Weblog

Friday July 29, 2005

Headline news!

It rained in Palm Springs today. Apparently this constitutes headline news so far as our TV stations are concerned. I just thought you'd all like to know...

Tag: Palm Springs

Thursday July 28, 2005

2006 target

I like to have some kind of a target event or events lined up. It helps me with motivation for my daily rides. I think next year, I'm going to aim to get Planet Ultra's King of the Mountains jersey. That involves completing three specific century rides in Southern California, each of which has more than 10,000' of climbing. One of them is the Breathless Agony, which I did this year, so I know it should be within reach. Equally, I was slow on the B.A. and my knee hurt a lot afterwards, so there is plenty of work to do to be more prepared this time.

That's my ideal kind of goal - challenging but definitly doable

Tag: Cycling

Wednesday July 27, 2005

Elevated heart rate after vacation

I didn't ride my bike at all during my recent vacation, so I had 8 days of almost no exercise. Now I've been back in the swing of things for several days, and I have an elevated heart rate. It seems to be 8-10 beats higher than normal, all the time. So I wake up with a mid-high fifties instead of a low forties, and when I'm riding at a regular pace, I have 170 instead of 160, and reasonable hills take me up to 185 instead of 175. What is strange is that normally I'd be breathing really hard at 185, but now I'm just starting to notice my breating.

I've never noticed anything like this before after a short break, so I'm keeping an eye on things. I hope everything will return to normal within a week or so. I'm slightly tempted to sprint up a really steep hill and see if my maximum has gone up 10 beats too, but it might not be advisable for medical reasons.

Tag: Cycling

Tuesday July 26, 2005

Word

Okay, but if I use the word, it'll mean this. It must be one of those words which has a specific technical meaning in certain fields which is slightly at odds with its meaning in normal usage.

Monday July 25, 2005

A cool toy

While I was on vacation, I got a chance to play with one of these cool indoor radio control helicopters. I've always wanted a radio control helicopter, but I've never quite gotten past the whole "expensive, hard to fly, easy to break" thing. I can say from experience that the Blade Runner is the opposite on all points. I had a fun time playing with this, and it was pretty easy to control (I already know how to fly fixed-wing radio control airplanes). I also crashed it a number of times without damage. However, it did break at one point — one of the two gearboxes failed. I opened up the moulded plastic fuselage and fixed it. The shaft had just popped out of its press-fit hole, so I squeezed it back in with some pliers. Embarassing to break someone else's toy though...

The only thing I don't like about this toy is that the controls are set up on the "wrong" sticks to give you practice for flying a more complex chopper. It doesn't have any cyclic control, so you have throttle for climb rate, a horizontal tail rotor to control pitch (and hence forward/backward flight), and differential speed between the contra-rotating rotors to control yaw. No roll control is provided. The stick assignment on the transmitter is

It seems that in the USA, most people fly Mode 2, which has pitch and roll on the right stick, and throttle and yaw on the left stick. However, I learned Mode 1, which is more common in the UK, where we have roll and throttle on the right and yaw and pitch on the left. So for me, it might be possible to swap the two stick assemblies and have the controls correct for a Mode 1 helo, which would be cool, since I might go for a Piccolo at a later date.

Tag: Radio Control

Sunday July 24, 2005

Back in the desert

I'm just back from a week's vacation^[1] on the east coast of the USA. The weather there was very humid, and I was really looking forward to getting back to the pleasant weather of the desert. Apparently it was 122 F (50 C) in our back yard while we were away, but as we like to say, "it's a dry heat". Imagine my chagrin when I awoke this morning to 89 F (32 C) and about 70% R.H. I did still go for my bike ride, although I considered skipping it. Later in the day we had a thunderstorm (rare) and rain (very rare in July). I hope this means the weather has "broken", and it'll be back to normal tomorrow. Since I'm still somewhat attuned to the Eastern time zone, I'm hoping I can get in a good long ride early tomorrow before work.

[1] yes, another one. This was a "make-up" due to my partner not being able to go to Utah with me and my parents earlier in the year.

Monday July 18, 2005

The unbounded optimism of youth

My partner's 7-year-old grandson, proposing a footrace to his same-age friend: You and me against this old guy — it'll be easy. I let them win two out of three...

Friday July 15, 2005

Gadgets, or not?

I like gadgets. I always ride with a GPS/heart rate monitor, and sometimes with a Power Tap hub as well. I've owned about five different HRMs, two GPSs that I used for cycling, probably tens of conventional bike computers. The thing is though, at my level of fitness/commitment, they don't really help. I improved way more by deciding I was going to do 10 hours a week instead of 7 hours a week than I did with months of sophisticated power measurements and periodized training, and I would have needed nothing more complex than a wrist watch to detect the improvement. But I'm not about to give up any of my toys. They are part of the fun for me, even if it is a bit Fred-ish to have Lance-like measurement systems to show that I'm old, fat and slow.

Tag: Cycling

Thursday July 14, 2005

Phew, what a scorcher!

I think yesterday was the hottest day of the year so far. There were reports of 120 F (49 C) temperatures, but I "only" saw about 116 F (47 C) in our back yard. It was unusually humid too, but "humid" in the desert is nothing that would worry any east-coaster.

Tags: Palm Springs, Weather

Sorry, dude...

I don't read Korean, but I'm guessing this says something along the lines of seeing 10 GHz mentioned in an RSS feed from Sun Microsystems, and anticipating the next generation ultra-fast CPU, only to find it was just about ham radio.

Win some, lose some...

Tag: meta

Wednesday July 13, 2005

product-server style installation

I'm currently working through some issues with product-server style installs. The idea being that you install the Sun Studio compilers and tools on a big machine with lots of disk and network bandwidth, and then multiple machines can NFS mount the installation directory instead of having to install the product. I've had some feedback to the effect that what people really want is to run the installers for each architecture directly on the server and just tell each installer to use a different directory (which would then be shared). Currently, we don't support this. We only support running the installer on the same architecture as the product it installs. One way people have of trying to make this work better for them is to use the -R (alternate root dir) flag to force every modification of the system to be under some directory. That way, you can NFS mount the server on an appropriate architecture client with the right root-access flags, and do the install without worrying about modifying the client system. I have a hard time recommending this though. For one thing, it makes it hard to patch the product. So in the current release, there really isn't a nice solution.

For the next release, I've already done something to ameliorate the problem with -R and patching. It turns out that patchadd really only wants to see a certain single file before it will "believe" that a directory is a valid root filesystem and apply patches. So I've made the installer startup script fake up that single file in the -R case. Although this is not a formal Solaris interface with an assigned stability level, I've been told by the engineering group concerned that it is unlikely to "ever" change.

The next thing I did was look at what, if anything, prevented the packages from the two Solaris architectures being installed on the same machine (without alternate root). Solaris says that the tuple {name, version, architecture} must not already have been installed, otherwise this constitutes an attempt to overwrite a package (rather than a fresh install). Also, the package in question must have fewer instances installed than the maximum specified in the package info file. All the packages in the product have a large number for MAXINST, so that shouldn't be a problem. Naturally, the version number will be the same for the same package on the two architectures, if they come from the same build. So we have to hope that the ARCH is unique. It turns out that this is the case for all but two packages in the product, which have ARCH=all on both cpu types. This is clearly wrong for one, and arguable for the other, so I've made the change so that all the packages have distinct ARCH on the two different CPUs.

Next the question is what do you have to do to get the Install SDK code to allow you to install on an architecture different from that specified in the package. This seems to be very easy. There is an internal install property that you can set, but if the installer itself doesn't set it, it comes from the Java system property os.arch. So you can just run the installer with -Dos.arch="sparc" and install your SPARC product on an AMD64 server. There is one problem with this, which is that there is a native-code executable which forms part of each installer. One of the things it seems to be used for is to find out how much disk space is available. So when you trick the installer into cross-installing, it does warn about insufficient disk space. I have not yet researched whether it is possible to provide multiple versions of this executable.

Anyway, progress is being made, and if anyone has any product-server use cases they'd like supported, please feel free to leave a comment or email me.

Tag: Sun Studio

Tuesday July 12, 2005

Thinking about 10 GHz

I'm a licensed amateur radio operator (ham). I've hardly been on the air at all in the last few years, but I think I'm getting the urge again. For me, ham radio isn't about talking to people. I've got a telephone for that. Rather it is that the FCC has given me a license to experiment with radio technology, over a quite large range of parameters. Hams are allowed to build their own equipment, and operate it without it needing to be certified by the FCC. We can invent our own modulation methods and data encodings — currently, low bandwidth digital modes are in vogue, and many new ones have been invented recently. We are allowed to use much higher power than typical consumer equipment, too.

So the thing that's got me interested again is discovering that there are several microwave clubs in Southern California, and that I live about mid-way between two of them. Furthermore, these clubs operate beacons on microwave frequencies. I was thinking I could get a 10 GHz transverter kit from DEM (more likely to succeed than home-brewing my first ever piece of microwave equipment), and use an all-mode 2m radio I already have as the IF. I could then listen for some of the "local" beacons. Unfortunately, I don't think I'd get anything from home, because the mountains either side of the valley obscure line-of-sight to all the beacons. But certainly from either the top of the tram or from Joshua Tree national park, I should be able to get something. From Joshu Tree, I might be able to work both the San Bernardino crowd and the San Diego folks.

Was that a bit geeky? Oh well...

Tag: Ham Radio

Monday July 11, 2005

Things I wish I could do, part two.

I wish I could get up in the mornings.

I mean, I can get up early if I absolutely have to — plane to catch, event to go to, whatever. But if it is just a regular morning, I'm never up as early as I would like. Mornings are the best time to exercise round here, since it gets very hot during the summer, so if I could get up at dawn, it would be great. But left to my own devices, I don't wake up until it's been light for at least an hour. And if I use the alarm clock to wake up earlier than that, I feel tired the whole morning. I'm just not a morning person, I guess.

Friday July 08, 2005

A "utility" bike

Chris's blog entry about his ideal winter bike struck a chord, as I was thinking along somewhat similar lines myself while out riding yesterday. There are things I can't or won't do with Son of Plastic Fantastic. I won't tow my trailer, or take it to the shops. I can't fit fenders (or mud guards, as I used to call them back in the Old Country), or big tires. I won't ride it in actual falling rain (although we don't get that much round here), and I'm loth to ford running water.

I already have a titanium cyclocross frame, which is built up with a Dura Ace triple group. The frame has eyelets that would allow fenders to be fitted, and sufficient clearance for big tires. Unfortunately, the frame has a 135 mm rear spacing (mountain bike standard), but the gits who sold it to me supplied a 130 mm rear wheel (modern road bike standard). I recently bought what will be the third fork to be fitted to this frame, it's a Nashbar (in other words, anonymous Chinese manufacturer's) Cyclocross fork with disk tab. If I were to get a new pair of wheels built, using mountain bike hubs, I could get an Avid mechanical disk brake with the road-specific cable pull, put a disk on the front wheel, and leave the cantilever brakes on the back (since the frame doesn't have a disk tab). Then I'd have wheels which fit with nice big tires, a disk brake for those winter floods, and a bike which would still be light enough to not be a chore to get up hills.

I'd also like to fit lights, because one of these days I'm going to do a double-century, even if it takes me 17 hours. Since riding after dark is not a regular thing for me, I'd stick with a battery-powered system, rather than a generator. Oh, and I'll take a Fizik Aliante for the saddle.

I'd really like to get this going, since there are a number of jeep trails I'd like to explore, and I find them a bit sketchy with my 700x23c tires. One thing we have lots of here is sand, and wider tires roll over loose surfaces better.

Tag: Cycling

Thursday July 07, 2005

What's up with pointy time trial helmets?

Since several people were kind enough to comment favourably on my post about hills and weight, I thought I'd say just a little about aerodynamics, and in particular, time trial helmets.

There are many different ways that drag can be caused. However, for ease of discussion, we can classify by the nature of the mechanism that carries away the energy. Looked at that way, there are the following types of drag:

1. Pressure drag
2. Skin Friction drag
3. Induced drag
4. Wave drag

Induced drag is drag due to lifting surfaces. The energy goes into forming a wake behind the lifting surface which contains vorticity. Wave drag is roughly speaking the energy carried away by shock waves in a supersonic flow. Neither of these are applicable to cycling, since we don't have wings, and we don't move at near- or supersonic speeds. So we'll say no more about them — refer to any undergraduate aerodynamics text for more details.

Skin Friction drag is the drag due to tangential forces at the surface of the object. It is like the friction you feel when you rub your finger-tip over a table top. The amount of drag varies in a complex way depending on the details of the surface, and the nature of the flow. In general, the frictional drag will be the least for laminar flows and very smooth surfaces. If we hold the nature of the flow and of the surface constant, then the amount of drag depends on the wetted area — the amount of surface exposed to the flow.

Pressure drag (also known as Form drag) is the resultant force obtained when you integrate the pressure field over the surface. That means, for each tiny square of the surface, figure out what the pressure force on it is, and add up the forces, taking into account their direction. You might wonder why the pressure would vary over the surface. Bernoulli's equation (which is really just the conservation of energy cast in continuum mechanics terms) tells us that the static pressure exerted by a fluid against a surface is lower when the fluid is moving faster. (You may have heard this as an explanation of how an airplane flys. In fact, this is just one of the details, not the whole story. But that's a whole other rant.)

Now if you had a fluid with no viscosity at all, you would find that the resultant force would be identically zero. It turns out that the pressure lost as the air accelerates over the front of a body is fully recovered as the flow decelerates again at the back. Sadly, air does have viscosity, although it is low enough that it can be ignored for many purposes. We find that there is a net backwards force on a real object moving through real air, even if we subtract the skin friction out. There is an incomplete recovery of the pressure.

So if we want to minimize form drag, the problem becomes to get the best possible pressure recovery. One thing which inhibits full pressure recovery is flow separation. This is when the flow of fluid no longer conforms to the shape of the object, but instead leaves the surface. There is then an area of "stagnant" flow between the main stream and the object. One of the things that causes this is too rapid of a pressure recovery — and the thing that drives the pressure recovery is the shape of the body. If it is narrowing quickly as we go downstream, the pressure recovery will be rapid, and separation will be more likely. (This is why the classical aerofoil shape has a blunt, curved front part, and a flattish pointy back part.)

So finally, I think we begin to see what drives the shape of the time trial helmet. The point on the back is intended to ease the pressure gradient, to keep the flow attached to the surface, and reduce the pressure drag. But notice, by adding the point on the back, we substantially increase the wetted area, and so the skin friction drag. There are other practical limits to be considered. For instance, no matter how much the aero guys ask them not to, all cyclists put their heads down at some point during the time trial. This leaves the cone on the back of the helmet sticking straight up in the air, which is not ideal. (Incidentally, I speculate that this is why Armstrong's helmet from the pre-saftey-rule days had a two-dimensional trailing edge cut at a raked angle, instead of a simple cone. On the rare occasions that he would put his head down, it seemed to me like the trailing edge of the helmet was almost level, not protruding upwards much at all.) Furthermore, the helmet is shaped with the assumption that the flow comes from in front. But of course, out in the real world, there are cross-winds. Having to cope with flow that isn't perfectly aligned would tend to drive the cone length downwards, because the longer it is, the more of it there is to catch the crosswind. And finally, we have to consider weight, since the cyclist has to hold this up with his or her neck muscles, but with modern materials, that probably isn't much of a concern.

Tag: Cycling