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  #11  
Old 04-30-2007, 05:59 PM
Gary Bricker Gary Bricker is offline
 
Join Date: Jun 2005
Posts: 371
Smile Gary Bricker

Where can I get the regulator and hose for nitro. I can get the bottle at a local welding supply but they were not sure about the regulator and hose.
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  #12  
Old 04-30-2007, 08:46 PM
Larry D Larry D is offline
 
Join Date: Jan 2007
Location: Atlanta, GA
Posts: 19
Default COSTCO article isn't accurate!

Any knowledgable chemist can tell you that there are statements in the Costco article that are factually incorrect. It is true that rubber is somewhat permeable and gases can leak out through the rubber sidewalls of a tire. However in practice I expect that the most important leak source is either the valve or the failure to seat the bead tightly on an auto tire. Aircraft tires use inner tubes so a leak at the bead can't happen. If you lose air you might want to use the special air retention inner tubes available for aircraft which are especially low in permeablility. The article indicated that oxygen would leak out three to four times as fast as nitrogen. This is just not chemically correct. The molecules are nearly the same size and weight. That means they should diffuse through the slightly porous tire wall at rates that are not very different ( 1.07: 1) with nitrogen the slightly faster. See you basic chemistry text - Graham's Law of Diffusion.

In an auto tire the presence of moisture could promote corrosion of the steel rim. There is no tube in an auto tire normally and the water that could be in air along with the oxygen could cause rust to form on the rim. This is not a problem in aircraft.

The expansion and contraction of nitrogen and oxygen (and all gases for that matter) are the same with temperature.

If you want to spend the money and use nitrogen that is your choice but it is unnecessary.

Larry Dickinson, chemist
RV-9A 160 hours
N95LD with air in the tires
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  #13  
Old 04-30-2007, 09:10 PM
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gvgoff99 gvgoff99 is offline
 
Join Date: Jan 2005
Location: Houston, TX
Posts: 454
Default

Quote:
Originally Posted by Larry D
If you want to spend the money and use nitrogen that is your choice but it is unnecessary.

Larry Dickinson, chemist
RV-9A 160 hours
N95LD with air in the tires
I agree with Larry completely and will continue to use "air" but don't want to discourage anyone that wants to feel good about their tires because they used nitrogen.

How readily available is nitrogen away from your regularly used place of inflation might be one question to consider?

Personally, I find that there are enough maintenance items to worry about on an aircraft and do not want to introduce one more.
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George Goff RV-6A (Flying 3/7/2006 )(Houston, TX)
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  #14  
Old 04-30-2007, 09:25 PM
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airguy airguy is offline
 
Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,145
Default

The reason some shops use nitrogen is because it is DRY - moisture promotes bacterial growth on the rubber, which degrades the tube and tire.

Run your air through a dessicant filter, you'll get the same effect.

Fellow Chemist....
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Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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  #15  
Old 05-01-2007, 10:48 AM
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osxuser osxuser is offline
 
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Location: Pasadena CA
Posts: 2,484
Default

Hmm, I use nitrogen in struts, but never in tires, seems like waste. Airstop tubes when you wear out the tires will take care of the problem. If you ever had a problem.
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RV4 wing in Jig @ KPOC
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  #16  
Old 05-01-2007, 11:01 AM
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mlw450802 mlw450802 is offline
 
Join Date: Jan 2005
Location: Payson, AZ
Posts: 436
Default Costco Article

Quote:
here is an article explaining Costco's rationale.
This sort of falls into the category of the New Science by Al Gore.
The media falls for it hook line and sinker and, before you know it, it becomes "fact".
It reminds me of many appropriate sayings I learned as a kid and I would provide attribution to these but have long forgotten the proper source:

"A fool and his money are soon parted"
"There's a fool born every minute"
"No one ever went broke underestimating the intelligence of the public"

-mike
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Michael L Wilson
Resuming building after a 4ish year hiatus! (life got in the way)
N194MW (reserved) RV9A SB
VAF# 148
Payson, AZ
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  #17  
Old 05-03-2007, 12:23 PM
jarhead jarhead is offline
 
Join Date: Jan 2006
Location: PA
Posts: 264
Default

Quote:
Originally Posted by Larry D
Aircraft tires use inner tubes so a leak at the bead can't happen.
Not 100% true. Most GA tires are tube-type, but nearly all business/airliner-type aircraft use tubeless tires. Nearly all helicopters with wheeled gear use tubeless tires as well.


Quote:
Originally Posted by Larry D
In an auto tire the presence of moisture could promote corrosion of the steel rim. There is no tube in an auto tire normally and the water that could be in air along with the oxygen could cause rust to form on the rim. This is not a problem in aircraft.
Corrosion on aircraft wheels is a common problem, whether they are tube-type or tubeless, filled with air or nitrogen. Just a matter of where the corrosion occurs...


Quote:
Originally Posted by Larry D
The expansion and contraction of nitrogen and oxygen (and all gases for that matter) are the same with temperature.
I always thought (and had been told numerous times) that nitrogen was more "consistent" re: expansion than air under high temp/pressure. Guess I should've paid more attention in high school chemistry...




Nitrogen is used in aircraft tires because it doesn't support combustion. Very important in the event of a brake fire after a heavyweight landing or RTO, or a wheelwell fire with the gear retracted.

I personally don't see a reason to use nitrogen in RV tires:
- there's plenty of flammable fiberglass surrounding brakes that 99% of builders fill with flammable MIL-H-5606 fluid.
- unless you can get the nitrogen for free, air is cheaper for 99% of owners.
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Ken

Helicopter mechanic (A&P)
USAFR KC-10 Boom Operator, on final approach to retirement
My RV-9/8/7 dream may be on life support, but it ain't dead yet!
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  #18  
Old 05-03-2007, 06:19 PM
szicree szicree is offline
 
Join Date: Jan 2005
Location: SoCal
Posts: 2,061
Default

Man, this nitrogen thing sounds like magic beans to me. Once and for all, air is mostly nitrogen. Now if dryness is the concern, can't I just use a drier on my compressor line (maybe wait for low humidity days to air up) and get most of it out?
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Steve Zicree
Fullerton, Ca. w/beautiful 2.5 year old son
RV-4 99% built and sold
Rag and tube project well under way

paid =VAF= dues through June 2013
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  #19  
Old 05-03-2007, 06:30 PM
Hwood Hwood is offline
 
Join Date: Feb 2005
Location: Central Alabama
Posts: 303
Default Easy

Easy math...Let's see, Small charge for nitrogen vs Air for free.

Sounds like a "no brainer" to me....this ain't rocket science, right Paul?
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N469SH / "Crazy Woman" (sold)
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  #20  
Old 05-03-2007, 08:22 PM
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Ironflight Ironflight is offline
VAF Moderator / Line Boy
 
Join Date: Jan 2005
Location: Dayton, NV
Posts: 12,256
Default

Quote:
Originally Posted by Hwood
Sounds like a "no brainer" to me....this ain't rocket science, right Paul?
Well, I know that we use Nitrogen in the Shuttle's tires....but the Val gets pure, unadulterated (humid) Houston "air" (if you can call it that....)
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Paul F. Dye
Editor at Large - KITPLANES Magazine
RV-8 - N188PD - "Valkyrie"
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
A&P, EAA Tech Counselor/Flight Advisor
Dayton Valley Airpark (A34)
http://Ironflight.com
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