Rod Rigging - Hype?
Sounds good to me, I don't belive tension (or compression) has anything
to with the speed of transmission in a solid. But to get the expected measurements in a solid structure that is being read for resonent feedback variances, wouldn't said feedback be effected if the the solid had a wide range of motion? Seems like it would require isolation for relaible readings. Out of my depth on this one, folks....just guessing based on what I've read from Bob C. RB 35s5 NY |
Rod Rigging - Hype?
"Martin Baxter" wrote in message ... Sounds good to me, I don't belive tension (or compression) has anything to with the speed of transmission in a solid. Assume a completely rigid guitar neck. Adjusting the tension of the string adjusts its resonant frequency. If the length does not change, but the resonant frequency does, then the velocity in the string must change. C = tension/linear density http://www.faqs.org/docs/sp/sp-172.html |
Rod Rigging - Hype?
Bob Crantz wrote:
"Martin Baxter" wrote in message ... Sounds good to me, I don't belive tension (or compression) has anything to with the speed of transmission in a solid. Assume a completely rigid guitar neck. Adjusting the tension of the string adjusts its resonant frequency. If the length does not change, but the resonant frequency does, then the velocity in the string must change. C = tension/linear density I don't think so, you are thinking of resonance in a transverse plane, not propagation of a sound wave through the medium. Your example is for a transverse wave, the TDR mode you propose to employ is in fact a compresion/rarefaction, not unlike the P wave in siesmology. The problem is going to be "injecting" this pulse, if you just tap the side of the rod you will generate transverse waves rather than the longitudinal wave you are seeking. I do not think that that transverse waves will be reflected by a crack in the rod or the connectors between rod sections. See http://prola.aps.org/abstract/PRD/v7/i6/p1590_1 for the general equation. Cheers Marty |
Rod Rigging - Hype?
Bob Cranz is correct, this would work for cracks in the rod, even when
it was attached at both ends. When rod fails, where does it fail, I'd bet at the ends where TDR would be harder. Given identical types of ends and repeatedly stressed, any engineer would expect that solid rod would fail before cable type. A crack in a single strand of wire cannot propogate anywhere except in that strand. A crack in solid can go all the way through and probably will because the crack itself becomes a stress concentrator. |
Rod Rigging - Hype?
Given identical types of ends and repeatedly stressed, any engineer
would expect that solid rod would fail before cable type. This guy is a funny troll. Even the makers of standing rigging admit that rod is more durable. It's also a supperior system due to lower weight. Just take care of it. Surveyors who have no market interest in selling either also say rod is longer lived. This guy is some engineer. RB 35s5 NY |
Rod Rigging - Hype?
You are right Marty, it is the case of S and P waves in geology. They travel
at two different velocities, both dependent on tension. The TDR wants the P wave. Inducing an S wave will cause a P wave. The S wave can be damped by putting clay on the rod to reduce transverse vibration. The two waves can be separated by their velocities and the design of the receiver transducer. If the receiver transducer is sensitive to only axial forces, then it will see only P type waves. Likewise for the transmit transducer. If it can displace only axially wrt to the rod, everything is ok. Good job on catching the distinction. A fine point that only a learned, diligent man such as yourself would catch. Try this link: http://quake.wr.usgs.gov/research/ph...shearwave.html Note they can measure cracks too. Amen! "Martin Baxter" wrote in message ... Bob Crantz wrote: "Martin Baxter" wrote in message ... Sounds good to me, I don't belive tension (or compression) has anything to with the speed of transmission in a solid. Assume a completely rigid guitar neck. Adjusting the tension of the string adjusts its resonant frequency. If the length does not change, but the resonant frequency does, then the velocity in the string must change. C = tension/linear density I don't think so, you are thinking of resonance in a transverse plane, not propagation of a sound wave through the medium. Your example is for a transverse wave, the TDR mode you propose to employ is in fact a compresion/rarefaction, not unlike the P wave in siesmology. The problem is going to be "injecting" this pulse, if you just tap the side of the rod you will generate transverse waves rather than the longitudinal wave you are seeking. I do not think that that transverse waves will be reflected by a crack in the rod or the connectors between rod sections. See http://prola.aps.org/abstract/PRD/v7/i6/p1590_1 for the general equation. Cheers Marty |
Rod Rigging - Hype?
Bob Cranz:
Do you do NDT? (Non-Destructive Testing) |
Rod Rigging - Hype?
Not primarily, electromagnetics R&D. DC - Millimeter Wave, IR-visible. Lots
of sensor work. Amen! wrote in message oups.com... Bob Cranz: Do you do NDT? (Non-Destructive Testing) |
Rod Rigging - Hype?
Cool, I used to do some IR sensor work on Star Wars, now I do x-ray
optics. |
Rod Rigging - Hype?
Bob Crantz wrote:
Good job on catching the distinction. A fine point that only a learned, diligent man such as yourself would catch. Try this link: http://quake.wr.usgs.gov/research/ph...shearwave.html Well shucks, thanks. Let's patent this idea PDQ, must be tens of dollars to be made selling this gizmo to budding marine surveyors! Cheers Marty |
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