In his tranquil suburban Washington, DC home in the early sixties, Chuck Popenoe was reading his Popular Mechanics magazine when a new product announcement got his attention. The article featured a bolt with a custom-designed head infused with glass, which would shatter upon reaching a desired tension.
“I knew immediately I could improve upon this design,” Chuck later recalled, “So I set out to create a bolt that would not only reliably inform a user when a desired tension is reached, but also indicate if tension were lost. Plus, the design I had in mind would also allow the bolt to be reusable and would last as long as any regular bolt.”
It was this ‘eureka moment’ when the concept of SmartBolts was born and was to ultimately become a modern day American success story…
In his well-equipped workshop, Chuck set out working on his revolutionary new bolt design. The prototype was simple: no wires or moving parts in a bolt which could remain reliable and reproducible through countless cycles of use. In 1965, the project’s preliminary goals were accomplished and the forerunner of the modern SmartBolt was created.
Chuck then got to work designing the basic functions of his visual tension indicating bolt, first identifying the most critical function as the response of an optical microindicator element to the stretching of a bolt under stress. “I concluded that the key to practical manufacturing of the optical microindicator would be to hermetically seal indicating fluid in a flexible envelope,” he explained.
It was this specialized microindicator technology that would transform miniscule relative movement into a dramatic and reproducible color change. This color change would be prominently visible to the naked eye on the bolt head. This technology was then patented by the new company Chuck founded as Stress Indicators, Inc. (SII) and the product would be trademarked as DTI (Direct Tension Indicating) SmartBolts®.
In the early years, Chuck constructed SmartBolts himself in his home workshop. He used a drill press and lathe to craft precsion recesses into industrial-grade bolts. A sturdy pin was secured to the base of the bolt. He manufactured the patented microindicators using a machine he custom-designed. Once the assembly of the SmartBolts was complete, each and every bolt was individually tested to ensure optimal quality. This important quality control step remains in place at the company to this day, as each SmartBolt is individually tested and verified multiple times during several critical project stages to ensure industry-leading reliability.
Chuck Popenoe Developed Other Inventions Independently and as a Physicist at NIST
An inventor at heart, Chuck Popenoe developed and manufactured this unique fastening solution along with other inventions including: knob-actuated locksets, improved coiling stabilizer-fins for tube-launched missiles, and hydrodynamic swim fins. He also invented novel goniometer positioning mounts for standard lamps, used to position the lamps precisely for accurate spectroradiometric calibrations.
He accomplished all these breakthroughs while employed full-time as a physicist, engineer, and later, a research engineer. During his long career at the National Institute of Standards and Technology (NIST), he was responsible for the development of the FASCAL and MIDAS systems. FASCAL is an automated system for calibrating lamp standards in spectral radiance or irradiance. The MIDAS system facilitates automated experiment control and data acquisition. Both systems remain in use at NIST to this day.
Chuck continued to focus the majority of his time and energy on his employer’s research projects, but he knew his visual tension-indicating bolt was an innovative design packed with potential.
“Originally, my goal was to license it to a major corporation,” he explained. “That way, I could continue my very satisfying work at NIST while receiving payments from the license. And after winning two gold medals at the 1971 Brussels International Invention Exposition, I had immediate feedback from attendees and offers to commercialize it. Everyone who saw SmartBolts loved the concept, so I believed there was enormous potential.”
Consequently, following an extensive and successful career spanning almost 30 years, Chuck decided to retire from NIST and pursue his entrepreneurial goals at Stress Indicators, Inc. At SII, he was able to focus on perfecting his previous bolt design and patented Direct Tension Indicating (DTI) SmartBolts®.
General Electric Puts SmartBolts to Work in Electrical Busways
Established industry leaders began showing increasing interest in obtaining SmartBolts for their projects. In 1997, Stress Indicators initiated a contract with General Electric, providing SmartBolts for GE Spectra Series electrical distribution busways. The transaction led to numerous gains for both companies within the electrical distribution market and solidified a partnership that continues to this day.
SmartBolts were becoming industry standard fasteners. Eventually, SII required help from various manufacturing and assembly companies to keep up with increasing demand. Using Chuck’s expertise, an innovative automation equipment manufacturer developed a production-focused microindicator assembly machine. The company would soon be contracted to manufacture and assemble SmartBolts on behalf of the company. In upcoming years, several other manufacturing, machining, and assembly corporations would be integrated within the SmartBolts production process.
Since 1999, the management of Stress Indicators has been in the capable hands of Chuck’s son, Charles Popenoe, III who serves as the company’s President. He commented, “My father created fantastic products that have enormous potential to impact the fastener market worldwide. I am fortunate to have the opportunity to lead Stress Indicators towards fulfilling that potential.”
Stress Indicators Consolidates Operations in New Facility Paving Way to Expansion
In 2010, SII decided to consolidate its operations in-house and now operates all production within its current facility. The company possesses high-tech machinery designed to streamline the manufacturing process. In 2011, management added a high-performance CNC (Computer Numerical Control) Turning Center from Doosan, further solidifying the efficiency of the facility.
Every step of the SmartBolts production process is controlled by experienced workers using advanced equipment within the SII facility to manufacture and assemble SmartBolts in America. By manufacturing its products domestically, Stress Indicators promotes American economic growth and industrial capacity. “We are proud to be participating in the growing wave of American manufacturers of U.S. technology that is creating skilled jobs,” says company President Charles Popenoe.
“Our mission here at Stress Indicators is to expand the worldwide use of our proprietary SmartBolts visual indicating fasteners,” Charles added. “We pride ourselves as designers of the most advanced, efficient bolt technology in the field. Since the introduction of our product line to the global marketplace in 1992, our SmartBolts have been exported to more than 20 countries in North and South America, Europe, Africa, Asia, and Australia.”
The international success of SmartBolts can be attributed to the unique benefits the invention provides to industry productiveness. At any time during maintenance or inspection schedules, the proper tension of our SmartBolts can be verified without physical contact, loosening of fasteners, or the use of tools. SmartBolts utilize a tension indicating fastener system providing an eye-catching visual identification of a potentially dangerous condition, obvious even from a distance and in moving machine elements. Loose fasteners may be rapidly identified and corrected before catastrophic failure occurs.
Currently, SmartBolts are used in a wide range of industrial applications and more applications are being identified constantly. SII is currently expanding its presence in various industrial-based fields, such as those of Electrical Distribution, Mining, Heavy Equipment, and Industrial Machinery.
Charles Popenoe concluded by adding, “The use of our proprietary SmartBolts provides a safer, accurate, and reliable tension-indicating fastener to our clients at an economical price. We proudly expect our products to gain influence in all markets in which we participate.”
Do You Have a Potential Application for SmartBolts?
Standard hex head SmartBolts are useful in a number of real world applications. We invite you to use our Application Qualifier questionnaire to learn if your application is appropriate for the SmartBolts solution. You can also receive price quotes for testing, as well as, roll out/annual usage quantities.
We’re here to serve your needs and to provide you with viable solutions to the fastener challenges you face. Please contact us today — we’d love to hear from you!