When is that new power-measuring device arriving?

wrote:
Robert Chung writes:

Ideally there would be a torsion bar (equipped with a strain
gauge)
between the gear cluster and body of the hub. Such a torque
sensor
would need a limit stop because rider output on standing starts
can
exceed any reasonable torque for which the sensor is designed.
Such a mechanism is hard to build inside a hub. Then, because the
load varies widely during each wheel rotation, an averaging method
must be employed to reduce data to some usable form, for instance
average torque per wheel rotation, and then this data must get out
of the wheel somehow. That requires a transmitter and power.
This
hub is getting larger all the time... and expensive. I believe
that this is more expensive and difficult than it first appears
and
will probably stay that way.

$700. http://www.cycle-ops.com/products/powertap.htm

Placing it in the BB seems even more difficult, the rotation rate
being even slower and forces greater with no more space than in a
rear hub.

$1299. http://ergomo-usa.com

This design does not generate much confidence or me. There is no
clear explanation how and where the optical sensors are located or
protected, although their need for careful protection is mentioned
almost as a warning to not use this under anything but the most ideal
conditions. As was mentioned, torque from the right crank (that
appears on the left in the web blurb) goes directly into the chain
and
is never "seen" by the sensor.

Not too good! but expensive.



Are you a walking encyclopedia of bicycle knowledge?
Come mantenete tutto il questo nella vostra esplosione capa del
withoug?
Going to Italia next year...gotta practice.
Maggie

wrote:

Placing it in the BB seems even more difficult, the rotation rate
being even slower and forces greater with no more space than in a
rear hub.

$1299. http://ergomo-usa.com

This design does not generate much confidence or me. There is no
clear explanation how and where the optical sensors are located or
protected, although their need for careful protection is mentioned
almost as a warning to not use this under anything but the most ideal
conditions. As was mentioned, torque from the right crank (that
appears on the left in the web blurb) goes directly into the chain and
is never "seen" by the sensor.

Not too good! but expensive.

http://mywebpage.netscape.com/rechun...ergomo-pt.html

Maggie wrote:
wrote:
[snip]
Are you a walking encyclopedia of bicycle knowledge?


Rolling.

Robert Chung writes:

Ideally there would be a torsion bar (equipped with a strain gauge)
between the gear cluster and body of the hub. Such a torque sensor
would need a limit stop because rider output on standing starts can
exceed any reasonable torque for which the sensor is designed.
Such a mechanism is hard to build inside a hub. Then, because the
load varies widely during each wheel rotation, an averaging method
must be employed to reduce data to some usable form, for instance
average torque per wheel rotation, and then this data must get out
of the wheel somehow. That requires a transmitter and power. This
hub is getting larger all the time... and expensive. I believe
that this is more expensive and difficult than it first appears and
will probably stay that way.

$700. http://www.cycle-ops.com/products/powertap.htm

Placing it in the BB seems even more difficult, the rotation rate
being even slower and forces greater with no more space than in a
rear hub.

$1299. http://ergomo-usa.com

This design does not generate much confidence for me. There is no
clear explanation how and where the optical sensors are located or
protected, although their need for careful protection is mentioned
almost as a warning to not use this under anything but the most ideal
conditions. As was mentioned, torque from the right crank (that
appears on the left in the web blurb) goes directly into the chain and
is never "seen" by the sensor.

Not too good! but expensive.

Robert Chung writes:

Placing it in the BB seems even more difficult, the rotation rate
being even slower and forces greater with no more space than in a
rear hub.

$1299. http://ergomo-usa.com

This design does not generate much confidence for me. There is no
clear explanation how and where the optical sensors are located or
protected, although their need for careful protection is mentioned
almost as a warning to not use this under anything but the most
ideal conditions. As was mentioned, torque from the right crank
(that appears on the left in the web blurb) goes directly into the
chain and is never "seen" by the sensor.

Not too good! but expensive.

http://mywebpage.netscape.com/rechun...ergomo-pt.html

I'm still not convinced the mechanism is reliable and will not get
contaminated by dry dirt, aside from rain and road splash. For singe
riders, this is a technically manageable measurement task but where it
might do more good is on tandems where balancing effort is one of the
difficulties in such riding. For tandem riders, quantified power is
not so much a problem as is effort. The two riders, not in competition
with anyone cannot easily determine how much effort each is exerting.

The measure could easily be determined by riding at maximum output and
speed and normalizing that effort as 100% and then having a percentage
readout of both riders on each handlebar to help assess what ones fair
share of effort should be. I believe this would be a boon to tandem
riders who currently have only indirect ways of knowing which of the
two is propelling the bicycle. This is a more complicated task than
power meters on a single bicycle but it would have a long term
practical value.

I'm still waiting for the Cateye CC-TR100, which, until I
bitched at xmastime, still said it's be avaliable in early
Summer of 2004...

--Blair
"Who knows what my heart
rate looks like..."

wrote:
As I mentioned, that isn't what the rider wants to know. Interesting

I want the power meter installed in my muscle cells so I
can tell how much power I'm actually expending.

--Blair
"My finish time will tell
me how efficient it is."

wrote:

I'm still not convinced the mechanism is reliable and will not get
contaminated by dry dirt, aside from rain and road splash.

Ergomo units have been on the market in the US for about 18 months now and
some riders have thus used it through two winters. I've heard several
complaints about the Ergomo (incuding the fact that replacing a worn-out
bottom bracket now becomes a several hundred dollar job) but water damage
doesn't appear to be one of them. Early versions of the Power Tap were
notorious for being unusable in anything worse than a heavy dew--current
versions are much better but get data dropouts whenever you pass by a high
voltage line. Calibration of the SRM Amateur (which only has two strain
gages) appears to depend on the orientation of the crank (i.e., whether
the crank was horizontal or vertical when you test it). Some SRM Pro
models got sent out with bad epoxy that resulted in calibration changing
over time. The Polar S710 chain speed-and-tension system is sensitive to
chainring-cog combinations (see
http://mywebpage.netscape.com/rechun...tprotocol.html
for an especially bad example).

"Maggie" wrote in message
oups.com...

wrote:
a bunch of stuff

Are you a walking encyclopedia of bicycle knowledge?
Come mantenete tutto il questo nella vostra esplosione capa
del
withoug?
Going to Italia next year...gotta practice.
Maggie

Jobst is more like a pedaling encyclopedia.
For lots more info, see the FAQ's to the bicycle newsgroups
which he wrote:
http://www.sheldonbrown.com/brandt/

"Fiddly" describing the Polar might be due to the wide scope of bicycle
frames which affect its application. On my Cannondale, it has provided
great data save the times I have accidently disturbed the ream mounted
speed sensor. The last time was during a flat fix and the sensor was
too close to the wheel, making the speed read twice actual.

Measuring torque on the rear wheel seems even more "fiddly" to me due
to the rotation. What would be better would be reaction torque or the
compression of the right chain stay. Bending would have to be
accounted but accurate compression measurement would indicate chain
tension. Knowing chain speed via a Polar type sensor or crank speed
and chainring position is easily done.


--
Weisse Luft