Thursday, October 23, 2014

Old La Honda: always calibrate Powertap after battery swap

Despite an early afternoon meeting for which I risked tardiness if anything went wrong, I felt a strong need to test my fitness on the Noon Ride, Wednesday edition, which climbs my favorite climb anywhere: Old La Honda Road.

After the cheap LR44 batteries I'd last installed in my Powertap gave up the ghost a few weeks into my Basel Switzerland experience, I found some superior 357's (silver oxide) in a local combo department store / food store. This should have had me up and running but I didn't have the tool to remove the cover on the hub. I eventually brought it to a local shop, to see if the guy there could remove it with an open-end adjustable wrench, but it was too tight and the metal wrench risked damaging the flats on the hub cover. So I decided I didn't need power all that much in Europe and to wait until I got home.

Indeed, the cover was on quite tight for some reason, and after applying some Tri-Flow to the interface between the cover and the hub, applying the plastic tool, carefully pressing my body weight against the tool and turning slowly, I was bit by bit able to get the cover off. Weird. I then replaced the battery and retightened the cover, albeit perhaps less tight than it had been.

Riding into work from the train I came to a traffic light which I wanted to make, so I sprinted. These sorts of sprints are substantially less than the sprints I'd do in a race or sprint workout: those are all out maximal efforts, this is a "speed up but stay aware of what's around me and in control" sprint. Yet afterwards my Garmin read 656 watts max power. That's not an uncommon number for me to see during a sprint workout. I was very pleased with this number, preferring to be very pleased to assessing if perhaps there was a measurement issue.

When it came time to leave for the Noon Ride, getting to which takes me up to approximately 30 minutes depending on my luck with the inhumanely long Peninsula traffic lights, I noticed I was cruising along at 280 watts without much trouble. Wow -- impressive power. Riding at over threshold hardly feels like work.

The ride went as usual, around the Portola Valley Loop and to the base of Old La Honda. Before we even hit the bridge, Chris Evans took off in close to a full sprint, easily double the speed of anyone else. Obviously he wouldn't sustain that, but the "start hard then manage the crash" approach is one I've seen before from riders with a strong top end. They want to make sure to empty the tank on the climb, and the best time to do that is when fresh, they feel. So blast off, then try to cut back to near threshold the rest of the way, holding on to the time boost from the first minute or so, This works on Old La Honda because the effort is short, around 16-17 minutes for good climbers. For a longer effort the penalty for the early anaerobic indulgence would be payed over a proportionally longer period.

However, not blessed with much top end I've always preferred to ride the climb more aerobically, going out at an optimistic pace, cracking off from that a bit during the ride, then in the final minutes ramping it up for the finish. Anaerobic efforts at the end of the duration don't contaminate the rest of the effort, unlike those at the beginning. But it's harder to make sure you empty the tank this way.

Consistent with my pacing strategy, I didn't want to see more than 300 watts on my Edge 500, which shows 3-second power on my lap page. So I try to keep that nice and steady close to but not more than 300 watts. Doing this will result in an average power less than 300, since when the grade transitions from steeper to shallower, there's a tendency for the power to sag a bit when spinning up the pedals. So I never average my target, as long as I treat the target as an upper bound.

I was feeling strangely good, spinning my 36/23 up the climb. Normally I'd ride a 36/21 or even 46/19. I set a PR with a 36/18. So 36/23 is low for me. But I found with a higher cadence I had no issues with my 300 watt target. Wow -- I'd really gotten more fitness than I imagined in Switzerland!

I finally started to feel the climb approaching the finish, but then it was time to ramp up the effort. I didn't look at the power meter here, rather focusing on spinning my 36/23. Then I was at the top. Looking at the lap timer approaching the finish I was dismayed to see I was over 19 minutes: 19:08.85 I later determined from the FIT file. But the display showed the laps's average power had been 289 watts. What??? That would be among my best-ever powers up Old La Honda. How was it possible I got such a good power with such a mediocre time, especially when I'm relatively light right now (56.9 kg when I weighed myself this morning).

I immediately turned around, headed back down the climb (normally I descent nearby Highway 84, but I was in a rush to make my meeting), then back around the loop the way we'd come and from there rode back to work. Along the way I rode a bit with Chris Evans, who caught up to me when I stopped to get some water. I mentioned the mystery of the high power + long time. "Time never lies," he responded, "your brakes were rubbing or it's power meter error." After we split up, he heading to his job at Stanford, me going further to Mountain View, I stopped to check for rubbing brakes. Nope. I realized it may have been related to the battery swap in the morning.

Eventually I got back to my office where I managed to get some lunch, upload my data, take a shower, get dressed, and make the meeting with a few seconds to spare, albeit with somewhat wet hair, eating some yogurts during the meeting.

Afterwards, I looked at the FIT file and was impressed. I'd gone out at close to 290-300 watts and essentially held that, average power dropping into the 280's but then rising up with my unusually strong late-climb surge to that 289 watt value. My average cadence was 83, which is good for me when climbing.

Tom Arnholt of AlphaMantis responded to my tweet by noting that after a battery change, it's important to do a manual zero of the Powertap: it may not be able to re-zero after this using just the automatic zero which occurs when coasting. This had been my mistake. Not only had my battery died, but I hadn't used the wheel in over a month. So I did the Garmin 500 "calibration" step. It said "calibration successful" and reported a huge offset. So hopefully things are better now.

Here's my data for the ride (yellow solid line) and the data scaled to give an average of 261 watts (estimated by Tim Clark's power estimator (dashed yellow).

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I was disappointed with the time. But then I probably shouldn't be. I was targeting the wrong power, which I was largely able to sustain, and I finished with a lot in the tank, since I was able to surge a lot more than normal even after adjusting the power. I obviously could have gone faster. How much faster? Oh, I don't want to guess. Maybe I can try again next Wednesday.

Wednesday, October 22, 2014

Tour de France 2015: 3344 km

The 2015 Tour was announced, and although it has a brutal series of Alpine finishes, it's a relatively short one. The total distance is only 3344 km, historically low, although this distance falls right on an exponentially decaying schedule I fit to the distances from 1945 to 2010. Here's the plot:

I like long Tours as I find them more epic. The "epic" aspect doesn't show up well on television, but I have limited exposure to the television coverage anyway. However, I appreciate the finishes more if the riders have worked harder to get there. Modern racing has, however, to a large degree neutralized long stages. There's a constant temptation to shorten the routes and focus more on providing novel aspects each day to get people to watch Eurosport.

Maybe I'll go to watch some of the race next year. The concentration of Alpine stages facilitates this.

Sunday, October 19, 2014

what not to do with your Garmin 610 at a race start line

For running races of up to 4 hours, my Garmin Forerunner 610 has been my GPS of choice. It's compact, relatively light, fits well on my wrist, and has decent recording accuracy. I have a wrist strap for the Edge 500, but that unit is cumbersome for a wrist-mount. And my iPhone is too heavy.

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DCRainmaker image of Forerunner 610. See his review here.

The issue with the Forerunner is it's very finicky. Here's what I did today during the Dolphin South End Runner's Club San Bruno Mountain "12 km" trail run (actually closer to 13 km, according to my GPS data).

  1. Turn on, acquiring GPS signal during warm-up run.
  2. Run with the GPS on, to record warm-up run.
  3. Finish warm-up run, then hit "stop" and "reset", to lock in the warm-up as a separate activity. Don't turn off the 610: intent is to keep GPS signal active so I'm ready to go at race start.
  4. Approximately 10 minutes later, with 10 seconds to go before race start, hit "start" to record a new activity.
  5. Run race

Seems reasonable, right? WRONG. Mega-fail. You'll start your run, the timer will be ticking away, but the distance will be stuck at 0. The reason is that the Forerunner, when it's not recording data concludes it has no use for GPS, and goes into "power save" mode by discarding its GPS connection. There's a way, I think, to tell it to re-acquire, but I can never figure that out, and the touch screen doesn't work so well anyway, so the simplest approach is to power it off then back on again, hoping it acquires GPS while I'm running, and then hit start when it finally does.

This is the second time in a race this year that I've done this. The real cost is in Strava, where I don't match Strava segments on climbs at the opening of the race. For example, today was a 12 km race and a 5 km race. Both courses did the 5 km loop, the 12 km group moving on to an additional loop. I'd have liked to compare my time on the opening loop (which is a Strava segment) to not only those doing the 12 km course, whom I ran with (I was 7th at this point, passing two of them later to finish 5th), but also those in the 5 km race.

But no luck. The data from the opening 500 meters or so are lost.

Instead what you need to do is turn it on for warm-up, but if you want to isolate that as a separate activity, turn it off, reset, then turn it immediately back on, to avoid it going into power-save mode, which it does only after a fixed delay. It actually issues a warning for a few seconds before shutting off GPS, but it's easily missed in the noisy environment of a race start.

I understand why they do this. As frustrating as it is to lose data at the beginning of the run in addition to the unit taking a lot of attention which is far better devoted to the actual race, it's equally frustrating to realize your battery is half-drained away when you need more to get through the race duration. But the present "solution" is too error-prone.

Other than the limited battery life (not enough for hilly ultras) I like it: it records data, it tells me my pace and distance, I can upload at the end of the ride. That's all I want, really. This business with dropping GPS is the biggest flaw.

Friday, October 17, 2014

heuristic error check for rider mass (kg) vs age

For Low-Key Hillclimbs I have a mass-adjusted climbing score, which is based on the product of the rider mass and the rate of vertical ascent. This isn't a power calculation, but is related to power, and the units differ from power only by a factor of the gravitiational acceleration, which is roughly constant.

The natural units of mass for international sports is kilograms, but this is the United States, and people here are more accustomed to dealing in pound-equivalents (pounds formally being a unit of force or weight, not mass). So rather than require riders to calculate their mass in kg, which they may be less likely to recall than their weight in pounds, I default to having them enter pounds, with an optional unit specification which can allow for other units (I presently support pounds, kilograms, stone for my Britophiles, and slugs to be pedantic).

But people mess up. One friend specified his mass as "10 stone 8 pounds", a mixed unit I can't handle (my parser considered that as "10 pounds"). But more often people will enter kg without a unit. That seems to happen once or twice per week.

So what to do? The pragmatic approach is to check the weight, and it's low (pounds and kg differ by a factor 0.454), then assume it is kg. But what about young riders? Sometimes people bring kids on the Low-Key in trailers. So I need a threshold for what I consider "too light for pounds" which is a function of age, yet which isn't so low that relatively heavier riders if they make the mistake won't get caught.

Of course, if I had height, that would help. But I don't. So I need to go with age.

To accomplish this, I developed an ad hoc age-to-mass conversion. First I needed to come up with a threshold for infinite age. 40 kg seems reasonable: 88 pounds. There's women lighter than this, but it's the infinite-age limit, and for finite age, my threshold would be reduced lower. Note I could use sex as well, except for tandem riders sex can be "mixed" due to the way I process results, so I decided to not use that.

On the other hand, if a rider were to enter 90 kg, a reasonable mass, then my code would still consider that to be a reading in pounds So there's a chance of bigger riders making the mistake and slipping through. Fortunately this is a hillclimb series, which tends to attract relatively thin people, so the substantial majority are under 90 kg.

Then I need to adjust the mass versus age. Once people reach adulthood, mass maxes out, so my function needs to asymptote beyond age 21 or so. The very young tend to grow at a certain rate, but since mass increases superlinearly with height (BMI suggests to the second-power, but it's more realistically a higher power, closer to 2.5). So in the early years the mass increases proportional to age to some power greater than 1. That power won't necessarily be constant with age, but I'll assume that's a good approximation.

So here's the equation I came up with:

kgmin = (40 kg) (age / 15 years)2 / sqrt [ 1 + (age / 15 years)4 ]

I picked 15 years because this seemed like an age at which growth stops increasing as rapidly as it does at younger ages.

The behavior of this equation is clear. For small ages, the denominator is essentially 1, and the mass increases proportional to the square of age. But at high ages, the 1 in the denominator becomes irrelevant, and the numerator and denominator cancel, leaving an asymptote of 40 kg.

I decided to check this against published data for mass versus age. Here's data for boys age 0 to 17:

And here's data from girls:

I used the 5%-tile data because I'm interested in a lower-bound limit, and in any case 50% and above are confounded by the obesity epidemic which tends to not afflict children of Low-Key hillclimbers.

Here's a comparison of my equation with these data:

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My curve is conservative, tracking women better than men, the girls' mass tracking the boys' until an age where they saturate while the boys keep going.

Thursday, October 16, 2014

Gallium Pro geometry

On Caltrain yesterday, I was surprised to see among the usual set of commuting bikes a SRAM Red-equipped Argon Gallium Pro. The bike immediately stole your attention. The design was one which has been trending: clear-coated carbon with plenty of text detail so the viewer is sure to realize he's gazing upon the result of advanced, proprietary engineering and not at yet another paint job on the same old OEM frames being pumped out of the same old Taiwanese factories. But it worked: the bottom bracket area was huge, the downtube a large-diameter "inverted Kamm tail" design seemingly designed to maximize wind resistance, the top tube a broad, eccentric shape which screamed "vertically compliant yet torsionally stiff". All it lacked were the pencil-think seat stays Cervelo popularized, but this was a machine designed for stiffness over anything else.

It seemed dramatic overkill, since the bike was small (the Argon "XS" I suspect). There wasn't much seatpost showing and the handlebars were spaced up to within a few cm of the saddle height. The spacers, however, weren't of the ordinary variety, but rather of similar diameter to the large-diameter head-tube, designed to appear at first glance as an extension of that tube rather than of the fork. Did this help front-end stiffness? Perhaps. I'd love to see test data.

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Web photo of Argon Gallium

The compromise from full race-readiness was the wheels: Al-rimmed clinchers. Bringing carbon rims onto the Caltrain bike car would be absurd, so I wasn't surprised to see this. There was a good chance the rider had race wheels safely at home.

All other things equal (same tube diameters, scaled geometry) a smaller frame will be stiffer than a larger one. The stiffness of a beam is inversely proportional to the cube of its length, so if you increase length by 10%, stiffness increases by a bit more than 30%. Additionally, smaller riders are lighter and less powerful as a population, so forces involved are reduced: since mass tends to go like height to between the 2nd and 3rd power, a rider 10% taller will likely generate forces around 25% greater. A combination of 30% more stiffness and 25% less force for a rider 10% lighter means a bike optimized for a rider of a given height will likely be over-built for one shorter. This definitely looked over-built.

I discretely looked around to see whose bike it might be. I expected a small guy, perhaps Asian, dressed in full racing kit. Of course he'd be sitting close to the bike to keep an eye on it, but there was only one passenger in the ground-floor seats, and he didn't look like he fit.

We were approaching a stop, when a small, thin Asian woman walked down the aisle. I didn't pay much attention to her until she took the bike off the rack and started walking with it. I smiled. The bike clearly did not fit with my perception of a female bike.

I asked her about it: did she race? She was thinking of it, she said, but had used it for AIDS Lifecycle, a charty tour from San Francisco to Los Angeles. It rode well, she said.

I decided to check out the geometry. Argon is entering the ProTour for 2015, so their bikes are coming into increased prominence.

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geometry for Nitrogen; Gallium Pro is equivalent

Their geometry chart is restrained, for example with head tube angle and head tube length notably absent. Stack and reach are included, these being the focus of the fit scaling. The chart is particularly useful because it provides fit guidance as a function of saddle height: the range of available handlebar drops for a given saddle height for each frame size. For my dimensions (72 cm saddle height, 8 cm drop) this puts me in the size small, which is the 3rd smallest size of the 6.

Here's how those compare with some other bikes of note: the Trek Madone and the Cervelo series:

image

The Argon scales down to an exceptionally low stack, lower even than Cervelo which is itself very low. Reach is relatively long, however, particularly in the small sizes where it rivals the Madone H1, which is among the most aggressively designed frames popularly available. In larger sizes it retreats a bit from the Madone's small stack-reach ratio. It nevertheless stays more aggressive than the 2015 Cervelo S5, which some among the Cervelo cult consider crazy-aggressive.

One differentiating aspect of the geometry is the low bottom bracket: 75 mm drop from the hub height. For small bikes, which are likely fitted with small cranks (165 - 170 mm), a low bottom bracket works, especially when fitted with compact pedals like Speedplay or (my current favorite) BeBop. With short cranks, the risk of clipping a pedal on the ground is reduced. But with large frames 75 mm seems risky. Cannondale, for example, raises the bottom bracket on larger frame sizes for this reason; larger frame implies longer cranks implies less lean angle to the point of pedal-ground or shoe-ground contact. Dan Martin lost Liege-Bastogne-Liege clipping a pedal in the final corner when he tried to pedal through to take the victory. He later won Lombardia coasting through the final corner. But for this woman's bike it wasn't likely an issue.

Another is the short head-tubes. Here's another version of he geometry chart showing head-tube length:

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9.1 cm and 9.6 cm for the smallest two frames is extraordinary. The low bottom bracket requires an even shorter than typical head tube to reach low stack values: with the bottom bracket lower, the wheel is relatively higher, and that means the head tube needs to be shorter.

I will readily admit I have an irrational obsession with bikes. Yet the number of bikes I've ridden is relatively small: I'm certainly not in the habit of going into shops and test-riding bikes I have no intention of purchasing (my recent test of the Parlee ESX, it being a "demo day", a rare exception). I felt little desire to ride the Argon since I value low mass, aerodynamics, and comfort over stiffness. The one bike I would like to test is the Cervelo R5, which if they adapted to the new S5 geometry would be particularly difficult to resist. But since I do and would continue to do the vast majority of my riding on my tried-and-true steel Ritchey Breakaway buying a new carbon fiber über-frame makes zero sense. The Fuji SL/1 (the same model recently ridden to a Low-Key Hillclimbs record and Strava KOM on Montebello Road) is more than good enough as an "event bike" for me.

Wednesday, October 15, 2014

culture shock: Back the the USA

After 6 weeks in Europe, a combination of some work and more vacation, there's a bit of culture shock coming back the the United States.

  1. Sprawl: flying into SFO, the sprawl across the East Bay was extensive. Residential development in Europe tends to be more clumped: areas of density immediately adjacent to rural. Suburbia is much, much less extensive.
  2. Being immersed in English: this feels wrong, sort of like cheating. I'm not complaining, though!
  3. tasteless food: I cooked some California brown rice and cooked it. The taste, or rather lack, was a bit of a shock. In Switzerland, all of the food I had was rich and flavorful, fresh and good. A lot of food in the US tastes empty and stale, produced for quantity rather than quality.
  4. California stops: after assembling the Ritchey Breakaway and riding to the train on Monday morning, after my return Sunday night, at the first intersection I hit where I had right of way and cross-traffic a stop sign, a driver did a California stop: drifting through the sign without actually stopping. He knew he was letting me go, but it wasn't obvious to me. A big part of being on shared roads is to communicate your actions.
  5. bumpy trains: the Swiss trains were smooth as silk. On Caltrain, on some trains I can't even type on my keyboard due to the bouncing suspension. I actually experienced this first on my way home from the airport, on BART, which is smoother than Caltrain but the trains still look old, worn, and weathered.
  6. wide suburban roads: after Caltrain, I have a 3+-km ride to work. My usual way essentially ends with a left from Middlefield in Mountain View onto a highway frontage road. Middlefield is a suburban road, yet is 8 lanes at this point, so I need to merge across 3 then make a left across the remaining 4. 8 lanes? Even the intercity roads I was on in Switzerland, France, and Germany never exceeded 4 (2 each way).
  7. parking lots: generally, the amount of land squandered on asphalt here is appalling, both roads and giant parking lots surrounding every building. Even in Meiringen Switzerland, which is in an agricultural valley and thus land is abundant, the public parking lot is buried.
  8. lack of cycling infrastructure: In Switzerland especially, but additionally in France and Germany, grade-separated bikeways were common. I rarely see these here. There's plenty of bike lanes, but generally to get around on a bike you need to know the best routes In Basel there was the challenge of navigating the streets, but on roads with too much traffic there was almost always bike infrastructure: I didn't need to have any insider knowledge on which subset of the roads were bike-friendly. It's ironic that Proposition L in San Francisco's November election is advocating a "restoration of balance" for car-infrastructure. A comparison with Europe shows the present situation is out of balance, but well in favor of private motor vehicles.
  9. Lack of mobility without a car: I want to go to Low-Key Hillclimb week 3, Welch Creek Road, this weekend, but just getting across the Bay without a car anywhere resembling early morning is a challenge. In Switzerland you could pretty much get where you wanted, when you wanted.
  10. Street people: in San Francisco, they're everywhere. In Basel, I didn't see anyone camping in the streets.

I really do like it in San Francisco. I don't know if I'd be happy living and working in Switzerland: it's a much more dynamic environment here. But I certainly miss a lot about my wonderful time spent there.

Monday, October 13, 2014

Axalp climb

Adding to my collection of profiles for climbs I've done, here's one for the Axalp climb, approximately 10 km west of Meiringen, Switzerland, on the south shore of Lake Brienzersee.

First the profile. I used my Garmin Edge 500 for position and altitude. On the climb up, I lost GPS signal for a bit, which resulted in a data gap. Since I take the data straight from the FIT file, I rely on Garmin's distance determination, which would normally be good if my Powertap had been functioning, but the super-cheap alkaline LR44 batteries I got off Amazon don't last as long as silver oxide 357's with which the Powertap ships. As a result, I needed to rely on the Garmin's GPS distance determination, which doesn't interpolate across gaps, unlike Strava's distance determination. It was easy enough to convert latitude and longitudes into distance, but the Garmin's smarter than that: local variation in position turn straight paths into zig-zags, and the result is a persistent overestimation of total distance. Honestly I don't know how Garmin does its position->distance conversion, but all I know is it doesn't handle gaps well.

But I was saved. I descended the same hill I'd climbed, so I was able to use the data from the descent, reverse the order of the points, and presto-magicko, I have climb data. Of course this isn't strictly accurate because I climb the opposite side of the road as I descent, so switchback insides become outsides and vice-versa, but on the narrow roadway the difference is small.

Using the descending data offers an additional advantage, which is that if barometric pressure changes due to weather, or temperature changes, corrupt the altitude data, these changes will likely be a lot less at descending speed than at much slower climbing speeds.

Anyway, here's the profile:

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My profiles all end up looking fairly similar because I use the entire plot from lower left to upper right. I then take characteristic subsets of the curve and do nonlinear regressions to fit a gradient and an offset to the segments, providing a feel for how the gradient of vairious subsets of the climb behave. But it's also useful to consider the grade extracted on a local basis. For this I first do a smoothing operation using a convolution function with characteristic length of 50 meters:

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Yes, this one is steep, peaking out in the middle at over 15%, but fairly consistenly hanging out at 10% or steeper. There was some relief through and beyond Axalp itself. I continued to a T-intersection with a street sign:

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It rated out at 160% of Old La Honda using my formula, as I rode it. However, the climb can be ridden a bit further, taking the right-hand option, until it turns to gravel/dirt.

But the light was fading and I wanted to reach the bottom of the descent before I needed my headlight. So I didn't dally too long, or explore the way further. I did, however, stop long enough to take this photo, not far from the top:

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But then I returned the relatively short distance to Axalp, filled my bottle at the fountain, then returned to the valley for the approximately 10 km back to Meiringen.