USA-Technical Details-Helium used

Discussion in 'Multihulls' started by Doug Lord, Mar 27, 2010.

  1. Chris Ostlind

    Chris Ostlind Previous Member

    Well, you're not the only one. I had this notion about nitrogen from way back in my motorcycle road racing days and had to go look it up.

    Laters,
     
  2. mark775

    mark775 Guest

    Well, Chris, I have to say that I believe that you are dead-wrong on this. Why does a race car team care if some air molecules escape from the tires over the next month? It's actually not about the nitrogen, at all. It's about reducing oxygen, water vapor and other gases.
    I also believe that it makes not one wit of difference to a passenger car under normal driving conditions what gas you put in there but that nitrogen has larger molecules and leak out after a longer period, like you said. It makes a HUGE difference in a race car to get the water vapor out of there and not create steam, which expands to a high volume relative to when it was water. The 21% of oxygen in air at 30 PSI in two cubic feet of tire volume, I guess I'll buy as being a bit of a safety decider. I don't think they would bother were it not the need for a dry gas to begin with - kinda full circle back to the use of helium in an ama if one is going to bother to pressurize anyway.
     
  3. Chris Ostlind

    Chris Ostlind Previous Member

    Well, if I'm dead wrong then you'll have to take it up with the industry web page from where I got it. If you Google yourself silly, you'll see the same things written over and over as data for nitrogen inflation. There's even a website dealing with the myths and facts of nitrogen in tires of all kinds, including racing and aircraft. That would be a good one for you to read first.

    Have fun.
     
  4. ancient kayaker
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    ancient kayaker aka Terry Haines

    Mark, oxygen and nitrogen molecules are not much different in size. As Chris has already said, using nitrogen can reduce the risk of a fire especially since race tires run hot.

    Using dry nitrogen would certainly reduce water content, but I doubt race car tires last long enough to accumulate much water anyway, and water vapour will behave like any other gas with varying temperature. Dehumidifying compressed air is pretty simple and standard practice in workshops the world over these days, so it's not going to be a problem in your car.
     
  5. peterraymond
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    peterraymond Junior Member

    Nitrogen

    It's interesting to listen to a bunch of sailors talking about race tires. If you take humid air and compress it the partial pressure of the water vapor will go up. The temperature will go up also, but as that air cools back to ambient, some of the moisture can condense. If you adjust the tire pressure cold, there can be condensed water in the tire. If you take that tire onto the track and run a few laps the temperature goes up and that water evaporates. You now have more gas molecules in the tire, so you get more than the normal gas law pressure rise.

    All gasses expand as they heat up, but it's not like the coefficient of thermal expansion of a solid. For any real pressure the size of any molecule is so small that all gases follow the ideal gas law and the pressure rise from cold to hot is the same. If all the water in a tire is in the form of a gas, it will expand just like any other gas, but a change of phase is different.

    One of the problems most racers have is that the tire pressures are set cold, but what's important is the hot pressure. You want to be able to set a cold pressure and get a consistent hot pressure, but that's impossible if you have too much humidity.

    In more than just theory, a very small molecule could cause a leakage problem. It varies from brand to brand, but race tires are made as light as possible and as a result, some of them do leak. It's not huge, almost never more than maybe 20%/day, but the pressure requirement is pretty tight. I don't think anyone would use Helium and dry Nitrogen is available.

    As far as fire danger, I have never heard that mentioned. Tires, and particularly brakes, get hot, but not enough for spontaneous combustion. The fire never starts inside that pressurized space. If there were a fire outside and there was a hole in the tire then it's conceivable that the air coming out of the tire would act to fan the flames. That's not why Nitrogen is used. Nitrogen is used because you get more consistent tire pressures. Now some people will just say that you get less pressure rise with Nitrogen, but that's something of an over simplification.

    As far as web sites are concerned, the truth is you can read a lot of junk on many of them. I shouldn't deal in stereotypes, but circle track racers in particular can get things backwards. One source that is generally reasonable is the series of books written by Carol Smith. If you can find something from Paul Vanvalkenberg (sp?) on a particular subject, that's even better.

    I just walked to the other end of the house and picked up a few books. All of which are a little old. Van Valkenburg (I can spell it now) says "Most race tires leak like sieves". Carroll Smith (I can spell his name too now) says "The first is that racing tires tend to leak a lot". He goes on to say that 3 psi/hr is too much to race on, but you can use up to 5 psi/hr for practice. I don't think race tires leak as much as they used to though. At least that's my experience.

    Carroll also says "All air is not the same-some contains more water vapor". And "The cold pressure necessary to achieve a given hot reading won't vary more than a pound or two from one track to another but can easily vary by three or four pounds due to moisture in the air. Dry Nitrogen solves this little problem, but it's a pain to carry around, expensive and not necessary".
     
  6. mark775

    mark775 Guest

    Peter knows of which he speaks.

    Now, "Mark, oxygen and nitrogen molecules are not much different in size. As Chris has already said, using nitrogen can reduce the risk of a fire especially since race tires run hot." Fire, as I said, not much of a factor but if one is going to select a gas, it may as well be inert. We were not comparing nitrogen to oxygen but helium.

    "Using dry nitrogen would certainly reduce water content, but I doubt race car tires last long enough to accumulate much water anyway, and water vapour will behave like any other gas with varying temperature. Dehumidifying compressed air is pretty simple and standard practice in workshops the world over these days, so it's not going to be a problem in your car." Dehumidified air (as we dehumidify it for shop use) is not necessarily very dry. Water expands 1,600 times as it becomes vapor - two drops of water are what we are talking about here. They bring a cold tire at 25PSI to dang-near popping and over-inflated (round-like the chamber of gas in the structure of the boat we were talking about early in the thread). If the rubber of the tire didn't also expand, they'd be in real trouble.
    If you pay Costco 10 extra dollars for nitrogen in your tires, you are the epitome of naivete but can feel good that if you have a devastating crash where all four tires pop and spill their contents on the Ford Pinto gas tank, you would not be contributing two cubic feet of oxygen to the inferno!
    I know I don't jibe well with you all and, eventually, I'll say something not founded in reality (it's happened before) but you don't really need to prove me wrong. I'll just say it - "I was wrong to bring it up".


    wwf_wrestlers.jpg

    Again, refer to Peter's timely explaination. Consider him "tagged in".
     
  7. daiquiri
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    daiquiri Engineering and Design

    Off topic - nitrogen and tyres

    :D :D :D

    That's the beauty of books - by reading them one learns how to spell correctly. ;)


    As about nitrogen vs. tyres - since we have everything from boats to cars in this thread, why not throwing an airplane into the scrum?
    Civil transport airplane tyres are required to be inflated with nitrogen or another inert gas, with max 5% oxygen content. The reasons are explained in this FAA page:
    http://rgl.faa.gov/Regulatory_and_G...8C17569AD3DED4128625694A005BB65D?OpenDocument

    To sum it up: it has been shown through lab tests that oxigen in the air mixture can cause an autoignition of (petrol-based) rubber material of the inner tyre liner at temperatures above 250 °C. It was observed that when oxygen content was less than 5%, the autoignition was inhibited even for temperatures above 350°C.
    Hence the requirement for filling them up with Nitrogen or with another inert gas with less than 5% O2.

    The favourable collateral effects are, as said by other people before:
    - more uniform expansion rates due to absence of humidity
    - no icing problems due to internal humidity (there's -50 °C at 10 km altitude)
    - nitrogen, like other inert gases, is non-corrosive
    - slightly reduced leakage

    Cheers guys!
     
  8. daiquiri
    Joined: May 2004
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    daiquiri Engineering and Design

  9. Doug Lord
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    Doug Lord Flight Ready

    Message from BOR

    Hey, guys if you don't want to discuss the subject of the thread, why don't you start another thread? Please......


    From Tom Ehman:

    "VLC, 1030 Thursday

    Doug,

    In reply to your question, "Can you confirm a Sailing World article that you used helium onboard USA?" received via our team website....

    We did a number of innovative things that we are not yet at liberty to discuss, but will in due course.

    You can quote me as GGYC/BOR spokesman, if that helps.

    Regards,

    Tom

    T F EHMAN JR
    External Affairs
    BMW ORACLE Racing

    ================================
    That explains the reluctance of my source to speak publically now. But you can believe that helium was used on USA -or not.......Those that have dug deep holes for themselves ridiculing this story will wallow in it sooner or later.
     
  10. Chris Ostlind

    Chris Ostlind Previous Member

    Bunch of stuff, here, Doug...

    First of all, the reference to Nitrogen/Helium came up as a normal pat of the discussion. As a sidebar, it has had its run and looks to be thoroughly considered. You should know by now that there are all sorts of ancillary sidebar discussions in pretty much all the threads on this forum. You, yourself, have contributed to that reality more than anyone I can quickly recall. To hop on the righteous soapbox at this point is considerably less than genuine.

    - - - - - -

    Nobody has dug any kind of deep hole from which they will, as you have put it..."wallow in it, sooner or later." You tossed out a goofy reference from a magazine article. One that was not supported in any way, shape, or form, by substantive quotes, photographs or links to a developed article from a credible source. In short, at the time, you willingly spread gossip based on pure vapor.

    You then proceeded to produce info from another vaporous source, which was conveniently omitted. Whether that source of yours will turnout to be substantive, or not, is outside the basic argument.

    1. It is not only the right, but also pretty much the responsibility of those reading a story/report, to call BS for any element they find to be lacking in depth, or substance. That does not mean that the topic never happened. It simply means that it has not been supported properly by he who has brought it forth. This is an objective discussion.

    2. You may be confusing the fact that people may simply find your style of reportage to be something less than credible. When that style is mixed with the business of dropping some inside dope on the gang and calling it good, it spells trouble.

    I would suggest that you are the only one who can fix that problem. An example of which is the attached piece that was supplied by Paul B at post #35 on page 3 of this very thread, with regards to your AeroSKIFF, its foiling realities and what you said about same on these pages. http://www.boatdesign.net/forums/multihulls/usa-technical-details-helium-used-32082-3.html Something there just doesn't come together cleanly with your current claims. It's that kind of stuff that hammers cred.

    Having your story raked over the coals does not mean that the story has no substance. It simply means that you likely did a poor job in presenting that substance and you asked the readers to make a colossal jump to gain the necessary credibility that this type of story demands.

    So, now that we have clarity on your affront, What About That Archived Quote Regarding Your AeroSKIFF and Your Open Statement That It Didn't Get Out Of The Water As You Later Claimed? (see below)

    No time like the present to reestablish a bit of that lost member cred. ;-)


    .
     

    Attached Files:

  11. Paul B

    Paul B Previous Member

    I don't see anywhere in that message where Ehman confirms they used any contained gasses in the boat.
     
  12. ancient kayaker
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    ancient kayaker aka Terry Haines

    I only have a bachelor’s degree in Physics. However, I do not claim to be a sailor, which may mitigate my ignorance somewhat.

    Let’s inflate a tire from flat on a hot and humid day. The air is a mixture of gases, including water vapor. You can cool the tire so the water condenses or even freezes but when you run the tire back up to the temperature at which it was inflated, it will still contain a mixture of gases (including the water vapor) which will all behave exactly the same according to the Gas Laws as it continues to heat up. Only when the tire is cold with the slightly greater than usual pressure drop betray the presence of water inside; adding more air to the cold tire might over-inflate the tire when heated again, but not by much.

    Granted, if you pour half a cupful of water into a tire before inflating it, you are asking for trouble if you run the tire fast for a long time on a hot day. The effect on tire pressure of only 2 drops of water once evaporated would be hard to detect.

    The use of dry nitrogen in a race tire sounds a good idea. I wouldn’t think the cost of it would be a factor considering the money that goes into racing cars. Gas Laws suggest the pressure could rise considerably if the tire was inflated at below freezing and the temperature rose to above boiling during the race, but I suspect race crews are alert to that possibility and car tires likely have some form of pressure control these days.

    As far as preferential loss of oxygen is concerned, I don’t have data on gas permeability. However, in my experience a car tire in good shape will lose only a few psi per year; if the oxygen leaked out it would lose 20% of it’s pressure and whenever I’ve had a tire do that it went right on leaking, didn’t slow down after the oxygen had presumably escaped. Race tires could be different, but I doubt they are often used on sailboats. :)
     
  13. mark775

    mark775 Guest

    "...confirms they used any contained gasses in the boat." - I'm afraid it was I that brought up the notion of filling a structure by inflation with helium. It could just as well have been used in some portion of the manufacturing process. Okay, that about does it.
     
  14. Doug Lord
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    Doug Lord Flight Ready


  15. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

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