Gollum Posted May 18, 2006 Share Posted May 18, 2006 So, late one night me and my brother had too much time on our hands and our minds got a little scientific (or has scientific as we get). What whould happen if you filled your tires with helium for a race day? How much weight would you save? How stable would be it? At what rate would the gas diffuse? So, does anyone know if helium is flamable at any rate? Or if it's pressure combustable? I found this decent article on the web. I'm sure there's more stuff out there. http://www.newton.dep.anl.gov/askasci/eng99/eng99085.htm Seems like a viable idea, just possible diminished returs. Although it seems like it couldn't hurt. Let me know what you guys thing. Quote Link to comment Share on other sites More sharing options...
frank280zx Posted May 18, 2006 Share Posted May 18, 2006 i know they use nitrogen in some formula cars and rallycars.. but helium.. ooh why not.. it is about 4 times lighter than air not ? Quote Link to comment Share on other sites More sharing options...
veritech-z Posted May 18, 2006 Share Posted May 18, 2006 It's probably due to rate of thermal expansion. I'm not sure what it is for helium, but i've seen balloons pop just from being in the sun (ie. just the sun shining on it caused it to expand so much it blew up), so I can only imagine that the stresses of high speed driving would take that to the next level... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 18, 2006 Share Posted May 18, 2006 SEARCH. Helium leaks out through the tire at about 10 psi per hour. For more details, find the same thread I did and read the rest yourself. Quote Link to comment Share on other sites More sharing options...
Gollum Posted May 18, 2006 Author Share Posted May 18, 2006 Sorry, I didn't even think of searching. I assumed I was the only person this insane. Parently I was wrong Thanks for the recomendation jon. Quote Link to comment Share on other sites More sharing options...
johnc Posted May 18, 2006 Share Posted May 18, 2006 Helium story... My nephew is a Navy Seal and when he went through BUDs training he and his squad end up spending a lot of time carrying around a big inflatable rubber boat. One of the other squads got smart and filled their rubber boat with helium. But, it seems the instructors knew about that little trick. The squad was caught and for one 24 hour period of training the squad had to carry their rubber boat around half filled with water. Then when they were allowed to drain the water back out, they had to inflate the boat using their lungs only. They started at 10:00pm and the instructors finally let them hit their racks at 4:00am. Quote Link to comment Share on other sites More sharing options...
2126 Posted May 18, 2006 Share Posted May 18, 2006 Helium story... My nephew is a Navy Seal and when he went through BUDs training he and his squad end up spending a lot of time carrying around a big inflatable rubber boat. One of the other squads got smart and filled their rubber boat with helium. But' date=' it seems the instructors knew about that little trick. The squad was caught and for one 24 hour period of training the squad had to carry their rubber boat around half filled with water. Then when they were allowed to drain the water back out, they had to inflate the boat using their lungs only. They started at 10:00pm and the instructors finally let them hit their racks at 4:00am.[/quote'] Conclusion.......helium is hazardous to your well being!!! John, at least your nephew and his partners are using their heads for something besides a hat rack. Quote Link to comment Share on other sites More sharing options...
bjhines Posted May 18, 2006 Share Posted May 18, 2006 THere are more considerations than weight/density of gases... Helium vs AIR mixture has little in the way of weight savings... I have not done the math... but it will be measured in grams for all 4 tires together... take a big crap right before you get in your car... you will have unloaded 2 orders of magnitude more weight in the bathroom... Thermal expansion and compressibility are the main considerations... CO2 and propane are highly compressible gasses... this is why they are soooooo popular with manufacturers of aerosol cans... they are not soo good in tires... one tends to be a fire hazard when mixed with oxygen and the other(CO2) changes pressure too much as temperature changes... Nitrogen... which is most of the air in which we live.... is not quite as compressible as other common, SAFE gases... it takes a relatively large pressure change to alter the density of nitrogen gas... With a little high school physics(GAS LAW) you will understand why a tire filled with nitrogen will not undergo as drastic a pressure change as airmixture filled tires when they get HOT... You cannot alter things very much by using pure nitrogen... it is mostly what we breathe anyway... if you do go that route you will need to come up with a way to purge other unwanted gasses from the wheel and tire assembly...... usually 2 diametrically opposed valve stems... one as a purge and the other as a fill... Helium WILL NOT LEAK out of your tires the way it passes through a thin rubber membrane(balloon)... It will stay in there as well as any other gas that does not dissolve the casing of the tire... Quote Link to comment Share on other sites More sharing options...
frank280zx Posted May 18, 2006 Share Posted May 18, 2006 Helium story... My nephew is a Navy Seal and when he went through BUDs training he and his squad end up spending a lot of time carrying around a big inflatable rubber boat. One of the other squads got smart and filled their rubber boat with helium. But' date=' it seems the instructors knew about that little trick. The squad was caught and for one 24 hour period of training the squad had to carry their rubber boat around half filled with water. Then when they were allowed to drain the water back out, they had to inflate the boat using their lungs only. They started at 10:00pm and the instructors finally let them hit their racks at 4:00am.[/quote'] There is no helium in those hoods is there john Haha fun story.. actually they should be rewarder for using their brains ! Quote Link to comment Share on other sites More sharing options...
bjhines Posted May 18, 2006 Share Posted May 18, 2006 To give you a good idea on how important this thermal expansion and compressibility can be.... BIG TIRES..like mining trucks and loaders use... are filled with water AND AIR.... they are not really that concerned with thermal characteristics as much as they are concerned with compressibility... A tire that big.. with that much weight on it... is acting as the suspension for that HUGE vehicle.... if the tires were filled using only air.. they would bounce over bumps in the ground like they were toys.... The tires would compress and store HUGE amounts of energy... then they would suddenly release all that energy and spring the heavy equipment right into the air.... Loaders would toss 10 ton rocks like a short order cook flipping pancakes... There is a very limited amount of damping that can be expected from a large tire like that.... the air filled tires act like an undamped spring.... The trick is to fill most of the tire with an incompressible liquid... water or oil.... then the rest of the space is filled with air... the smaller airspace does not store nearly as much energy.. the internal damping characteristics of the tire can more easily deal with the stored energy potential of the smaller airspace.... finer points of this design include ways to baffle or partition off the inside of the tires to keep the water from sloshing violently in the huge tires... Quote Link to comment Share on other sites More sharing options...
badjuju Posted May 18, 2006 Share Posted May 18, 2006 if you're drag racing you'd want to reduce the weight on the front only, if you have enough power to break the tires off you want more traction in the rear. load the tires in front up with whatever you want, it's actually better to weight down the rear. my uncle would put calcium in his rear tires and gain better times through being able to launch at a higher rpm Quote Link to comment Share on other sites More sharing options...
johnc Posted May 18, 2006 Share Posted May 18, 2006 Helium WILL NOT LEAK out of your tires the way it passes through a thin rubber membrane(balloon)... It will stay in there as well as any other gas that does not dissolve the casing of the tire... Uuuhhh, no. It does leak out quickly. Maybe not all through the casing but a helium filled tire will leak helium fast enough that its not safe to race or drive on. Helium does not interact with other molecules at the temperatures we are concerned with (remember, its a noble gas). A typical Helium molecule (which is always monatomic - one Helium atom) is .98 angstroms in diameter. Nitorgen and Oxygen both form molecules at the temperatures we are discussing. Typically a Nitorgen molecule is two Nitrogen atoms bound together with a ovoid shape that's about 2.0 angstroms across. The oxygen molecule is even bigger. At any particular temperature the Helium molecules are moving faster then the Oxygen or Nitrogen molecules. All molecules have energy, which comes from their constant motion. This energy of motion depends on two things: (1) the molecule's speed, and (2) the molecule's mass. At any temperature, different molecules have the same energy. Since helium is so much lighter than oxygen, at the same temperature the helium molecules must be moving faster in order to have the same energy. Because of their increased speed Helium atoms have many more collisions with the walls of the container (balloon or tire). Therefore they have many more opportunities to fine a way out, whether that's through the tire casing, tire bead to wheel interface, valve stem, or porous wheel casting. And there's very little to impede Helium's moverment through molecular structures due to its small size, their smooth valance outer shell, and because they rarely lose or gain electrons. Quote Link to comment Share on other sites More sharing options...
bjhines Posted May 18, 2006 Share Posted May 18, 2006 Now that is doing the math...!!! Quote Link to comment Share on other sites More sharing options...
frank280zx Posted May 18, 2006 Share Posted May 18, 2006 Uuuhhh' date=' no. It does leak out quickly. Maybe not all through the casing but a helium filled tire will leak helium fast enough that its not safe to race or drive on. Helium does not interact with other molecules at the temperatures we are concerned with (remember, its a noble gas). A typical Helium molecule (which is always monatomic - one Helium atom) is .98 angstroms in diameter. Nitorgen and Oxygen both form molecules at the temperatures we are discussing. Typically a Nitorgen molecule is two Nitrogen atoms bound together with a ovoid shape that's about 2.0 angstroms across. The oxygen molecule is even bigger. At any particular temperature the Helium molecules are moving faster then the Oxygen or Nitrogen molecules. Because of their increased speed Helium atoms have many more collisions with the walls of the container (balloon or tire). Therefore they have many more opportunities to fine a way out, whether that's through the tire casing, tire bead to wheel interface, valve stem, or porous wheel casting. And there's very little to impede Helium's moverment through molecular structures due to its small size, their smooth valance outer shell, and because they rarely lose or gain electrons.[/quote'] All we can say to that .. is amen .. now off to how stuff works.com !! Quote Link to comment Share on other sites More sharing options...
TheNeedForZ Posted May 18, 2006 Share Posted May 18, 2006 To figure out how much weight is saved using helium : Measure the weight of a fully air-inflated tire, then measure it fully deflated. Take the difference in weight and multiply by 0.86 is your weight saving. bjhines, Gases are equally compressible with almost no discernable differences, their absolute pressure change vs volume change is governed by the same gas law. Quote Link to comment Share on other sites More sharing options...
alexideways Posted May 27, 2006 Share Posted May 27, 2006 have not done the math... but it will be measured in grams for all 4 tires together... take a big crap right before you get in your car... you will have unloaded 2 orders of magnitude more weight in the bathroom... Maybe but a few grammes of unsprung weight is way better than a pound or two of sprung weight no? Quote Link to comment Share on other sites More sharing options...
Gollum Posted May 30, 2006 Author Share Posted May 30, 2006 Well the origonal idea is that you're not only saving unsprung weight, but you're also saving rotating mass. Looking back at this thred though I think a much more worth investment of time and money would be to find some rims that are 100% structual ONLY that might look dumb but use every ounce for strength, not looks. That should save you alot more weight and would be just as useful as removing tire weight. Although, this whole idea wouldn't even matter unless you were running an ultra light flywheel, carbon or aluminium driveshaft, ect. Basically, this would be one of those extreme "what else can I do" type things. But the pressure consistancy is what pushes me away from it more than the time limit issue. Quote Link to comment Share on other sites More sharing options...
TheNeedForZ Posted May 30, 2006 Share Posted May 30, 2006 With helium, you won't save any rotating mass because gas inside a tire is not attached to tire walls so it does not rotate with the tire. Structural rim+tire has been done http://en.wikipedia.org/wiki/Tweel Quote Link to comment Share on other sites More sharing options...
tube80z Posted May 30, 2006 Share Posted May 30, 2006 Nitrogen... which is most of the air in which we live.... is not quite as compressible as other common' date=' SAFE gases... it takes a relatively large pressure change to alter the density of nitrogen gas... With a little high school physics(GAS LAW) you will understand why a tire filled with nitrogen will not undergo as drastic a pressure change as airmixture filled tires when they get HOT... You cannot alter things very much by using pure nitrogen... it is mostly what we breathe anyway... if you do go that route you will need to come up with a way to purge other unwanted gasses from the wheel and tire assembly...... usually 2 diametrically opposed valve stems... one as a purge and the other as a fill... [/quote'] There are three accepted methods racers have used for a long time to do this. The easiest is to simply mount the tires on nitrogen in the first place. The second is to let the tire deflate (remove the valve stem) and reinflate. This is generally done three times to get the max benefit. The method I use to to hook a shop vac up to the tire and pull it down (it will shrivel up quite a bit) for about ten minutes. Then reinflate with nitrogen. There are three reasons I use nitrogen. It's dry and it is a little less reactive to the rubber. And lastly I can use air tools at the track. Cary Quote Link to comment Share on other sites More sharing options...
Gollum Posted May 31, 2006 Author Share Posted May 31, 2006 yes i'd seen that michelin tweel a while back and hadn't heard anything about it in a long time. But in my previous post I was just saying a high performance race rim would yeild much greater gains. Quote Link to comment Share on other sites More sharing options...
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