Tips for getting good profiles for track (fixed-gear) bike?

[dtrousdale]

I want to get at least four profiles for my new track bike. This would include using standard drop handlebars versus clip-on aerobars and using training wheels versus racing wheels. The 335 meter velodrome is outdoors, has a fairly new concrete surface, and has banking of 25 degrees. No DFPM yet for this bike, but I do have an iAero. Also almost all of the wattage I will care about in both training and racing will be at well above 20 mph. There are few windows of opportunity for me to perform the calibration procedures due to the velodrome schedule and availability, so any and all advice will save me time and will be appreciated.
1. To do the 2-mile Cal Ride, I assume that all I would need to do is ride around the track for the first mile (on my local track, about 5 laps), slow down enough to trigger the signal to turn around, and then complete the second mile. Would this be good enough for a Cal Ride?
2. Looking through the docs, I don't see a way to save a profile (to upload to the iAero whenever I want) to my computer without doing Coast-Downs. Is it correct that I cannot save a Cal Ride-only profile? I'm asking this primarily because doing CDs in a velodrome might be a challenge and because this is the first time I ever thought to use this method because of the special challenge of a track.
3. Since doing CDs seems to be my only option to get the multiple profiles I want, it also seems like I should probably use the method wherein I measure CdA and estimate Crr. My reasoning is that, since this is on a track, the surface is relatively smooth compared to the road and highly consistent. Also I would expect the Crr to be fairly low, so my question would be: what might be an appropriate number or range for the Crr for my situation?
4. Would I be correct in assuming that I must unclip from the pedals when performing CDs on a fixed-gear bike? It would seem so since the pedals have to keep going around, and I wouldn't want the weight of my legs on the pedals to be a factor in slowing down, would I?
5. Slowing down from 20 mph to 8 mph for CDs fast enough in a velodrome could be problem. I recall getting bad CDs when the CD took too long. Is that true that time is a factor in the quality of a CD? I have not timed this yet, but I assume the way to do it would be to go up the bank (as gradually as possible), and then stay at the top until I get to 8 mph, hopefully under the time limit. Does that make sense?

[Morocco Mole]

Amazing timing of your post, I am about to go through exactly the same process next week. My thought for the coastdowns are to take a 16 tooth freewheel to the track with me and do the coastdowns once everybody has finished for the night, I have a flip\flop hub on my training wheels. This is a weekly training track session and the coastdowns should only take 10 - 15 minutes to complete. I also think your proposal for the Cal Ride should be pretty good, you will be going into and against the wind in equal amounts which would be ideal. Actually it might make for a very good Cal ride, and any changes in the wind over the duration of the Cal ride will be minimized due to the short laps. I might even take my Road bike and try and do a new Cal ride for that. let us know how it works out.

Cheers
Jim

[Morocco Mole]

Update on previous. I have completed 2 Cal Rides over the last 2 weeks. Wind Scaling has been consistent 1.143 and 1.186 Tilt was also close on both CALS but returns positve values of .4 and .5 Now I understand that tilt should never be positve but maybe this is a symptom of banking on the track. Haven't tired any coastdowns but I have estimated Crr or 0.0032 (Continental Supersonic 20 x 700c + Latex Tubes), smooth cement track, and .CdA of .329. After applying the profile to the ride the numbers seem pretty good. Have attached both Cal Rides and Ride file from tonights track session. (Scratch race, point score, scratch race, Italian Pursuit) Any comments appreciated, especially regarding the positive tilt.

iBike_06_08_2010_1916_31_km.csv

(661.63 KiB) Downloaded 495 times

Track Bike.ibp

(334 Bytes) Downloaded 485 times

100601_cal_data.ibcd4m

(253.34 KiB) Downloaded 512 times

[lorduintah]

It is not surprising to get a positive tilt as centripetal force from the motion of the bike on the slope incline would make it appear that the bike is continually going "up".

Tom

[Morocco Mole]

So should I just go with it and keep the positive tilt in the profile, or make some sort of adjustment? Did some coast downs but they were all rubbish so maybe I should try them again on my normal coast down circuit near home.

[lorduintah]

I will that answer to John or Travis. Not knowing the whole calculation from sensor readings and how they feed into the math to get watts is their turf.

But I can also see that coast downs on a track would be a different challenge than the assumption that overall you are riding on a "flat" surface on average.

Tom

[Morocco Mole]

Ok, dredging up an old thread here, but I have access to a powertap track wheel so I thought I would try and get an accurate Profile created for my iAero. Performed the usual TILT and Wind Calibrations and did a CAL Ride. Following is the output from the DFPM fit in the software.

TrackCAL.png (232.18 KiB) Viewed 8493 times

CdA of .291 and Crr 0.0042 look believable, this is an outdoor cement track running continental tubulars riding in the drops. The big issue, as mentioned previously in this thread is the positive riding tilt 1.0 . You can see in the elevation chart that even though I had just done a TILT CAL, the iBike thinks I am going up and has correct the tilt. I cannot save the Profile because the FRIC is negative and out of range, although I was able to recreate this profile by entering the values directly into the profile editor. If I apply this profile after the ride to my track session for the rest of the evening, the numbers match my DFPM pretty closely. Problem is I cannot send this profile to my iBike because once again the FRIC value is "out of range"

Any thoughts?

[Velocomp]

Please post the ride file...

[Morocco Mole]

Sure, have attached the CAL ride and some ride data from the rest of the evening.