Cadence on a simple Cyclo Computer

[Vargas]

By what I read, the right pedal cadence (or RPM) for a recumbent should be in the range 60-90.

My cyclo computer is very simple and has no pedal cadence sensor. I thought on moving the magnet to the pedal instead of the spokes but didn't want to do it. So I thought the obvious solution; enter a wheel perimeter such that the computed speed would be equal to the pedal RPM.

It is very simple math and the result for metric units is such that by entering a wheel perimeter of 1666,66667 mm in your cyclo computer set up, the speed in Km/h will be one tenth of the pedal cadence.

For example, a speed of 6.2 Km/h means a cadence of 62 RPM; a speed of 7.8 Km/h means a cadence of 78 RPM.

Of course all the other computer functions will be useless. To me this was a handy way to know the cadence and when I want to use the computer as a true cyclo computer I just enter the correct wheel perimeter in the set up again.

 

[Charles.Plager]

You can buy a cycle computer

You can buy a cycle computer for around $20 that has speed and cadence. That being said, your calculation is fine (converting from RPsecond to RPM, you get a factor of 0.01666666).

 

[Charles.Plager]

(Grumble grumble no edit

(Grumble grumble no edit grumble grumble)....

The factor of 1/60 is right. The reason I gave is wrong. The bike computer is set to give per HOUR and we want per MINUTE and that is the factor of 60.

Now back to our regularly scheduled program...

 

[Vargas]

Here in Brazil they cost

Here in Brazil they cost *much* more than that. Anyway I didn't want to throw my old one away and since it has only the speed sensor I'll have to keep switching tire circunference .

 

[Charles.Plager]

Can you buy  a second cheap

Can you buy a second cheap computer? One for speed, other for cadence?

 

[Vargas]

Yes, that could be an option.

Yes, that could be an option.
But in case I need both information I'll use my GPS as the trip computer and the cyclocomputer for cadence.

 

[Jake]

Depends on which gear you're in

Surely this will depend on which gear you're in?

Moving the magnet to the crank seems to be a more robust solution.

At least one of the Android smartphone cycling apps also measures cadence, (but you have to strap the phone to your leg

Jake

 

[Charles.Plager]

Hi,
Jake's right.  I mis-read

Hi,

Jake's right. I mis-read your original post. Your calculation makes sense if you move the magnet/sensor to pick up the pedal, but not if you leave it on the wheel. As a simple check, start riding and stop pedalling. If it doesn't read 0, then you aren't picking up cadence.

Cheers,
Charles

 

[Vargas]

You are all right

The math was so simple that I did it wrong...
Zero reading would not be a problem since my brain would already know I wasn't pedaling and thus no reading would be necessary.
But it does depend on gear ratio.
What I'll do is move the magnet/sensor to the pedal and still enter the 1666.6667 mm as tire circunference.