Evaluating the effectiveness of a Lodengraf damping approach for string trimmers

Abstract

Reducing the magnitude of the vibrations transmitted to a user’s hands through the loop handle and grip of a string trimmer is a priority for maintaining both health and comfort. Prior work on internal-combustion (IC) powered string trimmers has indicated that Lodengraf™ damping may be effective in reducing vibration amplitude at both the loop handle and grip. Lodengraf damping utilizes lightweight, low-density particles added to a vibrating device, either as a fill in existing cavities or as a wrap surrounding the device. The mechanism for the damping is that vibrations generated by the device are absorbed into the Lodengraf particles, where the energy of the vibrations is converted to heat and released before they can be transmitted to the user. In this set of experiments performed on battery-powered string trimmers, the effectiveness of applying Lodengraf particles using specially designed 3D printed loop handles as well as a clam-shell shaft enclosure, all comprised from ABS is explored. The 3D printed parts were designed to be hollow, forming cavities to accommodate the Lodengraf materials. The Lodengraf was found to be effective at frequencies above 200 Hz. Both trimmers have a first fundamental frequency that falls below the cutoff frequency for effective Lodengraf damping, but the approach effectively reduced the amplitude of higher frequency harmonics generated.