Dear Jon, Here is the data I gathered today. Point 12 was used as a stationary reference with a speed of 1794 cpm. On the spreadsheet, I observed that at point 20 on axis Z, the red phase value was unstable and fluctuating. I selected the value that appeared to be more stable. Additionally, I collected data on another support angle, which is displayed in the accompanying picture in the Excel sheet. I placed a 2x4 under point 26, but did not notice a decrease in amplitude. I also observed a high 3X lobe pass frequency (~13,200 cpm) at approximately 1.5 in/sec between points 15-18. I attempted to respond to my original post, but encountered errors.
Check out the animation displaying an imbalance that is leading to the weak frame flexing on the outboard end of the blower. This issue is also causing the motor support to flex 180° out of phase with the blower support. Surprisingly, adding a foot under the blower did not result in improved readings.
To ensure optimal performance and alignment, it is important to inspect the blower pulley for eccentricity and runout. The lack of corner bracing on the frame may be contributing to potential misalignments of the pulleys. Check the frame for resonance in the "Y" direction, paying attention to possible mode shapes through 1, 2, 3, 4, and 5. Additionally, perform bump tests on the blower support around positions 26 and 27 in the vertical "Z" direction. This thorough assessment will help identify and address any issues affecting the equipment's operation.
I acknowledge the potential weakness in the frame structure. When observing a bent or twisted appearance in ODS animation, it may signal issues related to weakness or resonance. To confirm, conducting resonance testing (such as phase and magnitude measurements during run-up or coast-down, negative averaging, peak hold bump tests, single or dual channel impact testing) is recommended. Another way to differentiate between resonance and weakness is by examining the animation of another frequency if available in the test data. A weak frame will display the same shape regardless of the forcing frequency, while a resonating structure will demonstrate a unique mode shape at each natural frequency. Strengthening the frame may be necessary, and consideration should be given to including any additional structural members in the analysis. Incorporating cross bracing for the long rails and potentially using isolators for the frame could help address vibration issues. Balancing, alignment adjustments, or using more precise pulleys may also decrease forced vibration. Conducting a modal analysis will provide insight into all natural frequencies present, aiding in the identification and resolution of resonance problems. Utilizing ME'scope software for structural modifications based on modal survey results can help optimize the structure for reduced vibration. Feel free to reach out if further assistance is needed.
Hey Tony, I wanted to share with you a photo of the machine that xRacer is worried about.
Hi there, Thanks for the detailed update. The issue at Point 20 might be due to some vibration or equipment error; it could be beneficial to double-check the setup. Also, I find it intriguing that you didn't observe any amplitude decrease despite levering at Point 26 with a 2x4. That could point towards a more systemic issue. The high-frequency lobe pass you mentioned between Points 15-18 is concerning and needs further analysis. You've done a commendable job on data collection — your insights are really enriching this discussion.
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Answer: - When the red phase value is unstable and fluctuating at a specific point, it indicates potential issues with the stability or consistency of the data being collected. It is important to select the most stable value to ensure accurate analysis.
Answer: - Placing a support angle under a specific point can impact the vibration characteristics of the blower system. In this case, the user did not observe a decrease in amplitude when using a 2x4 under point 26, which may indicate that the support angle was not effectively addressing any vibration issues at that particular point.
Answer: - A high 3X lobe pass frequency indicates the presence of vibration harmonics that are three times the running speed of the blower. In this case, the frequency observed between points 15-18 (~13,200 cpm) suggests the presence of significant vibration at that particular range of points in the blower system.
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