jetdriven Posted July 9, 2022 Report Share Posted July 9, 2022 More expensive airplanes have tubeless tires with a O-ring between the wheel halves. That shouldn’t be too difficult to engineer these this for smaller planes but Cleveland is not known for innovation Quote Link to comment Share on other sites More sharing options...
PT20J Posted July 9, 2022 Report Share Posted July 9, 2022 On 7/6/2022 at 2:10 PM, M20Doc said: I’ll be the odd man out. I’ve seen more newer tubes fail than older ones. I replace them on condition, wrinkles, areas of abrasion are causes for replacement. Clarence I'm with Clarence. My mains were wearing unevenly and so I dismounted them and reversed them with new Airstop tubes. The tubes seemed fine a couple of years later when I replaced the tires, so I reused them. After inserting them in the tires and inflating slightly, I could see they were still a good fit and rotated easily without folding or wrinkling when I aligned the valve stem with the tire dot. Maybe the butyl tubes don't deform much. I don't know, but they certainly didn't seem to warrant replacement. I suspect a lot of tube failures are caused from pinching during assembly which is easy to do. Punctures in the tread area may not be visible on the tire. I recently had a puncture in a bicycle tire that bubbled soapy water, but was invisible in the tire when dismounted although the hole in the tube was clearly visible. Skip 1 Quote Link to comment Share on other sites More sharing options...
Guest Posted July 9, 2022 Report Share Posted July 9, 2022 5 hours ago, flyboy0681 said: Perhaps a stupid question, but why aren't small GA aircraft using tubeless tires? Tubes seem so early 20th century. Readily available with Beringer wheels on the newer Cirrus airframes and as an upgrade on older Cirrus airframes, but to the tune of about 10AMU. Clarence Quote Link to comment Share on other sites More sharing options...
MikeOH Posted July 9, 2022 Report Share Posted July 9, 2022 3 hours ago, GEE-BEE AEROPRODUCTS said: Use nitrogen .... doesn’t expand with temp Sorry, I must call BS on that statement! Quote Link to comment Share on other sites More sharing options...
amillet Posted July 9, 2022 Report Share Posted July 9, 2022 https://www.lesschwab.com/article/are-nitrogen-filled-tires-worth-the-cost.html 2 Quote Link to comment Share on other sites More sharing options...
MikeOH Posted July 10, 2022 Report Share Posted July 10, 2022 1 hour ago, GEE-BEE AEROPRODUCTS said: Care to wager ? GB https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC20-97B.pdf I just read that AC (which is NOT regulatory per its first paragraph, despite your earlier claim): "This AC is not mandatory and does not constitute a regulation." Further, I saw NOTHING that indicated proof of your claim that nitrogen "doesn't expand with temperature" Please cite the specific section that states that. Quote Link to comment Share on other sites More sharing options...
Guest Posted July 10, 2022 Report Share Posted July 10, 2022 From a few Mooney maintenance manuals that I grabbed pages from, generic air is mentioned for tires. Personally I prefer a mixture of proprietary gases, 78% nitrogen, 21% oxygen with 1% other assorted gases, it’s readily available in most places on earth and at a price to warm a CB’s heart. Clarence Quote Link to comment Share on other sites More sharing options...
PT20J Posted July 10, 2022 Report Share Posted July 10, 2022 I believe the claim of decreased pressure variance with temperature is due to the lack of moisture rather than any property of nitrogen which, like other gasses, will (to close approximation) obey the ideal gas law. 1 Quote Link to comment Share on other sites More sharing options...
MikeOH Posted July 10, 2022 Report Share Posted July 10, 2022 18 minutes ago, PT20J said: I believe the claim of decreased pressure variance with temperature is due to the lack of moisture rather than any property of nitrogen which, like other gasses, will (to close approximation) obey the ideal gas law. That sounds like good theory. In practice, given the low percentage of water vapor in air, I'd be interested in how significant that reduction in P vs. T actually is. I suspect it's pretty small; i.e, whether air or nitrogen, I think the variation is pretty close to ideal: P proportional to absolute T. EDIT: Well, a quick Google shows a couple of things: 1) At 86 F, saturated air contains 4% water vapor. 2) At normal temps and pressures water vapor is an ideal gas: Notice also from the h-s diagram for steam that at relatively low temperatures (<60°C) the water vapor in the air has a constant enthalpy at constant temperature from saturated vapor through the superheated region, thus can be treated as an ideal gas. 2 Quote Link to comment Share on other sites More sharing options...
PT20J Posted July 10, 2022 Report Share Posted July 10, 2022 3 minutes ago, MikeOH said: That sounds like good theory. In practice, given the low percentage of water vapor in air, I'd be interested in how significant that reduction in P vs. T actually is. I suspect it's pretty small; i.e, whether air or nitrogen, I think the variation is pretty close to ideal: P proportional to absolute T. I've never noticed a significant change in pressure with ambient temperature in my car tires. Maybe if you live in Fairbanks where it's 60 below in the winter and 90 above in the summer? Quote Link to comment Share on other sites More sharing options...
MikeOH Posted July 10, 2022 Report Share Posted July 10, 2022 Just now, PT20J said: I've never noticed a significant change in pressure with ambient temperature in my car tires. Maybe if you live in Fairbanks where it's 60 below in the winter and 90 above in the summer? Neither have I. That seems reasonable since we are dealing with absolute temperature. Quote Link to comment Share on other sites More sharing options...
carusoam Posted July 10, 2022 Report Share Posted July 10, 2022 Gents, I think there may be a point missing… Kind of a decimal point… in scale. The rubber tube we are using is somewhat porous, at the molecular level… The better the barrier to gas molecules the rubber is… the better the gas is kept inside over time…. Kind of a mass transfer discussion… So…. Have a look at the size of the gas molecules… N2, O2, CO2… I bet you find the O2 molecules are tinier than the rest… Getting a dry refill of N2 from GB is easier than separating your own N2 using your tire’s tube… Filling with air, and allowing the O2 to escape takes a long time to approach a high level of N2 naturally… Airstop tubes are fantastic… There is still plenty of room for improvement… Berringer does a nice job for the experimental world… wheel and brake combinations… high performance stopping power and light weight… they were the best designed parts of the whole Raptor Aircraft debacle… Show me a nose wheel brake, and we can really slow things rapidly…. Isn’t T/O distance more challenging than landing distance? Both get longer with low AirP… So… Add the fancy WiFi air pressure sensors in with the new rims…. Go MS! Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Mufflerbearing Posted July 10, 2022 Report Share Posted July 10, 2022 Using TPMS on our tires would be an interesting discovery to see how much the pressure changes at altitude in our tires. Quote Link to comment Share on other sites More sharing options...
MikeOH Posted July 10, 2022 Report Share Posted July 10, 2022 @carusoam Did you read the link amillet provided? The Cliff Notes cogent point: Over a YEAR, the difference in pressure decrease of air vs. pure nitrogen is only 1.3 psi. I check my tires more than once a year. How about you? Are you running pure nitrogen in your tires? This pure nitrogen fill concept totally smacks of hype; but, if you want to pay the premium, not to mention hassle, of putting pure nitrogen in your tires for that 1.3 psi/year benefit...knock yourself out Oh, and the argument that oxygen deteriorates the rubber.... well, there's not much you can do about the oxygen rotting from the OUTSIDE in! I've yet to see the INSIDE rotted away before the outside! But, maybe I've only seen the inside of tires that spent their life with only nitrogen fills Quote Link to comment Share on other sites More sharing options...
PT20J Posted July 10, 2022 Report Share Posted July 10, 2022 1 hour ago, MikeOH said: That sounds like good theory. In practice, given the low percentage of water vapor in air, I'd be interested in how significant that reduction in P vs. T actually is. I suspect it's pretty small; i.e, whether air or nitrogen, I think the variation is pretty close to ideal: P proportional to absolute T. EDIT: Well, a quick Google shows a couple of things: 1) At 86 F, saturated air contains 4% water vapor. 2) At normal temps and pressures water vapor is an ideal gas: Notice also from the h-s diagram for steam that at relatively low temperatures (<60°C) the water vapor in the air has a constant enthalpy at constant temperature from saturated vapor through the superheated region, thus can be treated as an ideal gas. Good work! I haven't looked at steam tables since my undergrad thermodynamics course (which I barely remember). I think it's clear: Spend money on Airstops and not nitrogen. 2 Quote Link to comment Share on other sites More sharing options...
MikeOH Posted July 10, 2022 Report Share Posted July 10, 2022 Just now, PT20J said: Good work! I haven't looked at steam tables since my undergrad thermodynamics course (which I barely remember). I think it's clear: Spend money on Airstops and not nitrogen. LOL! Yeah, me either. That whole enthalpy thing was a bit much for a EE like me! Quote Link to comment Share on other sites More sharing options...
carusoam Posted July 10, 2022 Report Share Posted July 10, 2022 30 minutes ago, MikeOH said: @carusoam Did you read the link amillet provided? The Cliff Notes cogent point: Over a YEAR, the difference in pressure decrease of air vs. pure nitrogen is only 1.3 psi. I check my tires more than once a year. How about you? Are you running pure nitrogen in your tires? This pure nitrogen fill concept totally smacks of hype; but, if you want to pay the premium, not to mention hassle, of putting pure nitrogen in your tires for that 1.3 psi/year benefit...knock yourself out Oh, and the argument that oxygen deteriorates the rubber.... well, there's not much you can do about the oxygen rotting from the OUTSIDE in! I've yet to see the INSIDE rotted away before the outside! But, maybe I've only seen the inside of tires that spent their life with only nitrogen fills I’m pretty sure we are on the same team… 1) Regular tubes in my M20C required filling monthly… 2) N2 couldn’t technically improve how porous those tubes are…. 3) All of my cars carry an air pump, Jumper battery, and can of fix-a-flat…. No N2 here either… 4) Going all N2 isn’t wrong… just it’s decimal point of improvement is outweighed by all of the other real world challenges… 5) I went to the airport yesterday with my big compressor to do the small job of topping off the O’s tires… (the small compressor is a decade old and is dead…) 6) Fortunately, the six month tire pressure check has worked pretty well…. The nose wheel in the O uses 49psi… and visually gets flatter with each missing psi… on a flat concrete surface. 7) I think I would refill my own O2 system with a wall mounted cascade O2 system in the hangar, before using my own N2 tire refill system… 8) If I were an aerospace engineer… I’d be all over these details… 9) If I were using my tires for racing….the stability of N2 might start hinting at improved stability… I don’t have a chance of being able to capitalize on the difference… 10) did I read what Alan wrote…? Which MS post didn’t I read over the last decade +… The real world is tough… I can’t make this small change add enough value for me… Tomorrow… I head back to the airport with the air hose that goes on the big air compressor… Did I mention… The real world is tough…. And… I like the Mooney’s factory built aspect the most… where I can learn from the thousands of other Mooniacs around here… who are flying with the same hardware… Best regards, -a- 2 Quote Link to comment Share on other sites More sharing options...
atpdave Posted July 10, 2022 Report Share Posted July 10, 2022 If a tire is pressurized to any given pressure with any gas composition at a certain temperature and the temperature is increased by a certain amount, the pressure will increase by the same amount. For example, if a tire at -40F is pressurized to 30 PSI with either pure nitrogen or atmospheric gas (or any other gas), the pressure at 200F will be approx. 47 PSI in any case, assuming the tire volume remains constant . The mass of the gas is the only difference, molar mass oxygen 15.9994 g/mol nitrogen 14.0067 g/mol atmosphere (approx.) 14.445094 g/mol Quote Link to comment Share on other sites More sharing options...
Will.iam Posted July 10, 2022 Report Share Posted July 10, 2022 Our nissan parhfinder came with nitrogen filled tires and i have to say for 2 years the tires did not change in pressure on the TPMS sensors. Then one tire got a nail in it and when we got it fixed they did not have nitrogen so filled that tire with air. I was amazed at how much the temperature changed approximately 3 to 4 psi as you drove and heated up the tires from traveling. And in the winter we would need to add a few psi in that tire but as the temp rises in the spring it would offset the slow air loss. As nice and convenient it was to not have to ever add any air to the 3 nitrogen filled tires it wasn’t worth it to me to pay for the extra fillup cost over air and when you are out traveling unless you can find a place that has nitrogen fills it’s very inconvenient to fill up when you do need more psi. I think airlines have nitrogen filled tires for safety to keep that inert and keep from expanding as much as air would do /exploding the tire since after a stop the brakes can heat up to over 300 degrees Celsius pretty regularly and i would think if regular air in the tire it could exceed the maximum psi for the tire and start popping fuse plugs which can still happen but it’s usually only when the brakes get over 600 degrees Celsius that you start to be concerned with that. Quote Link to comment Share on other sites More sharing options...
M20F Posted July 10, 2022 Report Share Posted July 10, 2022 Left tire is filled with gin, right tire is vermouth. Shaken not stirred on every landing. 2 Quote Link to comment Share on other sites More sharing options...
carusoam Posted July 10, 2022 Report Share Posted July 10, 2022 25 minutes ago, atpdave said: If a tire is pressurized to any given pressure with any gas composition at a certain temperature and the temperature is increased by a certain amount, the pressure will increase by the same amount. For example, if a tire at -40F is pressurized to 30 PSI with either pure nitrogen or atmospheric gas (or any other gas), the pressure at 200F will be approx. 47 PSI in any case, assuming the tire volume remains constant . The mass of the gas is the only difference, molar mass oxygen 15.9994 g/mol nitrogen 14.0067 g/mol atmosphere (approx.) 14.445094 g/mol Wait a sec… Good thinking, but…. Can we assume the volume of the tire stays constant? The more pressure I put in my tires… the smaller the foot print becomes… Something volumetric changes easily with increased AirP…. 1) The outside pressure is changing rapidly… 1” of mp as we climb 1k’…. Inches of water… 2) temperature can drop to -40° at altitude… you pick the system… °F or °C…. 3) Using the ideal gas law in the real world…? 4) Even here…. The benefits of N2 are going to be tiny… 5) It may become more important if we are shooting through a chicane… and our tire’s foot print is uber important…. Then… we would be discussing tire wall strength and stiffness with that… 6) imagine getting low profile tires for better cornering to clip the apex onto the first taxiway… 7) I’m going to need some new side bolsters for my Recaros for that! 8) Squishy sidewalls are best for stalling above the runway… Ordinary PP thoughts only, I haven’t squashed any of my own gear doors yet… Best regards, -a- Quote Link to comment Share on other sites More sharing options...
47U Posted July 10, 2022 Report Share Posted July 10, 2022 (edited) I found two references in Air Force tech data in my archives, (no restrictions on public release). From the tire T.O. (4T-1-3), reference pertinent to tires serviced with air: From a T.O. on an aircraft which specifies the tires are serviced with nitrogen (the tire pressure is in the mid-200 psi range, depending on gross weight): At the risk of public math, per the 4T, a change of 10 degrees on a 250 psi tire serviced with air would be about 5 psi. Per the aircraft T.O., a 10 degree change on a tire serviced with nitrogen is about 6 psi. Regardless, if QA finds your tire is more than 5 psi high or low from what it is supposed to be, you failed the inspection. Edited July 10, 2022 by 47U Fuzzy brain. Quote Link to comment Share on other sites More sharing options...
EricJ Posted July 10, 2022 Report Share Posted July 10, 2022 The nitrogen tire fill debate has been hashed out in racing for many years, since a 1psi change can change the handling of a car significantly. It's been pretty well demonstrated that the vast majority of the benefit of a nitrogen fill is because it'll be drier (i.e., low moisture content) than a typical air fill. If the air is dry, you'll get essentially the same benefit. Since I live in AZ, where our air has very little moisture, anyway, nobody here that I know bothered with nitrogen fills more than just an initial experimentation, and then abandoned it. Airliners and other large aircraft use nitrogen fills typically for safety rather than pressure control, so that a blowout (or fuse plug venting) doesn't feed oxygen to a brake fire. 3 1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted July 10, 2022 Report Share Posted July 10, 2022 Wait… Eric has brought up a good point… Weight… How much does the air in our tires weigh..? How much UL can we gain if we used dry N2 only… ideally…. The O2 is treated like any of the other gasses volumetrically in the tire but weighs less than N2, per mol… BCNOFNe (going across the periodic table from ancient memory, from light to heavy in order…) Including moisture into the discussion can get a bit wet… some times it is a well defined gas other times it has fallen out of solution and formed ice particles…. Hmmmmmm He / helium would make an interesting gas for tires…. High pressure, low weight… Except one thing… the atom is so tiny we would need an aluminum coated Mylar layer in our tubes to hold it in…. And we would still need to fill it up every month…. Lets look at Hydrogen just for fun… flammability and leaks aside… We might actually gain some UL here… We may need a strong mathematician to calculate the benefit… (inviting @aviatoreb) Volumetric calculation of a tire tube… Weight of the volume of air…. Weight of the same volume of dry N2… Experience of a bicycle racer… And any other experience that can be brought to the MS table… Best regards, -a- Quote Link to comment Share on other sites More sharing options...
47U Posted July 10, 2022 Report Share Posted July 10, 2022 58 minutes ago, carusoam said: Fuzzy spell check… Fuzzy brain… I’d better edit that, huh. Thank you… 1 Quote Link to comment Share on other sites More sharing options...
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