The Upgrade - Part 2, Mainly getting the VPN to work

Well, once I got Windows 7 running, everything seemed fine. For a while. For a stand-alone machine, Windows 7 is OK. Personally I don't find it any better or worse than XP - different sometimes, but not noticeably better. The graphics are all different but honestly they don't make any real difference. It's kind of cute the way taskbar items give you a preview before you expand them, but again it's not exactly life changing.

I can't comment on whether the performance is better than XP, as some people claim, because the machine was so badly broken before that it isn't a fair comparison. Some things are however much worse. For some reason re-sorting a large directory can take ages - tens of seconds - if the content consists mainly of images. I suspect it is re-extracting the thumbnails from the files. It's a typical example of trying to be gee-whizz helpful and just making the user experience painful, which unfortunately is fairly characteristic of Windows.

It was when I tried to install the VPN so I could use the machine to work from home that things started to go downhill rapidly. Like many companies, we have a Cisco PIX (well, it's called something else now) which provides VPN services among other things, and the Cisco VPN client. Getting hold of the Windows 7 client and getting the VPN to come up was amazingly easy. So far things were looking good. I could SSH to my Linux system, and I found a so-so free X server and that worked too. For some reason I stopped there, and it was a few days before I tried the next step.

Which was... to open a Windows Explorer window on the Linux filesystem. We have (just like lots of people) a server that runs Samba. When I tried to connect, it just hung for a long time and eventually said it couldn't reach the server. What's more, this time, I couldn't get SSH to work either. Using Wireshark, I could see that packets were being sent into the VPN client, but they were never coming out on the wire side. And in fact, the client's statistics window showed an increasing "discarded packet" count. It's impossible to find out why the client discards packets. The log shows nothing, even when you turn the logging level up to maximum for everything.

At this point I gave up for a while on the regular VPN client, and tried using the SSH client. This was amazingly easy to install. But it didn't work. I eventually discovered that even though I had my work network set as "trusted" in the ZoneAlarm firewall, I still had to turn the global internet security level all the way down, effectively disabling the firewall altogether. The SSH VPN came up that way, but of course this is way too dangerous as a normal setting. So much for that solution.

Luckily, I was able to ask for help from a security expert at Cisco, who parenthetically remarked that it's just about impossible to get the VPN to work with the ZoneAlarm firewall running. Aha! I turned it off, turned on the Windows firewall, and now everything except remote mounting my Linux server worked fine. So, lesson #1: don't use the ZoneAlarm firewall if you want VPN to work.

More Wiresharking showed that this time, packets were getting through to the wire, and were getting replies. Yippee! Strangely, the Windows file client was trying to connect to port 80 (i.e. HTTP) and getting an immediate reject from the server. I have no idea why it tries to connect to port 80. Another interesting thing I saw was that after a couple of failed attempts at connecting, Windows just sulks. When you click on "connect" it immediately comes back and says "can't" without even sending any messages. I suppose it has cached the failed result, but it's a real problem when you are making configuration changes to try and get it to work.

Then I suddenly remembered something. Windows remote file access uses a protocol called SMB. SMBv1, used up to XP, is a truly awful protocol. It sends literally hundreds of messages, and waits for the round trips, for even the simplest operation. That's why accessing a remote file system over a wide-area connection is so slow and painful. Finally, after a decade or so, this problem was addressed in Vista, with SMBv2, which supposedly makes things better. However Samba still only speaks SMBv1. Now Vista, and Windows 7, are supposed to auto-negotiate, i.e. if the server can't do SMBv2, they fall back to SMBv1. Supposed to, but evidently they don't. If the client doesn't get the answer it's expecting when it tries SMBv2, it just sits and waits an irritatingly long time, then tells you it can't do it. So, the obvious thing to do is look for a way to tell the client always to use SMBv1. I looked everywhere in the "advanced" configuration, but nowhere is there a checkbox that says "don't even think about using SMBv2".

So I Googled, and I found an excellent page on an Israeli IT-help site that says exactly what to do. It just involves typing two unbelievably complex commands at the Windows shell. However this isn't the whole story, because Windows 7 has this great idea that even if you have Administrator privilege, you don't actually get that privilege unless you ask nicely. So after you have typed this humungous command, the response you get is "access denied". Luckily, Google had the answer for that, too.

So the whole procedure for disabling SMBv2, assuming that you have Administrator privilege, is:

1. Right click on the "Command Window" icon, then select "Run as Administrator".
2. Type:
   sc config lanmanworkstation depend= bowser/mrxsmb10/nsi
   sc config mrxsmb20 start= auto
   
   

Don't miss out the spaces after the equal signs - they're important. Someone at MS evidently skipped parser school.

So, after a very frustrating couple of sessions, I can now fully access my work system from home. But (a common refrain I'm afraid), why is it so hard?

That wasn't all though. When I was physically rebuilding my system, I kept noticing that the CD/DVD drives stopped working. Each time, I'd remove all their cables, plug them back in again, and when I rebooted, they worked fine. The cables didn't seem loose or damaged, so it was a bit surprising, but I figured I must be disturbing things somehow. Later, I finally figured out why my DVD drive refused to write DVDs... it isn't a DVD writer, just a reader and a CD writer. Well, that was easy to fix, so it was off to Fry's for a fancy new SATA DVD drive. That was actually an amazingly simple and smooth installation. Absolutely nothing went wrong at all.

Then, while I was trying to solve my VPN problems... the CD drives wouldn't work. When I inserted disks, the lights would flash, and sometimes the drawers would pop open, but nothing showed up for the disks themselves. Now though, they use completely separate cables and adapters, right to the motherboard. So it can't be a cabling problem. Finally, I rebooted the machine... and they worked just fine. Turns out (thanks again to Google) that Windows 7 has a well-known bug that sometimes, CD drives don't work. How on earth did that get through the QA process?

On Upgrading - or "what were they thinking?"

My desktop machine at home has had creeping software sickness for a long time. It was new about 4 years ago and has gradually got less and less likely to succeed at any given task. Visual Studio crashes quite often, which I've never seen anywhere else. Google Earth kind-of runs but is pretty much unusable. And so on. I've no idea why these things happen, there's no logical reason why software should wear out, but it seems that it does.

I resisted Vista for all of its sorry lifetime, wisely as it turned out. But everyone seems to be saying nice things about Windows 7, so I decided it was time to upgrade. At the same time I decided to swap the 250 Gbyte hard drive for a brand new 2 terabyte one. Not that I have anything that will use up that much disk space, but 250 GB was getting full.

The machine is something called an HP Media Center. It was a distress purchase, my previous machine had scrambled its hard drive and I had exactly 10 hours to get something important done, so I just rushed out to Fry's and bought what they recommended. Until now, I'd never had any reason to take the covers off. When I did, I found that the hard drive was totally, utterly inaccessible, hidden inside the machine, and mounted vertically (rather than horizontally as usual). No normal screwdriver could access any of the mounting screws. I tried undoing various other things, but nothing gave access to the screws. Eventually I figured I could just put the new drive loose on the floor of the box. But, since I don't give up easily, I wondered how the factory had ever managed to assemble the machine. More on that later.

So, having swapped the drive cables over to my brand-new, unformatted 2 TB disk, it was time to install Windows 7, which I had (legitimately) on a USB memory stick. (As an aside, in about 1994 I worked on one of the very first video-on-demand projects, at DEC. Part of the system was a 1 TB drive farm, which occupied four full-size racks. Of course the whole project was more than a decade ahead of its time, and flopped completely).

Since I had a new disk, I actually wanted to do an install from scratch. But still there is a great mystery here. Microsoft built Windows 7 because the adoption rate of Vista was so low - I've seen estimates of 20%. Yet you can only do an in situ upgrade from Vista. So if you're one of the 80% who never moved from XP, you're out of luck. Or rather, Microsoft is, because that's who loses money if people don't upgrade. XP is a perfectly fine system, I would not have upgraded but for my "software wear-out" problem. Most not-very-technical users will be completely put off by the complication of a from-scratch installation, followed by reinstalling all of their apps, and in all probability just won't bother. So what was Microsoft thinking when they made this decision?

So, I booted from the memory stick, Windows 7 started and everything seemed fine. Then it put up a screen asking me which disk I wanted to use. When I selected my new drive, I got an error, "cannot create system partition". That's dumb, I thought, surely a from-scratch installer should be able to partition and format a disk? Still, I was able to rig things up so that I booted from the old system, with the new disk connected. That way I could format the new disk from XP. Then I restarted the Windows 7 system again. The same thing happened.

It took a lot of frustration, much bad language, and a lot of googling before I found the solution to this. It turns out that since the early days of Vista, the installer has not been able to cope with having more than one drive or partition visible to it. If it does, it gives this misleading error message which gives absolutely no clue as to the problem, and which will certainly stop most people dead in their tracks. Yet MS had at least a year to fix this, preferably so installer could handle multiple connected drives, but failing that at least to give a better error message. Once again, what were they thinking?

Once I had this figured out and unplugged everything except the target drive, everything went fine. The system installed remarkably quickly, and subsequent reinstallation of all my apps went smoothly too. It took quite a while for further problems to emerge.

Meanwhile, I hadn't given up on the disk mounting problem. I picked up various tools - stubby screwdriver, offset screwdriver - from my local TrueValue, but none of them could get all of the hidden screws. Finally a trip to Fry's got me a tiny ratchet offset screwdriver with interchangeable bits. Using that, and a lot of missing flesh from my hands, I was able to remove the drive and install the new one. Still I wondered how on earth they did this at the factory? Then by chance I tidied my office and found the original hardware manual for the machine. This revealed the secret latch which allows the whole drive bay to be dismantled and removed. Of course it is much easier that way, but there would be no way to identify the secret latch without the manual.

Windows 7 ran smoothly for a while, but then I ran into a very odd problem. Double clicking on certain system-ish folders gives the message "Access Denied". Now, I am the only user of the machine, and of course have Administrator privilege, so what is going on? I tried changing access rights, but of course since I didn't have access in the first place, that didn't work. Finally, some extensive googling found a way round this, which involves going into the deepest depths of "advanced options" in the security screen, and changing ownership of the parent directory. It's at times like this that Linux is so attractive - although the commands are arcane, it is always reasonably easy to figure out what is going on. With Windows, it's either easy or next-to-impossible. The dumbed-down user interfaces give you few alternatives when things are partly broken.

So now, my new system seems to be working fine, and does very nearly everything my old one did. (There are still a few things to reinstall). One mystery is a system-created "shortcut" (i.e. softlink) which points to itself. This confuses Explorer no end, but since I have no idea what the folder is for, I daren't delete it. I also still haven't managed to find the cache directory for IE8 - I've found one of them, but only some files show up there. That's another mystery.

Divisumma 24

Update August 2020: the person who supplied the manuals has sadly passed away, and they are no longer available from this source. I have placed them online here (Part 1) and here (Part 2). Be aware that they are very big - about 250 MB in total.

It's arrived! My circa 1960 Olivetti Divisumma 24 electromechanical calculator has arrived from Italy. It's in good condition although so far I haven't got it fully working.

First a little background. When I was about 17 (a long time ago!) I worked one summer at an advertising agency doing analysis of some surveys. For this I was equipped with a Divisumma 24. This was, for its time, an amazing machine. It could not only add and subtract, but also multiply and divide, for numbers up to 12 digits. It was very compact, unlike most such machines, and also a very nice piece of industrial design. It fascinated me, and I was especially intrigued as to how it worked. I wrote to Olivetti, and they kindly sent me a green booklet describing in complete detail how one of the simpler machines - just an adding/subtracting machine - worked. A while later I wrote to them again, thanking them profusely and practically begging them for information about the Divisumma. Obviously my letter went to someone else, because this time I got a reply more-or-less accusing me of stealing the book and asserting that Olivetti would never, ever, under any circumstances, give such information. So that was that.
I still have that little green book, and a few weeks ago I took it out of the bookcase and re-read it. I was as intrigued as ever about how the Divisumma worked. A lot has changed in 40 or so years - Olivetti no longer really exists, for one thing, and nobody has used mechanical calculators for three decades. So with Google's help I discovered this source for Olivetti manuals, and a great many others too. A few days later a parcel showed up with seven volumes of green-covered manuals, and I started reading. It's not that hard to understand how it works, but what is truly mind-boggling is that someone was able to design it. Even allowing that it was a process of evolution from simper machines, it is still extremely impressive. Unlike software, which has some structure to it, these are three-dimensional puzzles, where two completely unrelated functions that just happen to need to do something at the same time, can share the machinery. (For example, the mechanism that arranges double line-spacing for totals just happens to be in the right place to reset a lever that controls the way the registers engage for memory operations).
Of course reading these manuals just whetted my appetite again. A bit of searching showed someone in Italy who had one to sell. I paid about $150 for it, but of course the postage - even surface mail - nearly doubled that. And this week it arrived. The seller had done a super job of packaging, including a wooden framework to protect the machine inside the box. It was complete, apart from one minor knob on the keyboard, and the power cord. It even had a roll of yellowing paper.
I rigged up a power cord for it (don't tell the safety nannies about this) and plugged it in. Unfortunately, it didn't work - one of the keys was jammed, and the motor just ran without anything happening. Not really a surprise, but a bit of a disappointment. So then it was off with cover. That comes off surprisingly easy, no screws, just a couple of toggles.
The insides of the machine are in remarkably good condition. There was some fluff around the keyboard, but no rust or damage. All the metal parts seem to be cadmium plated, which means they look the same as the day they were assembled.

I need to say something about the manual, too. The Olivetti technical manuals are also works of art. Every tiny aspect of the machine's operation is described in great detail, with beautiful engineering drawings for every page showing the various levers, bridges, pins, racks, springs and so on - just those relevant to the current description. Once you've digested that, they also include complete instructions for assembling a machine from scratch. The numbering of the parts is consistent through the seven volumes, so once you read in chapter VIII (as befits an Italian product, much use is made or Roman numerals) that lever 73 is key to some particular function, whenever you see lever 73 later on, you know exactly what it does.

So with the help of the manual, I was able to figure out what was jammed, and unjam it. And the machine worked! Well, briefly. For about fifteen glorious minutes it would add, subtract, multiply, divide, and move numbers to and from the "memory" . Even the 30-year old ribbon worked, well enough to read anyway.
But then disaster struck. I started a divide, but instead of the usual kerchunk-kerchunk of the running machine there was just a faint hum, the horrifying noise of the stalled motor. I unplugged it and tried a few things, and eventually it unjammed. Phew! But then I realised things weren't working right, and when I looked, I realised that disaster had struck. Right in the very heart of the machine, a frame had got twisted so badly that it had let a metal rod fall out. This was a totally inaccessible place, without completely dismantling the machine. I was mortified. Just when things had been going so well (I had never really expected the machine to be working), and now, just so much scrap metal. I could almost have wept.
I studied the manuals again, and very carefully, removed the paper roller and associated bits and pieces, saving all the parts in little plastic bags. There was only one problem - a circlip which in the time-honored tradition flew across the room. Luckily I found it easily. That gave me access to the mechanism, from above. Then the real fun started. I found that I could just get a pair of tweezers between the individual elements of the register, and that way I could hold the rod in more or less the right place to insert it. But actually getting it into the holes at either side of the frame was another story. Let's just say it took a long time. Finally the trick was to hold everything in place with wire (actually green garden wire, which gave a certain rusticity to the whole operation). After several hours I had it back in place.
Very carefully I turned the machine over by hand. It seemed to work correctly. But then I discovered how delicate these machines really are. Just like an exceptionally old wine, which is wonderful when opened but undrinkable within ten minutes, so it seems that my early success with the Divisumma was not to last. Every operation revealed some new misalignment or jam, and when that was fixed, another one showed up.
There is really a lost trade and craft here. Back in the day when these machines were commonplace, every town had numerous little back-street workshops, where bent-backed mechanics in brown coats would pore over them when they jammed or refused to work. I'm sure it was a common occurrence. In the few weeks I was using the Divisumma all those years back, it jammed once and had to go for repairs. Probably every machine was in the shop every few weeks. "Oh yes," the brown-coated old guy would say, "looks like the returbitating cam has shifted again, just move it a bit and tighten up the unflurging spring while I'm at it..." and the machine would be as good as new... for a few more weeks.
Anyway, my Divisumma definitely needs some more tender loving care before it will be dividing again. It's a wonderful piece of engineering, and I'm very lucky to have it. It's certainly something to fill those long winter evenings!

Ergonomics, Cars and Turn Signals

There's a book called "Turn Signals are the Facial Expressions of Automobiles", which deals at length with the kind of dysfunctional man-machine interfaces that annoy all of us from time to time. If it's true, then the automobiles made by Opel (the European arm of GM, at least for now) must have eaten something very nasty.

Turn signals (direction indicators for my UK readers, if any) have been operated in the same way ever since flashing lights replaced pop-up arms that stuck out of the side of the car, which is to say the early 1950s. You push the little arm up to turn left, down to turn right, and it stays there, making the corresponding lights flash, until either you straighten the wheel up after the turn, or you turn them off manually. It's simple, it's intuitive, and it's easy to build.

It's a shame that, along the way, manufacturers have never been able to agree about which side this otherwise universal control should be. So every now and then, when you rent a car, you find yourself turning on the wipers instead of signalling. Even so, it's immediately obvious what you've done, and what to do about it. Since turning the signals on and off is never an emergency, it's no more than a minor nuisance.

Sometimes it takes real genius to look beyond the mould of convention and make the leap to a new and far better way of doing things. Unfortunately genii are rare, and when the non-genius tries the result is rarely a success.

Such is the case at Opel (and their UK badge-engineered variant, Vauxhall). If something has been in use for over half a century, works well, and is familiar to every driver on the planet, then surely it must be time to come up with something gratuitously different. And so they have.

My guess is that someone on the production side worked out that the mechanism that holds the arm in place, and returns it to the neutral position as the wheel turns, represents a few dimes that could be saved in the production of every car thanks to the miracle of electronics. Who needs springs and cams when you can do the same thing with some silicon?

And so if your rental car turns out to be an Opel you will find that the indicator stalk is sprung so it always returns to the neutral position. To turn left, you push it up, the silicon equivalent of a cam and a spring remembers it is there, the signals blink, but the memory is strictly non-mechanical. This is surprising at first, but you barely notice. You make your turn, and when you straighten the wheel out afterwards another miracle of the electronic era turns the signal off. So far, so good.

The problem comes when you make a lane change. In the US of course this problem doesn't arise. People rarely signal at all, and never (in my experience) for a lane change. But in Europe people still do, and it seems polite to follow suit. Since there are no large steering wheel movements, the signal does not automatically cancel. You have to do it yourself. You can't move the stalk back to the neutral position, because it's already there. So what do you do? Well, the only option is to push it in the opposite direction, i.e. downwards if you were signalling left. This works, in that the left signal stops signalling. Unfortunately, what happens now is that you are signalling right instead. Given that you probably just pulled into the left lane, this will certainly confuse following traffic (if they pay any attention to these things). So now, how do you stop the right signal? Only one choice... push the stalk upwards. You can guess what that does. At this point, you just have to hope that the police are not close behind you, because if they are they will certainly pull you over and give you a breath test. (Well, maybe not if they are driving an Opel too, because then they will understand the problem).

I can say from experience that there exists some combination of circumstance and action that does completely turn off the indicators. You don't have to make a 360 degree turn on the highway, although it may start to feel like the only solution. However it's not something you can ever figure out or remember. Sometimes, some amount of waggling the stupid arm stops the signals, sometimes it doesn't. I've even heard of a case - certainly not from personal experience, as I'm sure you will realise - where a driver has become so frustrated at the stupid @#$^^%$@# thing that they have ended up yanking the stalk right off. (It's made of some feeble soapy plastic, that breaks very easily. No doubt this saves another cent or two on the production. I've also heard - not that I would know personally - that superglue will hold it in place well enough to last until the next rental).

My first experience of this technological leap was several years ago, in a rented Opel Zafira. It was a terrible car; if blogs had existed at the time, I would certainly have written more about it. But this the worst of its many sorry misfeatures. However I'm pleased to say the engineers at Opel are not deterred by any kind of temporary setback. My son is now learning to drive, in a Vauxhall. He swears that he will never, ever buy one - because of their bizarre and dysfunctional indicators. (And no, I hadn't told him what I thought of them).

It's a reassuring constant that when people, and companies, make mistakes, the last thing they will do is correct them, since that would be showing weakness. Instead they persevere, in full denial that they could ever have done anything wrong. Occasional lapses from such behaviour (such as the Austin Allegro's square steering wheel - and no, I'm not making it up - which indeed was corrected very quickly) are satisfyingly rare.

Your Neighbors will be Astounded by...!

Like everyone in the US, we are bombarded by glossy catalogs for things we don't want. Every day brings two or three of them: clothes, household nick-nacks, guy stuff, garden stuff, just about any stuff you can think of.

These catalogs are in fact very sophisticated examples of applied psychology. For 99% of the things in them, you have lived your entire life without realising you need them, and you're unlikely to suddenly decide you need them all of a sudden now. So the motivation to purchase has to be something else. The most frequent appeal is to the common human desire to appear better - more sophisticated, stronger, more intelligent - than the next guy or gal. It's amazing how often the headline "Your Friends/Neighbors/Workmates will be Astounded by..." appears. "Your Neighbors will be astounded to see this giant, fully illuminated, solar powered inflatable Polar Bear". "Your Friends will be astounded by this 15-place table serving in genuine Orinocan Sustainable Mahogany". And so on.

Another frequent appeal is an application of "X does Y, so if you do Y too, you'll be X too". The crudest example of this is the scantily clad young ladies who adorn car adverts, and real cars at shows. The implication is of course that if you buy this car, suddenly your life will be filled with desirable nymphets. It's obvious to even the densest person that this can't possibly be so, that having a Geo Metro Sports Edition on your driveway is not really going to expand your life like this. Yet it works, or I suppose it must or people wouldn't still be doing it.

Last week's crop of catalogs produced an extension of this that I hadn't seen before, though, pushing the notion to new extremes. It includes a pen - a pretty expensive pen, at $70. And the headline says: "Straight from Italy, the Pen I Drove Around Ferrari's Fiorano Test Track at 185 mph!". (We can leave the question of why every word Begins With Capital Letters for Another Time).

So, let me get this straight. I should want this pen because someone had one just like it in their pocket while they were driving at 185 mph. The implication must be that if I have a pen like this, then I'll have as much fun as if I was driving at 185 mph. Can this appeal possibly really work? Are there people out there who say, gosh, I must have one of these because someone drove at 185 mph with one in their pocket? Or who buy them as gifts, telling the bemused recipient, "You'll love this pen, someone you've never heard of was driving at 185 mph with one in their pocket?"

Why stop at pens? Why not socks, or underwear, or denture retainer? "Straight from Malaysia, the Pack of Tissues I Flew in a Search-and-Rescue Helicopter!" (I think that's generally considered a fairly manly occupation).

Maybe I should just get used to human nature, and the clever ways of exploiting it for profit. But I just can't.

PPL-H!

Well, almost exactly one year after my "discovery flight", I passed my PPL-H checkride and became a qualified helicopter pilot. To my pleasure and surprise, my wife - who has never been at all keen on helis and until now has never flown in one - agreed to be my first passenger. So last weekend I did my first helicopter "Bay Tour", departing from Palo Alto towards the coast, with a slight detour to fly over the Montebello Ridge vineyards so she could see them from the air. Then out to San Gregorio, up the coast over Half Moon Bay, over the Golden Gate and back over the city. I've done this numerous times in airplanes, but the view from the heli is much better and of course you're lower too. The flight was a success from all points of view, with a very happy passenger who agreed - despite her attachment to our plane - that this was even better.

One of the hardest parts of flying helis, for me anyway, was to get a really smooth pickup. Hovering seems impossible at first, but after about five hours it's under control and getting better. Autorotations are fun, and if you're used to landing the Pitts then they don't seem too dramatic. Getting them right is tricky and takes some fairly aggressive manouvering, and (in my opinion) you can never practice them enough. But in the end, pickups were the hardest.

Here's the problem. While you're sitting firmly on the ground, the position of the controls isn't affecting anything. Hence, you have no feedback about whether they're in the right position or not. As soon as the skids completely leave the ground, you're flying, even though you're only an inch off the ground, and everything depends on the position of the cyclic and the pedals. A touch too much left cyclic and right pedal, and you're whizzing off to the left while spinning round to the right - not good, especially if you're in a confined area or on soft ground.

Instructors and textbooks say the same thing - lift the collective slowly until you're "light on the skids", correct the control position, then lift further. Easy to say, harder to get a feel for. It's just like learning coordinated turns in a plane - the instructor says, "but surely you can feel it, without even looking at the ball?" And you say (or at least I did), "errr, no, I can't". Now I can feel it, after over 1000 hours and 100+ hours of aerobatics, but it took a while.

So my experience was, you so-so-gently pull up on the collective, waiting to feel the heli come alive as the weight comes off the skids. And then it starts to turn or to move, and in an instant of panic you yank up the collective and you're three feet off the ground and you've zoomed off several feet from your starting point, before you brought things back under control. This is not the way to pass a checkride, something my instructor made very clear to me.

The fix, for me, was an exercise where I deliberately set the cyclic and the pedals way off where they should be, then, as the collective came up, gradually corrected them as I felt things starting to move. After a few times doing that, I'd overcome the panic instinct to yank on the collective, and after that it was just practice. It's very satisfying - now that I can feel what "light on the skids" means - to make small corrections just before the thing leaves the ground, and have it move smoothly and vertically through those first few inches.

The other hard thing, getting close to the checkride, was slope work, where you delberately have the weight partly supported by one skid and partly by the rotor. The amazing videos you see of helicopters touching a steep hillside, yet still flying, are all about this. Again it's all about feel for the controls during the critical moments, and tiny movements of the collective. It's a real feeling of victory when you can hold the heli, half on the ground and half off, then sooo gently let it down onto the other skid. And even better when you can smoothly lift it off again. It takes a lot of practice.

Finally, a couple more pictures from our Bay Tour. There are more on Flickr.

The Blue Cogwheel of Death

Last week I had the great good fortune to be invited to the Computer History Museum's Annual Fellow Awards event. I first visited the Museum when it was in Boston, shortly after it opened there, and I again find myself living close by. The collection is truly amazing - if you haven't been and you find yourself nearby, you should definitely go.

And of all the amazing items, the most outstanding is the Babbage Difference Engine, courtesy of Nathan Myhrvold, who paid the London Science Museum to build him one and then lent it to the Museum. It weighs four tons, and is eight feet high by about twelve feet long (I didn't have a tape measure with me so this may not be accurate). In principle it's extremely simple - repeated addition can be used to calculate any polynomial whose degree does not exceed the number of stages in the machine, and hence to approximate a great many interesting functions. However given that it is built with 18th century technology, the reality is anything but simple. To anyone who admires mechanics and machinery, it is truly a thing of beauty - four tons of gleaming brass and steel and cast iron, thousands of cams, levers, wires and pulleys. To sit down and design it from scratch now would be an achievement; that Babbage did so over two centuries ago is almost beyond belief.

The machine is operated by a large crank handle, which is turned slowly and evenly by a trained operator. Sadly though, when I was there to see it, a short way round the first turn the handle jammed solid. No amount of gentle persuasion would shift it. The docents (guides, for any British readers I may have) told us that this happens occasionally, and when it does, the machine needs to be reset. As you may imagine, this involves a lot more than pressing a button and waiting a couple of minutes. Screws have to be loosened, cams carefully reset to their starting position, and goodness only knows what. In any case it takes way too long to do in front of an audience.

I feel quite honored to have seen the first computer ever built, crash.