Nov 15

Nov 15, 2004

Good watts test finally!

It got to a high of about 15 degrees C today - not bad for the middle of November in Calgary. When I left the house this morning it was fairly calm, but by the time I got to the race track, winds were blowing steady at about 25 to 30 kph. I spent 90 minutes going around in circles and collecting loads of data with my SRM watts meter.

First - a quick ride report. Handling the streamer in the wind was nothing like it was the first time I was out - since everything is lower to the ground and more stable, I never felt like it was getting out of control at any speed or turning into any wind gust. This could partially be due to the better leverage on the above seat steering bar.

The steering bar is not right yet... My arms are jammed into the sides of the fairing and it's uncomfortable. At first, I couldn't figure out what was happening, then it occurred to me that because I am seated lower in the bottom half shell, there is now less width for my shoulders and arms. If my arms were out straight in front of me, it would be ok, but I'm not sure I have room there for a steering bar. I'll need to look at how I can raise that steering bar up to the ceiling of the fairing - that should get my elbows in front of me rather than right beside squished into the fairing.

I need to do something better with my current fairing top cover... It blew off twice and thankfully Ben showed up and was able to tape it on for me. Even the taped on cover eventually blew off.

I don't even notice the shorter cranks, so I guess that's good. My watts per heart rate was normal, so I guess there was no adverse physiological reaction to the 155mm cranks (kindly on loan from Jason Yanota - talk to Jason if you are thinking of getting an SRM watts meter). I had set my Q factor narrower by moving my shoes inward on the cleats to clear the sides of the fairing nose. I didn't like that at all! I need to move them back because my right foot/knee was getting sore.

The slightly higher seat angle was giving me a butt ache, but I think I'll have to condition myself to that because the only way to reduce that seat angle is to lift the seat bottom up. That will raise my center of gravity and degrade the stability. Although, it may be advantageous to be able to lift that seat bottom up a few inches periodically for a change of positions when conditions (corners and wind) allow.

Now - onto the watts data!

I was able to isolate 5 good series of consistent power output periods that consisted of at least 5 laps each (entire laps):

Watts Speed (kph)
142 37.12
155.6 39.2
175.4 41
149.3 38
100.9 31.75

Here is a plot of the above data:

The blue dashed line is the projected watts required to achieve 40 kph (somewhere around 165 watts).

There are a few reasons why these values may not be accurate. First is the fact that although the wind did die down quite a bit by the end, there was still a steady wind blowing and it is difficult to say for sure how that wind effected the performance of the vehicle. Secondly - and this is a major reason: the road surface is VERY, VERY bumpy. At 37 kph I was getting tossed around like a rag in a washing machine. That has GOT to negatively impact the rolling resistance in a big way - and also aerodynamic efficiency because the fairing was bouncing up and down like crazy. Third, the track seems shorter than the 1/2 mile they say it is (maybe it's 1/2 mile long at the very outside edge at the top of the steeply banked corners) and it feels like I'm always turning a corner. Both the turning of the corner and the countersteer to offset the bank of the corner also has to impact on the rolling resistance. Wait a sec... I have the exact distance in the SRM file. My route around the track was exactly .44 miles (.72 km).

I plugged the numbers into the pwrdrag2.xls spreadsheet to see if I could get some drag and rolling resistance numbers that made sense, but I got two very conflicting pairs. Since you can only enter 2 sets of speed/watts data runs, I tried a few pairs to see what the calculator would return. The first was a CdA of 1.19 (sq ft) and rr of .0042. There is NO way on that track that my rolling resistance is as low as .0042 so I know that has got to be wrong. The second return was a CdA of .667 (sq ft) and rr of .0064 which sounds much more realistic. To confirm the values, I entered them into the pdgusc11.xls calculator (by John Tetz) and it returned watts values that were WAY off of what I recorded, so I don't know... I still think my CdA might be around .7, but my rr has got to be around .0085 or so - especially on that rough track. Those values generally work with most of my data in Johns calculator, so I think that's probably about what I have.

That being the case, a better road surface will lower rr - also I haven't re-aligned my rear wheels, so a bit of a toe out is currently adversely affecting the roll. I can further lower the drag in big ways by adding my wheel fairings, a proper canopy top with a bubble (the current one has a big hole in the top where wind rushes into and fills up the fairing. I need to add fairing covers over the wheel strut slots. There are a few other general fairing shape refinements I can make - like rounding out the bottom a bit better, rounding out the top, sloping the nose down and rounding out the flat areas on the sides. Of course, another obvious improvement will be to get rid of the tape that is all bunched up at the nose, and around the fairing shell split line. Shaving 20 lbs off the total weight will also shave 10 watts off the power requirements, so that's a very important consideration!

Tomorrow morning I am going to fiddle with a new steering bar position and if the weather is good and the wind isn't too bad, I'll do some watts tests out on highway 22 (nearly flat, very smooth and mostly straight).


TCR2 (track) 2Do LIST:

1. Make a platform for the wind trainer (mini-rollers)
2. Add front caliper brake
3. Mount first fairing and all the work required with that
4. Make CF front wheel fairing
5. Make CF rear wheel discs
6. Make a new steering bar that rises up a bit higher - also takes up less room on the sides so fairing can be tighter
7. Adjustable seat height
8. Make fiberglass canopy top with acrylic bubble and tailbox
9. Paint this puppy!
10. Rear strut supports
11. lower and chop


TCR1 (cross country) 2Do LIST:

1 Add front derailleur
2 Run road, roll-over and watts tests for new suspension system
3 Worm gear steer prototype (Waiting for final design and parts list from Ben)

TOTAL distance on TCR1
806 km


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