|If I put helium in my tires will I go faster?||Sprockit|
Sep 25, 2001 9:22 AM
|It's lighter then air you know.|
Sep 25, 2001 9:32 AM
|you could also seal and fill the frame tubes, handle bars, seat post and crank arms (assuming Shimano hollowtech) with Helium as well - you'd be super fly then - or you could try going to hydrogen - lighter yet (just stay away from open flame.. :-)|
|re: If I put helium in my tires will I go faster?||Torv Carlsen|
Sep 25, 2001 9:35 AM
|No. But you will talk funny.|
|According to the latest scientific research...||Elefantino|
Sep 25, 2001 10:27 AM
|If you carry a very light helium gas cannister (16 gram will do), suck on it when you're at the rear of the paceline, then yell "on your left!" in that Alvin the Chipmunk voice, all the other cyclists will be startled and slow for a fraction of a second, allowing you to race by and APPEAR to be much faster. |
I believe this test was conducted by Bicycling Magazine.
|According to the latest scientific research...||davet|
Sep 25, 2001 11:19 AM
|Now that's funny!!|
|Try hydrogen, its even lighter...||Cima|
Sep 25, 2001 9:37 AM
|Of course it is also very flamable, and friction from the road and braking could cause your wheels to ignite like Hindenberg!! |
|yes, by .0000000001 seconds over 100 miles :-) nm||Dog|
Sep 25, 2001 9:38 AM
|Only if on a Zepplin -NM||Tig|
Sep 25, 2001 9:40 AM
|Of course, if you pedal harder. nm||MB1|
Sep 25, 2001 9:46 AM
|As long as you are not riding a huffy. nm :-)||nestorl|
Sep 25, 2001 9:46 AM
|No. Just go the bathroom first.nm||Empirion75|
Sep 25, 2001 9:51 AM
|re: If I put helium in my tires will I go faster?||Mike P.|
Sep 25, 2001 9:58 AM
|Better yet. . . rig up an adapter to connect your shop vac to the tube valves. Then just turn on the thing and suck everything out of the tubes. Leave it on a few minutes to make sure you work up a good suction. All those gasses have weight and aren't good for much anyway so suck away. Makes for a rough ride I would expect.
|Bottled Air from France (Perri-Air)||Rich Clark|
Sep 25, 2001 11:04 AM
|The same stuff Lance had in his tires when he won three Tours de France, now available in the US.
|re:Bottled Air from France (Perri-Air)||SamDC|
Sep 25, 2001 3:17 PM
|Hey, that's a Space Ball rip-off!|
|Hmm. Great Minds (nm)||Rich Clark|
Sep 25, 2001 5:19 PM
|Bottled Air from Wisconsin (Dairy-Air)||Rich Clark|
Sep 25, 2001 11:05 AM
|50% methane. For explosive sprints.
|Bottled Air from Uranus (Derriere)||grzy|
Sep 25, 2001 1:53 PM
|How do you light it in a vacuum? (nm)||Rich Clark|
Sep 25, 2001 2:34 PM
Sep 26, 2001 8:45 AM
|And your tires will sound like Donald Duck.||Brian C.|
Sep 25, 2001 11:09 AM
|Use Nitrogen...no, seriously||peloton|
Sep 25, 2001 11:37 AM
|I have actually seen reports that show a tire filled with Nitrogen will have less rolling resistance than the same tire filled with air. In real world applications, this may not drastically increase your speed with other factors invovled. I guess if you are trying to gain seconds though in that long time trial it could count for something.
A mechanic for a major team at a NORBA national told me that he uses nitrogen in the team's tires because he could fill the tires the night before, and the pressure would still be the same in the morning. Nitrogen doesn't seep out of the tube like regular air, apparently was the reason.
|Just don't lick'em! (nm)||Asphalt Addict|
Sep 25, 2001 11:52 AM
|But ordinary air is, what?, 70% nitrogen anyway||cory|
Sep 25, 2001 11:55 AM
|I forget exactly, but that's close. When you read about "nitrogen-charged" struts or shock absorbers or whatever, they're almost always talking about plain old air, of which N is the largest component.|
|struts and shocks||peloton|
Sep 25, 2001 12:37 PM
|The reason that they use Nitrogen in shocks and struts is because it is without the impurities of normal air. Namely water vapor that can condense on the inside of the shock and cause problems. Ordinary air is largely nitrogen, but it's the other stuff that brings some variables.|
Sep 25, 2001 1:56 PM
|Nitrogen is used in aircraft shocks and struts to avoid the vapor from condensing and freezing. Got 6 years in the Navy with first hand experience.|
|You already do||mr_spin|
Sep 25, 2001 11:58 AM
|I wonder if makes any difference. The air you breathe and pump into your tires is already about 80% nitrogen. No one has mentioned pure oxygen. I wonder how that would work.|
|nitrogen in auto racing tires:||alex the engineer|
Sep 25, 2001 12:21 PM
|Some teams use nitrogen for a couple of reasons:
Firstly, it is inert, so venting a tire near a flame won't result in a flare up. It might also prevent a tire spontaneously combusting when EXTREMELY hot, too.
The other reason why nitrogen is used is that it is has much lower density change due to heat than air. The tire pressure changes less when heated.
It is marginally lighter than air, too, but the difference is (28/29.5)* M(air), which doesn't really amount to much.
Sep 25, 2001 2:09 PM
|>The other reason why nitrogen is used is that it is has much lower density change due to |
heat than air. The tire pressure changes less when heated.
unless you chnage "n" the number of molecules in the container the pressure temperature relationship won't change. There is a very slight adjustment for non-ideal gasses, but it is a very small correction factor. What you could be talking about is the rate of heat transfer, but once the tires are up to temp and at erqulibrium it's a wash.
Again - what kind of engineer are you?
|Was thinking the same thing (nm)||Chris Zeller|
Sep 25, 2001 2:41 PM
|Right||alex the engineer|
Sep 26, 2001 6:19 AM
|First, that is the IDEAL GAS law. Air is NOT an ideal gas, but a combination of many gasses, several of which are less INERT than nitrogen. Air is mostly N2, O2, and CO2. Of the three, CO2 is the most reactive, and can, to a small degree, break down into CO and O2. The reaction goes like this:
3CO2 > 2CO + 2O2
This means that, at least for this small part, 3 moles (the "n" in the ideal gas law) of CO2 now becomes 4 moles of CO and O2 combined. Now that "n" is larger, P is also larger, given a similar volume.
There is also the law of partial pressures to consider, too. Liquid water is quite possible to have inside a tire filled with air, and should the temperature raise, a larger percentage than previous will be gassified, thereby also increasing pressure.
Your knowlege of this is obviously limited. Next time, get your facts straight before you put your foot in your mouth, and you won't look like such a dumb@$$.
|and one correction||alex the engineer|
Sep 26, 2001 6:24 AM
|Sorry, I was blinded by rage, and didn't doublecheck. The reaction:
3CO2 > 2CO + 2O2
is wrong. It should read:
4CO2 > 4CO + 2O2
and therefore, 4 moles now are 6, an increase of 50%.
I really should be more careful before I post. I am sorry.
|50% of what?||Chris Zeller|
Sep 26, 2001 8:38 AM
|Co2 is only .045% of air by mass anyway and only a small percentage of this will end up on the right side of this equlibrium equation anyway under incresed temps. So what is it that you are trying to prove? OK there is a very very very small difference. What does that mean? For the record, the constituents of air:
Component % by Mole % by weight
Nitrogen 78.084 75.5
Oxygen 20.946 23.2
Argon 0.934 1.33
Carbon Dioxide 0.0335 0.045
Neon 0.001818 -
Helium 0.000524 -
Methane 0.0002 -
Krypton 0.000114 -
Nitrous Oxide 0.00005 -
Xenon 0.0000087 -
|50% of what?||grzy|
Sep 26, 2001 8:44 AM
|Yeah, the order of magnitude concept really is ellusive to some. It's the difference between the lab and the real world, no?|
|Hey Dumb @ss||Chris Zeller|
Sep 26, 2001 8:21 AM
|None of what you mentioned would amount to a hill of beans. The reaction rates for the equilibrium equations you mentioned are so low that they are likely to be inconcequential, as you yourself mention "to a small degree". GRZY also mentioned that although the ideal gas law is imperfect for air, the correction factor is small. It is indeed small for the diatomics in air as are the van der walls forces for these constituants.
Pressures should not be of concern. Under 10 atmospheres of pressure or less, Ideal Gas Law predictions are very close to real amounts and do not generate serious error. I don't know much about racecar tire pressures, but I would imagine they are much less than 147 psi.
I think the most important thing to note is that air itself is about 70-80% N2 anyway. Any change in heat transfer rate, or reaction rate due to increased temperature is likely to be very similur to air.
I don't see any real advantage here. You can nibble to death basic formulas like the ideal gas law, but the orders of magnitude of the extra terms usually aren't significant. That's the difference between engineering and science--we engineers weigh the importance and insignificance of HOT (higher order terms) and only concern ourselves with the most important terms. Harping on things like this make you look smart on messageboards but it usually won't get you very far in terms of finding a real-word solution.
Sep 26, 2001 8:47 AM
|What about the BIG picture? You gonna be able to even measure the difference or see it in a lap time. I think not.|
Sep 26, 2001 8:15 AM
|The specific heat (btu per lb, deg F) of pure diatomic nitrogen (N2)is greater than that of the mixture of the gases in air. (but not by much), thus more heat is needed to raise the same mass of nitrogen than that of air.|
|But not by much||Chris Zeller|
Sep 26, 2001 8:26 AM
|I think this is the operartive phrase here. If you are concerned about this, you might also look into the consider that residual liquid H2O in air might increase the total CP of air a bit as well--considering that the heat of vaporization of water is likely to blow away any differences you state.
Heat transfer rates are likely similur as well.
Where is there a substantial imporvement? If air is 70-80% N2 anyway?
Sep 26, 2001 8:36 AM
|I actually acknowledged that there would be an effect during transition - once at steady state it no longer matters - especially when one considers that said mass of gas is surrounded by the tire and rim which are much more massive. Steady state temperture and heat transfer rate is not the same thing.|
Sep 25, 2001 2:05 PM
|I call bullsh!t. Once you understand the properties of gas and the Ideal Gas Law (law of partial pressures, etc.) you'd see what a bogus statement that is. What they may be trying to point out is that with a lighter gas you could have the same pressure for less weight inside the tire and therefore less mometn of inertia. On the TdF for a while they were using Helium since the only gas lighter is hydrogen and we all know what happens with an open flame. |
As far as the leaking out bit, that's also a bunch of folk lore - a diatomic oxygen molecule is larger and heavier than nitrogen. So the O2 must be sneaking out at night to go chase gals. Maybe the NORBA guy has a little to much pocololo on his hands?
Sep 25, 2001 9:56 PM
|i say lay off the damn twinkies and you'll go faster|
|re: If I put helium in my tires will I go faster?||Woof the dog|
Sep 26, 2001 1:19 AM
|See, there is a problem I am seeing. If wheels keep getting lighter and lighter with the rest of the stuff like frame blah blah blah, the bike will be too light for good cornering. No? or maybe it will be less stable. Well, maybe not. Any ideas?
Woof the dog.
Sep 26, 2001 8:42 AM
|You may not believe this, but in cornering the ability to pull "g" isn't a function of mass. Sort of like the free fall thing. When one does the free body diagram and reduces the equations the mass term drops out.|
|Double Check that||mk_42|
Sep 26, 2001 12:18 PM
|I usually agree with you, and even this time you're right in the general sense that a "too light" bike really won't matter at all next to rider weight in cornering.
But I don't think that the mass term drops out:
The apparent force pushing you out is related to speed and mass. If you lean at all in a turn some of that force is going to be pushing down. That downforce is what makes you stick. So it seems that the only ways to increase your cornering "stick" is to increase mass, increase speed, increase frictional coefficient or increase the bank angle.
Perhaps you were thinking of a car and forgot that bikes lean and that that's a good thing?
Just in case you think I'm being vicious or trying to be an ass I've included a smiley:
|All Ready Did||grzy|
Sep 26, 2001 12:44 PM
|When you work out all the gory math it does drop out and you're left with things like bank angle, velocity and coefficient of friction from the tires and "g". It's all detailed in The Theory of Ground Vehicles, by Wang. |
Not a flip answer- just the facts.
|I'd like to see it...||mk_42|
Sep 26, 2001 1:03 PM
|I stand corrected. It is not the first time that something "seemed to me" and wasn't in the end...
If you have the book handy (and the time) would you mind posting the reduced relationship, I'm interested to see it.
And is that book any good? Does it cover everything in general or does it have a specific section on bikes? How old is it?
|Lemme Look Around||grzy|
Sep 26, 2001 2:58 PM
|I've got a lot of my books still in boxes in the basement. We don't really have the room for the full library yet. the book is pretty good and gets quite technical - it is expensive to buy though so I'm not sure it's worth the $85 or so at Amazon.com. Maybe if you've got insomnia.... I had to get it for the course. The stuff in the book applies to all vehicles from tanks to bikes to tractors. I've also got other books on suspension design by Colin Chapman - the master mind behind Lotus. I've referenced it several times so maybe it's time I throw some stuff up - course there's the copyright laws. |
I guess it's important to make the distinction that while mass is in the analysis it isn't a determining factor. See while mass works against you in terms of requiring a larger force to change direction (i.e. accelerate) it also helps in terms of providing the downward force on the tires which give you the grip - it's kind of an all or nothing symbiotic deal. Given the trouble I had with expalining the free fall thing I'm not sure it's worth trying to get into this too deeply - but we can try.
|lightness and cornering||Dog|
Sep 26, 2001 12:49 PM
|OK, compare a Formula One and a Winston Cup car, by analogy. Lighter often means faster, if the right materials and design are used.
|lightness and cornering||grzy|
Sep 26, 2001 12:53 PM
|Sure, but that's an over simplification that will get you in trouble. Remember the free fall? Ultimately light is right, but not always for the first reasons that come to mind. Ultimately either class of car is governed by the rules of that class in addition to nature. Winston Cup cars use throttle restriction plates, for example.|
|I know, but||Dog|
Sep 26, 2001 12:57 PM
|I know it's a vast oversimplification, not accounting for downforce, tires, center of roll, driver skill, etc.
But, those guys spends millions to get those cars lighter (for accellerating and braking, too).
I'll never forget my first drive of a Formula Ford. A 1,000 pound car, no wings, not so big tires. Astounding performance for 110 horsepower.
|I know, but||grzy|
Sep 26, 2001 3:02 PM
|Sure, getting the weight down is always good from an overall racing perspective. Why accelerate mass that you don't have too? It gets into the root cause of things. |
Tip - take a new Subaru WRX for a test drive. AWD turbo 2.0 liter with 227 hp - the thing inhales the road, any road, paved or not. At around $24K it's an affordable street legal slot car. Try to resist buyiung one....
|please don't say weight doesn't affect cornering :-)||Dog|
Sep 26, 2001 1:10 PM
|I really hope you are not going to tell us that a heavier car (or bike) won't corner more slowly, all else equal. I'll cry.
|please don't say weight doesn't affect cornering :-)||grzy|
Sep 26, 2001 3:09 PM
|Naw - I wouldn't say that. You can get a heavier vehicle to out corner a lighter one or vice versa, but not everything else stays equal. If the lighter vehicle has realitvely better grip the viola! Without going any further I'll try and dig up the analysis in all it's gory detail. I think the question raised was that bikes might get too light to corner effectively - while this may happen it will be b/c of some factor other than the mass. Now if the bike is so light that the structure and stiffness is compromised, well.....|| |