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Recent content by Rob45

  1. Rob45

    Spark Arrestor / Flame Arrestor

    And spark arresters go on exhaust; this power plant undoubtedly needs both.
  2. Rob45

    Automotive cooling system

    It appears to OP is averse to reading... [glasses]
  3. Rob45

    T60 Reverberation Time Testing Question

    Greg, Thanks. The more I think about this, the less likely I think there'll be a problem: I think I'll just try the balloons first, then if necessary, a pistol using just a shotgun primer, no powder. If the mike were to overload, I'd just move the pistol farther from the measuring...
  4. Rob45

    T60 Reverberation Time Testing Question

    I am going to do a measurement on a larger space than I've tested before - where I've gotten by with a hand-clap - and I'm wondering if there are guidelines for the excitation sound level required? When can I use a large balloon (a friend uses a 36" dia. balloon), for example, and when would...
  5. Rob45

    Accelerometer as a vibraton detector

    VR Mobile gives good results; not for levels, of course, but for spectra
  6. Rob45

    Combining noises

    And naturally, when you speak of two identical sources (same frequency and level) being in-phase, you mean "at the receiver."
  7. Rob45

    Damping Measurement: Shaker Table vs Ping Test

    This is an interesting subject. Recently I have been doing quite a lot of damping material tests, to screen candidate materials for a new application. Not having a shaker, I have done this using my trusty hammer. I devised a panel test using the same substrate material & thickness as the...
  8. Rob45

    TMD to Improve Isolation at Mount?

    Yes, reducing the source would be ideal, and I am pursuing that, having already redesigned the engine mounts, which gave a worthwhile improvement. The source in this case btw is a 15L 6-cyl turbocharged Diesel engine making 450 HP and 1550 lb-ft of torque. But the reason for wanting a...
  9. Rob45

    TMD to Improve Isolation at Mount?

    I'm primarily interested in the TMD because of the lack of space to make a significant improvement in the isolator. It already has durabilitiy issues, and softening it would make them worse.
  10. Rob45

    TMD to Improve Isolation at Mount?

    We did in fact run a Transfer Path Analysis showing the cab mounts were major paths for powertrain noise to the driver's ear: mount FRFs were taken, sound and vibration levels were taken in operation. The mount FRFs are available, so I have or can re-take the inertance. This is a...
  11. Rob45

    Can Foam be used for reducing vibration

    You could also investigate Lodengraf damping; a paper on this by J.R. Fricke suggests that filling the closed frame with other light materials could also help, including even vermiculite.
  12. Rob45

    TMD to Improve Isolation at Mount?

    Greetings: I have a situation where an isolated vehicle cab structure has poor dynamic stiffness in one direction, at approximately 300 Hz, and therefore has poor isolation. This results in noise at the operator's ear at 300 Hz. Since in this case redesigning the structure is not an...
  13. Rob45

    Dynamic absorber presentation - for comment

    Pete: I like that presentation; it is simple, covers the bases. It occurs to me that as a safety feature, overtravel stops could be devised to limit travel of the damper mass in the event something changes in the mg set itself, thus preventing a fatigue failure of the TMD? Your presentation...
  14. Rob45

    Combining noises

    That is a nice simple explanation, Dr. P!
  15. Rob45

    Test Lab for modal analysis?

    An interesting paper on Lodengraf damping references work done on aluminum bats; it was published in Sound & Vibration and posted on their website.
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