If you open tins here's a must

So why is the Brabantia tin-opener so good? One reason is that significant forces are concentrated at the notched wheel (which drives the opener round the rim of the tin) and the disc blade (which is pressed into the tin end and does the cutting). On cheaper openers the spindles on which these two components rotate wear quickly and both wheel and blade become loose. When the play is so extensive it is almost impossible to squeeze the handles together sufficiently to drive the blade through the end of the tin.

The photo can't show how securely the notched wheel (on the right) is mounted but I can assure you the spindle diameter is twice that of cheaper openers. But the key to the design is the mounting of the blade (which has its own idling notched wheel to grip the other side of the rim of the tin). For one thing the spindle is mounted at an angle. Thus when the driven wheel and blade are squeezed together they operate optimally. Second, even when spindle and blade begin to wear, they are held in position by the curved spring which engages with the free end of the spindle.

I'm afraid it's all a bit wordy. The qualities are easier to understand when you see the Brabantia "in the metal". It only remains for me to add I am not in the pay of Brabantia. I simply like things that work, and this does.

Learn on the couch, not in the car

SATNAV - Part three No, I'm not in thrall to this technology and freely admit it has some way to go. But it's had an undeservedly bad press from people who've tried it for an afternoon, failed to realise its potential and - a particular bête noire - have written delightedly about their inability to penetrate its workings.

One accessory worth acquiring is the cable/transformer that allows you to plug the satnav in to your house supply and play around with it in the comfort of your own living room. You learn far more in this unstressed environment. When you try similar experimentation in the car it always seems too hot and your sweaty finger-tips skitter over the controls.

I think that's enough about satnav. To tell the truth I respond more viscerally to maps but satnav's proof I'm trying to be a child of our times.

TECHNO-ART Other than documentaries which are outside my scope I find TV rather barren of examples in which art fuses with technology. One exception was "Das Boot", the German multi-episode series about life in a WW2 submarine. Here men were surrounded by technology and threatened by it from above. Big batteries were big, too. But I'd appreciate an explanation about that greenish light emanating from small windows - apparently - on the side of the diesel engine cylinders.

Trains - it's not all bad news

"Descanting on his own deformity", Richard III points out he was not shaped for sportive tricks. What I'm not shaped for is mass transport. At 6 ft 2 in. I'm at an immediate disadvantage but the real killer is the distance between my patella and my buttocks. Notably on Japanese Airlines where the relevant seating dimension is a Procrustean 29 in. (vs. 32 in. on the US airline United). A cheap JAL flight to Christchurch, NZ - broken humanely at Tokyo after a mere 11 hr - was paid for in much personal agony.

Buses in Britain are even worse but at least I only use them for short hops. British trains not only cramp my legs but offer minimal space for my feet. Size 10½, since you ask.

Or so I thought for trains have moved on. A perfectly acceptable twin-coach diesel recently took me from Hereford to Newport where a gleaming blue First Great Western monster wafted me painlessly to Paddington.

I commend the seat designer. The accommodation is dense but without menacing my kneecaps or my gluteus maximus. And the seats are cantilevered leaving dance-floor space for my feet. But what I wasn't prepared for were the three-pin sockets, proof that I haven't used a train for yonks.

For years I had noticed people using laptops on trains and assumed they were more confident about their batteries than I have ever been. And then I saw my neighbour's computer was plugged into an unobtrusive 13 A socket. Did he pay for the power? I asked. Oh no.

Just think, I'd be free to compose my blog offline interspersed with innumerable excursions into Solitaire and Columns (a simplified Tetris), both beyond me when I'm driving a car. I may in fact let the train take the strain.

TECHNO-ART Another novel but with a name you'll always remember. "The Gold-bug Variations" by Richard Powers links the technicalities of Bach's music with the application of DNA. The latter field is one I've had difficulty absorbing although I found "The Double Helix" a real page-turner all those years ago. Gold-bug's proposition seemed daring and I read it with interest. But with less understanding. I needed a second opinion and had Amazon send a copy to a friend of mine with a physics background. When we next met he didn't volunteer an opinion and so I was forced to ask him outright. He sighed: "Well, it's very long". I changed the subject.

Why electricity and water don't mix

When you write for the Web you're allowed second thoughts. Typically, I've tweaked the blog explanation on my home page at least half a dozen times.

My piece about Ohm's Law ("Introducing two mega-stars", May 6) deserves a coda. The law itself - current equals voltage divided by resistance - is easily understood. But it's harder to grasp the nature of current and voltage. And, alas, I'm not about to define them. To do so within the confines of this post would be to run up against a barrier in teaching any technical subject where the elements are, and must be, invisible.

Electricity is good and invisible so the instructor uses analogies. "Think of electricity as water flowing through a tap. Voltage is the amount of water flowing, current is the pressure the water is subject to." Are we discussing electricity or hydraulics? And that's as nothing when the instructor must find analogies for coils (inductance) and capacitors (capacitance) which have no useful parallels outside electrical circuits.

It's going to sound like a cop-out but the answer's what you suspected all along. As soon as is humanly possible the instructor junks the analogy approach and starts attaching numerical values to these phenomena. Then he invokes a relationship like Ohm's Law and plugs in the appropriate values. Finally we have a cool clear sentence - as it were - that makes sense. And the language it uses is, of course, mathematics. Not terribly hard maths to begin with. But by the time it's got rather harder the initial maths has been digested.

This sneaky revelation doesn't invalidate my piece about Ohm (and John Donne). His law remains neat and concise, its effects are easily understood and I love it to bits. The next post will be about hammers and nails

More technology but it's getting more distant

We moved to Hereford ten years ago and this is our fourth phone system since then. Each has offered a - time for a cant techno-phrase! - step-function improvement over its predecessor. This one is part of a wi-fi trio and was acquired for two reasons. It stores thirty names and numbers and a small screen allows me to check the name of the person I'm dialling rather than rely on my vagrant memory and just the number.

More important I now have the luxury of a phone on my bedside table and can sleepily tell those who phone with a rising note of panic in their voice when it's still dark that, no, I am not Hereford Gas Services and why not dial 272329.

Parenthetically, the relationship with Hereford Gas Services has endured the full ten years. It reached its peak eight years ago when my shared-line fax (now surely as relevant as an illuminated manuscript) started cranking out an invoice for some gas parts one afternoon. I phoned HGS, not in anger - I enjoyed the illusion of a wider social life from these misdirected numbers - but to ask what they wanted me to do with the fax. After I'd explained things the telephonist wondered whether I might consider becoming one of their paid agents.

Back to the phones. They cost a mere £40 and have all the bells and whistles I need for the moment. What they don't provide are the extra memory cells whereby I can recall the procedures for activating these bells and whistles. I still haven't successfully transferred a call to one of the other phones.

Goodbye to the golden era of vehicle licensing

My daughter read this blog for the first time today and said, "Tell them about doing the car tax disc". And she's right. It's so fashionable to berate computer systems but with the DVLA website it's almost a pleasure to hand over the cash.

Especially if you can cast your mind back as far as I can. Standing in a long queue at an office in central Bradford, nervously checking that I'd brought the Certificate of Insurance and not the policy, fingering the dirty cardboard folder that represented the Log Book for my elderly BSA Bantam, shuffling forward a little and trying to imagine a reason why my application would be turned down.

Yes I'm well aware of all those Big Brother warnings but reducing this particular ritual to a two or three minute communion with the computer is possibly worth the sacrifice of a certain amount of personal privacy.

Where there's muck there's mind expansion

DERBLUH-VAY-SAY. Part One. Maintaining an oldish house in France is a good way of expanding your French vocabulary. I spent much time discussing things with the menuisier (rather grander than a carpenter), the macon (builder), the plombier, the zingueur (roofs), Société Générale des Eaux (water), EDF (electricity) and Trésor Publique (local taxes). None of it in English.

However, the most demanding exchange occurred when the mayor needed to explain the future to me. Ironically he was the only person in the village who had ever said anything to me in English. Encountering my brother and I moving an unwanted French AGA-type stove from the house to the garage, he asked, “How may I help you?” The question was rhetorical. He had no intention of sharing our quarter-tonne burden.

And English was off the agenda at the Mairie. We were about to see our fosse septique replaced by a connection to the new système d’assainissement d’eau; in short the unloved, concrete-lined cavity underneath the bathroom floor would be filled with sand and our lav would go online. Now there is much I do not know about sewage so all this would have been a sweat in any language. But after a barrage of technicalities I began to recognise that cash rather than plumbing was the real subject to hand.

“It’s going to cost two thousand pounds,” I told my wife afterwards, “but they say this is a heavily subsidised figure.”

“Pay it, whatever it costs,” said my wife with undisguised passion.

And the reasons for her passion will be covered in Part Two