dumb ass cadence question

dailuggs <[email hidden]> wrote in news:3f568691$1_3 @news.chariot.net.au:

Quoted message said:

how do computeres work out the cadence- i mean surely something has to go by the pedals of the
bike to work this out???

explain if you could

Your sig separator did not work 🙁

YES. you have to attach a magnet to your crank, and a receiver to your tube, then run a wire up to
the handlebars. I have not come across wireless cadence ones, but they may be out there.

Fragg

"dailuggs" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

how do computeres work out the cadence- i mean surely something has to go by the pedals of the
bike to work this out???

explain if you could

You can also work it out from your speed if you know your gearing and what gear you are in.

I think some of the shimano stuff works this way.

Frank X said:

"dailuggs" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

how do computeres work out the cadence- i mean surely something has to go by the pedals of the
bike to work this out???

explain if you could

You can also work it out from your speed if you know your gearing and what gear you are in.

I think some of the shimano stuff works this way.

Yep, it does. Shimano flightdeck knows what gear you're in (courtesy of STI shifter interfaces) and
the wheel revs/speed of bike, and works out cadence from that.

As has been said, other comps work it out from having a magnet on the crank arm, and sensor on
the rear frame that runs from BB to rear hub (no idea what it's called) that runs back up to
the computer.

Velvet

In message <[email hidden]>, Velvet <[email hidden]> writes

Quoted message said:

the rear frame that runs from BB to rear hub (no idea what it's called)

Chainstay

--
Chris French, Leeds

Frank X said:

You can also work it out from your speed if you know your gearing and what gear you are in.

It should also be possible to work out the gear from the speed and cadence. Do any
computers do that?

~PB

Fraggle said:

I have not come across wireless cadence ones, but they may be out there.

I think some of the Sigma models may do this, plus that all-singing all-dancing Polar job which does
speed, heart rate, cadence and lottery numbers.

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Pete Biggs <[email hidden]> wrote:

: It should also be possible to work out the gear from the speed and cadence. Do any computers
: do that?

Both the Shimano Flightdeck and the Campag whatever-it's-called computer do that.

Arthur

In article said:

how do computeres work out the cadence- i mean surely something has to go by the pedals of the
bike to work this out???

A really neat way would be from the speed variations possibly coupled with some knowledge of the
gear ratios available. But I don't think any computers do that. Hmmm I wonder if it would be worth
collecting some data.

Jon

[email hidden]. says...

Quoted message said:

In article said:

how do computeres work out the cadence- i mean surely something has to go by the pedals of the
bike to work this out???

A really neat way would be from the speed variations possibly coupled with some knowledge of the
gear ratios available. But I don't think any computers do that.

This is exactly what my Shimano Flightdeck does. It knows the gears I'm in, it knows my speed, it
tells me my cadence. Assuming it is correctly calibrated it is pretty much spot on when I'm
pedalling and pretty much completely wrong when I've spun out ;-)

Colin

"Pete Biggs" <[email hidden]> wrote in message
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Quoted message said:

Frank X said:

You can also work it out from your speed if you know your gearing and what gear you are in.

It should also be possible to work out the gear from the speed and cadence. Do any computers
do that?

Of course not, you want a speedo to show top speeds.

I dunno about you but I normally stop pedalling before I get to full speed ;o)

Arthur Clune said:

Pete Biggs <[email hidden]> wrote:

: It should also be possible to work out the gear from the speed and cadence. Do any computers
: do that?

Both the Shimano Flightdeck and the Campag whatever-it's-called computer do that.

Doesn't Campag's Ergobrain use the sensor that mounts on the chainstays and the magnet on the cranks
(or in the pedals) as well as having the gear change sensors in the shifters?

eat

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Ewan said:

Quoted message said:

Quoted message said:

It should also be possible to work out the gear from the speed and cadence. Do any computers
do that?

Both the Shimano Flightdeck and the Campag whatever-it's-called computer do that.

Doesn't Campag's Ergobrain use the sensor that mounts on the chainstays and the magnet on the
cranks (or in the pedals) as well as having the gear change sensors in the shifters?

I too thought the Campag Ergos had some kind of sensors/transmitter to detect gear changes so I'm a
bit confused. Why are both methods required? Does the Ergobrain use cadence to initially calibrate
but shifters for quicker detection in normal use, or what?

I wouldn't mind an ErgoBrain. It's a pain having to look through yer legs to see what gear you're in
when you forget or can't work it out from the "feel". That's the trouble with 27 gears!

cheers ~PB

Frank X said:

Quoted message said:

It should also be possible to work out the gear from the speed and cadence. Do any computers
do that?

Of course not, you want a speedo to show top speeds.

Eh? This is about functions in addition to the speedo. I was specifically wondering how the
Flightdeck and Ergobrain computers know what gear you're in (and wondering if any others have the
feature). They actually display the chainring and sprocket positions and numbers on the screen.

~PB

Arthur Clune said:

Pete Biggs <[email hidden]> wrote:

: It should also be possible to work out the gear from the speed and cadence. Do any computers
: do that?

Both the Shimano Flightdeck and the Campag whatever-it's-called computer do that.

Arthur

But as I said, the flightdeck computes cadence, based on knowing the gear, and knowing the speed. It
*doesn't* compute the gear based on cadence sensor (it doesn't have one) and speed.

Velvet

Pete Biggs said:

Frank X said:

Quoted message said:

It should also be possible to work out the gear from the speed and cadence. Do any computers
do that?

Of course not, you want a speedo to show top speeds.

Eh? This is about functions in addition to the speedo. I was specifically wondering how the
Flightdeck and Ergobrain computers know what gear you're in (and wondering if any others have the
feature). They actually display the chainring and sprocket positions and numbers on the screen.

~PB

Flightdeck has sensors mounted in the STI shifters under the hoods. This enables the sensor to know
what gear you're in. Looks like a tiny pcb with some contact points, presumably to interface to
switches inside the shifters. Works very well, and very useful. You do of course have to tell the
computer what sized chainrings and sprokets you have, so it can work out the cadence accurately.

Velvet

[email hidden]. says...

Quoted message said:

In article <MPG.19c13e03a1a4c121989c41@localhost>, [email hidden] (Colin

Blackburn) said:

This is exactly what my Shimano Flightdeck does. It knows the gears I'm in, it knows my speed,
it tells me my cadence. Assuming it is correctly calibrated it is pretty much spot on when I'm
pedalling and pretty much completely wrong when I've spun out ;-)

Colin

No I meant _purely_ from wheel speed. But your thing knows what gear you're really in. My
thing/idea might just use the knowledge of what the bike is fitted with as extra information. But
principally look at the variation in wheel speed.

Er, how do you envisage that working then?

cadence and gears -> wheel speed wheel speed and gears -> cadence wheel speed and cadence -> speed

Are you proposing to guess the cadence given the wheel speed? The other knowledge could only be the
cog and chain ring numbers, and thus the possible combinations. How would the computer *know* what
combination was selected?

By selecting different gears I can use the same cadence to achieve different speeds. Alternatively
in one gear I can use different cadences to achieve different speeds. How is you computer going to
know about this behaviour?

Colin

Velvet <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Frank X said:

"dailuggs" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

how do computeres work out the cadence- i mean surely something has to go by the pedals of the
bike to work this out???

explain if you could

You can also work it out from your speed if you know your gearing and what gear you are in.

I think some of the shimano stuff works this way.

Yep, it does. Shimano flightdeck knows what gear you're in (courtesy of STI shifter interfaces)
and the wheel revs/speed of bike, and works out cadence from that.

As has been said, other comps work it out from having a magnet on the crank arm, and sensor on the
rear frame that runs from BB to rear hub (no idea what it's called) that runs back up to the
computer.

Velvet

I don't have Flight-Deck, but the description suggests that if you coast fast enough downhill in a
low gear, you can sustain an (apparent) cadence that you could never hope to achieve when actually
pedalling.

Everyone knows that computers don't lie.

Peter Storey

(Who has been known to enhance his "Average Speed" by riding up to red lights at full speed and
braking to a full stop at the last possible second, rather than ghosting up to them in hopes that
they'll change before a foot has to go down).

In article <[email hidden]>, [email hidden] says...

Quoted message said:

I don't have Flight-Deck, but the description suggests that if you coast fast enough downhill in a
low gear, you can sustain an (apparent) cadence that you could never hope to achieve when actually
pedalling.

Yep. You just have to remember that when your legs ain't moving the computer's wrong :-)

Colin

[email hidden]. says...

Quoted message said:

In article <MPG.19c17bd1175d3882989c47@localhost>, [email hidden] (Colin

Blackburn) said:

Are you proposing to guess the cadence given the wheel speed?

I'm proposing to sense the slight variation in speed as the crank moves round, assuming you can't
supply a constant torque.

The fact you only get one pulse per wheel revolution makes this task somewhat more difficult but
not impossible.

I see what you are getting at but could such a system distinguish between chaining a chain ring and
a cog? Could it ever know where it was to start with without either initial input or some sort of
going down to the bottom and zeroing cycle? Could it distinguish between the change in speed
resulting from a gear change and one through some other mechanism, say the first push on the pedals
after freewheeling or the feet slipping on the pedals, or even spds engaging?

Colin