On Fri, 21 Dec 2018 07:57:03 +1100, James
wrote:

On 21/12/18 4:29 am, jbeattie wrote:
On Wednesday, December 19, 2018 at 10:04:58 PM UTC-8, James wrote:
On 20/12/18 4:19 pm, jbeattie wrote:
On Wednesday, December 19, 2018 at 6:42:50 PM UTC-8, James
wrote:

The iBike Newton does the maths & physics of what you theorise,
but it isn't perfect according to the reviews I've read.

https://cyclingtips.com/2013/09/ibik...-meter-review/



That's a power estimator. If you want a power meter, you have to
pay.

For a start, the iBike Newton measures a number of inputs and
*calculates* the input power according to the laws of physics. It
does measure power, just not in the same way. And there are others
like it, mentioned here;
https://www.dcrainmaker.com/2016/09/...6-edition.html



The Stages device, like most other power meters, uses strain gauges
(resistors) that detect elastic deformation in a part of the drive
train that is expected to have a predictable force/strain
relationship, and from that and other measured inputs like crank
position, for example, can calculate the input power.

Make no mistake, the Stages device does not measure power directly,
and is not infallible. The electronics are not perfect and even if
the device is calibrated in the beginning, it will not remain
calibrated for ever. For this reason people often compare power
meters to try to find the most accurate and stable.

https://www.cyclingweekly.com/news/l...-meters-330322


Yes, but a meter calculating power based on wind speed and gradient
is useless for indoor training and unreliable outdoors.

That depends on your indoor setup. On this inclined cycling mill, it
would work just fine. https://www.youtube.com/watch?v=PVxGFOb1KTY


The narrator commented that as they were indoors there was no wind and
thus not exactly the conditions as actually on the road but didn't I
read some years ago about Armstrong being tested in a wind tunnel?

(but it must have been dangerous as the test rider wasn't wearing a
helmet :-)

cheers,

John B.