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Frequently Asked Questions

Do you still exist?

The rumours of my non-existence are greatly exaggerated

How can I get a

Gently stroking my inner thigh, or sucking my ear lobe usually works ;)

Why did you write the bicycle software?

Because I wanted to use it my self, and because it became necessary to re-train my self for a career change.

How can I estimate a cyclists coefficient of drag without paying £150 per minute for the use of a wind tunnel?

If you look in the help file for any version of PowerCalc, under the section Measurement of Coefficient of Drag you will find that coefficient of drag can be obtained by freewheeling down a hill, of a known gradient, on a still day, using nothing more expensive than a bicycle computer. V1.4 has some added hypertext links pointing at this, so hopefully users will find this information a little easier to find.

I have downloaded your Cyclists Power Calculator program and intend to use it in conjunction with my new XXXXXXX Turbo Trainer. However, I have no idea how/where to find out the calibration data. Can you suggest how I can get this info?

Hmmmm I have had a number of emails like this, and each time XXXXXXX is a different static bike manufacturer. Try contacting XXXXXXXX, if they can supply calibration details I will be happy to include them for free along with the other turbo trainer calibrations already supplied. A method of calibration is given in one of the references in the power calculator's help file. Alternatively if the manufacturer is unable to do this, how about contacting the engineering department of your local university.

My bicycle has one freewheel and one front chainwheel.If I enter this data the graph is not available in the bicycle gear calculator (more than one freewheel or chainwheel gives the graph). Why is it so? I want the speed of the bike with one freewheel and one chainwheel.

*Giggle* What are you going to use a graph of one gear for? The bikes speed at your maximum and minimum cadence are given in the table in GearCalc Pro's main window. Alternatively the cadence calculator gives you your cadence at any given speed. If you are attempting to optimise a fixed wheel single speed bicycle for a particular ride you might find that PowerCalc's thrust calculator gives you a bit more help.
NEW! GearCalc Pro now ships with a special gear calculator for fixed wheel bikes (v2.2 onwards).

You tell that the gear and power calculators should be installed in the same directory for better results. Why?

So they can share the same table of standard and custom tyre sizes. I.e. When you add a custom tyre size in the cyclists power calculator, the bicycle gear calculator will read it in automatically and vice versa. Note: If you install with default settings with v2.x of either of these programs they will share this anyhow.

I reckon percentage differences give a better measure of gear spacing than inch/metre ratios or speed differences: Compare the 10in jump from 100 to 110 (10%) with that between 20 and 30 (50%). Why don't you do this instead? (Chris Juden CTC)

You have almost answered your own question. The step between 28T and 24T when used with a 700C tyre and a 28T front is about 4.4in, or 16%. I know from experience that this will 'feel' like a very small step indeed. By contrast the 11.5in step between 14T and 16T when used with a 48T front 'feels' okay (perhaps a bit larger than I would like), but this comes out at a mere 14%! Do you actually ride a bike Chris?

Why don't you use a logarithmic scale (A tweak that makes the gearing look more like it feels) in GearCalc's graphs? (Tony & Chris - CTC)

Why don't you try this on your spreadsheet Chris? My software is not 'recently produced' and some of my early prototypes included a lot of stupid things, that seemed like they might be a good idea at the time. The fact is log graphs don't help, they didn't help in my early prototypes, and they do not help in any of the other gear calculators. Log graphs really would make a simple thing complicated. If an x-y graph is too technical for your poor uneducated readers (as I am expected to believe), how are they going to cope with a log scale? I can see how this feature might benefit the odd corrupt bicycle shop proprietor wishing to distort the picture in order to get rid of some badly thought out freewheels/cassettes. But it isn't much use to a genuine cyclist.
Suggested further reading:
The art of finding the right graph paper to get a straight line, S.A.Rudin, Journal of Irroproducible Results, 12, No 3 (1964)

Why don't you supply the software on CD ROM?

The software is now availiable on CD ROM

What operating systems will it run on?

The operating system compatibility information is here

Why didn't you just produce a table of inch ratios, and a silly bar chart in GearCalc Pro - as preferred by Chris Juden and Tony Olivier at the C.T.C. ?

The whole point of GearCalc Pro is that tables of inch ratios (like you can get from the back of a book) are a pain to use. Although the inch/metre ratio is an excellent measure of gearing, the only people who understand them seem to work in the cycle trade. By contrast speed and cadence (rpm) are understood by everyone. GearCalc Pro does optionally do a bar chart, but the feedback so far from my 'guinea pigs' amounts to "How the hell do you use this?". This feature might well be dropped from future versions....

Why did you do the South Gloucestershire Council pages?

I was exercising my democratic right to take the piss. Whilst I consider my self fortunate to live in a country where I have this right. The plothermuckers have wrecked my favourite training ride 8(

Why is the demonstration version of GearCalc Pro Restricted to 12 gears?

The demonstration versions of the software are to demonstrate that it works. If I give it away in an un-restricted form you will probably just say thanks very much and not pay. Besides if you can afford to put more gears on the back wheel of your bike than I can, you can definitely afford to pay for an un-restricted copy of the bicycle gear calculator.

My fixed wheel bicycle has a fifteen inch chain stay length, 58T front and 11T rear cogs. When I use the javascript chain length calculator the accurate value before rounding is slightly shorter than the value given by ChainLengthCalc. Which calculator is correct?

Neither program is in error, however ChainLengthCalc works out the accurate value more accurately and rigorously than the javascript version. The javascript version uses the "rigorous equation" given on the park tools site. They have simplified it so you can do the sums on an abacus. The magic number of 0.0796 corresponds to the sine of an angle between the two straight lengths of chain which is assumed to be fixed. ChainLengthCalc doesn't assume any fixed angles, it does the full monty. The Park Tools equation gives best accuracy when angle between 2 straight bits of chain is about 4.5655 deg. Bigger angles will cause it to under estimate by increasing amounts and smaller angles will cause PT to over estimate by increasing amounts. Errors from using the Park equation are not large however and the likely hood of you ending up with a chain that is too short after rounding is very small.

Try the two programs side by side if you want to:
For Chain stay length of 15 inch with a standard 52 tooth chain ring, 4.56 degrees occurs somewhere between 44 and 45 tooth rear. I.e. 44 teeth or less with this bike and the park equation comes up a bit short, but 45 teeth or more and it quotes on the safe side

Why was it such a long time before the bicycle chain length calculator was released?

Because my brain evolved to be good at screaming at the monkeys in the next tree, not difficult mathematics!

Where are the guns?

There are no guns. Peace on you.

Is the counter on the Traffic Cone Page accurate?

Certainly not

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