Sep 27, 2001 12:33 PM
|I too am a mechanical engineer. I think we as engineers have something particularly interesting to contribute to the biking community because the bicycle is such a classic machine. I follow all the nit-picky discussions about aerodynamics, rolling resistance, mass and downhill speed with interest and I'm sad that they usually degenerate into a "I know more than you do" competition. I know a lot of engineers, I went to MIT (official mascot: the engineer) so I saw engineers made at the factory (so to speak) and I know this is very much the engineers' way but you guys make us ALL look bad with that bickering.
Some of you might like to put it all on alex the engineer. I don't think that's fair. I think that in the past he's definitely been wrong but I don't think it's because he's dumb or a bad engineer but because he posts without thinking it all the way through (and sometimes, by his admission without even reading it). Grz isn't much better with his rude rejections of other people's theories (esp. alex).
What I propose:
When an engineering topic comes up or you feel the need to add an engineering angle to some topic go ahead. Do not start with the title or even the attitude of "you're an idiot, this is how it really is" or "wrong again looser" etc. Try not to make the rebuttals so personal (even if you are right) which is to say try and keep your supremacy and rightness about the problem: yours vs. their solution of it, NOT about you and the other person.
My apologies to grz and alex the engineer if you've been insulted. I think both of you are fine, and I'm sure you're fine engineers, but when you get down to bickering and you keep sticking the "I'm an engineer" and "what kind of engineer are you" crap in there you make all of us engineers look like children. Just because you know something doesn't mean you should be a prick about it, no? If you're so right and you want to stick it to em' so bad that you can barely type, perhaps you shouldn't send it.
Can't we all just get along?
"Matt the mechanical engineer."
|Helium in the tires revisited:||mk_42|
Sep 27, 2001 12:35 PM
|In light of my plea for nice, technically oriented, responses I'd like to revisit the helium in the tires question:
For the lay person the answer is you could save about 8-10 grams of rotating weight depending on pressure, real tire size and if you currently use CO2 (that does mean the tire is filled with CO2, or is it only used as a pressure source to pump air?). Math below. I wonder how much people save by using titanium v. steel nipples? Some people will spend a pretty penny for a few grams.
For the arguments that anything really small has to be negligible consider that sometimes it's the small things that are considered negligible that end up having an effect. At first everyone thought that painting decals instead of stickers (in auto racing) was crap and now everyone does it. I'd believe that for their speeds and the resulting heat changes in the tires, different gas mixtures might make a noticeable difference for race cars. I agree that it doesn't apply to bikes.
Another note: For a project a while back I studied insect flight and there are several accepted and respected theories that conclusively prove that insects can't fly (it's all in the "negligible" terms). Don't be so sure of what the numbers say.
In this case this is what my numbers say:
Using the ideal gas law (PV=nRT) for a bicycle tire of 1.2 litres at 300K (~80F) at 95psi I got about .315 mols of gas.
Molar volumes of various gasses (g/mol):
Air (approximating 80% N2, 20% O2) ~29
Corresponding to gas weights of (g):
I've made mistakes before, I'll make em' again. Feel free to correct me.
Sep 27, 2001 12:42 PM
|every last one of us from time to time could take your advice.|
|Helium in the tires revisited:||MikeC|
Sep 27, 2001 1:24 PM
|Cool. Of course, I have problems keeping plain old air in my tires. Imagine how quickly He would leak out through those tubes!|
Sep 27, 2001 3:39 PM
|Yeah, the voice of reason - all good sugestions. Dunno why we get all worked up - guess it's b/c tone and sarcasm never seem to make it across the net. |
Totally agree with lots of littel things adding up to big things and my point was that you'd see it in the things related to inertia. Mr Alex was saying that the rolling resistance would somehow change since 120 psi of Helium was some how different from 120 psi of air. I also pointed out that the lower mass would affect heat transfer until steady state was reached. Then the guy claims vast thermo knowledge and forgets PV=nRT. Probably the thing that started to get to me was his claim of superior knowledge (implied in his title and on his own) then passing off some bum dope and not even getting units right. Some times when the emporer has no clothes you have to say something....
Ultimately, yes, we (OK, I) do look like a bunch of little boys in a pissing contest - old habits die hard. ;-)
Sorry to hear about you going to MIT! :-) I was "slumming" at Cornell.
|hey, asshole!||alex the engineer|
Sep 28, 2001 5:16 AM
|So when did I say anything about the rolling resistance of air being different because of the gas? NEVER! Maybe it's because you have had your head stuck so far up your ass that you can't remember what anybody said?
If you had actually READ my post, I said that:
1) the claimed advantage was SLIGHT
2) the differences in pressure increase were due to SMALL amounts of CO2 (and/or other gasses) reacting with themselves, and
3) gassification of water present in air
You can disagree with my theoretical explanation to something which might have resulted more from superstition than fact (racing teams using nitrogen in their tires), or you can disagree with the way I defend myself from your attacks, but I'll be DAMNED if I allow you to libel me!
Is this the way you behave in your professional work? How many times have you been sued for creating false quotations about another person's comment? Do you have NO integrity?
|no foul language, especially in the subject line, OK? nm||Dog|
Sep 28, 2001 5:17 AM
|Yes, please. nm||MB1|
Sep 28, 2001 5:21 AM
|sorry, I meant: "hey, @$$hole!" .please edit. nm||alex the engineer|
Sep 28, 2001 7:09 AM
Sep 28, 2001 7:23 AM
|Can't express yourself without the foul language? It adds nothing to the discussion nor to anyone's opinion of you. Name calling like that is immature, uncivil, and shows that you don't have the ability to discuss something intelligently. Why on earth would you feel the need to offend people like that? Think about it. Why even take the time to join the discussion and waste your time with immature name calling? Disguising it with other characters does not make it any better, either. Grow up.
Boy, the "we're in it together" attitude sure disappeared fast for some.
|I'm thinking "lost cause". -nm||mk_42|
Sep 28, 2001 7:31 AM
|Just love taps||scottfree|
Sep 28, 2001 9:01 AM
|That seems to be the way engineers talk to each other.|
Sep 28, 2001 9:57 AM
|Seems to be his preference, no? |
Mostly just an excitable boy in spew mode.
|Sure, not so||Roadie|
Sep 28, 2001 8:16 AM
|Grzy, you attack and insult any chance you get don't you?
Hey, I remember you trying to explain how things that are not moving (in a given frame of reference) are still accellerating !!!!!
Cornell must suck at teaching basic physics, no?
|as another engineer: 1 + 1 = 3||JohnG|
Sep 27, 2001 4:35 PM
|I can tell you that you are absolutely wasting your time trying to convey anything engineering related via these Usenet groups.
These semi-scientific 'dissertations' border on humorous stupidity actually.
|Are you saying we're not trainable? Not WORTH training? I||bill|
Sep 28, 2001 7:30 AM
|know when I've been insulted. I think.|
|would you preffer it in person||ishmael|
Sep 28, 2001 7:47 AM
|i think science can travel by text..why not the internet...its atleast safer this way...although i doubt alex would be so excited if he had to tell what he says to someones face...and we are all engeniers even if we cant spell it..tinking with a bike can give all the science to last a lifetime..|
|medium not problem||Dog|
Sep 28, 2001 8:09 AM
|It's not the medium, but rather the thought and time that goes into the posts, IMO.
|medium not problem... I agree.||JohnG|
Sep 28, 2001 3:46 PM
|I've tried to explain relatively simple college level physics problems on the web before and no matter how many (or different) ways you explain something there is always at least one ignoramus that responds with a comment or flame regarding the issue.
It's sad but true.... I liken it to mental masturbation. It might make you feel good to post some interesting and thoughtful dissertation but in the end it's totally unsatisfying. That's why I don't even try any more.
However, I do applaud you for posting thoughtful comments... you're a better man than I.
|Ok...my apologies to Alex||Chris Zeller|
Sep 28, 2001 8:23 AM
|Sorry I was so harsh on Alex in the helium discussion. I was only trying to turn his anger (pointed I think unfairly) around on him. I felt that nit picking on small details was inappropriate without considering the big picture.
Nonetheless, dumb@ss was harsh and my apologies.
Chris the Aerospace Engineer
|the board's content has weakened lately||peloton|
Sep 28, 2001 9:04 AM
|I think you are right on the money as far as the idea to have civil dilect here. I'm real sick of the people using one time handles turning every third post into a flame war. I'm also real sick of otherwise intelligent conversation being undermined by condesending comments of intellectual superiority. It's been getting worse and worse for a while. It's too bad too because it has driven away a lot of people who contributed here in a positve fashion. There are a few people here you can count on to bring up good topics, and always add something positive- Dog, Dino, Humma hah, Jon, and a few others I'm leaving out (sorry). I can tell you if things don't start getting better, I'm gonna be MIA too.|
|Yep, been pretty slow here since the tradgedy.||Chris Zeller|
Sep 28, 2001 9:10 AM
|I guess everyone's beed depressed and not thinking too much about cycling. I myself had trouble thinking about these "trivial" matters even though I did ride more to escape and let off frustration.
To be honest I entered the fray on these technical discussions out of pure boredom. Talking about basic freshman physics and chemistry is pretty lame.
|chemical poetry for engineers||Rusty McNasty|
Sep 28, 2001 9:29 AM
|Grzy had a little drink
but drink he will no more
'cause what he thought was H2O
was H2SO4 !!
Sep 28, 2001 9:54 AM
|That really burns me up.... inside! ;-)|
|chemical poetry for engineers||grzy|
Sep 28, 2001 9:55 AM