Machine Vibration Test Rig pt 1 of 4 - equipment setup

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youtube.com

Answer

Ask me anything about this video:

What is the purpose of the device (bearing defect detection, endurance testing, resonance excitation), and what performance targets do they mention (frequency range, amplitude, load, duration)? 2. What exactly creates the force/torque (electromagnet coil, permanent magnet + driven coil, motor stator, voice-coil, solenoid), and what evidence shows how it works? 3. Describe the geometry: where are the magnets/coils located relative to the disc/stator, and how does that translate into torque on the armature? 4. Is the armature motion purely rotational about a pivot, or is there a linkage that converts it into near-linear motion at the DUT? Show/describe that conversion. 5. What is the pivot mechanism (ball bearing, flexure, knife edge), and do they mention friction/stiction or wear considerations? 6. What is the “moving mass” (armature + fixtures + DUT), and how is the DUT clamped/loaded (radial/axial load, preload mechanism)? 7. What provides restoring stiffness (torsion spring, gravity, flexure, magnetic centering), and do they mention a natural frequency of the mechanism? 8. How do they generate the vibration signal (PWM, sine drive, audio amp, motor controller), and what waveforms do they demonstrate (sine, sweep, impulses, noise)? 9. What sensors are used to measure vibration (accelerometer, microphone, displacement sensor), where are they mounted, and what bandwidth/sampling is implied? 10. Do they show a feedback loop (holding constant amplitude, tracking a frequency profile), and what variable is controlled (current, displacement, acceleration)? 11. What frequency/amplitude range do they actually demonstrate on camera (rough values), and what limits show up (saturation, heating, mechanical stops, excessive noise)? 12. What unwanted motions occur (rocking, rotation at DUT, lateral motion), and how do they mitigate them (symmetry, guides, stiffening)? 13. What’s the key advantage they claim for this design versus a linear shaker (cost, simplicity, compactness), and what tradeoffs do they admit? 14. If the device is for bearings, what excitation direction(s) does it apply (radial, axial, torsional), and how does that map to typical bearing defect frequencies? 15. What parts list/cost do they mention, and which parts look critical/precision-made versus easy to DIY?

Answer

Machine Vibration Test Rig pt 1 of 4 - equipment setup

Sources

youtube.com

Machine Vibration Test Rig pt 1 of 4 - equipment setup

Answer

About this video

Video Title: Machine Vibration Test Rig pt 1 of 4 - equipment setup
Channel: Ben Halkon
Speakers: Dr. Ben Halkon
Duration: 00:05:46

Overview

This video provides a detailed explanation of the equipment setup for a machine vibration test rig used in vibration condition monitoring. Dr. Ben Halkon walks through the various components, including the motor, shaft, gear ratios, accelerometers, tachometers, eddy current brake, and data acquisition system, explaining their functions and how they are integrated into the experimental setup.

Key takeaways

Rotating Machinery Setup: The rig features a brushless DC motor driving a shaft through a flexible coupling, which in turn drives another shaft via a 2:1 gear ratio.
Instrumentation: Piezoelectric accelerometers are mounted on bearing housings. Retro-reflective tape on the shafts, used with tachometers, generates a square wave signal for once-per-revolution measurements.
Load Introduction: An eddy current brake with a controllable voltage supply is used to introduce a braking torque. A load cell is present for measuring force, and an encoder is available for position measurements.
Damaged Bearing Demonstration: A deliberately damaged bearing is installed to demonstrate how vibration measurements can be used to diagnose issues in rotating systems.
Data Acquisition System: Accelerometers are powered by inline charge amplifiers connected to a data acquisition system. The tachometer signal is also fed into this system.

Ask me anything about this video:

What is the purpose of the device (bearing defect detection, endurance testing, resonance excitation), and what performance targets do they mention (frequency range, amplitude, load, duration)? 2. What exactly creates the force/torque (electromagnet coil, permanent magnet + driven coil, motor stator, voice-coil, solenoid), and what evidence shows how it works? 3. Describe the geometry: where are the magnets/coils located relative to the disc/stator, and how does that translate into torque on the armature? 4. Is the armature motion purely rotational about a pivot, or is there a linkage that converts it into near-linear motion at the DUT? Show/describe that conversion. 5. What is the pivot mechanism (ball bearing, flexure, knife edge), and do they mention friction/stiction or wear considerations? 6. What is the “moving mass” (armature + fixtures + DUT), and how is the DUT clamped/loaded (radial/axial load, preload mechanism)? 7. What provides restoring stiffness (torsion spring, gravity, flexure, magnetic centering), and do they mention a natural frequency of the mechanism? 8. How do they generate the vibration signal (PWM, sine drive, audio amp, motor controller), and what waveforms do they demonstrate (sine, sweep, impulses, noise)? 9. What sensors are used to measure vibration (accelerometer, microphone, displacement sensor), where are they mounted, and what bandwidth/sampling is implied? 10. Do they show a feedback loop (holding constant amplitude, tracking a frequency profile), and what variable is controlled (current, displacement, acceleration)? 11. What frequency/amplitude range do they actually demonstrate on camera (rough values), and what limits show up (saturation, heating, mechanical stops, excessive noise)? 12. What unwanted motions occur (rocking, rotation at DUT, lateral motion), and how do they mitigate them (symmetry, guides, stiffening)? 13. What’s the key advantage they claim for this design versus a linear shaker (cost, simplicity, compactness), and what tradeoffs do they admit? 14. If the device is for bearings, what excitation direction(s) does it apply (radial, axial, torsional), and how does that map to typical bearing defect frequencies? 15. What parts list/cost do they mention, and which parts look critical/precision-made versus easy to DIY?

Answer

This video focuses on the setup of a machine vibration test rig for condition monitoring, not on the detailed mechanics of a specific actuator design like a shaker or exciter. Therefore, many of your questions are outside the scope of the provided transcript. However, I can address the parts that are relevant to the video's content.

The video does not describe:

Bearing defect detection, endurance testing, or resonance excitation as specific purposes of the entire rig.
Performance targets like frequency range, amplitude, load, or duration for such testing.
The exact mechanism that creates force/torque in terms of electromagnet coils, permanent magnets, motor stators, voice-coils, or solenoids for an actuator.
The geometry of an actuator's magnets/coils relative to a disc/stator to translate into torque.
The armature motion, pivot mechanisms, friction/stiction, wear considerations, moving mass, or clamping/loading of a DUT (Device Under Test) in the context of an actuator.
Restoring stiffness mechanisms or natural frequencies of a specific exciter.
How vibration signals are generated (PWM, sine drive, etc.) or waveforms demonstrated beyond basic rotating speeds.
The bandwidth/sampling rates of sensors, although accelerometers and a tachometer are mentioned.
Feedback loops, controlled variables, or specific demonstrated frequency/amplitude ranges beyond what can be inferred from the rotating setup.
Unwanted motions and mitigation strategies for a shaker-type device.
Key advantages or tradeoffs of the design versus a linear shaker.
The specific excitation directions applied to bearings or mapping to defect frequencies.
A parts list or cost information.

Based on the transcript, here's what is discussed regarding the components and sensors:

Purpose of the Rig (General): The rig is set up for vibration condition monitoring of rotating machinery.
Force/Torque Generation (Indirect): A brushless DC motor drives the shaft. An eddy current brake, consisting of a magnet and an aluminum rotor, is used to introduce a braking torque. The voltage applied to the magnet, controlled by a potentiometer, adjusts this braking torque.
Sensors Used:
- Accelerometers: Piezoelectric accelerometers are mounted to bearing housings to measure vibration. There are at least two visible, one on a bearing housing and another on a bearing block.
- Tachometer: Used to measure rotational speed. It works by detecting a piece of retro-reflective tape on the shaft, generating a square wave signal for each revolution. There's an integrated tachometer and a separate one mentioned.
- Load Cell: Present but not connected in the video. It is intended to measure load, likely related to the torque applied by the eddy current brake.
- Encoder: Mounted on the back of a shaft, but not currently in use. It would provide positional information in addition to once-per-revolution data.
Data Acquisition: The signals from the accelerometers (via charge amplifiers) and the tachometer are fed into a data acquisition system.
Mechanical Setup:
- A deliberately damaged bearing is installed in one of the bearing blocks to demonstrate vibration measurement techniques for detecting faults. The damage involves scoring on the bearing surface.
- A third, "free-floating" bearing block is mentioned, which allows for the introduction of an axial load via a screw, potentially causing bending in the shaft.
- Flexible couplings are used where shafts are not perfectly aligned.

The video does not describe:

Bearing defect detection, endurance testing, or resonance excitation as specific purposes of the entire rig.
Performance targets like frequency range, amplitude, load, or duration for such testing.
The exact mechanism that creates force/torque in terms of electromagnet coils, permanent magnets, motor stators, voice-coils, or solenoids for an actuator.
The geometry of an actuator's magnets/coils relative to a disc/stator to translate into torque.
The armature motion, pivot mechanisms, friction/stiction, wear considerations, moving mass, or clamping/loading of a DUT (Device Under Test) in the context of an actuator.
Restoring stiffness mechanisms or natural frequencies of a specific exciter.
How vibration signals are generated (PWM, sine drive, etc.) or waveforms demonstrated beyond basic rotating speeds.
The bandwidth/sampling rates of sensors, although accelerometers and a tachometer are mentioned.
Feedback loops, controlled variables, or specific demonstrated frequency/amplitude ranges beyond what can be inferred from the rotating setup.
Unwanted motions and mitigation strategies for a shaker-type device.
Key advantages or tradeoffs of the design versus a linear shaker.
The specific excitation directions applied to bearings or mapping to defect frequencies.
A parts list or cost information.

Based on the transcript, here's what is discussed regarding the components and sensors:

Purpose of the Rig (General): The rig is set up for vibration condition monitoring of rotating machinery.
Force/Torque Generation (Indirect): A brushless DC motor drives the shaft. An eddy current brake, consisting of a magnet and an aluminum rotor, is used to introduce a braking torque. The voltage applied to the magnet, controlled by a potentiometer, adjusts this braking torque.
Sensors Used:
- Accelerometers: Piezoelectric accelerometers are mounted to bearing housings to measure vibration. There are at least two visible, one on a bearing housing and another on a bearing block.
- Tachometer: Used to measure rotational speed. It works by detecting a piece of retro-reflective tape on the shaft, generating a square wave signal for each revolution. There's an integrated tachometer and a separate one mentioned.
- Load Cell: Present but not connected in the video. It is intended to measure load, likely related to the torque applied by the eddy current brake.
- Encoder: Mounted on the back of a shaft, but not currently in use. It would provide positional information in addition to once-per-revolution data.
Data Acquisition: The signals from the accelerometers (via charge amplifiers) and the tachometer are fed into a data acquisition system.
Mechanical Setup:
- A deliberately damaged bearing is installed in one of the bearing blocks to demonstrate vibration measurement techniques for detecting faults. The damage involves scoring on the bearing surface.
- A third, "free-floating" bearing block is mentioned, which allows for the introduction of an axial load via a screw, potentially causing bending in the shaft.
- Flexible couplings are used where shafts are not perfectly aligned.