Experiences with Tacx I Magic...?

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

Quoted message said:

Have a look around this forum, there are plenty of users of such ...

http://www.arborwood.com/awforums/show-toparea-1.php?fid=6272&taid=1&ut=1097589238

Regards, Jim.

From 2/03 in rbr by Danny C.:

Kevin,

I have an older Computrainer which was robust and served me well for years.
However, I just got an I-Magic and I love it. You have the ability to train
via virtual reality and use steering which is nearly like playing a video
game or you can use the "Catalyst" softweare and emulate an ergotrainer with
programmable slope, watts, distance, time, etc. Also, there is third party
software available through http://www.fitcentric.com which is also very
good.

In the end, it may depend on your specific needs but I have found myself
"playing" on the I-Magic for one to two hours which I was never able to do
on the Computrainer. At half the cost of a Computrainer, I would say it's
well worth serious consideration..!

Danny Callen

Thinking of getting one for this winter. Any users have feedback?

Thanks,
Hold my

"hold my beer and watch this..." <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Thinking of getting one for this winter. Any users have feedback?

Thanks,
Hold my

i think i posted about this a while back, but i'll post something
anyways.

i used one for a while, i'd recommend getting a tacx basic, excel or
flow for serious training (the new models might have better
calibration features).

the i-magic is more hassle to set up and the graphics and courses
don't do anything for me, plus it ties up your computer (ie. you can't
say, listen to tunes on it at the same time), not to mention the
interface is [censored]. the steering feature might be cool for a kid or for
kicks, but it doesn't resemble real riding at all (no surprise) and
adds nothing to the training value.

the most important feature for me is being able to control your
workload and the cheaper tacx (ergo) trainers let you do that.

Amit said:

i used one for a while, i'd recommend getting a tacx basic, excel or
flow for serious training (the new models might have better
calibration features).

The Basic appears to have been replaced in the Tacx line-up with the Flow.
AFAIK, the roll-down calibration feature from the Flow hasn't been added
to the Excel model. I have no idea whether it's on the I-Magic. As little
as a quarter of a turn on the roller adjustment knob makes an observable
difference to the power readings, so the Flow's roll-down calibration is
pretty handy.

Quoted message said:

the most important feature for me is being able to control your
workload and the cheaper tacx (ergo) trainers let you do that.

Last Spring, some guys on the Wattage list and I did some analysis of the
Flow and the Excel (but not the I-Magic). In both power-measuring mode and
in power-controlling mode (ergo mode), the Excel seemed to do pretty well.
Here's a plot of a 45-minute training session comparing the Excel to the
SRM:
http://anonymous.coward.free.fr/rbr/srm-tacx.png

I've found that my Tacx Flow is quite consistent in power mode. This graph
http://anonymous.coward.free.fr/rbr/flow.png
shows the indicated power at a given speed with four different scale
factors. The point of the graph is that in power mode the Flow seems to
measure wattage consistently, and I believe that if I had an SRM or Power
Tap against which to compare I could find a scaling factor that would
"envelope" the correct power curve reasonably well. That's not to say that
the fit would be perfect; there have been reports (for which I haven't
seen the data, so I can only report it anecdotally) that the Tacx power
curve scales up a bit slower than real power. Still, I was moderately
reassured that the Flow appears to be in the right ballpark.

Alas, despite sharing the same load generator across all three models (the
Flow, the Excel, and the I-Magic) the Flow's ability to control load in
ergo mode appears to be much weaker than for the Excel.
Another guy tried a series of experiments with a Flow in ergo mode. Here's
his description:
http://home.comcast.net/~rwwells/Tacx/DOEFlow.html
from which I calculated this error pattern for the Flow:
http://anonymous.coward.free.fr/rbr/tacx_correction.png

The chart may be a bit hard to interpret so I should probably explain. The
idea of an ergo is that you set the wattage you want (say, 250W) and off
you go (Ron Popeil would say, "set it and forget it"😉; the ergo will match
the load so that whatever speed you ride, you'll be generating 250 watts.
So in an ideal world you'd want the percent error to be independent of
your speed. The chart plots the error against kph (or, in this case, the
ratio of the wattage setting to the speed), and if the ergo worked well
the pattern would have zero slope.

The observed pattern doesn't have zero slope.

Instead, it says that in ergo mode the Flow's electronic braking system
fails to increase the load by the appropriate amount to keep power
constant as wheel speed increases. If you look only at the black dots
(where the scale factor is set at 100), it says that if you set the ergo
for a constant 250W, the Flow will only have zero error if you're riding
at 23kph. At 28kph, the Flow is only able to produce enough braking force
to generate an actual load of about 200W (about a 20% error). At 36kph,
the Flow was actually producing about 40% less load than it should have.
The scaling factor moves the curve up and down, but doesn't fix the basic
underlying problem.

The good news is that the error is stable and predictable. The bad news is
that the slope of the error is huge, which sort of defeats the entire
intent of the ergo feature.

I don't know whether the I-Magic controls the load more like the Excel or
more like the Flow, but if you're interested in how realistic the "virtual
reality" features of the I-Magic are, I'd think you'd want to know.

Cool graphics, though.

--
Trends and bias in 2004 election polls:
http://anonymous.coward.free.fr/polls/pollbias.html

I said:

I've found that my Tacx Flow is quite consistent in power mode. This
graph http://anonymous.coward.free.fr/rbr/flow.png
shows the indicated power at a given speed with four different scale
factors.

A correction: the curves are the indicated power at four different *slope*
factors, not scale factors. This was part of the basis for why I was
reassured by the Flow's performance: I think one might be able to come
close to mimicing the readings from a Power Tap or SRM over a reasonably
wide neighborhood of preferred speed by fiddling with both slope and scale
factors. You might be off outside that neighborhood, but if the
neighborhood is wide enough you wouldn't care.

A clarification: in that graph, the data shown by hollow circles were
collected first. Then, 14 weeks later, using the same tires, tire
pressure, and roll-down calibration settings, I collected the red dot data
to see whether there was any drift in the data points.

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

Quoted message said:

The Basic appears to have been replaced in the Tacx line-up with the Flow.
AFAIK, the roll-down calibration feature from the Flow hasn't been added
to the Excel model.

i checked out the tacx site and they only list the flow, excel and
i-magic. i don't think the i-magic has the roll down calibration
feature. if i was buying today i'd probably umm... go with the flow.

Quoted message said:

Instead, it says that in ergo mode the Flow's electronic braking system
fails to increase the load by the appropriate amount to keep power
constant as wheel speed increases.

Quoted message said:

At 36kph,
the Flow was actually producing about 40% less load than it should have.
The scaling factor moves the curve up and down, but doesn't fix the basic
underlying problem.

The good news is that the error is stable and predictable. The bad news is
that the slope of the error is huge, which sort of defeats the entire
intent of the ergo feature.

this is problematic. my solution is to keep speed and cadence in a
narrow range. though, according some other observations that were
posted at wattage the power requirements for the basic increased with
wheel speed in ergo mode, but it's not improbable that the basic and
flow control the load differently.

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

Quoted message said:

The Basic appears to have been replaced in the Tacx line-up with the Flow.
AFAIK, the roll-down calibration feature from the Flow hasn't been added
to the Excel model.

i checked out the tacx site and they only list the flow, excel and
i-magic. i don't think the i-magic has the roll down calibration
feature. if i was buying today i'd probably umm... go with the flow.

Quoted message said:

Instead, it says that in ergo mode the Flow's electronic braking system
fails to increase the load by the appropriate amount to keep power
constant as wheel speed increases.

Quoted message said:

At 36kph,
the Flow was actually producing about 40% less load than it should have.
The scaling factor moves the curve up and down, but doesn't fix the basic
underlying problem.

The good news is that the error is stable and predictable. The bad news is
that the slope of the error is huge, which sort of defeats the entire
intent of the ergo feature.

this is problematic. my solution is to keep speed and cadence in a
narrow range. though, according some other observations that were
posted at wattage the power requirements for the basic increased with
wheel speed in ergo mode, but it's not improbable that the basic and
flow control the load differently.