Wednesday, February 17, 2016
Butt and power update
On Friday I was pushing the bike through the parking lot, hand on the saddle, and the angle felt wrong -- too much tilt. Funny how what seems normal one day is anything but the next. Since then I have been fiddling with the tilt, hunting for that sweet spot between a stable platform for riding several hours at a time, and applying minimal pressure to sensitive places. Fore-aft position plays a role and I have not even gone there yet.
I also have an update on power. This week's Tantalus Tuesday gave me a chance to experiment with moving the pedals between bikes. Today's spin class should provide an additional data point. On Monday night I moved to pedals to the Merlin. I connected the pods but did not go for a ride. Tuesday morning I was careful not to start spinning until I was on relatively flat ground, then spun up to 70+, as smooth as possible. The L-R balance was around 30-70. Not good. So, I thought that this supported my theory that the first spin has to be done soon after plugging in the pods. I unplugged the pods and shut down the head until, waited a couple minutes, then brought everything back up. Still 30-70. Then I remembered that I had to set the head unit to the other bike; it was still set to Makani Kekoa, which has shorter cranks. After I switched to the Merlin the Edge 800 automatically re-scanned for the power meter. I was at the right place in the menu tree so I did a calibration. I did a brief test ride and balance was 50-50. Overall balance for the ride was 48.6/51.4%, which is as good as it gets. Today I will go through the same drill without unplugging the pods and see what I get. My goal is to have reliable results in a race after the bike has been sitting for hours. I really should not have to spin up, stop, dismount, do a calibration, then go again. That would be crazy.
This Saturday I will be attending a triathlon cycling clinic in Kailua hosted by Ben Williams and led by coach Clayton Hamilton. Should be a lot of fun. I plan on asking a lot of questions about power meters in general and Garmin Vector in particular.
Update #1: The clinic date has changed, now scheduled for March 19.
Update #2: My experiment for yesterday's spin class involved setting the crank angles -- the initial spin at 70+ RPM -- after installing and powering the pedals the night before. The result: better understanding but more tests required. After spinning up with the bike on the trainer I had 100-0%. Totally bad. Seeing that it was not improving and knowing I only had a few minutes to get ready I opted to start over. I pulled the plugs and shut down the Edge 800 head unit, waited a couple of minutes (still not sure how long it takes to fully reset the system), then plugged in the pods and fired up the head unit. The spin-up began the same as earlier, 100-0, but this time I kept at it a little longer and the balance gradually came to around 30-70. I stopped spinning, got off and did a calibration. Gt back on and as I peddled the balance gradually came to 50-50. Based on this and previous results I suspect that the calibration does more than zero out the residual imbalance, which is what the documentation says. I think selecting calibration puts the head unit into a balance period, during which it hunts for 50-50.
What remains? First, I need to do the exact same sequence minus the electrical power cycle. Second, I need to know how to get proper results on race day, without having to do the calibration. I think it is time to put the question to Garmin.