I Bike Power Meter

SteveA said:

I came across this power meter http://www.ibikesports.com/techinfo.html
at Performance Bike. Looking at the manual for it
http://www.ibikesports.com/documents/instructionsataglance032006.pdf,
makes me wonder why every maker of bike computers has not jumped on the
same band wagon (assuming it gives a reasonably accurate reading).

Physicists and engineers, please feel free to rip this piece of
equipment and its technology to bits. I fact I will be bloody
disappointed if you do not provide some critical comment.

it's working on air speed. How's your tyre pressure? How's your frame
& wheels aerodynamics? How's the road surface? How're your bearings?
Got an aero helmet on? 46cm bars? got a crosswind? etc etc

I guess you're putting out ... oh, 230 watts. Close enough!

On 2006-04-11, SteveA (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

I came across this power meter http://www.ibikesports.com/techinfo.html
at Performance Bike. Looking at the manual for it
http://www.ibikesports.com/documents/instructionsataglance032006.pdf,
makes me wonder why every maker of bike computers has not jumped on the
same band wagon (assuming it gives a reasonably accurate reading).

Primarily because it must be so bloody expensive that there won't be a
market for many companies to compete for it.

Quoted message said:

Physicists and engineers, please feel free to rip this piece of
equipment and its technology to bits. I fact I will be bloody
disappointed if you do not provide some critical comment.

Hmmm, it probably uses pressure, temperature and windspeed to
calculate how much air resistance you have. So it neglects the size
of your body, whether you are in the drop bars at the time, how much
friction you have in your chainline and tires, etc.

I guess the setup procedure (go fast, coast, go down, slow down) would
be to get the orientation right, so the accelarometer knows which way
is up and which way is front.

It's like my HRM -- it guesses how much kJ I've likely burnt, based
only on my HR, weight and sex. That surely can't be too accurate?
I'm not burning 20% more energy just because my resting HR today is
10bpm higher than yesterday due to too much caffeine (wheeee, boinc,
bounce, bounce, bounce!)?

I wouldn't expect it to get within a factor of 2.

However, still nifty. I wish I had a gradient meter on one of my
computers 🙂

--
TimC
"The application failed to fail"

"TimC" <[email hidden]> wrote in message

Quoted message said:

It's like my HRM -- it guesses how much kJ I've likely burnt, based
only on my HR, weight and sex. That surely can't be too accurate?

Depends on whether you can default the sex value to zero, Tim 🙂

Someone has stolen my mate's idea and put a power sensor in the bottom
bracket...check it out...

http://www.ergomo.net/

Adam

SteveA wrote -

Quoted message said:

Steve(there must be room for another gadget on the handlebars)A

I understand the next incarnation of a power meter will be a pressure plate
between your shoe and cleat with a sender at the heel of the shoe - an Oz
invention.

Will have its own chest band to measure hr and the other usual cyclometer
functions and obviously be moveable between any bike or trainer (wherever
your shoes go...). Much less pain than an SRM or PowerTap and about half the
cost.

Should be a prototype around November I am told. Sidi are looking at
selling shoes with the plate and sender pre-installed.

regards, andrew

TimC said:

Primarily because it must be so bloody expensive that there won't be a
market for many companies to compete for it.

--
TimC
"The application failed to fail"

The price I saw was US$350 which is as near as buggery to A$500 - a fair bit cheaper than other power meters.

That is the price, not the cost of production. I have an digital anenometer/thermometer/barometer/altimeter which cost me A$99. The quality is probably about the same as in this power meter. A basic el cheapo computer can be had for about $20. Add a gradient sensor (use the altimeter?) and you would have to be able to get them to market for less than A$150. (Intellectual property licence costs aside).

Power Tap from the same source is US$999. I expect the price of the I Bike thingy is probably set by reference to the real power meters' prices than cost of production.

That's' why I posed the question that linked accuracy to other makers bringing out something similar. 🙂

SteveA

Adam85 said:

Someone has stolen my mate's idea and put a power sensor in
the bottom bracket...check it out...

Quoted message said:

http://www.ergomo.net/

Cool - now you can know within 0.5% how much power your left leg is putting out, and still have no idea about the right one 🙂

Cheers,

Suzy