Selecting seats for steel industry mobile machines based on seat effective amplitude transmissibility and comfort.

OBJECTIVE: The purpose of this work was to help a steel industry partner select the most appropriate of three high end heavy equipment seats to retrofit a number of their heavy mobile machines used in the steel making process. PARTICIPANTS: The participants included 8 males (22.3 ± 2.0 yrs.) and 8 females (23.5 ± 1.8 yrs.) with no experience operating heavy mobile equipment. METHODS: Previously recorded 6-DOF chassis acceleration data from a Pot Hauler (a machine which picks up and transports pots of slag) were used to extract six, 20 second representative profiles for implementation on a lab-based heavy machine simulator (6-DOF Parallel Robotics System Corporation robot). Subjects sat on three heavy equipment seats (BeGe7150, Grammar MSG 95G1721, and a 6801 Isringhausen with the seat pan cushion retrofitted with a Skydex cushion) mounted on the simulator. Each subject completed three trials for each combination of seat (n=3) and vibration profile (n=6). Chassis and operator/seat interface vibration were measured by 2, 6-DOF vibration transducers. Variables included Seat Effective Amplitude Transmissibility (SEAT) (X,Y,Z,Roll,Pitch,Yaw,6DOF Vector Sum) to determine if the seat was attenuating or amplifying the vibration, 6-degree of freedom (DOF) vibration total value weighted predicted comfort (Avc) (according to ISO 2631-1) and operator reported comfort (ORC). RESULTS: Factorial ANOVAs revealed significant differences (p < or = 0.05) between seats for all SEAT variables but different seats performed better than others depending on the axis. Significant differences between males and females were observed for SEAT in X,Y, and Pitch as well as for Avs. As expected there were significant differences between vibration profiles for all assessed variables. A number of interaction effects were observed, the most frequently occurring of which was between seat and vibration profile. CONCLUSIONS: Based upon the number of seat and vibration profile interactions, results suggest that a single seat is not suited for all tested conditions. However, SEAT values for all of the seats tested were extremely low (e.g., 6-DOF SEAT < 30%) indicating that all of the seats were capable of providing good vibration attenuation.

The effectiveness of using two different types of anti-vibration gloves compared to bare hand condition at dampening the frequencies associated with hand-arm vibration syndrome.

The ability of a foam-padded and air-bladder glove to significantly attenuate hand-arm vibration compared to an individual's bare hands (after the effect of adipose content of the distal upper extremity had been removed) was studied. Subjects consisted of 3 male and 8 female university students' aged 20 to 22 years. After the effect of adipose content of the distal upper extremity was removed, the effect of the gloves on transmissibility was significant with F2,959 = 5.27, p<0.000. The effect of the frequencies was significant with F31,959 = 8.80, p<0.000. There was no significant interaction between the gloves and frequencies on transmissibility with F62,959 = 0.22, p = 1.000. Post-hoc analysis revealed that there was a significant difference was between bare hand and foam-padded glove conditions, F1,1052 = 8.13, p = 0.004, where foam-padded gloves had significantly greater transmissibility. Post-hoc analysis of the frequencies indicated that there were significant differences between frequencies at with the highest transmissibility occurring at 100 Hz.