tag:blogger.com,1999:blog-13887692.post7008467506723508816..comments2024-03-13T02:16:08.135-04:00Comments on Cozy Beehive: Heat Wave, Gas Laws & Your Bike TireRon Georgehttp://www.blogger.com/profile/18394865788996482667noreply@blogger.comBlogger21125tag:blogger.com,1999:blog-13887692.post-70712850341096430842013-10-31T04:27:58.533-04:002013-10-31T04:27:58.533-04:00The first several months of my site there were no ...The first several months of my site there were no comments; just give it time; now they come in like crazy every day! Thanks. <a href="http://geothermalflowcenters.com/" rel="nofollow">geothermal flow center</a><br /><br />David talpurhttps://www.blogger.com/profile/15600881829320806595noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-50055555172837581862011-09-24T01:25:07.640-04:002011-09-24T01:25:07.640-04:00Tire pressure is very important. Correct tyre pres...Tire pressure is very important. Correct tyre pressure can help to extend the life of your tyre, improve vehicle safety and maintain fuel efficiency. It is also advisable to always check your tire and you can also wash your tire daily.plumbinghttp://www.bes.co.uknoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-36595997744403620272011-08-28T23:37:17.619-04:002011-08-28T23:37:17.619-04:00Great and fresh site Ron! Just wished you'd bl...Great and fresh site Ron! Just wished you'd blog more frequently.Richard, AZnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-64874936958001640282011-08-28T22:08:45.005-04:002011-08-28T22:08:45.005-04:00@Anonymous above - To highlight this concept, taki...@Anonymous above - To highlight this concept, taking air as ideal gas at normal pressure and temperature is a valid approach for first order approximation. Feel free to enlighten me with a more rigorous mathematical model in your research paper. Ofcourse, easier said than done for anonymous posters!Ron Georgehttps://www.blogger.com/profile/18394865788996482667noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-79624580457838966672011-08-17T06:41:33.514-04:002011-08-17T06:41:33.514-04:00I came across this post somehow, and started to la...I came across this post somehow, and started to laugh. Good to see there are sharper engineers out there who caught some of the errors and misconceptions in the original post and sent in corrections!<br />Structural integrity of an inner tube…? Geez, I could comment all day.<br /><br />So, air is now an ideal gas?… ;)<br />Ron- if you profess to be proficient in understanding these things, you really do need to at least have a grasp of your fundamentals.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-90782770199948237772011-08-16T13:41:04.582-04:002011-08-16T13:41:04.582-04:00Pumping the tyres (I am English) up in the garage ...Pumping the tyres (I am English) up in the garage at 70F would not fill the tyre with 70F air. To compress to the 140 psi you have to put a lot of work into the air (just feel the bottom of your pump). I presume that the tires weren't pumped up so slowly, or thru' a cooler, to reduce this effect. Thus, the air in the tyre would be a greater than 70 psi to start.<br /><br />Great Blog!Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-84817021303026198242011-08-14T21:22:46.374-04:002011-08-14T21:22:46.374-04:00Another take on this that most readers might appre...Another take on this that most readers might appreciate is what happens in the winter. Pump your MTB tires up to 35psi in your warm garage, then go out and ride in 30 degree weather....pinch flat city on your favorite trail.----https://www.blogger.com/profile/14913975302166280156noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-81916429212747526192011-08-12T20:26:59.872-04:002011-08-12T20:26:59.872-04:00While I haven't been too scientifically rigoro...While I haven't been too scientifically rigorous in investigating the cause of his bike tires (factors such as age of wheel, type of terrain etc), I think over-inflation and the simple math behind it is representative of flats in hot weather. I seriously doubt inner tubes can maintain their structural integrity with over-inflation and pressure rise on top of that.Ron Georgehttps://www.blogger.com/profile/18394865788996482667noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-59108175863851357342011-08-11T18:46:00.446-04:002011-08-11T18:46:00.446-04:00The theory to which I referred was the one that he...The theory to which I referred was the one that heat caused the flats, not the laws involving compressible gases. He could probably pump those puppies 10psi over the posted max and have no problem all summer. He might complain about the harsh ride. Have any of his flats been what you'd expect from overinflation?Steve Ahttps://www.blogger.com/profile/13650405341304401203noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-30846750657727514722011-08-11T14:24:39.146-04:002011-08-11T14:24:39.146-04:00"If my friend religiously pumped up his press..."If my friend religiously pumped up his pressure to 140 psi (=P1) in the 70 degree F (=T1) comforts of his home, and then went out to ride in a muggy 100 degree F temperature (=T2, a 43% change from his house), we can solve for the pressure in his tire, P2"<br /><br />Correct me if I'm wrong, but a change from 70deg F to 100deg F isn't a 43% change in temperature as the zero point (0deg F) isn't really zero it's just a random point where the Fahrenheit scale happens to come to zero (there's still heat energy there at zero degrees Fahrenheit). To get the real percentage change in temperature you'd have have to convert to degrees Kelvin first. <br />70F = 294K<br />100F = 311K<br />So the actual percentage change is about 6% which, of course, is the same as the change in pressure in the tires.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-50298074207167539572011-08-11T10:32:44.802-04:002011-08-11T10:32:44.802-04:00You're back! Nice to read the blog again Ron!You're back! Nice to read the blog again Ron!Jeffnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-33302607328742232232011-08-11T10:31:52.427-04:002011-08-11T10:31:52.427-04:00The correction to the temperature conversion has b...The correction to the temperature conversion has been made. Thanks!Ron Georgehttps://www.blogger.com/profile/18394865788996482667noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-82433645799309567542011-08-11T09:52:12.875-04:002011-08-11T09:52:12.875-04:00Thank you for this, living in Phoenix where the te...Thank you for this, living in Phoenix where the temperature delta between pumping my tires up indoors and then riding on the summer asphalt can easily reach >50F, I've often wondered about this specific question. In summer I pump 7 to 10 lbs less than the recommended pressure, and hope that manufacturers account for some thermal expansion when they recommend pressure. Of course, there's also thermal contraction to consider in colder places in wintertime--I wonder what people who ride in Duluth experience in December, when the delta between indoors and out might be 80F.John Romeo Alphahttps://www.blogger.com/profile/01289456379789026152noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-48680572652552850102011-08-11T09:26:42.884-04:002011-08-11T09:26:42.884-04:00Steve: The Ideal Gas Law is not Ron's pet theo...Steve: The Ideal Gas Law is not Ron's pet theory. Its not really up for debate as its been proven over and over again since the mid 1800's.Nelshttps://www.blogger.com/profile/12629050169180587030noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-23175278312080414222011-08-11T06:57:34.995-04:002011-08-11T06:57:34.995-04:00Somehow, I'd be skeptical of your theory. I us...Somehow, I'd be skeptical of your theory. I usually run my tires towards the high end and have had no flats during record heat. I also got no pinch flats last winter when it was cold.<br /><br /> Still, perhaps your obsessive friend would welcome another correction factor!Steve Ahttps://www.blogger.com/profile/13650405341304401203noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-26244645145476213112011-08-11T03:25:01.564-04:002011-08-11T03:25:01.564-04:00Interesting thought, and I'd expect explosive ...Interesting thought, and I'd expect explosive decompression as the failure mode. I wouldn't want to bike next to him, that's for sure!Arjan Hulseboshttp://www.dehulst.nlnoreply@blogger.comtag:blogger.com,1999:blog-13887692.post-20710712046752382032011-08-11T03:20:15.661-04:002011-08-11T03:20:15.661-04:00Not only does tire pressure change with temperatur...Not only does tire pressure change with temperature, it changes with altitude. Where I live in Sacramento at 22 feet above sea level, in your 70 degree house, when you pump up your tires to their max, drive up the the mountains at 5000+ feet, and do a climb up to 6500/7000ft elevation, and ride in 80 degree temps, you have overinflation. Add to that most clincher rims are labeled "max inflation 130" and you're really asking for trouble. <br />There is a laboratory in Finland; wheelenergy.com, the only independent bicycle tire lab in the world, where rolling resistance has been measured to be LESS at lower pressures!Velocodgerhttps://www.blogger.com/profile/11461347465806639954noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-29177740117269170952011-08-11T02:55:30.544-04:002011-08-11T02:55:30.544-04:00yeah thats what the subtracting 32 and multiplying...yeah thats what the subtracting 32 and multiplying by 5/9 is forpeterabbithttps://www.blogger.com/profile/09727110964205200277noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-20827668173126105292011-08-11T01:09:35.388-04:002011-08-11T01:09:35.388-04:00Actually, you have to convert F to C (celsius) bef...Actually, you have to convert F to C (celsius) before adding 273 to obtain K. e.g. 70F ~ 21C ~ 294Ksugakenhttps://www.blogger.com/profile/15591884768641571155noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-36302514743802002212011-08-11T01:04:30.616-04:002011-08-11T01:04:30.616-04:00allow me to correct your calculations
To convert ...allow me to correct your calculations<br /><br />To convert Fahrenheit degrees to Kelvins you must subtract 32, multiply by 5/9 and then add 273.<br /><br />So your temperatures in Kelvins are: <br />T0 = 294.26 K<br />Tf = 310.93 K<br /><br />Your final pressure is then Pf = P0*Tf/T0 = 965266.02*310.93/294.26 = 1019948.9 Pag = 147.93 psig<br /><br />The compressibility factor for air at these conditions is .999 so ideal gas is a good assumption, but your friend is really only gaining about 8 psi, not 12.peterabbithttps://www.blogger.com/profile/09727110964205200277noreply@blogger.comtag:blogger.com,1999:blog-13887692.post-64641215943476211302011-08-11T01:04:03.453-04:002011-08-11T01:04:03.453-04:00Nitpick: K = C + 273.15, *not* F + 273.15.Nitpick: K = C + 273.15, *not* F + 273.15.keithmohttps://www.blogger.com/profile/15543160493854014802noreply@blogger.com