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#21
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Strangely enough, that is what I *DID* for a living when Spectral Dynamics
was the industry leader in machinery diagnostics. Unfortunately, my job was the circuit design, not the diagnostics itself, so all I concerned myself with was the black box that took a defined input and produced a defined output. There are times I wish that I had transferred to the applications department. They were the ones that seemed to have the most fun (and the most three martini Friday lunches). Jim " Stangely enough, this is what I do for a living. No kidding. I am an engineer at Bently Nevada, Corp, the industry leader in machinery diagnostics. |
#22
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Yes, all of the below.
Sometimes you drill a hole in a small magnet and use a small screw to hold it to the propeller backing plate. Sometimes you use a strip of reflective tape on the prop itself. Sometimes you use a pulse from the #1 magneto lead. Jim "Morgans" wrote in message ... "sleepy6" wrote That notch causes a much larger timing blip in the signal than any crank movement will cause. By measureing the time between the timing blips you can determine the amount of rotation after a timing blip that you see an up or down crank movement event. What sort of technology does a proxomity detector use? Magnetics, sonic, radio waves? -- Jim in NC |
#23
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Love to. You got my address?
Jim "George A. Graham" wrote in message ... Jim, I have a Memsic demo board, which displays LEDS on two axis with their tilt and motion sensor. I am done with it, would you like to play with it? George Graham RX-7 Powered Graham-EZ, N4449E Homepage http://bfn.org/~ca266 |
#24
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"RST Engineering" wrote in message ... Strangely enough, that is what I *DID* for a living when Spectral Dynamics was the industry leader in machinery diagnostics. Unfortunately, my job was the circuit design, not the diagnostics itself, so all I concerned myself with was the black box that took a defined input and produced a defined output. There are times I wish that I had transferred to the applications department. They were the ones that seemed to have the most fun (and the most three martini Friday lunches). Jim LOL. I've been an engineer designing in the dark many times. Fortunately at Bently, there is a large effort to train engineers in diagnostics. Then we can use personal experience in addition to requirements documents when designing a new product. Or, at least, we can determine if requirements make sense! Adam |
#25
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"sleepy6" wrote in message ... Of course this simple setup will not show side to side movement. That would require a second proximity detector 90 degrees from the first one. The 2 signals would require integration but would then show all movement in the rotational plane with the proper signal processing and calibration. Exactly. This two-dimensional shaft path is called an orbit. Adam |
#26
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Understood. What I started out to do (and still plan on doing) is to have a
device that will stay permanently mounted to the engine that can be calibrated (adjusted, signed, pick a verb) when the engine is known to be good and light a "your engine is about to come apart" lamp at the appropriate time. What this group seems to be leaning toward is a lab quality device that will allow for sophisticated diagnostics. That ain't the thrust of my Kitplanes columns. KISS and BURP. Jim |
#27
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"RST Engineering" wrote in message ... Understood. What I started out to do (and still plan on doing) is to have a device that will stay permanently mounted to the engine that can be calibrated (adjusted, signed, pick a verb) when the engine is known to be good and light a "your engine is about to come apart" lamp at the appropriate time. What this group seems to be leaning toward is a lab quality device that will allow for sophisticated diagnostics. That ain't the thrust of my Kitplanes columns. KISS and BURP. Jim As is tradition, we tend to get off topic ;-) I think you can accomplish this using the methods discussed. Mount 2 proximity probes 90 degrees apart. Calibrate the readings for normal low vibrations (be sure to account for any nonlinearities in the probe). Design the circuit to trip the buzzer/lamp when the vibration exceeds the normal level. You may need some analog circuitry to help (gain, etc). But you don't need to get much fancier than that. Adam |
#28
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Proximity probes? Or accelerometers?
I understand about the analog circuitry and actually plan on making a five or six channel filter at each of the possible resonance points relative to the fundamental ... and then strobing the filters to light a "normal", "low", "high" lamp for each channel. Jim As is tradition, we tend to get off topic ;-) I think you can accomplish this using the methods discussed. Mount 2 proximity probes 90 degrees apart. Calibrate the readings for normal low vibrations (be sure to account for any nonlinearities in the probe). Design the circuit to trip the buzzer/lamp when the vibration exceeds the normal level. You may need some analog circuitry to help (gain, etc). But you don't need to get much fancier than that. Adam |
#29
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"RST Engineering" wrote in message ... Yes, all of the below. Sometimes you drill a hole in a small magnet and use a small screw to hold it to the propeller backing plate. Sometimes you use a strip of reflective tape on the prop itself. Sometimes you use a pulse from the #1 magneto lead. Jim This guy was talking about a notch and proximity detector for the phase detection. I know about all of the things you mentioned, but the proximity detector's workings are new to me. -- Jim in NC |
#30
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I would use proximity probes if you are primarily going to measure
vibration. They are also the best choice if you are going to notch the shaft and do phase measurment. I'm not sure about other venders' prox probes, but the one's I'm used to have a linear range. The phase measurment can be gained so that it rails one way when over the notch and rails the other way when not, so you don't have to worry about the linear range. As for vibration measurments, you will have to make sure that you stay in the linear range of the probe. I want to make sure I understand what you meant by having a filter at the resonance points. Are you only going to measure vibration at resonance (i.e. bandpass)? Or, are you NOT going to measure at resonance (i.e. notch filter)? Keep in mind other events may cause vibration, such as impulse, rub, etc, which will likely occur synchronous to the shaft, and have nothing to do with resonance. This is where a phase reference may be handy because you could determine if it is happening 1X/rev, 2X/rev, etc. OR, are you assuming that an impulse/rub event will excite the case at the resonance frequency? At any rate, what you intend on doing is definitely do-able. I recommend playing with probes a bit to see what you get. Sounds like a fun project. Let me know if there's anything I can offer... Adam "RST Engineering" wrote in message ... Proximity probes? Or accelerometers? I understand about the analog circuitry and actually plan on making a five or six channel filter at each of the possible resonance points relative to the fundamental ... and then strobing the filters to light a "normal", "low", "high" lamp for each channel. Jim As is tradition, we tend to get off topic ;-) I think you can accomplish this using the methods discussed. Mount 2 proximity probes 90 degrees apart. Calibrate the readings for normal low vibrations (be sure to account for any nonlinearities in the probe). Design the circuit to trip the buzzer/lamp when the vibration exceeds the normal level. You may need some analog circuitry to help (gain, etc). But you don't need to get much fancier than that. Adam |
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