Shimano Nexus-7: how it works, how many teeth the gears have

Previously, I have tried to find “theoretically” the tooth counts of the Nexus-7 internal gear hub. Some nice numbers were obtained, but there were some suspects (you may think yourself what can be wrong with the numbers given in the link). Soon after, I disassembled the real hub and counted the teeth of all rings. Here are the real numbers. Continue reading

Nexus-7 gear tooth counts and exact transmission ratios – wrong version

ShimanoNexus7 Vendors of internal gear bicycle hubs naturally give the transmission ratios of own products. But I was always curious how exactly these ratios are obtained, i.e. which planet gears are engaged in which combination and how many teeth each gear has. This information was surprisingly hard to find – in fact, the only vendor who discloses this is Rohloff! It is certainly possible to just disassemble the hub, but, you know, sitting half-day at the computer screen is more attractive nowadays 🙂 I have Nexus-7 hub on one of my bikes, and I have “reverse engineered” the exact tooth counts. Continue reading

Difficult elementary school math problems

Many math problems are fascinating. Often they are also difficult, so that only those who have high enough education can understand their beauty. But sometimes a really simple problem – such that anyone with just the elementary school knowledge can solve it – can be quite cute as well. Most elementary school math questions are truly boring, but it’s possible to add some spice to this mass.

1 (I knew this earlier) “Dried cucumbers”:
Cucumber contains 99% of water. A box of cucumbers weighs 100kg. During winter storage, cucumbers dried out so that they now contain only 98% of water. How much does the box weigh now?

2 (I got this today, which inspired me for this post) “Probability for doctors”:
Assume a test for a rare disease (which affects 1 person in a million) is 99.99% accurate. A patient tests positive. What are the probabilities he actually has the disease?

Heavy-duty self-made mudflap

DIY heavy-duty bicycle mudflap
Bicycle mudguards are frequently made shorter than they should have been. I was not able to find a front mudguard which would protect front chainrings from water jets pouring from the front wheel. So I made my own from a 2mm thick rubber sheet. It is heavy and non-aerodynamic. It is heavy-duty! It makes difference when riding in the rain. It is tested. Highly recommended for bike commuters.

Wolfram Alpha: computation for everyone, for free

WolframAlpha exampleWolfram Research, probably most known for their Mathematica calculation product, has launched an online service which makes various calculations and visualizations for free, and with just a web browser:

This project makes me really respect Wolfram. I spent quite some time browsing the examples, almost exclusively from the “mathematics” part, picking like a shy visitor at other areas. Some of my online friends write that “knowledge becomes less of a fashion in our times”. I do not agree a bit. Just look at this product.

(La)TeX, 10 years later

tex-lion 10 and more years back, when I studied mathematics, I was an active user and promoter of the (La)TeX typesetting system. Since then, I almost did not use it, but kept the warmest memories of this creation “by mathematicians, for mathematicians”. Yesterday… I can’t say I changed my mind, but I’m not so sure any more about my attitude.

I had to remake a one-page document, for which I already had an old LaTeX template source. Edit the source, “make”, and a nice PDF is ready. Well, now the text which I inserted contained the @ sign. And of course (pdf)LaTeX did not compile.

I did not remember what should one do to typeset ‘@’ literally. I certainly remembered it 10 years back, but that’s not the kind of knowledge which stays alive when not used. It took me about 15 minutes to find the answer.

And now I’m not sure whether I shall promote TeX at all. From my viewpoint, this 15 minutes is unacceptably too much for such “problem” (actually, the very fact that this made a problem, is unacceptable in my current view). I expected the first link in Google search to give the solution, but the reality was very far from that. And – unfortunately for the others – I consider myself as a quite experienced (La)TeX user: I followed news:comp.text.tex, created own document classes, which were also used by other people, and so on. I knew well how it works. I knew where to look for documentation, and what kind of documentation I need. And still this thing, which should never be a stumble at all, took me 15 minutes. I can easily imagine that it takes full day from a person new to the TeX world.

Conclusion: sorry, none at the moment…

Trip report from Indian Himalayas – 2008

Lahaul valley
I’ve started writing about my last year bike trip in the Indian Himalayas. Before I had not forced myself to more than one blog post and an unsorted pile of photos. Now I’ve started with a short illustrated text about practical issues, answering questions which I had at the planning stage:

Cycling in Himachal Pradesh: practical issues

My next plan is to publish the daybook with facts and impressions. Stay tuned.

Summer has arrived: family tandem ride

We’ve done a great sunny full-day ride on our tandem with a kidback plus two other bikes. The target was Vanhankaupungin koski (stream and a waterfall), one of the city attractions we had not visited before.

This made 56 km and 10 hours door-to-door. I think it was the first day of the year when it was possible to cycle in shorts – not morning and evening though.
Map of the ride: Continue reading

Software update for Nokia phones

Picture from

A motivated-looking female character illustrates the software update process. Picture from

Nokia gives an option to update the phone’s software, at least, for the more expensive models. I do not know, and would like to know, how other mobile phone vendors score in this area. Below is my rant about Nokia way of doing it. The writing is in negative tone, because things are noticed only when they do not work as expected. I’m interested if there is a vendor who does it better (some do not allow the user to update firmware at all – you must go to the service center for that!)
Continue reading

Get rid of junk on your desktop!

What a vandalism is this? Turning a keyboard into two pieces of junk?

No, it’s just the opposite – Bringing the Order, and Getting Rid of Junk!

I never use the “numeric keypad” on the right side. And it takes valuable space from my right hand. So what’s the problem if I got the hacksaw? Read on how I did it (with pictures and instructions for followers).