Archive for February, 2011
Often in science a mistake or accident can prove to show you more than your original experiment, as I just confirmed with my informal testing of my Quarq CinQo powermeter. So here’s the backstory:
After a season of really enjoying my CinQo, I had it shipped back to Quarq to have it recalibrated and get some firmware updates,.
I have to pause here to say that Quarq are a model of customer service and I am happy to have invested in their product: it was trust well-placed and I’d do it again. As a matter of fact, I can’t think of any cycling company, and few companies at large, that have been as good to me as a customer than Quarq has.
Also, after badgering the busy guys over at Saris / Cycleops (thanks Jesse and Geoff!) I received the beta Joule 2.0 firmware, which adds a manual zeroing feature for Quarq users.
So I decided with all of this new tech that I would grab a weight, some cord, and hang weights off of my cranks to see how the small and big rings and left and right crankarm affect power measurements.Since I could now hit a button and get a report on the torque measured by the Quarq when a certain weight was applied, I could see what it reported for torque compared to what the theoretical value should be given I knew the weight and the crankarm (leverarm) length.
I had a 20-lb weight right there, and after scrounging around a bit, decided I’d use an old power cord to make a loop on it to hang over my pedals.
I used the instructions on the Quarq FAQ page and built a spreadsheet and was merrily on my way to geek nirvana when I noted a strange thing: every time the cord that I had used to tie the weight touched the ground, I saw about 2-3 fewer 32nds of a Nm than I had when the cord wasn’t touching the ground.
My attention shifted: was the Quarq so sensitive that it could tell a 30 gram weight difference on top of the suspended 20.5 lbs when the end of the cord was resting on the ground or not?
Oh yeah – the CinQo is that sensitive. I tried this at least 15 times, then also tried it with some smaller weights in the 10-15g range added or taken away from the 20.5lb suspended weight. And every time, my quarq reported the difference.For good measure, I did weigh the cord end too!
At this point I had seen a few things:
1. The Quarq is *remarkably* sensitive
2. The Quarq showed a remarkable consistency, but even 2 degrees of slope either way in my crankarm away from horizontal would affect my results in a huge way, so it’s very hard to test your CinQo with weights and improve anything.
3. I don’t own a scale that’s good enough to weigh an object well enough to test my Quarq!!
This is a crazy-good piece of kit.