Analytical Cycling and Power meters

Discussion in 'Power Training' started by swampy1970, Mar 26, 2008.

  1. swampy1970

    swampy1970 Well-Known Member

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    Has anyone here, who has a power meter, ever plugged data into the tools on analytical cycling and compared results?

    I have a very very hard time believing the "wattage" that's given at the end. I don't have a power meter, but my Polar does record speed, rpm and gradient (which I checked against various maps for that section of the road) so I plugged in that info, with my combined bike and rider weight, threw in a guestimate for the road surface and watched what popped out. This is for a 1.7 mile section of road that averages 20%, which is preceeded by a 3 mile climb at ~11% (varying between 7% and 16%). I normally climb this hill two or three times which makes me believe the result even less - given the way I feel riding up the hill I'd be happy with half the displayed amount.

    Before anyone tells me to stop eating pork pies, bbq and quit the beer, that weight is me with bike, water bottles, little saddle bag with random crap and the kitchen sink. :p Sometimes, when you're riding out in the boonies up a hill where mountain lions are around the kitchen sink could well come in handy.

    So, the numbers:

    [size=-1]Frontal Area[/size][size=-1]0.50[/size][size=-1]m2[/size][size=-1]Coefficient Wind Drag[/size][size=-1]0.50[/size][size=-1]dimensionless[/size][size=-1]Air Density[/size][size=-1]1.226[/size][size=-1]kg/m3[/size][size=-1]Weight[/size][size=-1]93.1[/size][size=-1]kg[/size][size=-1]Coefficient of Rolling[/size][size=-1]0.007[/size][size=-1]dimensionless[/size][size=-1]Grade[/size][size=-1]0.200[/size][size=-1]decimal[/size][size=-1]Wind Resistance[/size][size=-1]0.7[/size][size=-1]kg m/s2[/size][size=-1]Rolling Resistance[/size][size=-1]6.4[/size][size=-1]kg m/s2[/size][size=-1]Slope Force[/size][size=-1]182.6[/size][size=-1]kg m/s2[/size][size=-1]Cadence[/size][size=-1]55.[/size][size=-1]rev/min[/size][size=-1]Crank Length[/size][size=-1]180.[/size][size=-1]mm[/size][size=-1]Pedal Speed[/size][size=-1]1.04[/size][size=-1]m/s[/size][size=-1]Average Pedal Force[/size][size=-1]402.6[/size][size=-1]kg m/s2[/size][size=-1]Effective Pedaling Range[/size][size=-1]70.[/size][size=-1]degree[/size][size=-1]Effective Pedal Force[/size][size=-1]1035.3[/size][size=-1]kg m/s2[/size][size=-1]Speed[/size][size=-1]2.20[/size][size=-1]m/s[/size][size=-1]Power[/size][size=-1]417.4[/size][size=-1]watts[/size]
     
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  2. swimmer88

    swimmer88 New Member

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    interesting....your speed (2.2meters/second) converts to 4.9MPH, which is pretty darn good for 20% grade. Also, the combined weight of you, the bike, and the kitchen sink is appox 205 lbs, so you are no 140lb cat 1 climber either. Based on that information alone, I would say that wattage number is pretty close to being right. You have to remember, you are working a lot harder to go up that hill than you would be on the flats.
     
  3. postal_bag

    postal_bag New Member

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    Time to trade in the powercranks for a power meter. ;-)
     
  4. whoawhoa

    whoawhoa New Member

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    How sure are you of the gradient? 1.7 miles averaging 20% sounds pretty unreal. I've ridden a climb with pitches in the low 20s that made me want to cry.
     
  5. daveryanwyoming

    daveryanwyoming Well-Known Member

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    Yes and it agrees pretty well for sustained climbs. I used it to predict my time for a hill climb TT last season that climbs ~2800 feet in 5.5 miles. For the average power I sustained it managed a time estimate within 25 seconds of what I actually rode. Not bad given the number of assumptions you have to make.

    Speaking of assumptions it's very unlikely your frontal area is 0.5 m^2 while climbing a steep grade. It takes some effort for most folks to get down to that sort of frontal area in the drops much less while climbing. But that would only make the power estimate slightly higher and only very slightly at the predicted speed.

    Yeah 417 watts is a lot of power to sustain for a couple of miles of 11% and 20% grades. Are you sure about the grades. Have you tried Google Maps, Google Earth or Brad Culberson's Course Creator: http://cc2.bradculberson.com/flex/bin/CourseCreator.html

    for getting good elevation data? Brad's course creator is particularly good. Enter waypoint markers frequently along your chosen route and export the elevation data. You can take that info into Excel or other utility to plot accurate elevation plots, calculate grades for segments, etc.

    Also remember that it's unlikely your hill is steady at any grade for very long. IOW, it's best to simulate it in segments instead of one long average.

    Anyway, I've found the calulators at analytic cycling pretty good when compared to my PT data as long as I enter reasonable estimates.

    -Dave
     
  6. frenchyge

    frenchyge New Member

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    I'm reading 2.2 m/s at a cadence of 55 rpm. That'd require about 95 gear inches, or about a 53x16, which seems a tad stiff for a truly 20% gradient road (even for a big boy on 180mm cranks). What gear do you typically climb in?

    I know cadence or gearing don't affect the power output for the model, but the bottom line is that gradient and speed are going to hugely affect the output of that model if those inputs are off by even a small amount. I'm with Whoawhoa that road gradient is where I'd spend my effort refining the inputs.

    Care to post a google maps link to where this 4.5 mile section of road is located, in case someone with topo mapping software wants to give it a look?
     
  7. swampy1970

    swampy1970 Well-Known Member

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    Photo's of the hill, as climbed in the Solano Bicycle Classic, can be found here. Note in one of the pics someone getting off pushing. I doubt it was Chris Horner or Jon Vaughters though. ;) Vaughters, the record holder of the fastest Mt Ventoux climb for many years until Mayo broke that a couple of years ago, completed the 7.7 mile stage in 33minutes narrowly beating Chris Horner - and that's with the first 3 miles along Pleasant's Valley Rd being well paved and slightly downhill. The entire Saturn team went for it from the gun to get Horner to the bottom of the narrow climb towards the front - no sandbagging.

    http://www.cyclingnews.com/road/?id=2003/mar03/solano03/solano032

    Scroll down to the bottom for the picture list and check out the carnage that the hill caused to the results!

    The only topographical map I could find online is this one from topozone. The "fun" part starts just after the hairpin in the middle of the map. There's lots more of the lower slopes if you scroll to the right.

    http://www.topozone.com/map.asp?lat=38.41188&lon=-122.09703&datum=nad27&layer=DRG

    It's not the best, but I don't have access to Google Earth at work. The lat/lon is on there if you have something better.

    Gears - I tend to find that 30x27 at around 55rpm gets about 5mph, which is about 2.2m/sec. I think that 53x16 at around 60rpm would be over 15mph wouldn't it?
     
  8. frenchyge

    frenchyge New Member

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    Uh... yeah. Oops, my bad. :eek:

    Here's a tool that I use, since I don't have a fancy topo software, with a portion of that route plotted: http://www.gmap-pedometer.com/?r=1732305 Maybe someone else can help with that profile.

    Eyeballing is a bit dangerous if you want to calculate good power numbers, but it looks like a pretty steady slope for that 1-mile portion. The tool shows 830' of rise, over 1.0207 miles (5389') for a gradient of 15.4%. See if that matches your expectations better on www.analyticcycling.com
     
  9. swampy1970

    swampy1970 Well-Known Member

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    Cool link! Thanks.

    I was going off a printed topo map of the area and a little measuring wheel (yes I got the one with the correct scale. :p LOL)

    I know the Polar CS600 consistantly reads high on the % grade and shows nothing less than 22% for the section around the two sets of hairpins. Oddly on Ebbetts and Monitor Passes the gradient worked fine but the overall elevation was off, despite pre-calibration that day.

    I re-did a 1 mile section that starts a little lower than where you started and got an average of 18%. Even with an average of 16% it's still saying 337watts. That aint something that I believe I could hold for several times up that hill, given that the preceeding few miles are hardly easy.

    I was somewhere around 250watts given my state of detraining. (I'm currently working on detraining the detraining!) and this is backed up by being able to ride at 23, 24mph on the flat roads around here on a road bike but not being able to hold 25mph yet, which is about ~300watts. (Back in '96 my threshold was measured at 340watts... and back then we did a guestimate that went along the lines of HR at 300watts = x and when I ride at x HR on the road I get 25mph on the cycling computer) Hopefully sometime next year I'll be back there - until then I'm just hoping, sweating, grimacing, cursing the God of gravity etc etc...

    That rider in yellow (my avatar), was me riding up a 18% slope, into a freezing cold howling headwind - in 39x25 at around 70rpm. How times have changed. :(

    250watts at 16% gives me 1.6m/s which is a knee poppingly slow ~3.6mph. I think I may fall over or start pulling wheelies at that speed! Maybe I should ride on one wheel to reduce the rolling resistance. ;)

    Yes, I know I should get something to monitor power etc, but given my state of "lard" I'll wait (or should that be weight) until I've finished getting rid of that last 10kg.
     
  10. Fday

    Fday New Member

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    I take it you actually rode this section at the speeds you said and are trying to figure out what your power is/was.

    It is not to surprising that your power climbing might be much higher than your power on the flat, especially for 3 reasons.

    1. You are becoming PC trained and PC'ers typically see big power improvement first when climbing because of the next two reasons.
    2. Climbing tends to keep your cadence down to a cadence you can sustain on the PC's whereas on the road you tend to ride at higher cadences so you lose efficiency.
    3. You tend to open the hip angle climbing which again allows you to use your hip flexors more than you can when riding on the flats and in a more aero position.

    So, I don't know what your power actually is but it would not surprise me that it is substantially higher than what you are actually doing on the flats.

    Have you done this climb in prior years such that you have a time for the climb you can compare to know whether you are much more powerful now than you have been in the past for equivalent degrees of training?
     
  11. frenchyge

    frenchyge New Member

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    Heh. This isn't by any means meant to be a putdown, but I've looked at your avatar many times trying to figure out what the significance was. With all the stuff in the background, I thought it was a rider riding along a park path or something. Funny how deceiving those tiny little pictures can be. :)
     
  12. dhk2

    dhk2 Active Member

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    The AC calculations agree pretty well with a shortcut formula I picked out of a training book read for slow-speed climbing:

    Watts to ground = 2 x total weight (lbs) x gradient x mph
    = 2 x 205 x .20 x 4.95 = 406 watts

    Add in another 2-3% for drivetrain loss and we're right up to your estimate:

    406 x 1.03 = 418 watts (at the crank)

    I like this formula because it's simple to remember....2 x weight x slope x speed.

    Have also found that gradient is hard to nail down with any accuracy. I have Delorme Topo 5.0, but that's often incorrect because the registration of the road map with the topo maps can be off. Have been playing with Google Earth lately; it may be a better way to obtain fairly accurate average-slope data.
     
  13. swampy1970

    swampy1970 Well-Known Member

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    National Hillclimb back in England, 1991 if I recall correctly. Note the nice wooly socks cause it was so 'effing cold. The 25 sprocket was a "cop out/just in case gear" that we put on the day before cause some of the locals said it could get a little windy, especially further up the climb where it was more exposed. It wasn't a good day, or a good ride....

    I still have that Sachs/Maillard seven speed freewheel somewhere in the garage - and those "Bernard Hinault-esque" Look pedals. Anyone want a 14cm Cinelli 1A stem for a museum piece? :D

    A bigger version:
    http://www2.snapfish.com/slideshow/AlbumID=54855259/PictureID=2917679360/a=32940439_32940439/t_=32940439

    Frank,

    I have records from last year going up most of this climb. I am quite a bit faster this year up the first two-thirds of the climb but until this year I had no reason to climb to steeper top third, which ironically is not all that much fun to descend either. The only thing going for that climb is the view from the top of the ridge - Sacramento valley on one side and across Napa all the way to the tower tops of the Golden Gate bridge on the other. I've been toying with the idea of doing The Climb to Kaiser a few weeks before the Death Ride and since there's a nice longer and steep climb in that one I thought I better start riding the steeper stuff just incase I do decide to do it.

    I don't think it'll be too much longer before I dump the 30 ring and just run the 34 and 50 that's on the PCs right now. This climb is the only reason I keep the granny ring on.

    I am having issues with getting back into a more normal on-the-drops riding position, but what I've found is (and we did this just for a laugh but it ended up working pretty good but almost vomit inducing) was that if you pedal with both feet together "dolphin style" whilst on the drops in full aero position for about 5 minutes, not only do you end up with a killer abs and lower back workout but it actually seems very easy to ride on the drops for the following 15 to 20 minutes pedalling normally. It works on the trainer but not too sure about doing this on the road though. LOL
     
  14. daveryanwyoming

    daveryanwyoming Well-Known Member

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    Both are great rides and highly recommended. There's a couple of climbs on CtK that are quite a bit steeper than anything you'll see on the Death Ride. The backroad up to Huntington Lake is both really steep and really crummy pavement so it's a workout but a great climb.

    The thing about Kaiser isn't the climbs even though they're bloody hard, it's dealing with the central valley heat on the flats back into Fresno. If you're unlucky enough to get one of those hot headwind days those miles will feel endless after all that climbing. You might also consider doing the Tollhouse hillclimb time trial. Tollhouse grade is one of the big climbs on Kaiser and a really good one with euro style switchbacks. The Central Valley Cyclists run a time trial up it in the spring, it's gotta be happening in the next month or so.

    Good luck,
    -Dave
     
  15. swampy1970

    swampy1970 Well-Known Member

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    Thanks for the info on the CtK and the time trial. I'll have to look and see when the TT is and see if it fits in around work.

    I've done the Deathride a few times and it's a fun day out on the bike, great scenery and awesome support - although last years infernal heat on the bottom half of Carson Pass was actually worse than the thunder, lightening and large hail the year before. I've never had my feet swell due to heat before...

    edit...
    .: Tollhouse Time Trial
    The world-famous Tollhouse Time Trial will be held this Wednesday, June 13th. First rider will be off at 6:30 PM. Please park at Sierra Elementary School, at the intersection of Tollhouse Road and Lodge Road.

    Click here for a list of the top-10 recorded fast times for Tollhouse.
     
  16. daveryanwyoming

    daveryanwyoming Well-Known Member

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    No kidding, getting hosed down by volunteers at the Woodford's feed was a godsend last year in the heat.
     
  17. Fday

    Fday New Member

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    I am not sure you are at this level yet in your PC progression but I would be interested if you could do this climb on your PC's and compare that to your performance on your regular cranks. If your PC abilities are such that you could do such an effort on them I would predict that your time would actually be faster on the PC's than they would be on regular cranks, despite the extra weight of the PC's. Up for the challenge?
     
  18. swampy1970

    swampy1970 Well-Known Member

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    I know that I'm already faster on PC's now on this climb than I was at any time pre-PC during the last couple of years. I could try engaging the lockout and see what happens and how things feel.

    A couple of months ago I did put the PC's in lockout mode (the only time I've done this in training) to ride up this hill, but that was when I was testing different crank lengths (I have the basic adjustable with lockout).

    210mm = windmilling Godzilla strength! I'd need about 2 years of hardcore yoga to ride that length and get on the drops though but it seems real good on very steep hills. That 'project' can wait until I finish this years goal "Project: Gut-be-gone"

    I'm a bit cautious about swapping the cranks as I already "smushed" the o-ring on the endcaps a bit and don't fancy further "smushage" ;) I tried the suggestion of just undoing the 8mm crank bolt and using the endcap as an auto-crank extractor but even with excessive force I can't get the cranks off this way - I'll use the trusty crank extractor with the endcaps removed. I like my PC's in working order! Besides, my regular cranks are 185mm and I have the PC's set to 180mm for now.

    I'd like to ride them in both the Climb to Kaiser and Deathride but I'm not sure that 12 hours on PC's will be feasible and would also take away from the fun of the kamakaze descent of Ebbetts pass back towards Centerville... I guess I could always stop for 30 seconds an lockout the cranks for the downhill run in to lunch....

    ... but I am getting to master the art of one legged pedalling with the "outside" leg when cornering. :D
     
  19. Fday

    Fday New Member

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    So, you are doing this climb on PC's and seeing the improvement. Very cool.

    Actually, I don't think death ride on PC's is nearly as bad as it would seem at first blush, at least to those with an adequate base. Several people have told us they are going to do it on them this year. Remember, half the ride is basically coasting, letting those climbing muscles almost fully recover before the next effort. Andrew and I are thinking about doing one pass on a PC equipped tandem. Two fat guys on one bike should really be able to get up some speed coming down.

    Anyhow, I am glad to see you have taken the immersion approach to the PC training. You will be glad you did. In fact, it seems like you already are. [​IMG]

    Frank
     
  20. swampy1970

    swampy1970 Well-Known Member

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    PC equipped tandem? The possibilities for being out of sync are just endless! LOL. A video of that could be hilarious.

    It might be half the distance that you're going down hill - but that aint half the time. I wish it was - 55mph uphill if desired would be nice. The first time I rode up monitor pass, after 12 years off the bike and a 4 week crash training session, 5.5mph was bad enough on the 10% section. 210lb and big mountains = pain. Thankfully I'm a "couple of bikes" lighter now...

    Andrews was saying that his young daughter is riding a pass or two on a PowerCrank equiped bike. Wow.

    Hey, how about a PowerCranks cycling jersey for some advertising on course ;)
     
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