Search found 23 matches

by djconnel
Wed Feb 06, 2013 4:43 pm
Forum: Newton General Questions
Topic: At long last, the iBike Newton!
Replies: 165
Views: 124141

Re: At long last, the iBike Newton!

It would be interesting to compare iBike Newton to Stages for accuracy. My money's on the iBike.
by djconnel
Mon Jun 04, 2012 9:55 am
Forum: Newton General Questions
Topic: At long last, the iBike Newton!
Replies: 165
Views: 124141

Re: At long last, the iBike Newton!

Okay -- so I just realized since this is post-processing and doesn't need to be done on the fly user could use a UI to generate an arbitrary number of "anchor points" with Google Maps API to minimize interpolation so if algorithm becomes confused data can be corrected by addition of constr...
by djconnel
Mon Jun 04, 2012 9:34 am
Forum: Newton General Questions
Topic: At long last, the iBike Newton!
Replies: 165
Views: 124141

Re: At long last, the iBike Newton!

On the "something clever".... You have distance and acceleration and vertical orientation and altitude. A gyroscope as well? Gyroscopes aren't free, but cheaper than GPS, both power and dollar cost. If you've got a gyroscope you've got rate of change of orientation. It's a bit hard to take...
by djconnel
Tue Feb 23, 2010 3:05 pm
Forum: General Discussion
Topic: What's coming next?
Replies: 26
Views: 16937

Re: What's coming next?

It's getting close to March....

My guess is GPS.
by djconnel
Mon Nov 02, 2009 11:21 am
Forum: General Discussion
Topic: What's coming next?
Replies: 26
Views: 16937

Re: What's coming next?

I introduced this question in this thread.
by djconnel
Mon Oct 12, 2009 3:50 pm
Forum: General Discussion
Topic: coast down velocity range
Replies: 31
Views: 18342

Re: coast down velocity range

I'm not totally sure I understand your point..... The data fitting procedure to a coast-down uses all of the data values, not just the start and stop speeds, or at least I think so! So if you do multiple coast-downs, each should include as many speeds as possible. In other words, if you start one co...
by djconnel
Sat Sep 26, 2009 11:14 pm
Forum: General Discussion
Topic: Interbike 2009
Replies: 2
Views: 3465

Interbike 2009

"We could tell you, but then we would need to kill you." Well, not quite. According to Velocity Nation : iBike skipped the show floor for a private suite, where you had to sign a non disclosure agreement to see their newest innovation. It's due out in March 2010, and it has the potential t...
by djconnel
Sat Sep 26, 2009 2:26 pm
Forum: General Discussion
Topic: coast down velocity range
Replies: 31
Views: 18342

Re: coast down velocity range

Good discussion! If the model was perfect, and measurements were perfect, you could extract two unknowns (wind and rolling resistance coefficients) from two measurements (for example deceleration at 18 mph and 17 mph). However, none of these things are perfect. The key is to avoid small errors in th...
by djconnel
Wed Sep 16, 2009 6:25 pm
Forum: General Discussion
Topic: coast down velocity range
Replies: 31
Views: 18342

coast down velocity range

According to the firmware release 4, the coast down range is still 18 mph to 9 mph. This is quite low to differentiate CdA and Crr. For example, assuming Crr = 0.55% and M = 75 kg and CdA = 0.35 m² with rho = 1 kg/m³, that's 4.0 N of retarding force from rolling resistance and 11.3 N of retarding fo...
by djconnel
Wed Sep 16, 2009 6:16 pm
Forum: General Discussion
Topic: If you have a DFPM, can you block the wind port?
Replies: 2
Views: 2736

Re: If you have a DFPM, can you block the wind port?

You left out drivetrain losses. These are modeled by iBike as a fixed fraction of power, but reality is more complicated. For example, a small chainring with the small cog will have substantially higher losses than the big chainring with a larger cog in the same gear ratio. Additionally, chain condi...
by djconnel
Wed Sep 16, 2009 4:25 pm
Forum: General Discussion
Topic: Relationship of Fric, Riding Tilt, and Crr
Replies: 3
Views: 3402

Re: Relationship of Fric, Riding Tilt, and Crr

Isn't there a drivetrain loss factor of 2% as well? This could be folded into the friction term, or applied afterwards.
by djconnel
Wed Sep 16, 2009 3:56 pm
Forum: General Discussion
Topic: rough roads -- wattage drops
Replies: 6
Views: 4505

Re: rough roads -- wattage drops

Of course, in theory the iBike should report low on rough roads, due to the assumption of constant rolling resistance coefficient. Obviously it's harder to ride at the same speed on rough roads, yet the iBike will report the same power on any surface as long as the speed and gradient and headwind ar...
by djconnel
Thu Jan 22, 2009 11:12 pm
Forum: General Discussion
Topic: Where is your iBike mounted?
Replies: 14
Views: 8757

Re: Where is your iBike mounted?

I remembered where I saw the quote... it's from this early nyvelocity.com review : I spoke with the iBike's inventor Glen Cunningham at Interbike, and he said that part of the problem is that the coastdown calibration is done from 20 mph to 8 mph. It would be more accurate at a higher speed, but the...
by djconnel
Thu Jan 22, 2009 2:18 pm
Forum: General Discussion
Topic: Where is your iBike mounted?
Replies: 14
Views: 8757

Re: Where is your iBike mounted?

Was there any difference in procedure between the two calibration runs? I wonder if more consistency could be gained by raising the coast-down speed range to a top value of 30 mph from 20 mph. This would increase the peak ratio of wind resistance to rolling resistance by approximately 225%, allowing...
by djconnel
Thu Jan 22, 2009 12:39 pm
Forum: Gen III iPro and iAero
Topic: iAero feature request
Replies: 10
Views: 8166

Re: iAero feature request

I agree TSS tracking would be a nice feature, even if I have a thing about specifics of the TSS formula which could be solved with simple modifications. It's still obviously better in most cases than net work (kJ) alone! There is a licensing issue with the term "TSS", but not with the form...
by djconnel
Thu Jan 22, 2009 9:09 am
Forum: Gen III iPro and iAero
Topic: iAero feature request
Replies: 10
Views: 8166

Re: iAero feature request

I think this is a great suggestion, except I personally think the TSS formula is badly flawed. It can be run up by riding along at 1 watt following a much higher effort. The Ergomo had to deal with this problem by arbitrarily dropping points below some near-zero power threshold. I have my own formul...
by djconnel
Thu Jan 22, 2009 8:59 am
Forum: Gen III iPro and iAero
Topic: IAero and PT SL+ side by side comparison
Replies: 5
Views: 5425

Re: IAero and PT SL+ side by side comparison

There was a good data comparison done in a BikeTechReview thread. The iBike data tend to lag the PT data by around 1 second. So the best comparison optimizes an offset between the two to maximize the correlation coefficient. Then the iBike assumes a fixed 2% drivetrain loss. This is a bad model of a...
by djconnel
Thu Jan 15, 2009 2:22 pm
Forum: General Discussion
Topic: Is changing position (and CdA) really a problem? Answer= no!
Replies: 4
Views: 3484

Re: Is changing position (and CdA) really a problem? Answer= no!

At first I dismissed your idea as accidental, but after I thought a bit more about it, if your position is optimized, then to first order improvements in CdA will be canceled by changes in FTP. So in this instance your point is valid, for minor deviations from the optimal position, keeping the unit ...
by djconnel
Thu Jan 15, 2009 10:11 am
Forum: General Discussion
Topic: post ride
Replies: 2
Views: 2575

Re: post ride

A moral of the story, I think, is that for those of us for whom the primary attraction of an iBike is for use in conjunction with an ANT+ Sport enabled Powertap, make sure to bring the PowerTap wheel for interval sessions. For real-time CdA assessment, if there's a bit of a calibration error in the ...
by djconnel
Wed Jan 14, 2009 7:57 pm
Forum: Gen III iPro and iAero
Topic: iAero and PT+ Power rate of display
Replies: 1
Views: 2930

Re: iAero and PT+ Power rate of display

Since the PT reports average power over a fixed time interval, not (like the Quarq or SRM) over integral numbers of pedal strokes, sometimes intervals contain a more or less favorable sampling of the relatively higher torque segments of the pedal stroke. For example, I might hit a sweet spot with my...
by djconnel
Wed Jan 14, 2009 6:10 pm
Forum: General Discussion
Topic: Analyzing Wind Post Ride vs Real Time data
Replies: 10
Views: 6489

Re: Analyzing Wind Post Ride vs Real Time data

Velocomp does not want to give the impression that you need a degree in physics to get a good cal. I have a degree in physics and I have to admit to finding all of this pretty scary! It's enough of a challenge for me to make sure my tire pressure is good before a ride; allowing a computer to come i...
by djconnel
Wed Jan 14, 2009 5:10 pm
Forum: General Discussion
Topic: Difference between disc wheels and handlebars?
Replies: 2
Views: 3102

Re: Difference between disc wheels and handlebars?

More detail than the CyclingNews summary.
Some solid wind-tunnel data on wheels is available here.
Those data are for an isolated wheel, and since the rear wheel drafts the bike, it has substantially less influence.
by djconnel
Tue Jan 13, 2009 8:36 pm
Forum: Gen III troubleshooting
Topic: installing ibike for ubuntu linux
Replies: 13
Views: 13233

Re: installing ibike for ubuntu linux

The IBike Gen 3 product page says Windows XP or Vista is required. I'm also running Ubuntu Linux, and would prefer the relative slender Windows 2000 to one of these exponentially bloated beasts.... does the latest software in fact run with Windows 2000? Following the advice here, I was planning on i...