Cool Science

So above we talked about the molecules of N₂ and O₂ being essentially the same size. Sure the N atom is slighty larger, but this is not an exciting effect on the overall size of the molecule. Now O₂ is a neat thing since it's also paramagnetic, while N₂ is not, but I haven't been able to think of any way to connect that to tire issues, so that important difference between them will have to be set aside.

Click and Clack have weighed in on this and explained it nicely and in a way only they can. But not everybody is happy about it. But perhaps that's because there's big money involved in nitrogen tire inflation (sorry for the large pdf link there).

I've been wondering : why would industry, which to be fair has a pretty good track record of being stingy with investing, go into the nitrogen tire business? Well, they were already in it of course in NASCAR, airplanes, etc. where you have tires in incredibly extreme environments and there are plausible reasons to use nitrogen (see the above click and clack article). And to be fair, good business models always look for new markets and applications. But if you start to read between the lines, there is some surprise in the industry about the craze among passenger cars for this stuff. The next viable market that was being targeted was trucking, where tires operate under very high pressures, high temperatures, and for extended periods. It's probably the next closest thing to the demands of a race car, and there's a chance (I haven't thought about it, but it seems reasonable on the surface) that these conditions are extreme enough that you may realize some benefit from nitrogen in a heavily loaded semi traveling a thousand miles a day.

I just found the disclaimer by the way in the above pdf file - you will get 95-98% N₂. Now air is already 78% N₂. So you're not even getting pure nitrogen and you're changing your tire's inflation composition by only about 15-17%. Shoot, I forgot to do the van der waals calculation in this post. Next time.

Posted by Dave at 08:37 AM | Permalink | Comments (0) | TrackBacks (0)

First, awesome Jenn awesomely got me an awesome gift certificate at thinkgeek. I am beside myself. She's a doll.

The gas craze continues and recently on a road trip we saw an auto shop with the sign proclaiming something like "We have nitrogen : filling your tires with nitrogen saves gas". I'm certain I must have blogged about this before, but it's "hot" again. So let's dispel rumors and spread it out over a few posts for fun.

First, why might people do it? Legitimately, basic compressed air has a lot of moisture, which poses minor concerns for the lifetime of the tire but which is a pain in the neck for NASCAR. Why not use dry compressed air then? Well, I always assumed most air compressors in autoshops had dryers on them, but maybe I'm wrong about that. The moisture issue is nothing new, very minor in the grand scheme of things, and trivial to fix. That would help actually, but race cars and airplanes and the space shuttle also use nitrogen to reduce the fire hazard if a tire should explode. Perhaps Volvo will mandate this as one of its safety features? Hmmmm.

Myth 1. What size are the molecules? Nitrogen gas is composed of diatomic molecules; so is oxygen gas. They are practically the same "size" on a molecule per molecule basis. An individual O atom has a slightly smaller radius than an individual N atom. However nitrogen has a triple bond, while oxygen has a double bond, so that to a good approximation they are the same size. Nonetheless, you will encounter bizaare statements by columnists such as "it replaces skinny oxygen molecules with fat nitrogen molecules". In fact these two gases are so similar, they have nearly the same van der waals constants (please forgive the wikipedia link). That could turn out to be fun and interesting so we'll play with that on another post.

Posted by Dave at 08:24 AM | Permalink | Comments (0) | TrackBacks (0)

Click and clack were my commencement speakers, and they were awesome. Who wants to listen to a politician give a forgettable, canned speech? Who wants to hear a writer ramble self-indulgently on their own peculiar creative process? Who wants to hear pretentious celebrities or actors try to don the mantle of wisdom for 20 minutes? It usually leads to priceless commencement quotes like " Lots of hairy guys are pervs". (yes, it's fictional)

Here's a crazy idea: why not look through your roster and invite back two alums who have become wildly successful practicing some of the things they did at MIT and then share with the grads how they dit it? This should happen more often, but unfortunately Click and Clack were the exception, not the rule. And I'm floored I got them on my graduation! They went crazily over time, and I still remember the big picture message "unencumbered by the thought process", which was a reminder to open your mind, have the courage to do the things that you enjoy, that you're good at, and good things will follow. I'm not claiming anything about how well I followed any of that advice, but it's the sort of thing that when you hear it you feel as though you're a better person for just thinking about it! I think I was channeling Paris there.

Anyway, the point (I think) is that Click and Clack are out there making a career by using their brains. They never get to see any of the callers' actual vehicles, and they figure out the problems most of the time. You have to think to fix cars. There's a concept.

I'm working my way around to something I've been pretty excited about, which is a new PBS show coming up this summer: as the wrench turns with none other than click and clack. And I'm pretty psyched about it because the more people on television who actually think and use their brains and set a good example for the rest of us, the better off this crazy world is going to be.

Posted by Dave at 01:58 AM | Permalink | Comments (0) | TrackBacks (0)

...you were an astronaut, you'd be happily flushing the toilet again. Oh, and drooling over the mega-huge japanese research module just delivered that adds mucho square feet to the ISS (and maybe another toilet?). My question: how long does it take to get from one end of ISS to the other?

...you were a democrat, you'd be cracking open a beer and sighing in relief that there is finally a nominee. In these primaries we actually got a glimpse of substance. Obama rightly said that gas-tax relief was a reckless gimmick that would do more harm than good. And somewhere buried in their platform statements, there were tangible differences in their approaches to healthcare as well. If more things like this emerge in the next few months, maybe we can make a decision based on issues and not on PR blitzes.

...you were a commuter, you would be trying to figure out what the heck hypermiling is. Actually, it's just common sense like not racing to a red light, coasting up hill and accelerating down hill, driving at or below speed limits to reduce friction, unloading dead weight from your car and...wait, stuff I blogged bout a while ago, which anybody could figure out on their own anyway, and which I didn't think needed a silly trekkie name.

...you were looking for a way to save money on gas, you might buy into the HHO scam, which is nicely debunked on this wikipedia page (at least at the time I wrote this!). As a chemist I thought this was hilarious the first time I read it. But of course then there's the double take. OK - it's not HHO and many of the scammers know that (but interestingly not all - some of them seem to have duped themselves). But it is H₂ and O₂ gas, and they could improve combustion in an internal engine when fed into the intake, except that they'll also add a ton of moisture into the engine... So like all great scams, there is a little kernel of truth in this one and maybe somebody will find a way to 'de-scam' this one.

...you were me, you would stop procrastinating and get back to writing manuscripts!

Posted by Dave at 09:15 PM | Permalink | Comments (0) | TrackBacks (0)