Wattage and Power

Albert said:

Can someone explain to me about Wattage and Power when pedalling, how is it
calculated ?

Power is the amount of work performed in a specific time period. eg: if
you expend two hundred calories over the period of one hour, you have
averaged a power of (200 / 60) or 3.33 calories per minute. (No idea if
this is a reasonable figure or not -- I pulled the figures out of my
head. 🙂

Watts are a standard unit of power, expressed as joules per second.
You'll see it used pretty much anywhere that power ratings are provided.

As for how it's calculated whilst cycling -- no idea :-)

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Quoted message said:

Albert said:

Can someone explain to me about Wattage and Power when pedalling, how is

it

Quoted message said:

Quoted message said:

calculated ?

As for how it's calculated whilst cycling -- no idea :-)

www.cycle2max.com for an approximation
or shell out $500 + $700 for a Polar Power meter
or $1500+ for and SRM, Powertap etc. unit..

hippy

On Mon, 15 Nov 2004 at 05:06 GMT, Stuart Lamble (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

Albert said:

Can someone explain to me about Wattage and Power when pedalling, how is it
calculated ?

Power is the amount of work performed in a specific time period. eg: if
you expend two hundred calories over the period of one hour, you have
averaged a power of (200 / 60) or 3.33 calories per minute. (No idea if
this is a reasonable figure or not -- I pulled the figures out of my
head. 🙂

Watts are a standard unit of power, expressed as joules per second.
You'll see it used pretty much anywhere that power ratings are provided.

As for how it's calculated whilst cycling -- no idea :-)

I want to see someone decked out with a weather vane, a
flat-o-meter[TM], a friction-o-meter (for both tires, and all
surfaces), a surface-area-o-meter and aerodynamicness-o-meter, a
bicycle computer with RPMs and speed (OK, so the last one actually
exists). "Bicycle computer" here refers to the P4 needed to do all the
calculations. Might need to add a 200W dynamo to run the 'puter. I
have a feeling you would go *real* fast downhill.

--
TimC -- http://astronomy.swin.edu.au/staff/tconnors/
My dog is worried about the economy because Alpo is up to 99 cents a can.
Thats almost $7.00 in dog money. -Joe Weinstein in ARK

TimC said:

On Mon, 15 Nov 2004 at 05:06 GMT, Stuart Lamble (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

As for how it's calculated whilst cycling -- no idea :-)

I want to see someone decked out with a weather vane, a
flat-o-meter[TM], a friction-o-meter (for both tires, and all
surfaces), a surface-area-o-meter and aerodynamicness-o-meter, a
bicycle computer with RPMs and speed (OK, so the last one actually
exists). "Bicycle computer" here refers to the P4 needed to do all the
calculations. Might need to add a 200W dynamo to run the 'puter. I
have a feeling you would go *real* fast downhill.

Hm. On a more serious note,

dW
P = --
dt

whilst Work is the integral of Force with respect to position.

This suggests to me that all you need is a torque meter attached to the
crank arms, and an FPGA should be able to handle the maths to calculate
the power. You'll also get the energy expended at no extra charge. ;-)
'Course, you'd need to tell the computer how long the crankshafts are,
and how far from the centre of rotation the sensor is...

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

Quoted message said:

Can someone explain to me about Wattage and Power when pedalling, how is

it

Quoted message said:

calculated ?

Cheers,

I assume you mean how can you measure it. As Hippy has already pointed out
there are devices that do just that.

Here is a FAQ for starters and if you have any more questions feel free to
ask.
http://midweekclub.ca/powerFAQ.htm

Here is another simple power calculator which I prefer to the cycle2max one.
(In my experience the cycle 2 max one is not that accurate due to some of
the assumptions it makes)
http://w3.iac.net/~curta/bp/velocityMetric/velocity.html

The most accurate calculator is here but it is also more complicated. This
webpage has some other excellent technical info... not the least of which is
about wheel selection
http://www.analyticcycling.com/

enjoy
Peter

Also worth a look is the calculator at:

kreuzotter.deespeed.htmOpen ↗

(careful with the units)

Albert said:

Can someone explain to me about Wattage and Power when pedalling, how is it
calculated ?

You want to know how to calculate your own power?

The easy way is on a slow steep hill climb, where friction (air, tyres)
is relatively small.

power = mass x gravity x vertical speed.
= mass (kg) x 10 x bike-speed (m/s) x grade (e.g. 10% = 0.1)
( = mass x speed (km/hr) x grade x 2.8 )

e.g. 100 kg x 10 x 2m/s (7.2km/hr) x 10% = 200W

200W is supposed to be a typical cycling power. Thats what the powered
bikes are limited to.

Albert said:

Can someone explain to me about Wattage and Power when pedalling, how is it
calculated ?

Cheers,

Somewhere, sometime, I heard or read that a human on a bike produces
about 0.2 "horsepower" or so. Horsepower being an ancient measure of
"Work", which is (mind weak, body strong... or prolly more like, memory
weak, body even weaker) Power x Time... umm, I think an average human on
an average bike produces 0.42 kilowatts per hour, or something (brain
weak... must remember year 11 physics despite being stoopid ... must
not... reply to newsgroup...)
Aw, dang.
[censored]
p

fred_kneeman said:

Somewhere, sometime, I heard or read that a human on a bike produces
about 0.2 "horsepower" or so. Horsepower being an ancient measure of
"Work", which is (mind weak, body strong... or prolly more like, memory
weak, body even weaker) Power x Time... umm, I think an average human on
an average bike produces 0.42 kilowatts per hour, or something (brain
weak... must remember year 11 physics despite being stoopid ... must
not... reply to newsgroup...)
Aw, dang.
[censored]
p

0.42 kW/hour??? Only if they are elite and peaking for the olympics or the worlds. There is no 'typical' cycling power (needs to be scaled to mass, frontal area, etc to be a useful measure of performance), but it would be reasonable to guess that A graders might be able to hold a bit over 320w for an hour, while div I pro's get close to or occasionally over 400w.

Power is calculated on-bike with a torque meter in the crank (SRM) or the hub (powertap) and a device that measures the rate of rotation of the crank or hub.

fred_kneeman said:

Albert said:

Can someone explain to me about Wattage and Power when pedalling, how
is it
calculated ?

Quoted message said:

Somewhere, sometime, I heard or read that a human on a bike produces
about 0.2 "horsepower" or so. Horsepower being an ancient measure of
"Work", which is (mind weak, body strong... or prolly more like, memory
weak, body even weaker) Power x Time... umm, I think an average human on
an average bike produces 0.42 kilowatts per hour, or something (brain
weak... must remember year 11 physics despite being stoopid ... must
not... reply to newsgroup...)

did a similar thing in year 12 physics.
time how long it took to go from a standing start to a standing stop,
over a given hight. ie, climb a set of stairs. measure you weight, do
math. i pushed out about 1.4kw[1], typical class numbers between 0.6 -
0.8 kw

how this compare to a bicycle is another matter 😉

cheers,

Kim

[1] this could be why i bent my smallest sprocket on my mtb. =/

TimC said:

I want to see someone decked out with a weather vane, a
flat-o-meter[TM], a friction-o-meter (for both tires, and all
surfaces), a surface-area-o-meter and aerodynamicness-o-meter, a
bicycle computer with RPMs and speed (OK, so the last one actually
exists).

So does the flat-o-meter[TM]

I don't have a "here's a link I prepared earlier", but
the German bicycle touring shops sell them. Maybe have
a look at http://globetrotter.de or search google for
bicycle inclinometer.

There was a huge thread about these on the bicycle touring
list last year or so. For whatever reason the idea of
knowing the grade of the hill you were climbing upset some
folks... *shrug*

Theoretically a GPS with altitude also gives you the hill
profiles.

hmm, rambling again.
-kt

The best calculator I've seen for power is at Analytic Cycling:
-- http://www.analyticcycling.com/ --

You would need to know your coefficient of drag, rolling resistance of the road, etc, to calculate accurately without an on-bike power meter (analytic cycling allows you to enter these variables). Without this info any data you get is highly suspect.

Stuart Lamble said:

This suggests to me that all you need is a torque meter attached to

the

Quoted message said:

crank arms, and an FPGA should be able to handle the maths to

calculate

Quoted message said:

the power. You'll also get the energy expended at no extra charge.

;-)

Quoted message said:

'Course, you'd need to tell the computer how long the crankshafts

are,

Quoted message said:

and how far from the centre of rotation the sensor is...

*FPGA*? isn't that mildly overkill? a $1 avr or pic probably has the
computing power to calculate cyclist power.

an actual torque meter doesn't need to know those things, but would be
quite difficult to incorporate in a standard crankarm. you could put a
load cell into the pedal and couple that with cadence/crankarm length
to calculate power.

the way commercial sensors calculate power is either through torque at
the hub (the powertap) or through measuring chain tension (which says
how much force you're applying at the crank) and multiplying that by
chain speed.

-A

qtq said:

Stuart Lamble said:

This suggests to me that all you need is a torque meter attached to

the

Quoted message said:

crank arms, and an FPGA should be able to handle the maths to

calculate

Quoted message said:

the power. You'll also get the energy expended at no extra charge.

;-)

Quoted message said:

'Course, you'd need to tell the computer how long the crankshafts

are,

Quoted message said:

and how far from the centre of rotation the sensor is...

*FPGA*? isn't that mildly overkill?

Yep. But hey -- it's always fun playing around with miscellaneous
hardware, and FPGAs are nifty, so why not? 🙂

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the mail bounces, try changing the bit before the "@ to usenet".

fred_kneeman said:

Somewhere, sometime, I heard or read that a human on a bike produces
about 0.2 "horsepower" or so. Horsepower being an ancient measure of
"Work", which is (mind weak, body strong... or prolly more like,

memory

Quoted message said:

weak, body even weaker) Power x Time... umm, I think an average human

on

Quoted message said:

an average bike produces 0.42 kilowatts per hour, or something (brain

Quoted message said:

weak... must remember year 11 physics despite being stoopid ... must
not... reply to newsgroup...)

a horsepower is between 550 and 700ish W.

100W on a bike is nothing, 200W sustained is a fair effort, 300 is
pretty good.
for short sprints up hills, I've gotten 500W or so, but that's standing
up and mashing, and my thighs hurt like buggery afterwards.

Stuart Lamble said:

Yep. But hey -- it's always fun playing around with miscellaneous
hardware, and FPGAs are nifty, so why not? 🙂

because I have no desire to reimplement an FPU in verilog.

-A

qtq said:

Stuart Lamble said:

Yep. But hey -- it's always fun playing around with miscellaneous
hardware, and FPGAs are nifty, so why not? 🙂

because I have no desire to reimplement an FPU in verilog.

Oh, come on. You're no fun at all.

*evil grin*

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

Quoted message said:

fred_kneeman said:

Somewhere, sometime, I heard or read that a human on a bike produces
about 0.2 "horsepower" or so. Horsepower being an ancient measure of
"Work", which is (mind weak, body strong... or prolly more like,

memory

Quoted message said:

weak, body even weaker) Power x Time... umm, I think an average human

on

Quoted message said:

an average bike produces 0.42 kilowatts per hour, or something (brain

Quoted message said:

weak... must remember year 11 physics despite being stoopid ... must
not... reply to newsgroup...)

a horsepower is between 550 and 700ish W.

100W on a bike is nothing, 200W sustained is a fair effort, 300 is
pretty good.
for short sprints up hills, I've gotten 500W or so, but that's standing
up and mashing, and my thighs hurt like buggery afterwards.

A horse power = 746watts (from memory)
What we are now looking at is a table like this
http://www.cyclingpeakssoftware.com/powerprofiling.xls
If that page doesn't work try here
http://www.cyclingpeakssoftware.com/profile.html
and scroll down to Application and Interpretation.

What the table shows is that to be a world class sprinter
you need to produce 24.04 w/kg of bodyweight for a 5 second burst.
ie if you weigh 100kg that would mean you need to produce 100 x 24.04 = 2404
watts!

The column "FT" refers to functional threshold. ie roughly the power you can
maintain for a 40km time trial or perhaps up to an hour. This power is
actually a bit higher to the effort scientifically described as Lactate
Threshold.

Again in the case of worlds best a Chris Boardman type can produce 6.40
watts at FT (but he was also super aerodynamic as well). At his recognised
racing weight of 68kg this means about 435watts. (it is estimated that he
produced 442 watts)

Personally I'm a fairly poor club level racer who has no chance of breaking
away from our C grade bunch but can do OK in the sprint if I hang on.
I can produce 950 or so watts for 5 secs at the end of a race, and 500w for
a minute is pretty routine in a race.
This puts me somewhere in the middle of the moderate category at 70kg
weight.

Peter

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

Quoted message said:

The best calculator I've seen for power is at Analytic Cycling:
-- http://www.analyticcycling.com/ --

You would need to know your coefficient of drag, rolling resistance of
the road, etc, to calculate accurately without an on-bike power meter
(analytic cycling allows you to enter these variables). Without this
info any data you get is highly suspect.

--
Roadie_scum

Or you do a time trial on a given day and compare data from somebody else
who has a power meter and can back-derive all those parameters.
This is the reason I believe most of the other online calculators are not
that accurate as you cannot enter Crr, FSA, etc etc. They only assume an
"average" value.

Peter