Helium in tires??unsprung weight savings??
10-14-2008, 05:52 PM
#16
Rennlist Member
I don't think Helium will work to lift your car in the garage, in case that's what you had in mind. 4-post lifts rock.
As for Nitrogen, I suppose if you drive a Ford Explorer with underinflated recalled tires, then using Costco's nitrogen might be useful. For everybody else, except track junkies, it's a gimmick.
As for Nitrogen, I suppose if you drive a Ford Explorer with underinflated recalled tires, then using Costco's nitrogen might be useful. For everybody else, except track junkies, it's a gimmick.
10-14-2008, 06:42 PM
#18
Rennlist Member
Just to clarify my previous post... its the lack of moisture... not the change in gas that causes the .25psi change at temp...
also
There is some really poor air availible too.... tanks whose separators aren't emptied, rust, oil, all kinds of schmeg.... and I still dont think it makes a different... other than a mess...
On the track, at temp, and at speed, yes I can tell the difference in a pound or two, but not .25lb... On the street, my SUV was 5lbs low due to a slow leak, I had no idea.. until I checked with a guage (which I do when the temps drop for the winter)...
also
There is some really poor air availible too.... tanks whose separators aren't emptied, rust, oil, all kinds of schmeg.... and I still dont think it makes a different... other than a mess...
On the track, at temp, and at speed, yes I can tell the difference in a pound or two, but not .25lb... On the street, my SUV was 5lbs low due to a slow leak, I had no idea.. until I checked with a guage (which I do when the temps drop for the winter)...
10-14-2008, 07:47 PM
#19
Rennlist Member
Last time I looked, hydrogen, helieum, nitrogen, oxygen, and several others qualified as ideal gasses , each subject to the Ideal Gas laws of classic physics written by Boyles, Charles and Gay Lussac. Toss in the mole constant of Avogadro, and there is the iconic summary PV = nRT.
Any one of these gasses .... or any mixture therof .... will display identical behavior wrt temperature, pressure and volume ...... as long as they are in the gas phase. ie - it makes not one iota of difference what one pressurizes a tire with to achieve constant performance within the temperature range of normal operation - that includes max. track temps.
The pisser in the equation is water: while water can behave as a gas, it is a liquid at ambient temps .... and is entrained as miniscule droplets in compressed gasses that were not subject to driers and/or distillation: when heated to above 100C, this residual water mist expands ~ 22X faster than a dry gas .... which obviously increases pressure in a 'non ideal' fashion if contained inside a tire. ie., it can jack up a tires pressure beyond what would be expected for a dry gas ..... not good for track performance.
The tire is better thought of as a pressure vessel - and will behave predictably ( and idealy) if filled with DRY gas .... or any mixture of dry gasses: the one we happen to breath is ~ 80/20 ratio of nitrogen/oxygen - and is perfectly fine if dried.
If a tire were pressurized with helium vs air or nitrogen to identical pressures, the same number of molecules would be required; therefore, a quick guesstimate suggests that one could lower the unsprung weight by a whopping 25 - 30 grams/tire assembly: that is 1 oz in a typical assembly of 50 lbs =~ 0.1% ..... or about the amount of rubber one would scrub off in missing the first apex
Any one of these gasses .... or any mixture therof .... will display identical behavior wrt temperature, pressure and volume ...... as long as they are in the gas phase. ie - it makes not one iota of difference what one pressurizes a tire with to achieve constant performance within the temperature range of normal operation - that includes max. track temps.
The pisser in the equation is water: while water can behave as a gas, it is a liquid at ambient temps .... and is entrained as miniscule droplets in compressed gasses that were not subject to driers and/or distillation: when heated to above 100C, this residual water mist expands ~ 22X faster than a dry gas .... which obviously increases pressure in a 'non ideal' fashion if contained inside a tire. ie., it can jack up a tires pressure beyond what would be expected for a dry gas ..... not good for track performance.
The tire is better thought of as a pressure vessel - and will behave predictably ( and idealy) if filled with DRY gas .... or any mixture of dry gasses: the one we happen to breath is ~ 80/20 ratio of nitrogen/oxygen - and is perfectly fine if dried.
If a tire were pressurized with helium vs air or nitrogen to identical pressures, the same number of molecules would be required; therefore, a quick guesstimate suggests that one could lower the unsprung weight by a whopping 25 - 30 grams/tire assembly: that is 1 oz in a typical assembly of 50 lbs =~ 0.1% ..... or about the amount of rubber one would scrub off in missing the first apex
10-14-2008, 08:32 PM
#20
Rennlist Member
the hellium molecule is so small you probably have a difficult time maintaining pressure. We use hellium for checking for leaks in hermetic products because of this quality.
Fred
Fred
10-15-2008, 08:56 AM
#26
Instructor
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Alternatively, you could ask a politician to ride shotgun which undoubtably would reduce unsprung weight via an increase in the amount of hot air generated during the drive.
Note: not applicable in California due to the potential increase in greenhouse gases...
Note: not applicable in California due to the potential increase in greenhouse gases...
10-15-2008, 01:53 PM
#28
Force = Mass x Acceleration.
Weight = Mass x Acceleration (due to gravity), and could be stated as Force due to gravity. The same person would weigh less on the moon than on earth due the moon's lower gravitational acceleration.
If you change the mass you change the resulting force, which is what the suspension is reacting to.
Mike
Weight = Mass x Acceleration (due to gravity), and could be stated as Force due to gravity. The same person would weigh less on the moon than on earth due the moon's lower gravitational acceleration.
If you change the mass you change the resulting force, which is what the suspension is reacting to.
Mike
