4-c) provides more flexibility and allows workers to take the tool under the platform and comfortably perform tasks such as drilling the floor. The manufacturer claims that the training time to achieve competency with this tool is only 30 minutes. Zero-gravity arms also are very low maintenance and do not require electricity or compressed air to operate.
 

One of the main advantages of adopting this technology on construction sites, other than enhancing safety, is the improvement of productivity. This improvement could be achieved by reducing the cost of overexertion injuries; requiring fewer workers’ breaks and rotations due to less fatigue; using more powerful (although heavier) tools; allowing workers to focus on the work; and reducing mistakes. Field tests have shown that using zero-gravity arms can keep workers’ heart rates in a lower range, resulting in much less fatigue and much faster performance.

In a return-on-investment (ROI) study (https://2t2ine2n47g337am722tf6ek-wpengine.netdna-ssl.com/wp-content/uploads/2017/05/Ekso-Bionics-Corporate-Presentation-2017.pdf), the manufacturer claimed that a specific task requiring 3,024 work hours could be done in 1,296 hours when using eighteen zero-gravity arms. Based on a labor cost of $40, and a rent price of $300 per week for each tool, this study reported a $63,720 decrease in cost associated with rental of zero-gravity solutions. Considering the purchase option (with a list price of $11,000), the report concluded that a savings of 45 days of a worker’s time could pay for the price of the tool.

In another case in Hong Kong, IOT network news reported that for drilling work, the zero-gravity system improved productivity by over 50%. (https://www.iot-nn.com/2017/04/25/innovative-zero-gravity-arms-recognised-by-construction-company/). Women and older workers in the construction industry also could benefit from zero-gravity arms and similar tools, which could help create a more equitable workplace in the industry and increase diversity.

•  Similar ideas have been adopted in other industries such as manufacturing, aerospace, and defense.
•  The training time is short: less than 30 minutes.
•  The system requires zero external power and needs minimal maintenance (regular cleaning and occasional lubrication).
•  More focus on work and less fatigue could arguably result in fewer mistakes and higher work quality.
•  The system is compatible with a wide range of tools.
•  The system provides much more flexibility in maneuvering the tools compared to conventional tool balancers.
•  It’s also easier to mount zero-gravity arms than tool balancers in construction sites (they usually need large infrastructures).
•  The only advantage of tool balancers (which is more apparent in manufacturing than in construction) is their higher load capacity.

Jean Christophe Le, MPH - CPWR The Center for Construction Research and Training
Behzad Esmaeili, PhD - Geroge Mason University
Pouya Gholizadeh - Geroge Mason University
Bruce Lippy, PhD - CPWR The Center for Construction Research and Training
David Chan, CIH, CSP