Skeeve Posted April 15, 2009 Posted April 15, 2009 I made a mistake based on the false assumption that a cc of air would change its temperature, faster than a cc of aluminum or copper. But I stand by the FACT that in your design, Aluminum is better than brass for a mounting stud. For the OE sensor holder I do not contend that aluminum would be better than copper. I contend that aluminum would be better than brass for the brass adapter design, and I suspect aluminum would be better than copper, in that design, but I could be wrong about that. I figure the lower mass trumps the higher conductivity, but as I said I could be wrong about that. But I am not wrong about aluminum being a better stud than brass. You are wrong about brass being better than aluminum. What is your proof or evidence, that brass would be better? I have no proof but based on aluminum's superior conductivity and lower density, it seems pretty obvious that aluminum would be the better choice. Aluminum has nearly twice the conductivity of Brass http://www.engineeringtoolbox.com/thermal-...tals-d_858.html The density of brass 8.4 to 8.73 grams per cubic centimeter. The density of aluminum 2.70 grams per cubic centimeter--wikipedia "Yeah but..." Dave, the only reason I can think of to make the sensor holder partly [or in case of the original design, wholly] out of brass is because aluminum oxidizes rapidly, forming a layer of aluminum oxide within minutes of exposing fresh metal. No big deal, this is part of what makes aluminum better than other materials in some applications. But in this case, you'd have two layers of Al2O3 coating the threads in the head and the threads on the sensor holder. That's two layers of an insulator [a very effective one, too, I might add: your coffee mug is made out of it! ] vs. only one w/ a brass holder. Aluminum-on-aluminum mating surfaces might be problematic, mechanically too: self-fusing & galling issues come to mind as potential reasons for Guzzi spec'ing brass. Copper is definitely better, but it tarnishes upon exposure to weather, so maybe that was a non-starter for "warranty" issues? WRT aluminum's lower density, it's a non-issue for this discussion: thermal diffusivity is given per unit volume, as the density of the respective materials is factored out of this physical definition.
Skeeve Posted April 15, 2009 Posted April 15, 2009 OMFG. Could we really hit 50 pages? Greg: Do you sit watching the thread counting posts so you can keep getting the top post on the respective page#XX saying "Can we possibly hit page#XX?" 'Cause if not, your timing is phenomenal!
Skeeve Posted April 15, 2009 Posted April 15, 2009 But seriously, I am having trouble grasping the air gaps importance for anything other than getting the sensor output to match the engineers intentions, or to keep the plastic from heat damage in Ratchet's setup. Well, given an insulating mount and a temp sensor w/ a probe tip sufficiently isolated from the rest of the sensor body, relying upon radiated heat instead of conducted heat would allow for the decreased influence of heat transients while allowing correct sensing of substantive changes in heat output. Also, it would mean that since so much less heat was being input to the sensor body, it would remain far more sensitive to slight but consistent changes vs. those too small to overcome its own heat soak. I think ol' Ratch' might just be on the right track w/ his GM sensor kludge... All hail Empiricist Ming! 'er, Hatchracket! er, Hackratchet? Well, whatever his name is... he's empirical! Experimental. Whatever. That's what counts!
dlaing Posted April 15, 2009 Posted April 15, 2009 snip Thanks! that is interesting. Maybe those lean surging beemers would benefit from what has been discussed here???
dlaing Posted April 15, 2009 Posted April 15, 2009 "Yeah but..." Dave, the only reason I can think of to make the sensor holder partly [or in case of the original design, wholly] out of brass is because aluminum oxidizes rapidly, forming a layer of aluminum oxide within minutes of exposing fresh metal. No big deal, this is part of what makes aluminum better than other materials in some applications. But in this case, you'd have two layers of Al2O3 coating the threads in the head and the threads on the sensor holder. That's two layers of an insulator [a very effective one, too, I might add: your coffee mug is made out of it! ] vs. only one w/ a brass holder. Aluminum-on-aluminum mating surfaces might be problematic, mechanically too: self-fusing & galling issues come to mind as potential reasons for Guzzi spec'ing brass. Copper is definitely better, but it tarnishes upon exposure to weather, so maybe that was a non-starter for "warranty" issues? WRT aluminum's lower density, it's a non-issue for this discussion: thermal diffusivity is given per unit volume, as the density of the respective materials is factored out of this physical definition. Thanks, I posted about the weather resistance of brass, but Ratchet ignored it. That could be a good enough reason, to go with brass. For the stud the conductance is more important than the diffusivity, but the diffusivity difference between brass and aluminum should be very large. The density of brass is factored out, or rather not factored in, but the density is a likely indicator that brass will retain more heat. But the weathering issues of aluminum could be a concern. How about titanium?
dlaing Posted April 15, 2009 Posted April 15, 2009 Thanks, I posted about the weather resistance of brass, but Ratchet ignored it.That could be a good enough reason, to go with brass. For the stud the conductance is more important than the diffusivity, but the diffusivity difference between brass and aluminum should be very large. The density of brass is factored out, or rather not factored in, but the density is a likely indicator that brass will retain more heat. If we new the thermal diffusivity of brass, I would not be speculating based on density. But the weathering issues of aluminum could be a concern. How about titanium?
Greg Field Posted April 15, 2009 Posted April 15, 2009 Greg: Do you sit watching the thread counting posts so you can keep getting the top post on the respective page#XX saying "Can we possibly hit page#XX?" 'Cause if not, your timing is phenomenal! Yes, but purely a matter of chance.
Guest ratchethack Posted April 15, 2009 Posted April 15, 2009 Well, given an insulating mount and a temp sensor w/ a probe tip sufficiently isolated from the rest of the sensor body, relying upon radiated heat instead of conducted heat would allow for the decreased influence of heat transients while allowing correct sensing of substantive changes in heat output. Also, it would mean that since so much less heat was being input to the sensor body, it would remain far more sensitive to slight but consistent changes vs. those too small to overcome its own heat soak. Skeeve, I do b'lieve you've got a full grasp o' the entire enchilada here. This is just me, and it's strictly a matter of (slight) amusement, but by my count, that makes 3 of us on this thread. Now I don't think there's any way I could possibly care less than I do about CONSENSUS. But given the sheer magnitude of the Great Wallopping Group Dork Wrap Wad around the ol' Driveshaft that's been building up to truly alarming proportions over the last 50 pages (on an accelerating basis yet!) , wot d'you figure the chances might be of gaining a CONSENSUS of those here with much've any clue about wot's been um, "discussed" here for 50 pages? Considering the great heap of astoundingly persistent displays of idiocy and ignorance we've witnessed here (both willful and, um, inherent and natural) -- some being the most flamboyant varieties ever spotted heretofore on this Forum by Yours Truly -- I'm thinkin' somewhere between slim and ZIP, but that's just me (Part II). . . Enquiring minds. . . (well, you know). . .
Greg Field Posted April 16, 2009 Posted April 16, 2009 The BQ on this thread continues a near vertical ascent. Perhaps it's time to start a contest to guess on what page the BQ will have reached its apogee? I say the fabled "three" who actually "understand" what's going on are still in BQ acceleration mode and won't even begin slowing down for another 30 pages. Good for a laugh to watch anyway.
Skeeve Posted April 16, 2009 Posted April 16, 2009 Skeeve, I do b'lieve you've got a full grasp o' the entire enchilada here. What, that the whole injection setup on our Guzzis is one factory-produced kludge stacked on top of another, and we'd be better off figuring out some way to plumb in a MAF from some Ford [or Fjord, if you prefer Norwegian otto-makers! ] and a sparkplug-washer CHT sensor, & converting the hole used by the Guzzi engine temp sensor into some sort of dual-plug application? Yes, in that case, I do have a full grasp of this particularly slippery enchilada! Mas salsa roja y queso, por favor! But I'm fairly certain that in my case, I'm just going to pull out the stock plastic standoff, drill a hole for a copper rod in the base, add the heat sink under the sensor, and put some teflon tape on the threads when I reinstall the modded stock part. I figure that'll get me 50% of the way to your GM sensor, be fun to do, and I won't have to hunt down some linen-reinforced phenolic to make a new standoff out of, altho' that could be fun in its own way. Oh, & lane split ["share"] religiously on hot days! Luckily, I still live in CA where that's legal... Eventually, I hope to $crape up the ducat$ to TuneBoyeeee or PCXXIV&1/2 the durn thing & forget about such devilish little details...
Guest ratchethack Posted April 16, 2009 Posted April 16, 2009 . . . I'm fairly certain that in my case, I'm just going to pull out the stock plastic standoff, drill a hole for a copper rod in the base, add the heat sink under the sensor, and put some teflon tape on the threads when I reinstall the modded stock part. I figure that'll get me 50% of the way to your GM sensor, be fun to do, and I won't have to hunt down some linen-reinforced phenolic to make a new standoff out of. . . You lost me back at the hole for a copper rod in the base, Skeeve. The base of the OE holder IS copper. Please advise?
Greg Field Posted April 16, 2009 Posted April 16, 2009 Will it run more perfectly if you use another material? Enquiring minds, well, you know . . . (sorry, even in sarcasm, I can't resort to smarmy-snarkey smileys)
helicopterjim R.I.P. Posted April 16, 2009 Posted April 16, 2009 The BQ on this thread continues a near vertical ascent. Perhaps it's time to start a contest to guess on what page the BQ will have reached its apogee? I say the fabled "three" who actually "understand" what's going on are still in BQ acceleration mode and won't even begin slowing down for another 30 pages. Good for a laugh to watch anyway. It will never end. There will be a technically verbalized code such as "linen-reinforced phenolic" meaning "I'm posting last" followed by more code using more technical terms like "thermal diffusivity" but actually meaning "No. I'm posting last!" and thus it shall go on to infinity!!
Steve G. Posted April 16, 2009 Posted April 16, 2009 It will never end. There will be a technically verbalized code such as "linen-reinforced phenolic" meaning "I'm posting last" followed by more code using more technical terms like "thermal diffusivity" but actually meaning "No. I'm posting last!" and thus it shall go on to infinity!! I think it's just a continuation of the Global Warming thread, but in 'code'! "Temp Sensor" is really "Al Gore", "Thermal Diffusivity" is really "Rising Oceans". Steve
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